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[/] [openrisc/] [trunk/] [gnu-src/] [gcc-4.2.2/] [gcc/] [config/] [cris/] [mulsi3.asm] - Blame information for rev 455

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1 38 julius 
;; This code used to be expanded through interesting expansions in
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;; the machine description, compiled from this code:
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;;
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;; #ifdef L_mulsi3
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;; long __Mul (unsigned long a, unsigned long b) __attribute__ ((__const__));
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;;
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;; /* This must be compiled with the -mexpand-mul flag, to synthesize the
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;;    multiplication from the mstep instructions.  The check for
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;;    smaller-size multiplication pays off in the order of .5-10%;
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;;    estimated median 1%, depending on application.
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;;     FIXME: It can be further optimized if we go to assembler code, as
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;;    gcc 2.7.2 adds a few unnecessary instructions and does not put the
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;;    basic blocks in optimal order.  */
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;; long
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;; __Mul (unsigned long a, unsigned long b)
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;; {
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;; #if defined (__CRIS_arch_version) && __CRIS_arch_version >= 10
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;;   /* In case other code is compiled without -march=v10, they will
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;;      contain calls to __Mul, regardless of flags at link-time.  The
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;;      "else"-code below will work, but is unnecessarily slow.  This
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;;      sometimes cuts a few minutes off from simulation time by just
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;;      returning a "mulu.d".  */
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;;   return a * b;
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;; #else
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;;   unsigned long min;
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;;
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;;   /* Get minimum via the bound insn.  */
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;;   min = a < b ? a : b;
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;;
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;;   /* Can we omit computation of the high part?       */
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;;   if (min > 65535)
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;;     /* No.  Perform full multiplication.  */
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;;     return a * b;
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;;   else
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;;     {
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;;       /* Check if both operands are within 16 bits.  */
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;;       unsigned long max;
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;;
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;;       /* Get maximum, by knowing the minimum.
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;;          This will partition a and b into max and min.
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;;          This is not currently something GCC understands,
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;;          so do this trick by asm.  */
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;;       __asm__ ("xor %1,%0\n\txor %2,%0"
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;;                : "=r" (max)
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;;                :  "r" (b), "r" (a), "0" (min));
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;;
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;;     if (max > 65535)
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;;       /* Make GCC understand that only the low part of "min" will be
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;;          used.  */
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;;       return max * (unsigned short) min;
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;;     else
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;;       /* Only the low parts of both operands are necessary.  */
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;;       return ((unsigned short) max) * (unsigned short) min;
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;;     }
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;; #endif /* not __CRIS_arch_version >= 10 */
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;; }
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;; #endif /* L_mulsi3 */
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;;
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;; That approach was abandoned since the caveats outweighted the
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;; benefits.  The expand-multiplication machinery is also removed, so you
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;; can't do this anymore.
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;;
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;; For doubters of there being any benefits, some where: insensitivity to:
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;; - ABI changes (mostly for experimentation)
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;; - assembler syntax differences (mostly debug format).
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;; - insn scheduling issues.
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;; Most ABI experiments will presumably happen with arches with mul insns,
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;; so that argument doesn't really hold anymore, and it's unlikely there
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;; being new arch variants needing insn scheduling and not having mul
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;; insns.
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;; ELF and a.out have different syntax for local labels: the "wrong"
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;; one may not be omitted from the object.
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#undef L
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#ifdef __AOUT__
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# define L(x) x
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#else
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# define L(x) .x
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#endif
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        .global ___Mul
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        .type   ___Mul,@function
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___Mul:
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#if defined (__CRIS_arch_version) && __CRIS_arch_version >= 10
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;; Can't have the mulu.d last on a cache-line (in the delay-slot of the
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;; "ret"), due to hardware bug.  See documentation for -mmul-bug-workaround.
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;; Not worthwhile to conditionalize here.
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        .p2alignw 2,0x050f
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        mulu.d $r11,$r10
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        ret
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        nop
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#else
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        move.d $r10,$r12
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        move.d $r11,$r9
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        bound.d $r12,$r9
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        cmpu.w 65535,$r9
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        bls L(L3)
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        move.d $r12,$r13
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        movu.w $r11,$r9
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        lslq 16,$r13
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        mstep $r9,$r13
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        mstep $r9,$r13
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        mstep $r9,$r13
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        mstep $r9,$r13
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        mstep $r9,$r13
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        mstep $r9,$r13
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        mstep $r9,$r13
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        mstep $r9,$r13
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        mstep $r9,$r13
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        mstep $r9,$r13
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        mstep $r9,$r13
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        mstep $r9,$r13
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        mstep $r9,$r13
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        mstep $r9,$r13
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        mstep $r9,$r13
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        mstep $r9,$r13
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        clear.w $r10
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        test.d $r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        movu.w $r12,$r12
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        move.d $r11,$r9
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        clear.w $r9
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        test.d $r9
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        mstep $r12,$r9
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        mstep $r12,$r9
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        mstep $r12,$r9
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        mstep $r12,$r9
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        mstep $r12,$r9
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        mstep $r12,$r9
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        mstep $r12,$r9
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        mstep $r12,$r9
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        mstep $r12,$r9
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        mstep $r12,$r9
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        mstep $r12,$r9
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        mstep $r12,$r9
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        mstep $r12,$r9
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        mstep $r12,$r9
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        mstep $r12,$r9
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        mstep $r12,$r9
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        add.w $r9,$r10
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        lslq 16,$r10
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        ret
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        add.d $r13,$r10
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L(L3):
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        move.d $r9,$r10
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        xor $r11,$r10
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        xor $r12,$r10
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        cmpu.w 65535,$r10
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        bls L(L5)
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        movu.w $r9,$r13
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        movu.w $r13,$r13
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        move.d $r10,$r9
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        lslq 16,$r9
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        mstep $r13,$r9
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        mstep $r13,$r9
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        mstep $r13,$r9
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        mstep $r13,$r9
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        mstep $r13,$r9
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        mstep $r13,$r9
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        mstep $r13,$r9
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        mstep $r13,$r9
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        mstep $r13,$r9
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        mstep $r13,$r9
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        mstep $r13,$r9
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        mstep $r13,$r9
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        mstep $r13,$r9
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        mstep $r13,$r9
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        mstep $r13,$r9
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        mstep $r13,$r9
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        clear.w $r10
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        test.d $r10
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        mstep $r13,$r10
191 
        mstep $r13,$r10
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        mstep $r13,$r10
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        mstep $r13,$r10
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        mstep $r13,$r10
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        mstep $r13,$r10
196 
        mstep $r13,$r10
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        mstep $r13,$r10
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        mstep $r13,$r10
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        mstep $r13,$r10
200 
        mstep $r13,$r10
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        mstep $r13,$r10
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        mstep $r13,$r10
203 
        mstep $r13,$r10
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        mstep $r13,$r10
205 
        mstep $r13,$r10
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        lslq 16,$r10
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        ret
208 
        add.d $r9,$r10
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210 
L(L5):
211 
        movu.w $r9,$r9
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        lslq 16,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        mstep $r9,$r10
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        ret
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        mstep $r9,$r10
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#endif
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L(Lfe1):
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        .size   ___Mul,L(Lfe1)-___Mul

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