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Address issues found by Duncan during post-commit review of r177856. 

llvm-svn: 177863
This commit is contained in:
Arnaud A. de Grandmaison 2013-03-25 11:47:38 +00:00
parent 9328ba400a
commit 3ee88e8a77
2 changed files with 21 additions and 34 deletions
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51
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -139,38 +139,27 @@ static bool isSignBitCheck(ICmpInst::Predicate pred, ConstantInt *RHS,
}
}
/// Returns true if the exploded icmp can be expressed as a comparison to zero
/// and update the predicate accordingly. The signedness of the comparison is
/// Returns true if the exploded icmp can be expressed as a signed comparison
/// to zero and updates the predicate accordingly.
/// The signedness of the comparison is preserved.
static bool isSignTest(ICmpInst::Predicate &pred, const ConstantInt *RHS) {
if (!ICmpInst::isSigned(pred))
return false;
if (RHS->isZero())
return true;
return ICmpInst::isRelational(pred);
if (RHS->isOne())
switch (pred) {
case ICmpInst::ICMP_SGE:
pred = ICmpInst::ICMP_SGT;
return true;
case ICmpInst::ICMP_SLT:
if (RHS->isOne()) {
if (pred == ICmpInst::ICMP_SLT) {
pred = ICmpInst::ICMP_SLE;
return true;
default:
return false;
}
if (RHS->isAllOnesValue())
switch (pred) {
case ICmpInst::ICMP_SLE:
pred = ICmpInst::ICMP_SLT;
return true;
case ICmpInst::ICMP_SGT:
} else if (RHS->isAllOnesValue()) {
if (pred == ICmpInst::ICMP_SGT) {
pred = ICmpInst::ICMP_SGE;
return true;
default:
return false;
}
}
return false;
}
@ -1322,17 +1311,15 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
ConstantInt *Val = dyn_cast<ConstantInt>(LHSI->getOperand(1));
if (!Val) break;
if (!ICI.isEquality()) {
// If this is a signed comparison to 0 and the mul is sign preserving,
// use the mul LHS operand instead.
ICmpInst::Predicate pred = ICI.getPredicate();
if (isSignTest(pred, RHS) && !Val->isZero() &&
cast<BinaryOperator>(LHSI)->hasNoSignedWrap())
return new ICmpInst(Val->isNegative() ?
ICmpInst::getSwappedPredicate(pred) : pred,
LHSI->getOperand(0),
Constant::getNullValue(RHS->getType()));
}
// If this is a signed comparison to 0 and the mul is sign preserving,
// use the mul LHS operand instead.
ICmpInst::Predicate pred = ICI.getPredicate();
if (isSignTest(pred, RHS) && !Val->isZero() &&
cast<BinaryOperator>(LHSI)->hasNoSignedWrap())
return new ICmpInst(Val->isNegative() ?
ICmpInst::getSwappedPredicate(pred) : pred,
LHSI->getOperand(0),
Constant::getNullValue(RHS->getType()));
break;
}
@ -1613,7 +1600,7 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
}
break;
case Instruction::Mul:
if (RHSV == 0) {
if (RHSV == 0 && BO->hasNoSignedWrap()) {
if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
// The trivial case (mul X, 0) is handled by InstSimplify
// General case : (mul X, C) != 0 iff X != 0

4
llvm/test/Transforms/InstCombine/icmp.ll
View File

@ -858,7 +858,7 @@ define i1 @icmp_mul(i32 %x) {
; CHECK: @icmp_mul_neq0
; CHECK-NEXT: icmp ne i32 %x, 0
define i1 @icmp_mul_neq0(i32 %x) {
%mul = mul i32 %x, -12
%mul = mul nsw i32 %x, -12
%cmp = icmp ne i32 %mul, 0
ret i1 %cmp
}
@ -866,7 +866,7 @@ define i1 @icmp_mul_neq0(i32 %x) {
; CHECK: @icmp_mul_eq0
; CHECK-NEXT: icmp eq i32 %x, 0
define i1 @icmp_mul_eq0(i32 %x) {
%mul = mul i32 %x, 12
%mul = mul nsw i32 %x, 12
%cmp = icmp eq i32 %mul, 0
ret i1 %cmp
}