forked from OSchip/llvm-project
InstCombine: simplify signed range checks
Try to convert two compares of a signed range check into a single unsigned compare. Examples: (icmp sge x, 0) & (icmp slt x, n) --> icmp ult x, n (icmp slt x, 0) | (icmp sgt x, n) --> icmp ugt x, n llvm-svn: 223224
This commit is contained in:
Erik Eckstein
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25383ac01b
commit
d181752be0
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@ -162,6 +162,7 @@ public:
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Instruction *visitUDiv(BinaryOperator &I);
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Instruction *visitSDiv(BinaryOperator &I);
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Instruction *visitFDiv(BinaryOperator &I);
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Value *simplifyRangeCheck(ICmpInst *Cmp0, ICmpInst *Cmp1, bool Inverted);
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Value *FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS);
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Value *FoldAndOfFCmps(FCmpInst *LHS, FCmpInst *RHS);
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Instruction *visitAnd(BinaryOperator &I);
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@ -785,6 +785,63 @@ static Value *foldLogOpOfMaskedICmps(ICmpInst *LHS, ICmpInst *RHS, bool IsAnd,
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return nullptr;
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}
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/// Try to fold a signed range checked with lower bound 0 to an unsigned icmp.
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/// Example: (icmp sge x, 0) & (icmp slt x, n) --> icmp ult x, n
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/// If \p Inverted is true then the check is for the inverted range, e.g.
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/// (icmp slt x, 0) | (icmp sgt x, n) --> icmp ugt x, n
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Value *InstCombiner::simplifyRangeCheck(ICmpInst *Cmp0, ICmpInst *Cmp1,
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bool Inverted) {
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// Check the lower range comparison, e.g. x >= 0
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// InstCombine already ensured that if there is a constant it's on the RHS.
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ConstantInt *RangeStart = dyn_cast<ConstantInt>(Cmp0->getOperand(1));
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if (!RangeStart)
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return nullptr;
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ICmpInst::Predicate Pred0 = (Inverted ? Cmp0->getInversePredicate() :
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Cmp0->getPredicate());
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// Accept x > -1 or x >= 0 (after potentially inverting the predicate).
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if (!((Pred0 == ICmpInst::ICMP_SGT && RangeStart->isMinusOne()) ||
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(Pred0 == ICmpInst::ICMP_SGE && RangeStart->isZero())))
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return nullptr;
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ICmpInst::Predicate Pred1 = (Inverted ? Cmp1->getInversePredicate() :
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Cmp1->getPredicate());
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Value *Input = Cmp0->getOperand(0);
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Value *RangeEnd;
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if (Cmp1->getOperand(0) == Input) {
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// For the upper range compare we have: icmp x, n
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RangeEnd = Cmp1->getOperand(1);
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} else if (Cmp1->getOperand(1) == Input) {
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// For the upper range compare we have: icmp n, x
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RangeEnd = Cmp1->getOperand(0);
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Pred1 = ICmpInst::getSwappedPredicate(Pred1);
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} else {
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return nullptr;
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}
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// Check the upper range comparison, e.g. x < n
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ICmpInst::Predicate NewPred;
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switch (Pred1) {
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case ICmpInst::ICMP_SLT: NewPred = ICmpInst::ICMP_ULT; break;
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case ICmpInst::ICMP_SLE: NewPred = ICmpInst::ICMP_ULE; break;
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default: return nullptr;
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}
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// This simplification is only valid if the upper range is not negative.
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bool IsNegative, IsNotNegative;
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ComputeSignBit(RangeEnd, IsNotNegative, IsNegative, DL, 0, AT,
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Cmp1, DT);
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if (!IsNotNegative)
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return nullptr;
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if (Inverted)
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NewPred = ICmpInst::getInversePredicate(NewPred);
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return Builder->CreateICmp(NewPred, Input, RangeEnd);
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}
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/// FoldAndOfICmps - Fold (icmp)&(icmp) if possible.
