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Jan Hubicka <hubicka@freesoft.cz> 

* i386.md (ffs expander): Emit Pentium friendly code for
        TARGET_PENTIUM.

From-SVN: r29769
This commit is contained in:
Jan Hubicka 1999-10-02 19:54:05 +02:00 committed by Richard Henderson
parent fc78679f9e
commit e0dc26ffad
2 changed files with 58 additions and 3 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
Sat Oct 2 10:53:22 1999 Jan Hubicka <hubicka@freesoft.cz>
* i386.md (ffs expander): Emit Pentium friendly code for
TARGET_PENTIUM.
Sat Oct 2 02:48:21 1999 Mark P. Mitchell <mark@codesourcery.com>
* tree.c (build): Don't look at TREE_SIDE_EFFECTS or TREE_RAISES

56
gcc/config/i386/i386.md
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@ -6779,6 +6779,57 @@
const0_rtx),
tmp,
out)));
emit_insn (gen_addsi3 (out, out, const1_rtx));
emit_move_insn (operands[0], out);
}
/* Pentium bsf instruction is extremly slow. Following code is recommended by
the Intel Optimizing Manual as resonable replacement:
TEST EAX,EAX
JZ SHORT BS2
XOR ECX,ECX
MOV DWORD PTR [TEMP+4],ECX
SUB ECX,EAX
AND EAX,ECX
MOV DWORD PTR [TEMP],EAX
FILD QWORD PTR [TEMP]
FSTP QWORD PTR [TEMP]
WAIT ; WAIT only needed for compatibility with
; earlier processors
MOV ECX, DWORD PTR [TEMP+4]
SHR ECX,20
SUB ECX,3FFH
TEST EAX,EAX ; clear zero flag
BS2:
Following piece of code expand ffs to similar beast.
*/
else if (TARGET_PENTIUM && !optimize_size && TARGET_80387)
{
rtx label = gen_label_rtx ();
rtx lo, hi;
rtx mem = assign_386_stack_local (DImode, 0);
rtx fptmp = gen_reg_rtx (DFmode);
split_di (&mem, 1, &lo, &hi);
emit_move_insn (out, const0_rtx);
emit_cmp_and_jump_insns (in, const0_rtx, EQ, 0, SImode, 1, 0, label);
emit_move_insn (hi, out);
emit_insn (gen_subsi3 (out, out, in));
emit_insn (gen_andsi3 (out, out, in));
emit_move_insn (lo, out);
emit_insn (gen_floatdidf2 (fptmp,mem));
emit_move_insn (gen_rtx_MEM (DFmode, XEXP (mem, 0)), fptmp);
emit_move_insn (out, hi);
emit_insn (gen_lshrsi3 (out, out, GEN_INT (20)));
emit_insn (gen_subsi3 (out, out, GEN_INT (0x3fe)));
emit_label (label);
LABEL_NUSES (label) = 1;
emit_move_insn (operands[0], out);
}
else
{
@ -6790,10 +6841,9 @@
const0_rtx)));
emit_insn (gen_negsi2 (tmp, tmp));
emit_insn (gen_iorsi3 (out, out, tmp));
emit_insn (gen_addsi3 (out, out, const1_rtx));
emit_move_insn (operands[0], out);
}
emit_insn (gen_addsi3 (out, out, const1_rtx));
emit_move_insn (operands[0], out);
DONE;
}")