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/* Alias analysis for GNU C Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc. Contributed by John Carr (jfc@mit.edu). This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see <http://www.gnu.org/licenses/>. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tm.h" #include "rtl.h" #include "tree.h" #include "tm_p.h" #include "function.h" #include "alias.h" #include "emit-rtl.h" #include "regs.h" #include "hard-reg-set.h" #include "basic-block.h" #include "flags.h" #include "output.h" #include "diagnostic-core.h" #include "cselib.h" #include "splay-tree.h" #include "ggc.h" #include "langhooks.h" #include "timevar.h" #include "target.h" #include "cgraph.h" #include "tree-pass.h" #include "df.h" #include "tree-ssa-alias.h" #include "pointer-set.h" #include "tree-flow.h" /* The aliasing API provided here solves related but different problems: Say there exists (in c) struct X { struct Y y1; struct Z z2; } x1, *px1, *px2; struct Y y2, *py; struct Z z2, *pz; py = &px1.y1; px2 = &x1; Consider the four questions: Can a store to x1 interfere with px2->y1? Can a store to x1 interfere with px2->z2? (*px2).z2 Can a store to x1 change the value pointed to by with py? Can a store to x1 change the value pointed to by with pz? The answer to these questions can be yes, yes, yes, and maybe. The first two questions can be answered with a simple examination of the type system. If structure X contains a field of type Y then a store thru a pointer to an X can overwrite any field that is contained (recursively) in an X (unless we know that px1 != px2). The last two of the questions can be solved in the same way as the first two questions but this is too conservative. The observation is that in some cases analysis we can know if which (if any) fields are addressed and if those addresses are used in bad ways. This analysis may be language specific. In C, arbitrary operations may be applied to pointers. However, there is some indication that this may be too conservative for some C++ types. The pass ipa-type-escape does this analysis for the types whose instances do not escape across the compilation boundary. Historically in GCC, these two problems were combined and a single data structure was used to represent the solution to these problems. We now have two similar but different data structures, The data structure to solve the last two question is similar to the first, but does not contain have the fields in it whose address are never taken. For types that do escape the compilation unit, the data structures will have identical information. */ /* The alias sets assigned to MEMs assist the back-end in determining which MEMs can alias which other MEMs. In general, two MEMs in different alias sets cannot alias each other, with one important exception. Consider something like: struct S { int i; double d; }; a store to an `S' can alias something of either type `int' or type `double'. (However, a store to an `int' cannot alias a `double' and vice versa.) We indicate this via a tree structure that looks like: struct S / \ / \ |/_ _\| int double (The arrows are directed and point downwards.) In this situation we say the alias set for `struct S' is the `superset' and that those for `int' and `double' are `subsets'. To see whether two alias sets can point to the same memory, we must see if either alias set is a subset of the other. We need not trace past immediate descendants, however, since we propagate all grandchildren up one level. Alias set zero is implicitly a superset of all other alias sets. However, this is no actual entry for alias set zero. It is an error to attempt to explicitly construct a subset of zero. */ struct GTY(()) alias_set_entry_d { /* The alias set number, as stored in MEM_ALIAS_SET. */ alias_set_type alias_set; /* Nonzero if would have a child of zero: this effectively makes this alias set the same as alias set zero. */ int has_zero_child; /* The children of the alias set. These are not just the immediate children, but, in fact, all descendants. So, if we have: struct T { struct S s; float f; } continuing our example above, the children here will be all of `int', `double', `float', and `struct S'. */ splay_tree GTY((param1_is (int), param2_is (int))) children; }; typedef struct alias_set_entry_d *alias_set_entry; static int rtx_equal_for_memref_p (const_rtx, const_rtx); static int memrefs_conflict_p (int, rtx, int, rtx, HOST_WIDE_INT); static void record_set (rtx, const_rtx, void *); static int base_alias_check (rtx, rtx, enum machine_mode, enum machine_mode); static rtx find_base_value (rtx); static int mems_in_disjoint_alias_sets_p (const_rtx, const_rtx); static int insert_subset_children (splay_tree_node, void*); static alias_set_entry get_alias_set_entry (alias_set_type); static int aliases_everything_p (const_rtx); static bool nonoverlapping_component_refs_p (const_tree, const_tree); static tree decl_for_component_ref (tree); static int write_dependence_p (const_rtx, const_rtx, int); static void memory_modified_1 (rtx, const_rtx, void *); /* Set up all info needed to perform alias analysis on memory references. */ /* Returns the size in bytes of the mode of X. */ #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X))) /* Returns nonzero if MEM1 and MEM2 do not alias because they are in different alias sets. We ignore alias sets in functions making use of variable arguments because the va_arg macros on some systems are not legal ANSI C. */ #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \ mems_in_disjoint_alias_sets_p (MEM1, MEM2) /* Cap the number of passes we make over the insns propagating alias information through set chains. 10 is a completely arbitrary choice. */ #define MAX_ALIAS_LOOP_PASSES 10 /* reg_base_value[N] gives an address to which register N is related. If all sets after the first add or subtract to the current value or otherwise modify it so it does not point to a different top level object, reg_base_value[N] is equal to the address part of the source of the first set. A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS expressions represent certain special values: function arguments and the stack, frame, and argument pointers. The contents of an ADDRESS is not normally used, the mode of the ADDRESS determines whether the ADDRESS is a function argument or some other special value. Pointer equality, not rtx_equal_p, determines whether two ADDRESS expressions refer to the same base address. The only use of the contents of an ADDRESS is for determining if the current function performs nonlocal memory memory references for the purposes of marking the function as a constant function. */ static GTY(()) VEC(rtx,gc) *reg_base_value; static rtx *new_reg_base_value; /* We preserve the copy of old array around to avoid amount of garbage produced. About 8% of garbage produced were attributed to this array. */ static GTY((deletable)) VEC(rtx,gc) *old_reg_base_value; #define static_reg_base_value \ (this_target_rtl->x_static_reg_base_value) #define REG_BASE_VALUE(X) \ (REGNO (X) < VEC_length (rtx, reg_base_value) \ ? VEC_index (rtx, reg_base_value, REGNO (X)) : 0) /* Vector indexed by N giving the initial (unchanging) value known for pseudo-register N. This array is initialized in init_alias_analysis, and does not change until end_alias_analysis is called. */ static GTY((length("reg_known_value_size"))) rtx *reg_known_value; /* Indicates number of valid entries in reg_known_value. */ static GTY(()) unsigned int reg_known_value_size; /* Vector recording for each reg_known_value whether it is due to a REG_EQUIV note. Future passes (viz., reload) may replace the pseudo with the equivalent expression and so we account for the dependences that would be introduced if that happens. The REG_EQUIV notes created in assign_parms may mention the arg pointer, and there are explicit insns in the RTL that modify the arg pointer. Thus we must ensure that such insns don't get scheduled across each other because that would invalidate the REG_EQUIV notes. One could argue that the REG_EQUIV notes are wrong, but solving the problem in the scheduler will likely give better code, so we do it here. */ static bool *reg_known_equiv_p; /* True when scanning insns from the start of the rtl to the NOTE_INSN_FUNCTION_BEG note. */ static bool copying_arguments; DEF_VEC_P(alias_set_entry); DEF_VEC_ALLOC_P(alias_set_entry,gc); /* The splay-tree used to store the various alias set entries. */ static GTY (()) VEC(alias_set_entry,gc) *alias_sets; /* Build a decomposed reference object for querying the alias-oracle from the MEM rtx and store it in *REF. Returns false if MEM is not suitable for the alias-oracle. */ static bool ao_ref_from_mem (ao_ref *ref, const_rtx mem) { tree expr = MEM_EXPR (mem); tree base; if (!expr) return false; ao_ref_init (ref, expr); /* Get the base of the reference and see if we have to reject or adjust it. */ base = ao_ref_base (ref); if (base == NULL_TREE) return false; /* The tree oracle doesn't like to have these. */ if (TREE_CODE (base) == FUNCTION_DECL || TREE_CODE (base) == LABEL_DECL) return false; /* If this is a pointer dereference of a non-SSA_NAME punt. ??? We could replace it with a pointer to anything. */ if ((INDIRECT_REF_P (base) || TREE_CODE (base) == MEM_REF) && TREE_CODE (TREE_OPERAND (base, 0)) != SSA_NAME) return false; if (TREE_CODE (base) == TARGET_MEM_REF && TMR_BASE (base) && TREE_CODE (TMR_BASE (base)) != SSA_NAME) return false; /* If this is a reference based on a partitioned decl replace the base with an INDIRECT_REF of the pointer representative we created during stack slot partitioning. */ if (TREE_CODE (base) == VAR_DECL && ! TREE_STATIC (base) && cfun->gimple_df->decls_to_pointers != NULL) { void *namep; namep = pointer_map_contains (cfun->gimple_df->decls_to_pointers, base); if (namep) ref->base = build_simple_mem_ref (*(tree *)namep); } else if (TREE_CODE (base) == TARGET_MEM_REF && TREE_CODE (TMR_BASE (base)) == ADDR_EXPR && TREE_CODE (TREE_OPERAND (TMR_BASE (base), 0)) == VAR_DECL && ! TREE_STATIC (TREE_OPERAND (TMR_BASE (base), 0)) && cfun->gimple_df->decls_to_pointers != NULL) { void *namep; namep = pointer_map_contains (cfun->gimple_df->decls_to_pointers, TREE_OPERAND (TMR_BASE (base), 0)); if (namep) ref->base = build_simple_mem_ref (*(tree *)namep); } ref->ref_alias_set = MEM_ALIAS_SET (mem); /* If MEM_OFFSET or MEM_SIZE are unknown we have to punt. Keep points-to related information though. */ if (!MEM_OFFSET_KNOWN_P (mem) || !MEM_SIZE_KNOWN_P (mem)) { ref->ref = NULL_TREE; ref->offset = 0; ref->size = -1; ref->max_size = -1; return true; } /* If the base decl is a parameter we can have negative MEM_OFFSET in case of promoted subregs on bigendian targets. Trust the MEM_EXPR here. */ if (MEM_OFFSET (mem) < 0 && (MEM_SIZE (mem) + MEM_OFFSET (mem)) * BITS_PER_UNIT == ref->size) return true; ref->offset += MEM_OFFSET (mem) * BITS_PER_UNIT; ref->size = MEM_SIZE (mem) * BITS_PER_UNIT; /* The MEM may extend into adjacent fields, so adjust max_size if necessary. */ if (ref->max_size != -1 && ref->size > ref->max_size) ref->max_size = ref->size; /* If MEM_OFFSET and MEM_SIZE get us outside of the base object of the MEM_EXPR punt. This happens for STRICT_ALIGNMENT targets a lot. */ if (MEM_EXPR (mem) != get_spill_slot_decl (false) && (ref->offset < 0 || (DECL_P (ref->base) && (!host_integerp (DECL_SIZE (ref->base), 1) || (TREE_INT_CST_LOW (DECL_SIZE ((ref->base))) < (unsigned HOST_WIDE_INT)(ref->offset + ref->size)))))) return false; return true; } /* Query the alias-oracle on whether the two memory rtx X and MEM may alias. If TBAA_P is set also apply TBAA. Returns true if the two rtxen may alias, false otherwise. */ static bool rtx_refs_may_alias_p (const_rtx x, const_rtx mem, bool tbaa_p) { ao_ref ref1, ref2; if (!ao_ref_from_mem (&ref1, x) || !ao_ref_from_mem (&ref2, mem)) return true; return refs_may_alias_p_1 (&ref1, &ref2, tbaa_p && MEM_ALIAS_SET (x) != 0 && MEM_ALIAS_SET (mem) != 0); } /* Returns a pointer to the alias set entry for ALIAS_SET, if there is such an entry, or NULL otherwise. */ static inline alias_set_entry get_alias_set_entry (alias_set_type alias_set) { return VEC_index (alias_set_entry, alias_sets, alias_set); } /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that the two MEMs cannot alias each other. */ static inline int mems_in_disjoint_alias_sets_p (const_rtx mem1, const_rtx mem2) { /* Perform a basic sanity check. Namely, that there are no alias sets if we're not using strict aliasing. This helps to catch bugs whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or where a MEM is allocated in some way other than by the use of gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to use alias sets to indicate that spilled registers cannot alias each other, we might need to remove this check. */ gcc_assert (flag_strict_aliasing || (!MEM_ALIAS_SET (mem1) && !MEM_ALIAS_SET (mem2))); return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), MEM_ALIAS_SET (mem2)); } /* Insert the NODE into the splay tree given by DATA. Used by record_alias_subset via splay_tree_foreach. */ static int insert_subset_children (splay_tree_node node, void *data) { splay_tree_insert ((splay_tree) data, node->key, node->value); return 0; } /* Return true if the first alias set is a subset of the second. */ bool alias_set_subset_of (alias_set_type set1, alias_set_type set2) { alias_set_entry ase; /* Everything is a subset of the "aliases everything" set. */ if (set2 == 0) return true; /* Otherwise, check if set1 is a subset of set2. */ ase = get_alias_set_entry (set2); if (ase != 0 && (ase->has_zero_child || splay_tree_lookup (ase->children, (splay_tree_key) set1))) return true; return false; } /* Return 1 if the two specified alias sets may conflict. */ int alias_sets_conflict_p (alias_set_type set1, alias_set_type set2) { alias_set_entry ase; /* The easy case. */ if (alias_sets_must_conflict_p (set1, set2)) return 1; /* See if the first alias set is a subset of the second. */ ase = get_alias_set_entry (set1); if (ase != 0 && (ase->has_zero_child || splay_tree_lookup (ase->children, (splay_tree_key) set2))) return 1; /* Now do the same, but with the alias sets reversed. */ ase = get_alias_set_entry (set2); if (ase != 0 && (ase->has_zero_child || splay_tree_lookup (ase->children, (splay_tree_key) set1))) return 1; /* The two alias sets are distinct and neither one is the child of the other. Therefore, they cannot conflict. */ return 0; } /* Return 1 if the two specified alias sets will always conflict. */ int alias_sets_must_conflict_p (alias_set_type set1, alias_set_type set2) { if (set1 == 0 || set2 == 0 || set1 == set2) return 1; return 0; } /* Return 1 if any MEM object of type T1 will always conflict (using the dependency routines in this file) with any MEM object of type T2. This is used when allocating temporary storage. If T1 and/or T2 are NULL_TREE, it means we know nothing about the storage. */ int objects_must_conflict_p (tree t1, tree t2) { alias_set_type set1, set2; /* If neither has a type specified, we don't know if they'll conflict because we may be using them to store objects of various types, for example the argument and local variables areas of inlined functions. */ if (t1 == 0 && t2 == 0) return 0; /* If they are the same type, they must conflict. */ if (t1 == t2 /* Likewise if both are volatile. */ || (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2))) return 1; set1 = t1 ? get_alias_set (t1) : 0; set2 = t2 ? get_alias_set (t2) : 0; /* We can't use alias_sets_conflict_p because we must make sure that every subtype of t1 will conflict with every subtype of t2 for which a pair of subobjects of these respective subtypes overlaps on the stack. */ return alias_sets_must_conflict_p (set1, set2); } /* Return true if all nested component references handled by get_inner_reference in T are such that we should use the alias set provided by the object at the heart of T. This is true for non-addressable components (which don't have their own alias set), as well as components of objects in alias set zero. This later point is a special case wherein we wish to override the alias set used by the component, but we don't have per-FIELD_DECL assignable alias sets. */ bool component_uses_parent_alias_set (const_tree t) { while (1) { /* If we're at the end, it vacuously uses its own alias set. */ if (!handled_component_p (t)) return false; switch (TREE_CODE (t)) { case COMPONENT_REF: if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1))) return true; break; case ARRAY_REF: case ARRAY_RANGE_REF: if (TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0)))) return true; break; case REALPART_EXPR: case IMAGPART_EXPR: break; default: /* Bitfields and casts are never addressable. */ return true; } t = TREE_OPERAND (t, 0); if (get_alias_set (TREE_TYPE (t)) == 0) return true; } } /* Return the alias set for the memory pointed to by T, which may be either a type or an expression. Return -1 if there is nothing special about dereferencing T. */ static alias_set_type get_deref_alias_set_1 (tree t) { /* If we're not doing any alias analysis, just assume everything aliases everything else. */ if (!flag_strict_aliasing) return 0; /* All we care about is the type. */ if (! TYPE_P (t)) t = TREE_TYPE (t); /* If we have an INDIRECT_REF via a void pointer, we don't know anything about what that might alias. Likewise if the pointer is marked that way. */ if (TREE_CODE (TREE_TYPE (t)) == VOID_TYPE || TYPE_REF_CAN_ALIAS_ALL (t)) return 0; return -1; } /* Return the alias set for the memory pointed to by T, which may be either a type or an expression. */ alias_set_type get_deref_alias_set (tree t) { alias_set_type set = get_deref_alias_set_1 (t); /* Fall back to the alias-set of the pointed-to type. */ if (set == -1) { if (! TYPE_P (t)) t = TREE_TYPE (t); set = get_alias_set (TREE_TYPE (t)); } return set; } /* Return the alias set for T, which may be either a type or an expression. Call language-specific routine for help, if needed. */ alias_set_type get_alias_set (tree t) { alias_set_type set; /* If we're not doing any alias analysis, just assume everything aliases everything else. Also return 0 if this or its type is an error. */ if (! flag_strict_aliasing || t == error_mark_node || (! TYPE_P (t) && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node))) return 0; /* We can be passed either an expression or a type. This and the language-specific routine may make mutually-recursive calls to each other to figure out what to do. At each juncture, we see if this is a tree that the language may need to handle specially. First handle things that aren't types. */ if (! TYPE_P (t)) { tree inner; /* Give the language a chance to do something with this tree before we look at it. */ STRIP_NOPS (t); set = lang_hooks.get_alias_set (t); if (set != -1) return set; /* Get the base object of the reference. */ inner = t; while (handled_component_p (inner)) { /* If there is a VIEW_CONVERT_EXPR in the chain we cannot use the type of any component references that wrap it to determine the alias-set. */ if (TREE_CODE (inner) == VIEW_CONVERT_EXPR) t = TREE_OPERAND (inner, 0); inner = TREE_OPERAND (inner, 0); } /* Handle pointer dereferences here, they can override the alias-set. */ if (INDIRECT_REF_P (inner)) { set = get_deref_alias_set_1 (TREE_OPERAND (inner, 0)); if (set != -1) return set; } else if (TREE_CODE (inner) == TARGET_MEM_REF) return get_deref_alias_set (TMR_OFFSET (inner)); else if (TREE_CODE (inner) == MEM_REF) { set = get_deref_alias_set_1 (TREE_OPERAND (inner, 1)); if (set != -1) return set; } /* If the innermost reference is a MEM_REF that has a conversion embedded treat it like a VIEW_CONVERT_EXPR above, using the memory access type for determining the alias-set. */ if (TREE_CODE (inner) == MEM_REF && TYPE_MAIN_VARIANT (TREE_TYPE (inner)) != TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (TREE_OPERAND (inner, 1))))) return get_deref_alias_set (TREE_OPERAND (inner, 1)); /* Otherwise, pick up