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Value *InstCombiner::FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
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ICmpInst::Predicate LHSCC = LHS->getPredicate(), RHSCC = RHS->getPredicate();
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@ -807,6 +864,14 @@ Value *InstCombiner::FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
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if (Value *V = foldLogOpOfMaskedICmps(LHS, RHS, true, Builder))
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return V;
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// E.g. (icmp sge x, 0) & (icmp slt x, n) --> icmp ult x, n
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if (Value *V = simplifyRangeCheck(LHS, RHS, /*Inverted=*/false))
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return V;
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// E.g. (icmp slt x, n) & (icmp sge x, 0) --> icmp ult x, n
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if (Value *V = simplifyRangeCheck(RHS, LHS, /*Inverted=*/false))
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return V;
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// This only handles icmp of constants: (icmp1 A, C1) & (icmp2 B, C2).
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Value *Val = LHS->getOperand(0), *Val2 = RHS->getOperand(0);
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ConstantInt *LHSCst = dyn_cast<ConstantInt>(LHS->getOperand(1));
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@ -1724,6 +1789,14 @@ Value *InstCombiner::FoldOrOfICmps(ICmpInst *LHS, ICmpInst *RHS,
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Builder->CreateAdd(B, ConstantInt::getSigned(B->getType(), -1)), A);
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}
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// E.g. (icmp slt x, 0) | (icmp sgt x, n) --> icmp ugt x, n
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if (Value *V = simplifyRangeCheck(LHS, RHS, /*Inverted=*/true))
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return V;
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// E.g. (icmp sgt x, n) | (icmp slt x, 0) --> icmp ugt x, n
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if (Value *V = simplifyRangeCheck(RHS, LHS, /*Inverted=*/true))
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return V;
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// This only handles icmp of constants: (icmp1 A, C1) | (icmp2 B, C2).
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if (!LHSCst || !RHSCst) return nullptr;
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@ -0,0 +1,159 @@
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; RUN: opt < %s -instcombine -S | FileCheck %s
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; Check simplification of
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; (icmp sgt x, -1) & (icmp sgt/sge n, x) --> icmp ugt/uge n, x
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; CHECK-LABEL: define i1 @test_and1
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; CHECK: [[R:%[0-9]+]] = icmp ugt i32 %nn, %x
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; CHECK: ret i1 [[R]]
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define i1 @test_and1(i32 %x, i32 %n) {
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%nn = and i32 %n, 2147483647
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%a = icmp sge i32 %x, 0
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%b = icmp slt i32 %x, %nn
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%c = and i1 %a, %b
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ret i1 %c
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}
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; CHECK-LABEL: define i1 @test_and2
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; CHECK: [[R:%[0-9]+]] = icmp uge i32 %nn, %x
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; CHECK: ret i1 [[R]]
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define i1 @test_and2(i32 %x, i32 %n) {
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%nn = and i32 %n, 2147483647
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%a = icmp sgt i32 %x, -1
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%b = icmp sle i32 %x, %nn
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%c = and i1 %a, %b
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ret i1 %c
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}
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; CHECK-LABEL: define i1 @test_and3
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; CHECK: [[R:%[0-9]+]] = icmp ugt i32 %nn, %x
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; CHECK: ret i1 [[R]]
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define i1 @test_and3(i32 %x, i32 %n) {
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%nn = and i32 %n, 2147483647
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%a = icmp sgt i32 %nn, %x
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%b = icmp sge i32 %x, 0
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%c = and i1 %a, %b
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ret i1 %c
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}
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; CHECK-LABEL: define i1 @test_and4
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; CHECK: [[R:%[0-9]+]] = icmp uge i32 %nn, %x
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; CHECK: ret i1 [[R]]
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define i1 @test_and4(i32 %x, i32 %n) {
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%nn = and i32 %n, 2147483647
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%a = icmp sge i32 %nn, %x
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%b = icmp sge i32 %x, 0
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%c = and i1 %a, %b
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ret i1 %c
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}
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; CHECK-LABEL: define i1 @test_or1
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; CHECK: [[R:%[0-9]+]] = icmp ule i32 %nn, %x
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; CHECK: ret i1 [[R]]
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define i1 @test_or1(i32 %x, i32 %n) {
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%nn = and i32 %n, 2147483647
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%a = icmp slt i32 %x, 0
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%b = icmp sge i32 %x, %nn
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%c = or i1 %a, %b
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ret i1 %c
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}
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; CHECK-LABEL: define i1 @test_or2
