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Merged
merged 1 commit into from
Jan 11, 2025
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VT: teach isImpliedCondMatchingOperands about samesign #122474

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8 changes: 0 additions & 8 deletions llvm/include/llvm/IR/InstrTypes.h
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Original file line number Diff line number Diff line change
Expand Up @@ -967,14 +967,6 @@ class CmpInst : public Instruction {
/// Determine if the predicate is false when comparing a value with itself.
static bool isFalseWhenEqual(Predicate predicate);

/// Determine if Pred1 implies Pred2 is true when two compares have matching
/// operands.
static bool isImpliedTrueByMatchingCmp(Predicate Pred1, Predicate Pred2);

/// Determine if Pred1 implies Pred2 is false when two compares have matching
/// operands.
static bool isImpliedFalseByMatchingCmp(Predicate Pred1, Predicate Pred2);

/// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const Instruction *I) {
return I->getOpcode() == Instruction::ICmp ||
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10 changes: 10 additions & 0 deletions llvm/include/llvm/IR/Instructions.h
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Expand Up @@ -1266,6 +1266,16 @@ class ICmpInst: public CmpInst {
return getFlippedSignednessPredicate(getPredicate());
}

/// Determine if Pred1 implies Pred2 is true when two compares have matching
/// operands.
static bool isImpliedTrueByMatchingCmp(CmpPredicate Pred1,
CmpPredicate Pred2);

/// Determine if Pred1 implies Pred2 is false when two compares have matching
/// operands.
static bool isImpliedFalseByMatchingCmp(CmpPredicate Pred1,
CmpPredicate Pred2);

void setSameSign(bool B = true) {
SubclassOptionalData = (SubclassOptionalData & ~SameSign) | (B * SameSign);
}
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16 changes: 9 additions & 7 deletions llvm/include/llvm/SandboxIR/Instruction.h
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Expand Up @@ -2511,13 +2511,6 @@ class CmpInst : public SingleLLVMInstructionImpl<llvm::CmpInst> {
WRAP_STATIC_PREDICATE(isOrdered);
WRAP_STATIC_PREDICATE(isUnordered);

static bool isImpliedTrueByMatchingCmp(Predicate Pred1, Predicate Pred2) {
return llvm::CmpInst::isImpliedTrueByMatchingCmp(Pred1, Pred2);
}
static bool isImpliedFalseByMatchingCmp(Predicate Pred1, Predicate Pred2) {
return llvm::CmpInst::isImpliedFalseByMatchingCmp(Pred1, Pred2);
}

/// Method for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const Value *From) {
return From->getSubclassID() == ClassID::ICmp ||
Expand Down Expand Up @@ -2554,6 +2547,15 @@ class ICmpInst : public CmpInst {
WRAP_STATIC_PREDICATE(isGE);
WRAP_STATIC_PREDICATE(isLE);

static bool isImpliedTrueByMatchingCmp(CmpPredicate Pred1,
CmpPredicate Pred2) {
return llvm::ICmpInst::isImpliedTrueByMatchingCmp(Pred1, Pred2);
}
static bool isImpliedFalseByMatchingCmp(CmpPredicate Pred1,
CmpPredicate Pred2) {
return llvm::ICmpInst::isImpliedFalseByMatchingCmp(Pred1, Pred2);
}

static auto predicates() { return llvm::ICmpInst::predicates(); }
static bool compare(const APInt &LHS, const APInt &RHS,
ICmpInst::Predicate Pred) {
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9 changes: 4 additions & 5 deletions llvm/lib/Analysis/ValueTracking.cpp
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Expand Up @@ -9374,12 +9374,11 @@ isImpliedCondOperands(CmpInst::Predicate Pred, const Value *ALHS,
/// Return true if "icmp1 LPred X, Y" implies "icmp2 RPred X, Y" is true.
/// Return false if "icmp1 LPred X, Y" implies "icmp2 RPred X, Y" is false.
/// Otherwise, return std::nullopt if we can't infer anything.
static std::optional<bool>
isImpliedCondMatchingOperands(CmpInst::Predicate LPred,
CmpInst::Predicate RPred) {
if (CmpInst::isImpliedTrueByMatchingCmp(LPred, RPred))
static std::optional<bool> isImpliedCondMatchingOperands(CmpPredicate LPred,
CmpPredicate RPred) {
if (ICmpInst::isImpliedTrueByMatchingCmp(LPred, RPred))
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Seems like isImpliedTrueByMatchingCmp and isImpliedFalseByMatchingCmp are always called together. We can replace them with a helper std::optional<bool> isImpliedByMatchingCmp in the future.