the outermost object that we could have a pointer to, processing conversions as above. */ while (component_uses_parent_alias_set (t)) { t = TREE_OPERAND (t, 0); STRIP_NOPS (t); } /* If we've already determined the alias set for a decl, just return it. This is necessary for C++ anonymous unions, whose component variables don't look like union members (boo!). */ if (TREE_CODE (t) == VAR_DECL && DECL_RTL_SET_P (t) && MEM_P (DECL_RTL (t))) return MEM_ALIAS_SET (DECL_RTL (t)); /* Now all we care about is the type. */ t = TREE_TYPE (t); } /* Variant qualifiers don't affect the alias set, so get the main variant. */ t = TYPE_MAIN_VARIANT (t); /* Always use the canonical type as well. If this is a type that requires structural comparisons to identify compatible types use alias set zero. */ if (TYPE_STRUCTURAL_EQUALITY_P (t)) { /* Allow the language to specify another alias set for this type. */ set = lang_hooks.get_alias_set (t); if (set != -1) return set; return 0; } t = TYPE_CANONICAL (t); /* The canonical type should not require structural equality checks. */ gcc_checking_assert (!TYPE_STRUCTURAL_EQUALITY_P (t)); /* If this is a type with a known alias set, return it. */ if (TYPE_ALIAS_SET_KNOWN_P (t)) return TYPE_ALIAS_SET (t); /* We don't want to set TYPE_ALIAS_SET for incomplete types. */ if (!COMPLETE_TYPE_P (t)) { /* For arrays with unknown size the conservative answer is the alias set of the element type. */ if (TREE_CODE (t) == ARRAY_TYPE) return get_alias_set (TREE_TYPE (t)); /* But return zero as a conservative answer for incomplete types. */ return 0; } /* See if the language has special handling for this type. */ set = lang_hooks.get_alias_set (t); if (set != -1) return set; /* There are no objects of FUNCTION_TYPE, so there's no point in using up an alias set for them. (There are, of course, pointers and references to functions, but that's different.) */ else if (TREE_CODE (t) == FUNCTION_TYPE || TREE_CODE (t) == METHOD_TYPE) set = 0; /* Unless the language specifies otherwise, let vector types alias their components. This avoids some nasty type punning issues in normal usage. And indeed lets vectors be treated more like an array slice. */ else if (TREE_CODE (t) == VECTOR_TYPE) set = get_alias_set (TREE_TYPE (t)); /* Unless the language specifies otherwise, treat array types the same as their components. This avoids the asymmetry we get through recording the components. Consider accessing a character(kind=1) through a reference to a character(kind=1)[1:1]. Or consider if we want to assign integer(kind=4)[0:D.1387] and integer(kind=4)[4] the same alias set or not. Just be pragmatic here and make sure the array and its element type get the same alias set assigned. */ else if (TREE_CODE (t) == ARRAY_TYPE && !TYPE_NONALIASED_COMPONENT (t)) set = get_alias_set (TREE_TYPE (t)); /* From the former common C and C++ langhook implementation: Unfortunately, there is no canonical form of a pointer type. In particular, if we have `typedef int I', then `int *', and `I *' are different types. So, we have to pick a canonical representative. We do this below. Technically, this approach is actually more conservative that it needs to be. In particular, `const int *' and `int *' should be in different alias sets, according to the C and C++ standard, since their types are not the same, and so, technically, an `int **' and `const int **' cannot point at the same thing. But, the standard is wrong. In particular, this code is legal C++: int *ip; int **ipp = &ip; const int* const* cipp = ipp; And, it doesn't make sense for that to be legal unless you can dereference IPP and CIPP. So, we ignore cv-qualifiers on the pointed-to types. This issue has been reported to the C++ committee. In addition to the above canonicalization issue, with LTO we should also canonicalize `T (*)[]' to `T *' avoiding alias issues with pointer-to element types and pointer-to array types. Likewise we need to deal with the situation of incomplete pointed-to types and make `*(struct X **)&a' and `*(struct X {} **)&a' alias. Otherwise we will have to guarantee that all pointer-to incomplete type variants will be replaced by pointer-to complete type variants if they are available. With LTO the convenient situation of using `void *' to access and store any pointer type will also become more apparent (and `void *' is just another pointer-to incomplete type). Assigning alias-set zero to `void *' and all pointer-to incomplete types is a not appealing solution. Assigning an effective alias-set zero only affecting pointers might be - by recording proper subset relationships of all pointer alias-sets. Pointer-to function types are another grey area which needs caution. Globbing them all into one alias-set or the above effective zero set would work. For now just assign the same alias-set to all pointers. That's simple and avoids all the above problems. */ else if (POINTER_TYPE_P (t) && t != ptr_type_node) set = get_alias_set (ptr_type_node); /* Otherwise make a new alias set for this type. */ else { /* Each canonical type gets its own alias set, so canonical types shouldn't form a tree. It doesn't really matter for types we handle specially above, so only check it where it possibly would result in a bogus alias set. */ gcc_checking_assert (TYPE_CANONICAL (t) == t); set = new_alias_set (); } TYPE_ALIAS_SET (t) = set; /* If this is an aggregate type or a complex type, we must record any component aliasing information. */ if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE) record_component_aliases (t); return set; } /* Return a brand-new alias set. */ alias_set_type new_alias_set (void) { if (flag_strict_aliasing) { if (alias_sets == 0) VEC_safe_push (alias_set_entry, gc, alias_sets, 0); VEC_safe_push (alias_set_entry, gc, alias_sets, 0); return VEC_length (alias_set_entry, alias_sets) - 1; } else return 0; } /* Indicate that things in SUBSET can alias things in SUPERSET, but that not everything that aliases SUPERSET also aliases SUBSET. For example, in C, a store to an `int' can alias a load of a structure containing an `int', and vice versa. But it can't alias a load of a 'double' member of the same structure. Here, the structure would be the SUPERSET and `int' the SUBSET. This relationship is also described in the comment at the beginning of this file. This function should be called only once per SUPERSET/SUBSET pair. It is illegal for SUPERSET to be zero; everything is implicitly a subset of alias set zero. */ void record_alias_subset (alias_set_type superset, alias_set_type subset) { alias_set_entry superset_entry; alias_set_entry subset_entry; /* It is possible in complex type situations for both sets to be the same, in which case we can ignore this operation. */ if (superset == subset) return; gcc_assert (superset); superset_entry = get_alias_set_entry (superset); if (superset_entry == 0) { /* Create an entry for the SUPERSET, so that we have a place to attach the SUBSET. */ superset_entry = ggc_alloc_cleared_alias_set_entry_d (); superset_entry->alias_set = superset; superset_entry->children = splay_tree_new_ggc (splay_tree_compare_ints, ggc_alloc_splay_tree_scalar_scalar_splay_tree_s, ggc_alloc_splay_tree_scalar_scalar_splay_tree_node_s); superset_entry->has_zero_child = 0; VEC_replace (alias_set_entry, alias_sets, superset, superset_entry); } if (subset == 0) superset_entry->has_zero_child = 1; else { subset_entry = get_alias_set_entry (subset); /* If there is an entry for the subset, enter all of its children (if they are not already present) as children of the SUPERSET. */ if (subset_entry) { if (subset_entry->has_zero_child) superset_entry->has_zero_child = 1; splay_tree_foreach (subset_entry->children, insert_subset_children, superset_entry->children); } /* Enter the SUBSET itself as a child of the SUPERSET. */ splay_tree_insert (superset_entry->children, (splay_tree_key) subset, 0); } } /* Record that component types of TYPE, if any, are part of that type for aliasing purposes. For record types, we only record component types for fields that are not marked non-addressable. For array types, we only record the component type if it is not marked non-aliased. */ void record_component_aliases (tree type) { alias_set_type superset = get_alias_set (type); tree field; if (superset == 0) return; switch (TREE_CODE (type)) { case RECORD_TYPE: case UNION_TYPE: case QUAL_UNION_TYPE: /* Recursively record aliases for the base classes, if there are any. */ if (TYPE_BINFO (type)) { int i; tree binfo, base_binfo; for (binfo = TYPE_BINFO (type), i = 0; BINFO_BASE_ITERATE (binfo, i, base_binfo); i++) record_alias_subset (superset, get_alias_set (BINFO_TYPE (base_binfo))); } for (field = TYPE_FIELDS (type); field != 0; field = DECL_CHAIN (field)) if (TREE_CODE (field) == FIELD_DECL && !DECL_NONADDRESSABLE_P (field)) record_alias_subset (superset, get_alias_set (TREE_TYPE (field))); break; case COMPLEX_TYPE: record_alias_subset (superset, get_alias_set (TREE_TYPE (type))); break; /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their element type. */ default: break; } } /* Allocate an alias set for use in storing and reading from the varargs spill area. */ static GTY(()) alias_set_type varargs_set = -1; alias_set_type get_varargs_alias_set (void) { #if 1 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the varargs alias set to an INDIRECT_REF (FIXME!), so we can't consistently use the varargs alias set for loads from the varargs area. So don't use it anywhere. */ return 0; #else if (varargs_set == -1) varargs_set = new_alias_set (); return varargs_set; #endif } /* Likewise, but used for the fixed portions of the frame, e.g., register save areas. */ static GTY(()) alias_set_type frame_set = -1; alias_set_type get_frame_alias_set (void) { if (frame_set == -1) frame_set = new_alias_set (); return frame_set; } /* Inside SRC, the source of a SET, find a base address. */ static rtx find_base_value (rtx src) { unsigned int regno; #if defined (FIND_BASE_TERM) /* Try machine-dependent ways to find the