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//========================================================================== // // mipsfp.c // // HAL miscellaneous functions // //========================================================================== //####ECOSGPLCOPYRIGHTBEGIN#### // ------------------------------------------- // This file is part of eCos, the Embedded Configurable Operating System. // Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc. // // eCos 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 2 or (at your option) any later version. // // eCos 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 eCos; if not, write to the Free Software Foundation, Inc., // 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. // // As a special exception, if other files instantiate templates or use macros // or inline functions from this file, or you compile this file and link it // with other works to produce a work based on this file, this file does not // by itself cause the resulting work to be covered by the GNU General Public // License. However the source code for this file must still be made available // in accordance with section (3) of the GNU General Public License. // // This exception does not invalidate any other reasons why a work based on // this file might be covered by the GNU General Public License. // // Alternative licenses for eCos may be arranged by contacting Red Hat, Inc. // at http://sources.redhat.com/ecos/ecos-license/ // ------------------------------------------- //####ECOSGPLCOPYRIGHTEND#### //========================================================================== //#####DESCRIPTIONBEGIN#### // // Author(s): jlarmour // Contributors: jlarmour // Date: 1999-07-13 // Purpose: Emulate unimplemented FP operations on MIPS architectures // Description: This catches the unimplemented operation excetion only, // and if possible deals with it so processing can continue // as if the MIPS had a proper IEEE FPU // // //####DESCRIPTIONEND#### // //========================================================================*/ // CONFIGURATION #include <pkgconf/hal.h> #ifdef CYGHWR_HAL_MIPS_FPU // INCLUDES #include <cyg/infra/cyg_type.h> // Standard eCos types #include <cyg/infra/cyg_ass.h> // Standard eCos assertion support #include <cyg/infra/cyg_trac.h> // Standard eCos tracing support #include <cyg/hal/hal_intr.h> // HAL interrupt vectors #include <cyg/hal/hal_arch.h> // Architecture types such as // HAL_SavedRegisters #define CYGARC_HAL_COMMON_EXPORT_CPU_MACROS #include <cyg/hal/mips-regs.h> // MIPS register and bitmask definitions // TYPES // The following types were taken from <sys/ieeefp.h> from libm. #if (CYG_BYTEORDER == CYG_MSBFIRST) // Big endian typedef union { cyg_int32 asi32[2]; cyg_int64 asi64; double value; struct { #if (CYG_DOUBLE_BYTEORDER == CYG_MSBFIRST) unsigned int sign : 1; unsigned int exponent: 11; unsigned int fraction0:4; unsigned int fraction1:16; unsigned int fraction2:16; unsigned int fraction3:16; #else unsigned int fraction2:16; unsigned int fraction3:16; unsigned int sign : 1; unsigned int exponent: 11; unsigned int fraction0:4; unsigned int fraction1:16; #endif } number; struct { #if (CYG_DOUBLE_BYTEORDER == CYG_MSBFIRST) unsigned int sign : 1; unsigned int exponent: 11; unsigned int quiet:1; unsigned int function0:3; unsigned int function1:16; unsigned int function2:16; unsigned int function3:16; #else unsigned int function2:16; unsigned int function3:16; unsigned int sign : 1; unsigned int exponent: 