return true;
if (CmpInst::isImpliedFalseByMatchingCmp(LPred, RPred))
if (ICmpInst::isImpliedFalseByMatchingCmp(LPred, RPred))
return false;

return std::nullopt;
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13 changes: 10 additions & 3 deletions llvm/lib/IR/Instructions.cpp
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Expand Up @@ -3886,12 +3886,18 @@ bool CmpInst::isFalseWhenEqual(Predicate predicate) {
}
}

bool CmpInst::isImpliedTrueByMatchingCmp(Predicate Pred1, Predicate Pred2) {
bool ICmpInst::isImpliedTrueByMatchingCmp(CmpPredicate Pred1,
CmpPredicate Pred2) {
// If the predicates match, then we know the first condition implies the
// second is true.
if (Pred1 == Pred2)
if (CmpPredicate::getMatching(Pred1, Pred2))
return true;

if (Pred1.hasSameSign() && CmpInst::isSigned(Pred2))
Pred1 = ICmpInst::getFlippedSignednessPredicate(Pred1);
else if (Pred2.hasSameSign() && CmpInst::isSigned(Pred1))
Pred2 = ICmpInst::getFlippedSignednessPredicate(Pred2);

switch (Pred1) {
default:
break;
Expand All @@ -3911,7 +3917,8 @@ bool CmpInst::isImpliedTrueByMatchingCmp(Predicate Pred1, Predicate Pred2) {
return false;
}

bool CmpInst::isImpliedFalseByMatchingCmp(Predicate Pred1, Predicate Pred2) {
bool ICmpInst::isImpliedFalseByMatchingCmp(CmpPredicate Pred1,
CmpPredicate Pred2) {
return isImpliedTrueByMatchingCmp(Pred1, getInversePredicate(Pred2));
}

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8 changes: 4 additions & 4 deletions llvm/lib/Transforms/Scalar/NewGVN.cpp
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Expand Up @@ -1964,15 +1964,15 @@ NewGVN::ExprResult NewGVN::performSymbolicCmpEvaluation(Instruction *I) const {
if (PBranch->TrueEdge) {
// If we know the previous predicate is true and we are in the true
// edge then we may be implied true or false.
if (CmpInst::isImpliedTrueByMatchingCmp(BranchPredicate,
OurPredicate)) {
if (ICmpInst::isImpliedTrueByMatchingCmp(BranchPredicate,
OurPredicate)) {
return ExprResult::some(
createConstantExpression(ConstantInt::getTrue(CI->getType())),
PI);
}

if (CmpInst::isImpliedFalseByMatchingCmp(BranchPredicate,
OurPredicate)) {
if (ICmpInst::isImpliedFalseByMatchingCmp(BranchPredicate,
OurPredicate)) {
return ExprResult::some(
createConstantExpression(ConstantInt::getFalse(CI->getType())),
PI);
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7 changes: 2 additions & 5 deletions llvm/test/Analysis/ValueTracking/implied-condition-samesign.ll
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Expand Up @@ -118,8 +118,7 @@ define i1 @sgt_implies_ge_via_assume(i32 %i, i32 %j) {
; CHECK-SAME: i32 [[I:%.*]], i32 [[J:%.*]]) {
; CHECK-NEXT: [[I_SGT_J:%.*]] = icmp sgt i32 [[I]], [[J]]
; CHECK-NEXT: call void @llvm.assume(i1 [[I_SGT_J]])
; CHECK-NEXT: [[I_GE_J:%.*]] = icmp samesign uge i32 [[I]], [[J]]
; CHECK-NEXT: ret i1 [[I_GE_J]]
; CHECK-NEXT: ret i1 true
;
%i.sgt.j = icmp sgt i32 %i, %j
call void @llvm.assume(i1 %i.sgt.j)
Expand All @@ -134,9 +133,7 @@ define i32 @gt_implies_sge_dominating(i32 %a, i32 %len) {
; CHECK-NEXT: [[A_GT_LEN:%.*]] = icmp samesign ugt i32 [[A]], [[LEN]]
; CHECK-NEXT: br i1 [[A_GT_LEN]], label %[[TAKEN:.*]], label %[[END:.*]]
; CHECK: [[TAKEN]]:
; CHECK-NEXT: [[A_SGE_LEN:%.*]] = icmp sge i32 [[A]], [[LEN]]
; CHECK-NEXT: [[RES:%.*]] = select i1 [[A_SGE_LEN]], i32 30, i32 0
; CHECK-NEXT: ret i32 [[RES]]
; CHECK-NEXT: ret i32 30
; CHECK: [[END]]:
; CHECK-NEXT: ret i32 -1
;
Expand Down
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