base term. */ src = FIND_BASE_TERM (src); #endif switch (GET_CODE (src)) { case SYMBOL_REF: case LABEL_REF: return src; case REG: regno = REGNO (src); /* At the start of a function, argument registers have known base values which may be lost later. Returning an ADDRESS expression here allows optimization based on argument values even when the argument registers are used for other purposes. */ if (regno < FIRST_PSEUDO_REGISTER && copying_arguments) return new_reg_base_value[regno]; /* If a pseudo has a known base value, return it. Do not do this for non-fixed hard regs since it can result in a circular dependency chain for registers which have values at function entry. The test above is not sufficient because the scheduler may move a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */ if ((regno >= FIRST_PSEUDO_REGISTER || fixed_regs[regno]) && regno < VEC_length (rtx, reg_base_value)) { /* If we're inside init_alias_analysis, use new_reg_base_value to reduce the number of relaxation iterations. */ if (new_reg_base_value && new_reg_base_value[regno] && DF_REG_DEF_COUNT (regno) == 1) return new_reg_base_value[regno]; if (VEC_index (rtx, reg_base_value, regno)) return VEC_index (rtx, reg_base_value, regno); } return 0; case MEM: /* Check for an argument passed in memory. Only record in the copying-arguments block; it is too hard to track changes otherwise. */ if (copying_arguments && (XEXP (src, 0) == arg_pointer_rtx || (GET_CODE (XEXP (src, 0)) == PLUS && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx))) return gen_rtx_ADDRESS (VOIDmode, src); return 0; case CONST: src = XEXP (src, 0); if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS) break; /* ... fall through ... */ case PLUS: case MINUS: { rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1); /* If either operand is a REG that is a known pointer, then it is the base. */ if (REG_P (src_0) && REG_POINTER (src_0)) return find_base_value (src_0); if (REG_P (src_1) && REG_POINTER (src_1)) return find_base_value (src_1); /* If either operand is a REG, then see if we already have a known value for it. */ if (REG_P (src_0)) { temp = find_base_value (src_0); if (temp != 0) src_0 = temp; } if (REG_P (src_1)) { temp = find_base_value (src_1); if (temp!= 0) src_1 = temp; } /* If either base is named object or a special address (like an argument or stack reference), then use it for the base term. */ if (src_0 != 0 && (GET_CODE (src_0) == SYMBOL_REF || GET_CODE (src_0) == LABEL_REF || (GET_CODE (src_0) == ADDRESS && GET_MODE (src_0) != VOIDmode))) return src_0; if (src_1 != 0 && (GET_CODE (src_1) == SYMBOL_REF || GET_CODE (src_1) == LABEL_REF || (GET_CODE (src_1) == ADDRESS && GET_MODE (src_1) != VOIDmode))) return src_1; /* Guess which operand is the base address: If either operand is a symbol, then it is the base. If either operand is a CONST_INT, then the other is the base. */ if (CONST_INT_P (src_1) || CONSTANT_P (src_0)) return find_base_value (src_0); else if (CONST_INT_P (src_0) || CONSTANT_P (src_1)) return find_base_value (src_1); return 0; } case LO_SUM: /* The standard form is (lo_sum reg sym) so look only at the second operand. */ return find_base_value (XEXP (src, 1)); case AND: /* If the second operand is constant set the base address to the first operand. */ if (CONST_INT_P (XEXP (src, 1)) && INTVAL (XEXP (src, 1)) != 0) return find_base_value (XEXP (src, 0)); return 0; case TRUNCATE: /* As we do not know which address space the pointer is refering to, we can handle this only if the target does not support different pointer or address modes depending on the address space. */ if (!target_default_pointer_address_modes_p ()) break; if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode)) break; /* Fall through. */ case HIGH: case PRE_INC: case PRE_DEC: case POST_INC: case POST_DEC: case PRE_MODIFY: case POST_MODIFY: return find_base_value (XEXP (src, 0)); case ZERO_EXTEND: case SIGN_EXTEND: /* used for NT/Alpha pointers */ /* As we do not know which address space the pointer is refering to, we can handle this only if the target does not support different pointer or address modes depending on the address space. */ if (!target_default_pointer_address_modes_p ()) break; { rtx temp = find_base_value (XEXP (src, 0)); if (temp != 0 && CONSTANT_P (temp)) temp = convert_memory_address (Pmode, temp); return temp; } default: break; } return 0; } /* Called from init_alias_analysis indirectly through note_stores. */ /* While scanning insns to find base values, reg_seen[N] is nonzero if register N has been set in this function. */ static char *reg_seen; /* Addresses which are known not to alias anything else are identified by a unique integer. */ static int unique_id; static void record_set (rtx dest, const_rtx set, void *data ATTRIBUTE_UNUSED) { unsigned regno; rtx src; int n; if (!REG_P (dest)) return; regno = REGNO (dest); gcc_checking_assert (regno < VEC_length (rtx, reg_base_value)); /* If this spans multiple hard registers, then we must indicate that every register has an unusable value. */ if (regno < FIRST_PSEUDO_REGISTER) n = hard_regno_nregs[regno][GET_MODE (dest)]; else n = 1; if (n != 1) { while (--n >= 0) { reg_seen[regno + n] = 1; new_reg_base_value[regno + n] = 0; } return; } if (set) { /* A CLOBBER wipes out any old value but does not prevent a previously unset register from acquiring a base address (i.e. reg_seen is not set). */ if (GET_CODE (set) == CLOBBER) { new_reg_base_value[regno] = 0; return; } src = SET_SRC (set); } else { if (reg_seen[regno]) { new_reg_base_value[regno] = 0; return; } reg_seen[regno] = 1; new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode, GEN_INT (unique_id++)); return; } /* If this is not the first set of REGNO, see whether the new value is related to the old one. There are two cases of interest: (1) The register might be assigned an entirely new value that has the same base term as the original set. (2) The set might be a simple self-modification that cannot change REGNO's base value. If neither case holds, reject the original base value as invalid. Note that the following situation is not detected: extern int x, y; int *p = &x; p += (&y-&x); ANSI C does not allow computing the difference of addresses of distinct top level objects. */ if (new_reg_base_value[regno] != 0 && find_base_value (src) != new_reg_base_value[regno]) switch (GET_CODE (src)) { case LO_SUM: case MINUS: if (XEXP (src, 0) != dest && XEXP (src, 1) != dest) new_reg_base_value[regno] = 0; break; case PLUS: /* If the value we add in the PLUS is also a valid base value, this might be the actual base value, and the original value an index. */ { rtx other = NULL_RTX; if (XEXP (src, 0) == dest) other = XEXP (src, 1); else if (XEXP (src, 1) == dest) other = XEXP (src, 0); if (! other || find_base_value (other)) new_reg_base_value[regno] = 0; break; } case AND: if (XEXP (src, 0) != dest || !CONST_INT_P (XEXP (src, 1))) new_reg_base_value[regno] = 0; break; default: new_reg_base_value[regno] = 0; break; } /* If this is the first set of a register, record the value. */ else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno]) && ! reg_seen[regno] && new_reg_base_value[regno] == 0) new_reg_base_value[regno] = find_base_value (src); reg_seen[regno] = 1; } /* Return REG_BASE_VALUE for REGNO. Selective scheduler uses this to avoid using hard registers with non-null REG_BASE_VALUE for renaming. */ rtx get_reg_base_value (unsigned int regno) { return VEC_index (rtx, reg_base_value, regno); } /* If a value is known for REGNO, return it. */ rtx get_reg_known_value (unsigned int regno) { if (regno >= FIRST_PSEUDO_REGISTER) { regno -= FIRST_PSEUDO_REGISTER; if (regno < reg_known_value_size) return reg_known_value[regno]; } return NULL; } /* Set it. */ static void set_reg_known_value (unsigned int regno, rtx val) { if (regno >= FIRST_PSEUDO_REGISTER) { regno -= FIRST_PSEUDO_REGISTER; if (regno < reg_known_value_size) reg_known_value[regno] = val; } } /* Similarly for reg_known_equiv_p. */ bool get_reg_known_equiv_p (unsigned int regno) { if (regno >= FIRST_PSEUDO_REGISTER) { regno -= FIRST_PSEUDO_REGISTER; if (regno < reg_known_value_size) return reg_known_equiv_p[regno]; } return false; } static void set_reg_known_equiv_p (unsigned int regno, bool val) { if (regno >= FIRST_PSEUDO_REGISTER) { regno -= FIRST_PSEUDO_REGISTER; if (regno < reg_known_value_size) reg_known_equiv_p[regno] = val; } } /* Returns a canonical version of X, from the point of view alias analysis. (For example, if X is a MEM whose address is a register, and the register has a known value (say a SYMBOL_REF), then a MEM whose address is the SYMBOL_REF is returned.) */ rtx canon_rtx (rtx x) { /* Recursively look for equivalences. */ if (REG_P (x) && REGNO (x) >= FIRST_PSEUDO_REGISTER) { rtx t = get_reg_known_value (REGNO (x)); if (t == x) return x; if (t) return canon_rtx (t); } if (GET_CODE (x) == PLUS) { rtx x0 = canon_rtx (XEXP (x, 0)); rtx x1 = canon_rtx (XEXP (x, 1)); if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1)) { if (CONST_INT_P (x0)) return plus_constant (x1, INTVAL (x0)); else if (CONST_INT_P (x1)) return plus_constant (x0, INTVAL (x1)); return gen_rtx_PLUS (GET_MODE (x), x0, x1); } } /* This gives us much better alias analysis when called from the loop optimizer. Note we want to leave the original MEM alone, but need to return the canonicalized MEM with all the flags with their original values. */ else if (MEM_P (x)) x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0))); return x; } /* Return 1 if X and Y are identical-looking rtx's. Expect that X and Y has been already canonicalized. We use the data in reg_known_value above to see if two registers with different numbers are, in fact, equivalent. */ static int rtx_equal_for_memref_p (const_rtx x, const_rtx y) { int i; int j; enum rtx_code code; const char *fmt; if (x == 0 && y == 0) return 1; if (x == 0 || y == 0) return 0; if (x == y) return 1; code = GET_CODE (x); /* Rtx's of different codes cannot be equal. */ if (code != GET_CODE (y)) return 0; /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. (REG:SI x) and (REG:HI x) are NOT equivalent. */ if (GET_MODE (x) != GET_MODE (y)) return 0; /* Some RTL can be compared without a recursive examination. */ switch (code) { case REG: return REGNO (x) == REGNO (y); case LABEL_REF: return XEXP (x, 0) == XEXP (y, 0); case SYMBOL_REF: return XSTR (x, 0) == XSTR (y, 0); case VALUE: case CONST_INT: case CONST_DOUBLE: case CONST_FIXED: /* There's no need to compare the contents of CONST_DOUBLEs or CONST_INTs because pointer equality is a good enough comparison for these nodes. */ return 0; default: break; } /* canon_rtx knows how to handle plus. No need to canonicalize. */ if (code == PLUS) return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)) && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1))) || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1)) && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0)))); /* For commutative operations, the RTX match if the operand match in any order. Also handle the simple binary and unary cases without a loop. */ if (COMMUTATIVE_P (x)) { rtx xop0 = canon_rtx (XEXP (x, 0)); rtx yop0 = canon_rtx (XEXP (y, 0)); rtx yop1 = canon_rtx (XEXP (y, 1)); return ((rtx_equal_for_memref_p (xop0, yop0) && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop1)) || (rtx_equal_for_memref_p (xop0, yop1) && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop0))); } else if (NON_COMMUTATIVE_P (x)) { return (rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)), canon_rtx (XEXP (y, 0))) && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), canon_rtx (XEXP (y, 1)))); } else if (UNARY_P (x)) return rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)), canon_rtx (XEXP (y, 0))); /* Compare the elements. If any pair of corresponding elements fail to match, return 0 for the whole things. Limit cases to types which actually appear in addresses. */ fmt = GET_RTX_FORMAT (code); for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) { switch (fmt[i]) { case 'i': if (XINT (x, i) != XINT (y, i)) return 0; break; case 'E': /* Two vectors must have the same length. */ if (XVECLEN (x, i) != XVECLEN (y, i)) return 0; /* And the corresponding elements must match. */ for (j = 0; j < XVECLEN (x, i); j++) if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x, i, j)), canon_rtx (XVECEXP (y, i, j))) == 0) return 0; break; case 'e': if (rtx_equal_for_memref_p (canon_rtx (XEXP (x, i)), canon_rtx (XEXP (y, i))) == 0) return 0; break; /* This can happen for asm operands. */ case 's': if (strcmp (XSTR (x, i), XSTR (y, i))) return 0; break; /* This can happen for an asm which clobbers memory. */ case '0': break; /* It is believed that rtx's at this level will never contain anything but integers and other rtx's, except for within LABEL_REFs and SYMBOL_REFs. */ default: gcc_unreachable (); } } return 1; } rtx find_base_term (rtx x) { cselib_val *val; struct elt_loc_list *l, *f; rtx ret; #if defined (FIND_BASE_TERM) /* Try machine-dependent ways to find the base term. */ x = FIND_BASE_TERM (x); #endif switch (GET_CODE (x)) { case REG: return REG_BASE_VALUE (x); case TRUNCATE: /* As we do not know which address space the pointer is refering to, we can handle this only if the target does not support different pointer or address modes depending on the address space. */ if (!target_default_pointer_address_modes_p ()) return 0; if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode)) return 0; /* Fall through. */ case HIGH: case PRE_INC: case PRE_DEC: case POST_INC: case POST_DEC: case PRE_MODIFY: case POST_MODIFY: return find_base_term (XEXP (x, 0)); case ZERO_EXTEND: case SIGN_EXTEND: /* Used for Alpha/NT pointers */ /* As we do not know which address space the pointer is refering to, we can handle this only if the target does not support different pointer or address modes depending on the address space. */ if (!target_default_pointer_address_modes_p ()) return 0; { rtx temp = find_base_term (XEXP (x, 0)); if (temp != 0 && CONSTANT_P (temp)) temp = convert_memory_address (Pmode, temp); return temp; } case VALUE: val = CSELIB_VAL_PTR (x); ret = NULL_RTX; if (!val) return ret; f = val->locs; /* Temporarily reset val->locs to avoid infinite recursion. */ val->locs = NULL; for (l = f; l; l = l->next) if (GET_CODE (l->loc) == VALUE && CSELIB_VAL_PTR (l->loc)->locs && !CSELIB_VAL_PTR (l->loc)->locs->next && CSELIB_VAL_PTR (l->loc)->locs->loc == x) continue; else if ((ret = find_base_term (l->loc)) != 0) break; val->locs = f; return ret; case LO_SUM: /* The standard form is (lo_sum reg sym) so look only at the second operand. */ return find_base_term (XEXP (x, 1)); case CONST: x = XEXP (x, 0); if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS) return 0; /* Fall through. */ case PLUS: case MINUS: { rtx tmp1 = XEXP (x, 0); rtx tmp2 = XEXP (x, 1); /* This is a little bit tricky since we have to determine which of the two operands represents the real base address. Otherwise this routine may return the index register instead of the base register. That may cause us to believe no aliasing was possible, when in fact aliasing is possible. We use a few simple tests to guess the base register. Additional tests can certainly be added. For example, if one of the operands is a shift or multiply, then it must be the index register and the other operand is the base register. */ if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2)) return find_base_term (tmp2); /* If either operand is known to be a pointer, then use it to determine the base term. */ if (REG_P (tmp1) && REG_POINTER (tmp1)) { rtx base = find_base_term (tmp1); if (base) return base; } if (REG_P (tmp2) && REG_POINTER (tmp2)) { rtx base = find_base_term (tmp2); if (base) return base; } /* Neither operand was known to be a pointer. Go ahead and find the base term for both operands. */ tmp1 = find_base_term (tmp1); tmp2 = find_base_term (tmp2); /* If either base term is named object or a special address (like an argument or stack reference), then use it for the base term. */ if (tmp1 != 0 && (GET_CODE (tmp1) == SYMBOL_REF || GET_CODE (tmp1) == LABEL_REF || (GET_CODE (tmp1) == ADDRESS && GET_MODE (tmp1) != VOIDmode))) return tmp1; if (tmp2 != 0 && (GET_CODE (tmp2) == SYMBOL_REF || GET_CODE (tmp2) == LABEL_REF || (GET_CODE (tmp2) == ADDRESS && GET_MODE (tmp2) != VOIDmode))) return tmp2; /* We could not determine which of the two operands was the base register and which was the index. So we can determine nothing from the base alias check. */ return 0; } case AND: if (CONST_INT_P (XEXP (x, 1)) && INTVAL (XEXP (x, 1)) != 0) return find_base_term (XEXP (x, 0)); return 0; case SYMBOL_REF: case LABEL_REF: return x; default: return 0; } } /* Return 0 if the addresses X and Y are known to point to different objects, 1 if they might be pointers to the same object. */ static int base_alias_check (rtx x, rtx y, enum machine_mode x_mode, enum machine_mode y_mode) { rtx x_base = find_base_term (x); rtx y_base = find_base_term (y); /* If the address itself has no known base see if a known equivalent value has one. If either address still has no known base, nothing is known about aliasing. */ if (x_base == 0) { rtx x_c; if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x) return 1; x_base = find_base_term (x_c); if (x_base == 0) return 1; } if (y_base == 0) { rtx y_c; if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y) return 1; y_base = find_base_term (y_c); if (y_base == 0) return 1; } /* If the base addresses are equal nothing is known about aliasing. */ if (rtx_equal_p (x_base, y_base)) return 1; /* The base addresses are different expressions. If they are not accessed via AND, there is no conflict. We can bring knowledge of object alignment into play here. For example, on alpha, "char a, b;" can alias one another, though "char a; long b;" cannot. AND addesses may implicitly alias surrounding objects; i.e. unaligned access in DImode via AND address can alias all surrounding object types except those with aligment 8 or higher. */ if (GET_CODE (x) == AND && GET_CODE (y) == AND) return 1; if (GET_CODE (x) == AND && (!CONST_INT_P (XEXP (x, 1)) || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1)))) return 1; if (GET_CODE (y) == AND && (!CONST_INT_P (XEXP (y, 1)) || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1)))) return 1; /* Differing symbols not accessed via AND never alias. */ if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS) return 0; /* If one address is a stack reference there can be no alias: stack references using different base registers do not alias, a stack reference can not alias a parameter, and a stack reference can not alias a global. */ if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode) || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode)) return 0; return 1; } /* Callback for for_each_rtx, that returns 1 upon encountering a VALUE whose UID is greater than the int uid that D points to. */ static int refs_newer_value_cb (rtx *x, void *d) { if (GET_CODE (*x) == VALUE && CSELIB_VAL_PTR (*x)->uid > *(int *)d) return 1; return 0; } /* Return TRUE if EXPR refers to a VALUE whose uid is greater than that of V. */ static bool refs_newer_value_p (rtx expr, rtx v) { int minuid = CSELIB_VAL_PTR (v)->uid; return for_each_rtx (&expr, refs_newer_value_cb, &minuid); } /* Convert the address X into something we can use. This is done by returning it unchanged unless it is a value; in the latter case we call cselib to get a more useful rtx. */ rtx get_addr (rtx x) { cselib_val *v; struct elt_loc_list *l; if (GET_CODE (x) != VALUE) return x; v = CSELIB_VAL_PTR (x); if (v) { v = canonical_cselib_val (v); for (l = v->locs; l; l = l->next) if (CONSTANT_P (l->loc)) return l->loc; for (l = v->locs; l; l = l->next) if (!REG_P (l->loc) && !MEM_P (l->loc) && GET_CODE (l->loc) != VALUE && !refs_newer_value_p (l->loc, x)) return l->loc; for (l = v->locs; l; l = l->next) if (REG_P (l->loc) || (GET_CODE (l->loc) != VALUE && !refs_newer_value_p (l->loc, x))) return l->loc; /* Return the canonical value. */ return v->val_rtx; } return x; } /* Return the address of the (N_REFS + 1)th memory reference to ADDR where SIZE is the size in bytes of the memory reference. If ADDR is not modified by the memory reference then ADDR is returned. */ static rtx addr_side_effect_eval (rtx addr, int size, int n_refs) { int offset = 0; switch (GET_CODE (addr)) { case PRE_INC: offset = (n_refs + 1) * size; break; case PRE_DEC: offset = -(n_refs + 1) * size; break; case POST_INC: offset = n_refs * size; break; case POST_DEC: offset = -n_refs * size; break; default: return addr; } if (offset) addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset)); else addr = XEXP (addr, 0); addr = canon_rtx (addr); return addr; } /* Return one if X and Y (memory addresses) reference the same location in memory or if the references overlap. Return zero if they do not overlap, else return minus one in which case they still might reference the same location. C is an offset accumulator. When C is nonzero, we are testing aliases between X and Y + C. XSIZE is the size in bytes of the X reference, similarly YSIZE is the size in bytes for Y. Expect that canon_rtx has been already called for X and Y. If XSIZE or YSIZE is zero, we do not know the amount of memory being referenced (the reference was BLKmode), so make the most pessimistic assumptions. If XSIZE or YSIZE is negative, we may access memory outside the object being referenced as a side effect. This can happen when using AND to align memory references, as is done on the Alpha. Nice to notice that varying addresses cannot conflict with fp if no local variables had their addresses taken, but that's too hard now. ??? Contrary to the tree alias oracle this does not return one for X + non-constant and Y + non-constant when X and Y are equal. If that is fixed the TBAA hack for union type-punning can be removed. */ static int memrefs_conflict_p (int xsize, rtx x, int ysize, rtx y, HOST_WIDE_INT c) { if (GET_CODE (x) == VALUE) { if (REG_P (y)) { struct elt_loc_list *l = NULL; if (CSELIB_VAL_PTR (x)) for (l = canonical_cselib_val (CSELIB_VAL_PTR (x))->locs; l; l = l->next) if (REG_P (l->loc) && rtx_equal_for_memref_p (l->loc, y)) break; if (l) x = y; else x = get_addr (x); } /* Don't call get_addr if y is the same VALUE. */ else if (x != y) x = get_addr (x); } if (GET_CODE (y) == VALUE) { if (REG_P (x)) { struct elt_loc_list *l = NULL; if (CSELIB_VAL_PTR (y)) for (l = canonical_cselib_val (CSELIB_VAL_PTR (y))->locs; l; l = l->next) if (REG_P (l->loc) && rtx_equal_for_memref_p (l->loc, x)) break; if (l) y = x; else y = get_addr (y); } /* Don't call get_addr if x is the same VALUE. */ else if (y != x) y = get_addr (y); } if (GET_CODE (x) == HIGH) x = XEXP (x, 0); else if (GET_CODE (x) == LO_SUM) x = XEXP (x, 1); else x = addr_side_effect_eval (x, xsize, 0); if (GET_CODE (y) == HIGH) y = XEXP (y, 0); else if (GET_CODE (y) == LO_SUM) y = XEXP (y, 1); else y = addr_side_effect_eval (y, ysize, 0); if (rtx_equal_for_memref_p (x, y)) { if (xsize <= 0 || ysize <= 0) return 1; if (c >= 0 && xsize > c) return 1; if (c < 0 && ysize+c > 0) return 1; return 0; } /* This code used to check for conflicts involving stack references and globals but the base address alias code now handles these cases. */ if (GET_CODE (x) == PLUS) { /* The fact that X is canonicalized means that this PLUS rtx is canonicalized. */ rtx x0 = XEXP (x, 0); rtx x1 = XEXP (x, 1); if (GET_CODE (y) == PLUS) { /* The fact that Y is canonicalized means that this PLUS rtx is canonicalized. */ rtx y0 = XEXP (y, 0); rtx y1 = XEXP (y, 1); if (rtx_equal_for_memref_p (x1, y1)) return memrefs_conflict_p (xsize, x0, ysize, y0, c); if (rtx_equal_for_memref_p (x0, y0)) return memrefs_conflict_p (xsize, x1, ysize, y1, c); if (CONST_INT_P (x1)) { if (CONST_INT_P (y1)) return memrefs_conflict_p (xsize, x0, ysize, y0, c - INTVAL (x1) + INTVAL (y1)); else return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1)); } else if (CONST_INT_P (y1)) return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1)); return -1; } else if (CONST_INT_P (x1)) return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1)); } else if (GET_CODE (y) == PLUS) { /* The fact that Y is canonicalized means that this PLUS rtx is canonicalized. */ rtx y0 = XEXP (y, 0); rtx y1 = XEXP (y, 1); if (CONST_INT_P (y1)) return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1)); else return -1; } if (GET_CODE (x) == GET_CODE (y)) switch (GET_CODE (x)) { case MULT: { /* Handle cases where we expect the second operands to be the same, and check only whether the first operand would conflict or not. */ rtx x0, y0; rtx x1 = canon_rtx (XEXP (x, 1)); rtx y1 = canon_rtx (XEXP (y, 1)); if (! rtx_equal_for_memref_p (x1, y1)) return -1; x0 = canon_rtx (XEXP (x, 0)); y0 = canon_rtx (XEXP (y, 0)); if (rtx_equal_for_memref_p (x0, y0)) return (xsize == 0 || ysize == 0 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0)); /* Can't properly adjust our sizes. */ if (!CONST_INT_P (x1)) return -1; xsize /= INTVAL (x1); ysize /= INTVAL (x1); c /= INTVAL (x1); return memrefs_conflict_p (xsize, x0, ysize, y0, c); } default: break; } /* Treat an access through an AND (e.g. a subword access on an Alpha) as an access with indeterminate size. Assume that references besides AND are aligned, so if the size of the other reference is at least as large as the alignment, assume no other overlap. */ if (GET_CODE (x) == AND && CONST_INT_P (XEXP (x, 1))) { if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1))) xsize = -1; return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, y, c); } if (GET_CODE (y) == AND && CONST_INT_P (XEXP (y, 1))) { /* ??? If we are indexing far enough into the array/structure, we may yet be able to determine that we can not overlap. But we also need to that we are far enough from the end not to overlap a following reference, so we do nothing with that for now. */ if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1))) ysize = -1; return memrefs_conflict_p (xsize, x, ysize, canon_rtx (XEXP (y, 0)), c); } if (CONSTANT_P (x)) { if (CONST_INT_P (x) && CONST_INT_P (y)) { c += (INTVAL (y) - INTVAL (x)); return (xsize <= 0 || ysize <= 0 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0)); } if (GET_CODE (x) == CONST) { if (GET_CODE (y) == CONST) return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, canon_rtx (XEXP (y, 0)), c); else return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, y, c); } if (GET_CODE (y) == CONST) return memrefs_conflict_p (xsize, x, ysize, canon_rtx (XEXP (y, 0)), c); if (CONSTANT_P (y)) return (xsize <= 0 || ysize <= 0 || (rtx_equal_for_memref_p (x, y) && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0)))); return -1; } return -1; } /* Functions to compute memory dependencies. Since we process the insns in execution order, we can build tables to keep track of what registers are fixed (and not aliased), what registers are varying in known ways, and what registers are varying in unknown ways. If both memory references are volatile, then there must always be a dependence between the two references, since their order can not be changed. A volatile and non-volatile reference can be interchanged though. We also must allow AND addresses, because they may generate accesses outside the object being referenced. This is used to generate aligned addresses from unaligned addresses, for instance, the alpha storeqi_unaligned pattern. */ /* Read dependence: X is read after read in MEM takes place. There can only be a dependence here if both reads are volatile. */ int read_dependence (const_rtx mem, const_rtx x) { return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem); } /* Returns nonzero if something about the mode or address format MEM1 indicates that it might well alias *anything*. */ static int aliases_everything_p (const_rtx mem) { if (GET_CODE (XEXP (mem, 0)) == AND) /* If the address is an AND, it's very hard to know at what it is actually pointing. */ return 1; return 0; } /* Return true if we can determine that the fields referenced cannot overlap for any pair of objects. */ static bool nonoverlapping_component_refs_p (const_tree x, const_tree y) { const_tree fieldx, fieldy, typex, typey, orig_y; if (!flag_strict_aliasing) return false; do { /* The comparison has to be done at a common type, since we don't know how the inheritance hierarchy works. */ orig_y = y; do { fieldx = TREE_OPERAND (x, 1); typex = TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldx)); y = orig_y; do { fieldy = TREE_OPERAND (y, 1); typey = TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldy)); if (typex == typey) goto found; y = TREE_OPERAND (y, 0); } while (y && TREE_CODE (y) == COMPONENT_REF); x = TREE_OPERAND (x, 0); } while (x && TREE_CODE (x) == COMPONENT_REF); /* Never found a common type. */ return false; found: /* If we're left with accessing different fields of a structure, then no overlap. */ if (TREE_CODE (typex) == RECORD_TYPE && fieldx != fieldy) return true; /* The comparison on the current field failed. If we're accessing a very nested structure, look at the next outer level. */ x = TREE_OPERAND (x, 0); y = TREE_OPERAND (y, 0); } while (x && y && TREE_CODE (x) == COMPONENT_REF && TREE_CODE (y) == COMPONENT_REF); return false; } /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */ static tree decl_for_component_ref (tree x) { do { x = TREE_OPERAND (x, 0); } while (x && TREE_CODE (x) == COMPONENT_REF); return x && DECL_P (x) ? x : NULL_TREE; } /* Walk up the COMPONENT_REF list in X and adjust *OFFSET to compensate for the offset of the field reference. *KNOWN_P says whether the offset is known. */ static void adjust_offset_for_component_ref (tree x, bool *known_p, HOST_WIDE_INT *offset) { if (!