11; unsigned int quiet:1; unsigned int function0:3; unsigned int function1:16; #endif } nan; struct { #if (CYG_DOUBLE_BYTEORDER == CYG_MSBFIRST) cyg_uint32 msw; cyg_uint32 lsw; #else cyg_uint32 lsw; cyg_uint32 msw; #endif } parts; } Cyg_libm_ieee_double_shape_type; typedef union { cyg_int32 asi32; float value; struct { unsigned int sign : 1; unsigned int exponent: 8; unsigned int fraction0: 7; unsigned int fraction1: 16; } number; struct { unsigned int sign:1; unsigned int exponent:8; unsigned int quiet:1; unsigned int function0:6; unsigned int function1:16; } nan; } Cyg_libm_ieee_float_shape_type; #else // Little endian typedef union { cyg_int32 asi32[2]; cyg_int64 asi64; double value; struct { #if (CYG_DOUBLE_BYTEORDER == CYG_MSBFIRST) // Big endian unsigned int fraction1:16; unsigned int fraction0: 4; unsigned int exponent :11; unsigned int sign : 1; unsigned int fraction3:16; unsigned int fraction2:16; #else unsigned int fraction3:16; unsigned int fraction2:16; unsigned int fraction1:16; unsigned int fraction0: 4; unsigned int exponent :11; unsigned int sign : 1; #endif } number; struct { #if (CYG_DOUBLE_BYTEORDER == CYG_MSBFIRST) // Big endian unsigned int function1:16; unsigned int function0:3; unsigned int quiet:1; unsigned int exponent: 11; unsigned int sign : 1; unsigned int function3:16; unsigned int function2:16; #else unsigned int function3:16; unsigned int function2:16; unsigned int function1:16; unsigned int function0:3; unsigned int quiet:1; unsigned int exponent: 11; unsigned int sign : 1; #endif } nan; struct { #if (CYG_DOUBLE_BYTEORDER == CYG_MSBFIRST) // Big endian cyg_uint32 msw; cyg_uint32 lsw; #else cyg_uint32 lsw; cyg_uint32 msw; #endif } parts; } Cyg_libm_ieee_double_shape_type; typedef union { cyg_int32 asi32; float value; struct { unsigned int fraction0: 7; unsigned int fraction1: 16; unsigned int exponent: 8; unsigned int sign : 1; } number; struct { unsigned int function1:16; unsigned int function0:6; unsigned int quiet:1; unsigned int exponent:8; unsigned int sign:1; } nan; } Cyg_libm_ieee_float_shape_type; #endif // little-endian typedef enum { ADD_INSN=0, // 0 SUB_INSN, MUL_INSN, DIV_INSN, SQRT_INSN, ABS_INSN, // 5 MOV_INSN, NEG_INSN, ROUNDL_INSN, TRUNCL_INSN, CEILL_INSN, // 10 FLOORL_INSN, ROUNDW_INSN, TRUNCW_INSN, CEILW_INSN, FLOORW_INSN, // 15 // ... CVTS_INSN=32, CVTD_INSN, // ... CVTW_INSN=36, CVTL_INSN, // ... // // 48-63 are floating point compare - treated separately } fp_operation; typedef enum { S_FORMAT=16, D_FORMAT=17, W_FORMAT=20, L_FORMAT=21 } fp_format; // FUNCTIONS #define issubnormal(_x_) ((_x_).number.exponent == 0) // These functions convert between single precision floating point numbers // represented in register or union form. This is required because endian-ness // matters when a 32-bit float is in a 64-bit register. static __inline__ void reg2flt( CYG_HAL_FPU_REG *fpu_reg_p, Cyg_libm_ieee_float_shape_type *flt) { #if defined(CYGHWR_HAL_MIPS_FPU_32BIT) || (CYG_BYTEORDER == CYG_LSBFIRST) flt->asi32 = *(cyg_int32 *)fpu_reg_p; #else flt->asi32 = *((cyg_int32 *)fpu_reg_p + 1); # endif } // reg2flt() static __inline__ void flt2reg( Cyg_libm_ieee_float_shape_type *flt, CYG_HAL_FPU_REG *fpu_reg_p ) { #if defined(CYGHWR_HAL_MIPS_FPU_32BIT) || (CYG_BYTEORDER == CYG_LSBFIRST) *(cyg_int32 *)fpu_reg_p = flt->asi32; #else *((cyg_int32 *)fpu_reg_p + 1) = flt->asi32; # endif } // flt2reg() static __inline__ void reg2dbl( CYG_HAL_FPU_REG *fpu_reg_p, Cyg_libm_ieee_double_shape_type *flt) { flt->asi64 = *(cyg_int64 *)fpu_reg_p; } // reg2dbl() static __inline__ void dbl2reg( Cyg_libm_ieee_double_shape_type *flt, CYG_HAL_FPU_REG *fpu_reg_p ) { *(cyg_uint64*)fpu_reg_p = flt->asi64; } // dbl2reg() // This function returns non-zero if the exception has been handled // successfully. // FIXME: Arguably we should raise underflow exceptions in some of the cases // below e.g. sqrt(subnormal). And perhaps we should round appropriately to // +/- 2^^Emin if round to +/- infinity is enabled, as per the FS bit. Not sure. externC cyg_uint8 cyg_hal_mips_process_fpe( HAL_SavedRegisters *regs ) { CYG_WORD insn; CYG_HAL_FPU_REG *srcreg1, *srcreg2, *dstreg; cyg_uint8 handled=0; fp_format format; cyg_uint8 fp64bit=0; // true if format is 64bit, false if 32bit cyg_uint8 fixedpoint=0; // true if format is fixed point, false if // floating point cyg_uint8 computational_insn=1; // computational FP instruction cyg_bool delay_slot; // did it happen in a delay slot CYG_REPORT_FUNCNAMETYPE("cyg_hal_mips_process_fpe", "returning %d"); CYG_CHECK_DATA_PTR( regs, "cyg_hal_mips_process_fpe() called with invalid regs ptr"); CYG_PRECONDITION( (regs->vector>>2) == CYGNUM_HAL_VECTOR_FPE, "Asked to process non-FPE exception"); // First of all, we only handle the unimplemented operation exception // here, so if we don't have that, we just exit if ((regs->fcr31 & FCR31_CAUSE_E) == 0) { CYG_REPORT_RETVAL(0); return 0; } // Get the contents of the instruction that caused the exception. This // may have been in a branch delay slot however, so we have to check // the BD bit in the cause register first. if (regs->cause & CAUSE_BD) { insn = *(((CYG_WORD *) regs->pc) + 1); delay_slot = true; } else { insn = *(CYG_WORD *) regs->pc; delay_slot = false; } CYG_TRACE2(true, "exception at pc %08x containing %08x", regs->pc, insn); CYG_ASSERT( (insn>>26) == 0x11, "Instruction at pc doesn't have expected opcode COP1"); // Determine the format format = (insn >> 21) & 0x1f; switch (format) { case S_FORMAT: break; case D_FORMAT: fp64bit++; break; case W_FORMAT: fixedpoint++; break; case L_FORMAT: fixedpoint++; fp64bit++; break; default: computational_insn=0; break; } // switch // This module only emulates computational floating point instructions if (computational_insn && !fixedpoint) { // Decode the registers used dstreg = ®s->f[ (insn >> 6) & 0x1f ]; srcreg1 = ®s->f[ (insn >> 11) & 0x1f ]; srcreg2 = ®s->f[ (insn >> 16) & 0x1f ]; // Determine the operation requested switch (insn & 0x3f) { case ADD_INSN: case SUB_INSN: case MUL_INSN: case DIV_INSN: if (fp64bit) { Cyg_libm_ieee_double_shape_type s1, s2; reg2dbl( srcreg1, &s1 ); reg2dbl( srcreg2, &s2 ); if ( issubnormal( s1 ) ) { // flush to 0 and restart // but preserve sign if (s1.number.sign) s1.value = -0.0; else s1.value = 0.0; dbl2reg( &s1, srcreg1 ); handled++; } // We could try flushing both to 0 at the same time, but // that's inadvisable if both numbers are very small. // Particularly if this is DIV_INSN, when we could therefore // get 0/0 even when the program explicitly checked for // denominator != 0. That's also why we check s1 first. else if ( issubnormal( s2 ) ) { // flush to 0 and restart // but preserve sign if (s2.number.sign) s2.value = -0.0; else s2.value = 0.0; dbl2reg( &s2, srcreg2 ); handled++; } } else { // 32-bit Cyg_libm_ieee_float_shape_type s1, s2; reg2flt( srcreg1, &s1 ); reg2flt( srcreg2, &s2 ); if ( issubnormal( s1 )) { // flush to 0 and restart // but preserve sign if (s1.number.sign) s1.value = -0.0; else s1.value = 0.0; flt2reg( &s1, srcreg1 ); handled++; } else if ( issubnormal( s2 ) ) { // flush to 0 and restart // but preserve sign if (s2.number.sign) s2.value = -0.0; else s2.value = 0.0; flt2reg( &s2, srcreg2 ); handled++; } } break; case SQRT_INSN: if ( fp64bit ) { Cyg_libm_ieee_double_shape_type d, s; reg2dbl( dstreg, &d ); reg2dbl( srcreg1, &s ); if ( issubnormal( s ) ) { // Sqrt of something tiny is 0 // if this is a delay slot, we can't restart properly // so if it is subnormal, clear the source register instead if ( delay_slot ) { // but preserve sign if (s.number.sign) s.value = -0.0; else s.value = 0.0; dbl2reg( &s, srcreg1 ); } else { // but preserve sign if (s.number.sign) d.value = -0.0; else d.value = 0.0; dbl2reg( &d, dstreg ); regs->pc += 4; // We've dealt with this so move on } handled++; } } else { // 32-bit Cyg_libm_ieee_float_shape_type d, s; reg2flt( dstreg, &d ); reg2flt( srcreg1, &s ); if ( issubnormal( s ) ) { // Sqrt of something tiny is 0 // if this is a delay slot, we can't restart properly // so if it is subnormal, clear the source register instead if ( delay_slot ) { // but preserve sign if (s.number.sign) s.value = -0.0; else s.value = 0.0; flt2reg( &s, srcreg1 ); } else { // but preserve sign if (s.number.sign) d.value = -0.0; else d.value = 0.0; flt2reg( &d, dstreg ); regs->pc += 4; // We've dealt with this so move on } handled++; } } break; case ABS_INSN: // We may as well do this right if we can if ( fp64bit ) { Cyg_libm_ieee_double_shape_type d, s; reg2dbl( dstreg, &d ); reg2dbl( srcreg1, &s ); // if this is a delay slot, we can't restart properly // so if it is subnormal, clear the source register instead if ( delay_slot ) { if ( issubnormal( s ) ) { // The sign is still important for abs in case // there are any further operations on the same // register if (s.number.sign) s.value = -0.0; else s.value = 0.0; dbl2reg( &s, srcreg1 ); handled++; } } else { d.asi64 = s.asi64; d.number.sign = 0; dbl2reg( &d, dstreg ); regs->pc += 4; handled++; } } else { // 32-bit Cyg_libm_ieee_float_shape_type d, s; reg2flt( dstreg, &d ); reg2flt( srcreg1, &s ); // if this is a delay slot, we can't restart properly // so if it is subnormal, clear the source register instead if ( delay_slot ) { if ( issubnormal( s ) ) { // The sign is still important for abs in case // there are any further operations on the same // register if (s.number.sign) s.value = -0.0; else s.value = 0.0; flt2reg( &s, srcreg1 ); handled++; } } else { d.asi32 = s.asi32; d.number.sign = 0; flt2reg( &d, dstreg ); regs->pc += 4; handled++; } } break; case MOV_INSN: // We may as well do this right if we can if ( fp64bit ) { Cyg_libm_ieee_double_shape_type d, s; reg2dbl( dstreg, &d ); reg2dbl( srcreg1, &s ); // if this is a delay slot, we can't restart properly // so if it is subnormal, clear the source register instead if ( delay_slot ) { if ( issubnormal( s ) ) { // but preserve sign if (s.number.sign) s.value = -0.0; else s.value = 0.0; dbl2reg( &s, srcreg1 ); handled++; } } else { d.asi64 = s.asi64; dbl2reg( &d, dstreg ); regs->pc += 4; handled++; } } else { // 32-bit Cyg_libm_ieee_float_shape_type d, s; reg2flt( dstreg, &d ); reg2flt( srcreg1, &s ); // if this is a delay slot, we can't restart properly // so if it is subnormal, clear the source register instead if ( delay_slot ) { if ( issubnormal( s ) ) { // The sign is still important for abs in case // there are any further operations on the same // register if (s.number.sign) s.value = -0.0; else s.value = 0.0; flt2reg( &s, srcreg1 ); handled++; } } else { d.asi32 = s.asi32; flt2reg( &d, dstreg ); regs->pc += 4; handled++; } } break; case NEG_INSN: // We may as well do this right if we can if ( fp64bit ) { Cyg_libm_ieee_double_shape_type d, s; reg2dbl( dstreg, &d ); reg2dbl( srcreg1, &s ); // if this is a delay slot, we can't restart properly // so if it is subnormal, clear the source register instead if ( delay_slot ) { if ( issubnormal( s ) ) { // but preserve sign if (s.number.sign) s.value = -0.0; else s.value = 0.0; dbl2reg( &s, srcreg1 ); handled++; } } else { d.asi64 = s.asi64; d.number.sign = s.number.sign ? 0 : 1; dbl2reg( &d, dstreg ); regs->pc += 4; handled++; } } else { // 32-bit Cyg_libm_ieee_float_shape_type d, s; reg2flt( dstreg, &d ); reg2flt( srcreg1, &s ); // if this is a delay slot, we can't restart properly // so if it is subnormal, clear the source register instead if ( delay_slot ) { if ( issubnormal( s ) ) { // but preserve sign if (s.number.sign) s.value = -0.0; else s.value = 0.0; flt2reg( &s, srcreg1 ); handled++; } } else { d.asi32 = s.asi32; d.number.sign = s.number.sign ? 0 : 1; flt2reg( &d, dstreg ); regs->pc += 4; handled++; } } break; // We can't do much about floating-point to fixed-point arithmetic // without emulating the FPU here ourselves! // So simply zero denormalized numbers case ROUNDL_INSN: case TRUNCL_INSN: case CEILL_INSN: case FLOORL_INSN: case ROUNDW_INSN: case TRUNCW_INSN: case CEILW_INSN: case FLOORW_INSN: case CVTS_INSN: case CVTD_INSN: case CVTW_INSN: case CVTL_INSN: if ( fp64bit ) { Cyg_libm_ieee_double_shape_type s; reg2dbl( srcreg1, &s ); // just try and 0 the source register if it is subnormal if ( issubnormal( s ) ) { // but preserve sign if (s.number.sign) s.value = -0.0; else s.value = 0.0; dbl2reg( &s, srcreg1 ); handled++; } } else { // 32-bit Cyg_libm_ieee_float_shape_type s; reg2flt( srcreg1, &s ); // just try and 0 the source register if it is subnormal if ( issubnormal( s ) ) { // but preserve sign if (s.number.sign) s.value = -0.0; else s.value = 0.0; flt2reg( &s, srcreg1 ); handled++; } } break; default: // check for floating-point compare (C.cond.fmt) if ( (insn & 0x30) == 0x30 ) { if (fp64bit) { Cyg_libm_ieee_double_shape_type s1, s2; reg2dbl( srcreg1, &s1 ); reg2dbl( srcreg2, &s2 ); if ( issubnormal( s1 ) ) { // flush to 0 and restart // but preserve sign if (s1.number.sign) s1.value = -0.0; else s1.value = 0.0; dbl2reg( &s1, srcreg1 ); handled++; } if ( issubnormal( s2 ) ) { // flush to 0 and restart // but preserve sign if (s2.number.sign) s2.value = -0.0; else s2.value = 0.0; dbl2reg( &s2, srcreg2 ); handled++; } } else { // 32-bit Cyg_libm_ieee_float_shape_type s1, s2; reg2flt( srcreg1, &s1 ); reg2flt( srcreg2, &s2 ); if ( issubnormal( s1 )) { // flush to 0 and restart // but preserve sign if (s1.number.sign) s1.value = -0.0; else s1.value = 0.0; flt2reg( &s1, srcreg1 ); handled++; } if ( issubnormal( s2 ) ) { // flush to 0 and restart // but preserve sign if (s2.number.sign) s2.value = -0.0; else s2.value = 0.0; flt2reg( &s2, srcreg2 ); handled++; } } // else } // if break; } // switch } // if (computational_insn && !fixedpoint) if ( handled != 0) { // We must clear the cause and flag bits before restoring FPCR31 regs->fcr31 &= ~(FCR31_CAUSE_E | FCR31_CAUSE_V | FCR31_CAUSE_Z | FCR31_CAUSE_O | FCR31_CAUSE_U | FCR31_CAUSE_I | FCR31_FLAGS_V | FCR31_FLAGS_Z | FCR31_FLAGS_O | FCR31_FLAGS_U | FCR31_FLAGS_I); } CYG_REPORT_RETVAL( handled ); return handled; } // cyg_hal_mips_process_fpe() #endif // ifdef CYGHWR_HAL_MIPS_FPU // EOF mipsfp.c
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