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InstSimplify: Optimize signed icmp of -(zext V)
Summary: We know that -(zext V) will always be <= zero, simplify signed icmps that have these. Uncovered using http://www.cs.utah.edu/~regehr/souper/ Reviewers: nicholas Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D3754 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208809 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -2280,6 +2280,28 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
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}
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}
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// 0 - (zext X) pred C
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if (!CmpInst::isUnsigned(Pred) && match(LHS, m_Neg(m_ZExt(m_Value())))) {
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if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) {
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if (RHSC->getValue().isStrictlyPositive()) {
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if (Pred == ICmpInst::ICMP_SLT)
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return ConstantInt::getTrue(RHSC->getContext());
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if (Pred == ICmpInst::ICMP_SGE)
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return ConstantInt::getFalse(RHSC->getContext());
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if (Pred == ICmpInst::ICMP_EQ)
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return ConstantInt::getFalse(RHSC->getContext());
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if (Pred == ICmpInst::ICMP_NE)
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return ConstantInt::getTrue(RHSC->getContext());
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}
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if (RHSC->getValue().isNonNegative()) {
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if (Pred == ICmpInst::ICMP_SLE)
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return ConstantInt::getTrue(RHSC->getContext());
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if (Pred == ICmpInst::ICMP_SGT)
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return ConstantInt::getFalse(RHSC->getContext());
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}
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}
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}
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// icmp pred (urem X, Y), Y
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if (LBO && match(LBO, m_URem(m_Value(), m_Specific(RHS)))) {
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bool KnownNonNegative, KnownNegative;
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@ -757,3 +757,63 @@ define <4 x i8> @vectorselectfold2(<4 x i8> %a, <4 x i8> %b) {
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; CHECK-LABEL: @vectorselectfold
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; CHECK-NEXT: ret <4 x i8> %a
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}
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define i1 @compare_always_true_slt(i16 %a) {
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%1 = zext i16 %a to i32
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%2 = sub nsw i32 0, %1
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%3 = icmp slt i32 %2, 1
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ret i1 %3
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; CHECK-LABEL: @compare_always_true_slt
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; CHECK-NEXT: ret i1 true
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}
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define i1 @compare_always_true_sle(i16 %a) {
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%1 = zext i16 %a to i32
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%2 = sub nsw i32 0, %1
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%3 = icmp sle i32 %2, 0
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ret i1 %3
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; CHECK-LABEL: @compare_always_true_sle
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; CHECK-NEXT: ret i1 true
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}
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define i1 @compare_always_false_sgt(i16 %a) {
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%1 = zext i16 %a to i32
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%2 = sub nsw i32 0, %1
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%3 = icmp sgt i32 %2, 0
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ret i1 %3
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; CHECK-LABEL: @compare_always_false_sgt
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; CHECK-NEXT: ret i1 false
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}
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define i1 @compare_always_false_sge(i16 %a) {
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%1 = zext i16 %a to i32
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%2 = sub nsw i32 0, %1
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%3 = icmp sge i32 %2, 1
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ret i1 %3
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; CHECK-LABEL: @compare_always_false_sge
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; CHECK-NEXT: ret i1 false
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}
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define i1 @compare_always_false_eq(i16 %a) {
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%1 = zext i16 %a to i32
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%2 = sub nsw i32 0, %1
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%3 = icmp eq i32 %2, 1
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ret i1 %3
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; CHECK-LABEL: @compare_always_false_eq
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; CHECK-NEXT: ret i1 false
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}
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define i1 @compare_always_false_ne(i16 %a) {
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%1 = zext i16 %a to i32
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%2 = sub nsw i32 0, %1
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%3 = icmp ne i32 %2, 1
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ret i1 %3
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; CHECK-LABEL: @compare_always_false_ne
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; CHECK-NEXT: ret i1 true
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}
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