*known_p) return; do { tree xoffset = component_ref_field_offset (x); tree field = TREE_OPERAND (x, 1); if (! host_integerp (xoffset, 1)) { *known_p = false; return; } *offset += (tree_low_cst (xoffset, 1) + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1) / BITS_PER_UNIT)); x = TREE_OPERAND (x, 0); } while (x && TREE_CODE (x) == COMPONENT_REF); } /* Return nonzero if we can determine the exprs corresponding to memrefs X and Y and they do not overlap. If LOOP_VARIANT is set, skip offset-based disambiguation */ int nonoverlapping_memrefs_p (const_rtx x, const_rtx y, bool loop_invariant) { tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y); rtx rtlx, rtly; rtx basex, basey; bool moffsetx_known_p, moffsety_known_p; HOST_WIDE_INT moffsetx = 0, moffsety = 0; HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem; /* Unless both have exprs, we can't tell anything. */ if (exprx == 0 || expry == 0) return 0; /* For spill-slot accesses make sure we have valid offsets. */ if ((exprx == get_spill_slot_decl (false) && ! MEM_OFFSET_KNOWN_P (x)) || (expry == get_spill_slot_decl (false) && ! MEM_OFFSET_KNOWN_P (y))) return 0; /* If both are field references, we may be able to determine something. */ if (TREE_CODE (exprx) == COMPONENT_REF && TREE_CODE (expry) == COMPONENT_REF && nonoverlapping_component_refs_p (exprx, expry)) return 1; /* If the field reference test failed, look at the DECLs involved. */ moffsetx_known_p = MEM_OFFSET_KNOWN_P (x); if (moffsetx_known_p) moffsetx = MEM_OFFSET (x); if (TREE_CODE (exprx) == COMPONENT_REF) { tree t = decl_for_component_ref (exprx); if (! t) return 0; adjust_offset_for_component_ref (exprx, &moffsetx_known_p, &moffsetx); exprx = t; } moffsety_known_p = MEM_OFFSET_KNOWN_P (y); if (moffsety_known_p) moffsety = MEM_OFFSET (y); if (TREE_CODE (expry) == COMPONENT_REF) { tree t = decl_for_component_ref (expry); if (! t) return 0; adjust_offset_for_component_ref (expry, &moffsety_known_p, &moffsety); expry = t; } if (! DECL_P (exprx) || ! DECL_P (expry)) return 0; /* With invalid code we can end up storing into the constant pool. Bail out to avoid ICEing when creating RTL for this. See gfortran.dg/lto/20091028-2_0.f90. */ if (TREE_CODE (exprx) == CONST_DECL || TREE_CODE (expry) == CONST_DECL) return 1; rtlx = DECL_RTL (exprx); rtly = DECL_RTL (expry); /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they can't overlap unless they are the same because we never reuse that part of the stack frame used for locals for spilled pseudos. */ if ((!MEM_P (rtlx) || !MEM_P (rtly)) && ! rtx_equal_p (rtlx, rtly)) return 1; /* If we have MEMs refering to different address spaces (which can potentially overlap), we cannot easily tell from the addresses whether the references overlap. */ if (MEM_P (rtlx) && MEM_P (rtly) && MEM_ADDR_SPACE (rtlx) != MEM_ADDR_SPACE (rtly)) return 0; /* Get the base and offsets of both decls. If either is a register, we know both are and are the same, so use that as the base. The only we can avoid overlap is if we can deduce that they are nonoverlapping pieces of that decl, which is very rare. */ basex = MEM_P (rtlx) ? XEXP (rtlx, 0) : rtlx; if (GET_CODE (basex) == PLUS && CONST_INT_P (XEXP (basex, 1))) offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0); basey = MEM_P (rtly) ? XEXP (rtly, 0) : rtly; if (GET_CODE (basey) == PLUS && CONST_INT_P (XEXP (basey, 1))) offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0); /* If the bases are different, we know they do not overlap if both are constants or if one is a constant and the other a pointer into the stack frame. Otherwise a different base means we can't tell if they overlap or not. */ if (! rtx_equal_p (basex, basey)) return ((CONSTANT_P (basex) && CONSTANT_P (basey)) || (CONSTANT_P (basex) && REG_P (basey) && REGNO_PTR_FRAME_P (REGNO (basey))) || (CONSTANT_P (basey) && REG_P (basex) && REGNO_PTR_FRAME_P (REGNO (basex)))); /* Offset based disambiguation not appropriate for loop invariant */ if (loop_invariant) return 0; sizex = (!MEM_P (rtlx) ? (int) GET_MODE_SIZE (GET_MODE (rtlx)) : MEM_SIZE_KNOWN_P (rtlx) ? MEM_SIZE (rtlx) : -1); sizey = (!MEM_P (rtly) ? (int) GET_MODE_SIZE (GET_MODE (rtly)) : MEM_SIZE_KNOWN_P (rtly) ? MEM_SIZE (rtly) : -1); /* If we have an offset for either memref, it can update the values computed above. */ if (moffsetx_known_p) offsetx += moffsetx, sizex -= moffsetx; if (moffsety_known_p) offsety += moffsety, sizey -= moffsety; /* If a memref has both a size and an offset, we can use the smaller size. We can't do this if the offset isn't known because we must view this memref as being anywhere inside the DECL's MEM. */ if (MEM_SIZE_KNOWN_P (x) && moffsetx_known_p) sizex = MEM_SIZE (x); if (MEM_SIZE_KNOWN_P (y) && moffsety_known_p) sizey = MEM_SIZE (y); /* Put the values of the memref with the lower offset in X's values. */ if (offsetx > offsety) { tem = offsetx, offsetx = offsety, offsety = tem; tem = sizex, sizex = sizey, sizey = tem; } /* If we don't know the size of the lower-offset value, we can't tell if they conflict. Otherwise, we do the test. */ return sizex >= 0 && offsety >= offsetx + sizex; } /* Helper for true_dependence and canon_true_dependence. Checks for true dependence: X is read after store in MEM takes place. If MEM_CANONICALIZED is FALSE, then X_ADDR and MEM_ADDR should be NULL_RTX, and the canonical addresses of MEM and X are both computed here. If MEM_CANONICALIZED, then MEM must be already canonicalized. If X_ADDR is non-NULL, it is used in preference of XEXP (x, 0). Returns 1 if there is a true dependence, 0 otherwise. */ static int true_dependence_1 (const_rtx mem, enum machine_mode mem_mode, rtx mem_addr, const_rtx x, rtx x_addr, bool mem_canonicalized) { rtx base; int ret; gcc_checking_assert (mem_canonicalized ? (mem_addr != NULL_RTX) : (mem_addr == NULL_RTX && x_addr == NULL_RTX)); if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) return 1; /* (mem:BLK (scratch)) is a special mechanism to conflict with everything. This is used in epilogue deallocation functions, and in cselib. */ if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH) return 1; if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH) return 1; if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER) return 1; /* Read-only memory is by definition never modified, and therefore can't conflict with anything. We don't expect to find read-only set on MEM, but stupid user tricks can produce them, so don't die. */ if (MEM_READONLY_P (x)) return 0; /* If we have MEMs refering to different address spaces (which can potentially overlap), we cannot easily tell from the addresses whether the references overlap. */ if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x)) return 1; if (! mem_addr) { mem_addr = XEXP (mem, 0); if (mem_mode == VOIDmode) mem_mode = GET_MODE (mem); } if (! x_addr) { x_addr = XEXP (x, 0); if (!((GET_CODE (x_addr) == VALUE && GET_CODE (mem_addr) != VALUE && reg_mentioned_p (x_addr, mem_addr)) || (GET_CODE (x_addr) != VALUE && GET_CODE (mem_addr) == VALUE && reg_mentioned_p (mem_addr, x_addr)))) { x_addr = get_addr (x_addr); if (! mem_canonicalized) mem_addr = get_addr (mem_addr); } } base = find_base_term (x_addr); if (base && (GET_CODE (base) == LABEL_REF || (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base)))) return 0; if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode)) return 0; x_addr = canon_rtx (x_addr); if (!mem_canonicalized) mem_addr = canon_rtx (mem_addr); if ((ret = memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr, SIZE_FOR_MODE (x), x_addr, 0)) != -1) return ret; if (DIFFERENT_ALIAS_SETS_P (x, mem)) return 0; if (nonoverlapping_memrefs_p (mem, x, false)) return 0; if (aliases_everything_p (x)) return 1; /* We cannot use aliases_everything_p to test MEM, since we must look at MEM_ADDR, rather than XEXP (mem, 0). */ if (GET_CODE (mem_addr) == AND) return 1; /* ??? In true_dependence we also allow BLKmode to alias anything. Why don't we do this in anti_dependence and output_dependence? */ if (mem_mode == BLKmode || GET_MODE (x) == BLKmode) return 1; return rtx_refs_may_alias_p (x, mem, true); } /* True dependence: X is read after store in MEM takes place. */ int true_dependence (const_rtx mem, enum machine_mode mem_mode, const_rtx x) { return true_dependence_1 (mem, mem_mode, NULL_RTX, x, NULL_RTX, /*mem_canonicalized=*/false); } /* Canonical true dependence: X is read after store in MEM takes place. Variant of true_dependence which assumes MEM has already been canonicalized (hence we no longer do that here). The mem_addr argument has been added, since true_dependence_1 computed this value prior to canonicalizing. */ int canon_true_dependence (const_rtx mem, enum machine_mode mem_mode, rtx mem_addr, const_rtx x, rtx x_addr) { return true_dependence_1 (mem, mem_mode, mem_addr, x, x_addr, /*mem_canonicalized=*/true); } /* Returns nonzero if a write to X might alias a previous read from (or, if WRITEP is nonzero, a write to) MEM. */ static int write_dependence_p (const_rtx mem, const_rtx x, int writep) { rtx x_addr, mem_addr; rtx base; int ret; if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) return 1; /* (mem:BLK (scratch)) is a special mechanism to conflict with everything. This is used in epilogue deallocation functions. */ if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH) return 1; if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH) return 1; if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER) return 1; /* A read from read-only memory can't conflict with read-write memory. */ if (!writep && MEM_READONLY_P (mem)) return 0; /* If we have MEMs refering to different address spaces (which can potentially overlap), we cannot easily tell from the addresses whether the references overlap. */ if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x)) return 1; x_addr = XEXP (x, 0); mem_addr = XEXP (mem, 0); if (!