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More tuning of the eflags machinery.

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git-svn-id: svn://svn.valgrind.org/vex/trunk@739
This commit is contained in:
Julian Seward
2005-01-23 11:39:02 +00:00
parent 8f63b956be
commit e151892d26
1 changed files with 22 additions and 3 deletions
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25
VEX/priv/guest-x86/ghelpers.c
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@@ -765,6 +765,12 @@ IRExpr* guest_x86_spechelper ( Char* function_name,
binop(Iop_CmpEQ32, cc_dep1, cc_dep2));
}
if (isU32(cc_op, X86G_CC_OP_SUBL) && isU32(cond, X86CondNZ)) {
/* long sub/cmp, then NZ --> test dst!=src */
return unop(Iop_1Uto32,
binop(Iop_CmpNE32, cc_dep1, cc_dep2));
}
if (isU32(cc_op, X86G_CC_OP_SUBL) && isU32(cond, X86CondL)) {
/* long sub/cmp, then L (signed less than)
--> test dst <s src */
@@ -853,6 +859,15 @@ IRExpr* guest_x86_spechelper ( Char* function_name,
return unop(Iop_1Uto32,binop(Iop_CmpLE32S, cc_dep1, mkU32(0)));
}
if (isU32(cc_op, X86G_CC_OP_LOGICL) && isU32(cond, X86CondBE)) {
/* long and/or/xor, then BE
LOGIC sets ZF according to the result and makes CF be zero.
BE computes (CF | ZF), but CF is zero, so this reduces ZF
-- which will be 1 iff the result is zero. Hence ...
*/
return unop(Iop_1Uto32,binop(Iop_CmpEQ32, cc_dep1, mkU32(0)));
}
/*---------------- LOGICW ----------------*/
if (isU32(cc_op, X86G_CC_OP_LOGICW) && isU32(cond, X86CondZ)) {
@@ -894,14 +909,18 @@ IRExpr* guest_x86_spechelper ( Char* function_name,
/* This can happen, as a result of x87 FP compares: "fcom ... ;
fnstsw %ax ; sahf ; jbe" for example. */
if (isU32(cc_op, X86G_CC_OP_COPY) && isU32(cond, X86CondBE)) {
if (isU32(cc_op, X86G_CC_OP_COPY) &&
(isU32(cond, X86CondBE) || isU32(cond, X86CondNBE))) {
/* COPY, then BE --> extract C and Z from dep1, and test (C
or Z == 1). */
/* COPY, then NBE --> extract C and Z from dep1, and test (C
or Z == 0). */
UInt nnn = isU32(cond, X86CondBE) ? 1 : 0;
return
unop(
Iop_1Uto32,
binop(
Iop_CmpNE32,
Iop_CmpEQ32,
binop(
Iop_And32,
binop(
@@ -911,7 +930,7 @@ IRExpr* guest_x86_spechelper ( Char* function_name,
),
mkU32(1)
),
mkU32(0)
mkU32(nnn)
)
);
}