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; CHECK: [[R:%[0-9]+]] = icmp ult i32 %nn, %x
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; CHECK: ret i1 [[R]]
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define i1 @test_or2(i32 %x, i32 %n) {
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%nn = and i32 %n, 2147483647
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%a = icmp sle i32 %x, -1
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%b = icmp sgt i32 %x, %nn
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%c = or i1 %a, %b
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ret i1 %c
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}
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; CHECK-LABEL: define i1 @test_or3
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; CHECK: [[R:%[0-9]+]] = icmp ule i32 %nn, %x
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; CHECK: ret i1 [[R]]
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define i1 @test_or3(i32 %x, i32 %n) {
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%nn = and i32 %n, 2147483647
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%a = icmp sle i32 %nn, %x
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%b = icmp slt i32 %x, 0
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%c = or i1 %a, %b
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ret i1 %c
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}
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; CHECK-LABEL: define i1 @test_or4
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; CHECK: [[R:%[0-9]+]] = icmp ult i32 %nn, %x
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; CHECK: ret i1 [[R]]
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define i1 @test_or4(i32 %x, i32 %n) {
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%nn = and i32 %n, 2147483647
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%a = icmp slt i32 %nn, %x
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%b = icmp slt i32 %x, 0
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%c = or i1 %a, %b
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ret i1 %c
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}
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; Negative tests
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; CHECK-LABEL: define i1 @negative1
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; CHECK: %a = icmp
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; CHECK: %b = icmp
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; CHECK: %c = and i1 %a, %b
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; CHECK: ret i1 %c
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define i1 @negative1(i32 %x, i32 %n) {
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%nn = and i32 %n, 2147483647
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%a = icmp slt i32 %x, %nn
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%b = icmp sgt i32 %x, 0 ; should be: icmp sge
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%c = and i1 %a, %b
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ret i1 %c
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}
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; CHECK-LABEL: define i1 @negative2
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; CHECK: %a = icmp
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; CHECK: %b = icmp
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; CHECK: %c = and i1 %a, %b
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; CHECK: ret i1 %c
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define i1 @negative2(i32 %x, i32 %n) {
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%a = icmp slt i32 %x, %n ; n can be negative
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%b = icmp sge i32 %x, 0
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%c = and i1 %a, %b
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ret i1 %c
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}
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; CHECK-LABEL: define i1 @negative3
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; CHECK: %a = icmp
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; CHECK: %b = icmp
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; CHECK: %c = and i1 %a, %b
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; CHECK: ret i1 %c
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define i1 @negative3(i32 %x, i32 %y, i32 %n) {
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%nn = and i32 %n, 2147483647
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%a = icmp slt i32 %x, %nn
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%b = icmp sge i32 %y, 0 ; should compare %x and not %y
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%c = and i1 %a, %b
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ret i1 %c
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}
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; CHECK-LABEL: define i1 @negative4
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; CHECK: %a = icmp
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; CHECK: %b = icmp
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; CHECK: %c = and i1 %a, %b
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; CHECK: ret i1 %c
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define i1 @negative4(i32 %x, i32 %n) {
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%nn = and i32 %n, 2147483647
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%a = icmp ne i32 %x, %nn ; should be: icmp slt/sle
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%b = icmp sge i32 %x, 0
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%c = and i1 %a, %b
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ret i1 %c
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}
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; CHECK-LABEL: define i1 @negative5
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; CHECK: %a = icmp
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; CHECK: %b = icmp
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; CHECK: %c = or i1 %a, %b
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; CHECK: ret i1 %c
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define i1 @negative5(i32 %x, i32 %n) {
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%nn = and i32 %n, 2147483647
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%a = icmp slt i32 %x, %nn
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%b = icmp sge i32 %x, 0
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%c = or i1 %a, %b ; should be: and
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ret i1 %c
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}
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