((GET_CODE (x_addr) == VALUE && GET_CODE (mem_addr) != VALUE && reg_mentioned_p (x_addr, mem_addr)) || (GET_CODE (x_addr) != VALUE && GET_CODE (mem_addr) == VALUE && reg_mentioned_p (mem_addr, x_addr)))) { x_addr = get_addr (x_addr); mem_addr = get_addr (mem_addr); } if (! writep) { base = find_base_term (mem_addr); if (base && (GET_CODE (base) == LABEL_REF || (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base)))) return 0; } if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), GET_MODE (mem))) return 0; x_addr = canon_rtx (x_addr); mem_addr = canon_rtx (mem_addr); if ((ret = memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr, SIZE_FOR_MODE (x), x_addr, 0)) != -1) return ret; if (nonoverlapping_memrefs_p (x, mem, false)) return 0; return rtx_refs_may_alias_p (x, mem, false); } /* Anti dependence: X is written after read in MEM takes place. */ int anti_dependence (const_rtx mem, const_rtx x) { return write_dependence_p (mem, x, /*writep=*/0); } /* Output dependence: X is written after store in MEM takes place. */ int output_dependence (const_rtx mem, const_rtx x) { return write_dependence_p (mem, x, /*writep=*/1); } /* Check whether X may be aliased with MEM. Don't do offset-based memory disambiguation & TBAA. */ int may_alias_p (const_rtx mem, const_rtx x) { rtx x_addr, mem_addr; if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) return 1; /* ??? In true_dependence we also allow BLKmode to alias anything. */ if (GET_MODE (mem) == BLKmode || GET_MODE (x) == BLKmode) return 1; if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER) return 1; /* Read-only memory is by definition never modified, and therefore can't conflict with anything. We don't expect to find read-only set on MEM, but stupid user tricks can produce them, so don't die. */ if (MEM_READONLY_P (x)) return 0; /* If we have MEMs refering to different address spaces (which can potentially overlap), we cannot easily tell from the addresses whether the references overlap. */ if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x)) return 1; x_addr = XEXP (x, 0); mem_addr = XEXP (mem, 0); if (!((GET_CODE (x_addr) == VALUE && GET_CODE (mem_addr) != VALUE && reg_mentioned_p (x_addr, mem_addr)) || (GET_CODE (x_addr) != VALUE && GET_CODE (mem_addr) == VALUE && reg_mentioned_p (mem_addr, x_addr)))) { x_addr = get_addr (x_addr); mem_addr = get_addr (mem_addr); } if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), GET_MODE (mem_addr))) return 0; x_addr = canon_rtx (x_addr); mem_addr = canon_rtx (mem_addr); if (nonoverlapping_memrefs_p (mem, x, true)) return 0; if (aliases_everything_p (x)) return 1; /* We cannot use aliases_everything_p to test MEM, since we must look at MEM_ADDR, rather than XEXP (mem, 0). */ if (GET_CODE (mem_addr) == AND) return 1; /* TBAA not valid for loop_invarint */ return rtx_refs_may_alias_p (x, mem, false); } void init_alias_target (void) { int i; memset (static_reg_base_value, 0, sizeof static_reg_base_value); for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) /* Check whether this register can hold an incoming pointer argument. FUNCTION_ARG_REGNO_P tests outgoing register numbers, so translate if necessary due to register windows. */ if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i)) && HARD_REGNO_MODE_OK (i, Pmode)) static_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode, gen_rtx_REG (Pmode, i)); static_reg_base_value[STACK_POINTER_REGNUM] = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx); static_reg_base_value[ARG_POINTER_REGNUM] = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx); static_reg_base_value[FRAME_POINTER_REGNUM] = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx); #if !HARD_FRAME_POINTER_IS_FRAME_POINTER static_reg_base_value[HARD_FRAME_POINTER_REGNUM] = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx); #endif } /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed to be memory reference. */ static bool memory_modified; static void memory_modified_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED, void *data) { if (MEM_P (x)) { if (anti_dependence (x, (const_rtx)data) || output_dependence (x, (const_rtx)data)) memory_modified = true; } } /* Return true when INSN possibly modify memory contents of MEM (i.e. address can be modified). */ bool memory_modified_in_insn_p (const_rtx mem, const_rtx insn) { if (!INSN_P (insn)) return false; memory_modified = false; note_stores (PATTERN (insn), memory_modified_1, CONST_CAST_RTX(mem)); return memory_modified; } /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE array. */ void init_alias_analysis (void) { unsigned int maxreg = max_reg_num (); int changed, pass; int i; unsigned int ui; rtx insn; timevar_push (TV_ALIAS_ANALYSIS); reg_known_value_size = maxreg - FIRST_PSEUDO_REGISTER; reg_known_value = ggc_alloc_cleared_vec_rtx (reg_known_value_size); reg_known_equiv_p = XCNEWVEC (bool, reg_known_value_size); /* If we have memory allocated from the previous run, use it. */ if (old_reg_base_value) reg_base_value = old_reg_base_value; if (reg_base_value) VEC_truncate (rtx, reg_base_value, 0); VEC_safe_grow_cleared (rtx, gc, reg_base_value, maxreg); new_reg_base_value = XNEWVEC (rtx, maxreg); reg_seen = XNEWVEC (char, maxreg); /* The basic idea is that each pass through this loop will use the "constant" information from the previous pass to propagate alias information through another level of assignments. This could get expensive if the assignment chains are long. Maybe we should throttle the number of iterations, possibly based on the optimization level or flag_expensive_optimizations. We could propagate more information in the first pass by making use of DF_REG_DEF_COUNT to determine immediately that the alias information for a pseudo is "constant". A program with an uninitialized variable can cause an infinite loop here. Instead of doing a full dataflow analysis to detect such problems we just cap the number of iterations for the loop. The state of the arrays for the set chain in question does not matter since the program has undefined behavior. */ pass = 0; do { /* Assume nothing will change this iteration of the loop. */ changed = 0; /* We want to assign the same IDs each iteration of this loop, so start counting from zero each iteration of the loop. */ unique_id = 0; /* We're at the start of the function each iteration through the loop, so we're copying arguments. */ copying_arguments = true; /* Wipe the potential alias information clean for this pass. */ memset (new_reg_base_value, 0, maxreg * sizeof (rtx)); /* Wipe the reg_seen array clean. */ memset (reg_seen, 0, maxreg); /* Mark all hard registers which may contain an address. The stack, frame and argument pointers may contain an address. An argument register which can hold a Pmode value may contain an address even if it is not in BASE_REGS. The address expression is VOIDmode for an argument and Pmode for other registers. */ memcpy (new_reg_base_value, static_reg_base_value, FIRST_PSEUDO_REGISTER * sizeof (rtx)); /* Walk the insns adding values to the new_reg_base_value array. */ for (insn = get_insns (); insn; insn = NEXT_INSN (insn)) { if (INSN_P (insn)) { rtx note, set; #if defined (HAVE_prologue) || defined (HAVE_epilogue) /* The prologue/epilogue insns are not threaded onto the insn chain until after reload has completed. Thus, there is no sense wasting time checking if INSN is in the prologue/epilogue until after reload has completed. */ if (reload_completed && prologue_epilogue_contains (insn)) continue; #endif /* If this insn has a noalias note, process it, Otherwise, scan for sets. A simple set will have no side effects which could change the base value of any other register. */ if (GET_CODE (PATTERN (insn)) == SET && REG_NOTES (insn) != 0 && find_reg_note (insn, REG_NOALIAS, NULL_RTX)) record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL); else note_stores (PATTERN (insn), record_set, NULL); set = single_set (insn); if (set != 0 && REG_P (SET_DEST (set)) && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER) { unsigned int regno = REGNO (SET_DEST (set)); rtx src = SET_SRC (set); rtx t; note = find_reg_equal_equiv_note (insn); if (note && REG_NOTE_KIND (note) == REG_EQUAL && DF_REG_DEF_COUNT (regno) != 1) note = NULL_RTX; if (note != NULL_RTX && GET_CODE (XEXP (note, 0)) != EXPR_LIST && ! rtx_varies_p (XEXP (note, 0), 1) && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0))) { set_reg_known_value (regno, XEXP (note, 0)); set_reg_known_equiv_p (regno, REG_NOTE_KIND (note) == REG_EQUIV); } else if (DF_REG_DEF_COUNT (regno) == 1 && GET_CODE (src) == PLUS && REG_P (XEXP (src, 0)) && (t = get_reg_known_value (REGNO (XEXP (src, 0)))) && CONST_INT_P (XEXP (src, 1))) { t = plus_constant (t, INTVAL (XEXP (src, 1))); set_reg_known_value (regno, t); set_reg_known_equiv_p (regno, 0); } else if (DF_REG_DEF_COUNT (regno) == 1 && ! rtx_varies_p (src, 1)) { set_reg_known_value (regno, src); set_reg_known_equiv_p (regno, 0); } } } else if (NOTE_P (insn) && NOTE_KIND (insn) == NOTE_INSN_FUNCTION_BEG) copying_arguments = false; } /* Now propagate values from new_reg_base_value to reg_base_value. */ gcc_assert (maxreg == (unsigned int) max_reg_num ()); for (ui = 0; ui < maxreg; ui++) { if (new_reg_base_value[ui] && new_reg_base_value[ui] != VEC_index (rtx, reg_base_value, ui) && ! rtx_equal_p (new_reg_base_value[ui], VEC_index (rtx, reg_base_value, ui))) { VEC_replace (rtx, reg_base_value, ui, new_reg_base_value[ui]); changed = 1; } } } while (changed && ++pass < MAX_ALIAS_LOOP_PASSES); /* Fill in the remaining entries. */ for (i = 0; i < (int)reg_known_value_size; i++) if (reg_known_value[i] == 0) reg_known_value[i] = regno_reg_rtx[i + FIRST_PSEUDO_REGISTER]; /* Clean up. */ free (new_reg_base_value); new_reg_base_value = 0; free (reg_seen); reg_seen = 0; timevar_pop (TV_ALIAS_ANALYSIS); } /* Equate REG_BASE_VALUE (reg1) to REG_BASE_VALUE (reg2). Special API for var-tracking pass purposes. */ void vt_equate_reg_base_value (const_rtx reg1, const_rtx reg2) { VEC_replace (rtx, reg_base_value, REGNO (reg1), REG_BASE_VALUE (reg2)); } void end_alias_analysis (void) { old_reg_base_value = reg_base_value; ggc_free (reg_known_value); reg_known_value = 0; reg_known_value_size = 0; free (reg_known_equiv_p); reg_known_equiv_p = 0; } #include "gt-alias.h"
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