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Improve constant folding of undef for cmp and select operators.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134223 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -2204,15 +2204,15 @@ Value *llvm::SimplifySelectInst(Value *CondVal, Value *TrueVal, Value *FalseVal,
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if (TrueVal == FalseVal)
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if (TrueVal == FalseVal)
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return TrueVal;
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return TrueVal;
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if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X
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return FalseVal;
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if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X
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return TrueVal;
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if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y
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if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y
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if (isa<Constant>(TrueVal))
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if (isa<Constant>(TrueVal))
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return TrueVal;
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return TrueVal;
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return FalseVal;
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return FalseVal;
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}
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}
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if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X
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return FalseVal;
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if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X
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return TrueVal;
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return 0;
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return 0;
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}
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}
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@ -730,9 +730,12 @@ Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond,
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}
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}
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if (isa<UndefValue>(Cond)) {
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if (isa<UndefValue>(V1)) return V1;
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return V2;
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}
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if (isa<UndefValue>(V1)) return V2;
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if (isa<UndefValue>(V1)) return V2;
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if (isa<UndefValue>(V2)) return V1;
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if (isa<UndefValue>(V2)) return V1;
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if (isa<UndefValue>(Cond)) return V1;
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if (V1 == V2) return V1;
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if (V1 == V2) return V1;
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if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) {
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if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) {
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@ -1851,7 +1854,9 @@ Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
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if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
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if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
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// For EQ and NE, we can always pick a value for the undef to make the
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// For EQ and NE, we can always pick a value for the undef to make the
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// predicate pass or fail, so we can return undef.
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// predicate pass or fail, so we can return undef.
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if (ICmpInst::isEquality(ICmpInst::Predicate(pred)))
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// Also, if both operands are undef, we can return undef.
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if (ICmpInst::isEquality(ICmpInst::Predicate(pred)) ||
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(isa<UndefValue>(C1) && isa<UndefValue>(C2)))
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return UndefValue::get(ResultTy);
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return UndefValue::get(ResultTy);
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// Otherwise, pick the same value as the non-undef operand, and fold
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// Otherwise, pick the same value as the non-undef operand, and fold
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// it to true or false.
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// it to true or false.
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@ -97,3 +97,31 @@ define i64 @test13() {
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%r = lshr i64 undef, undef
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%r = lshr i64 undef, undef
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ret i64 %r
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ret i64 %r
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}
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}
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; @test14
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; CHECK: ret i1 undef
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define i1 @test14() {
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%r = icmp slt i64 undef, undef
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ret i1 %r
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}
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; @test15
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; CHECK: ret i1 undef
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define i1 @test15() {
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%r = icmp ult i64 undef, undef
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ret i1 %r
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}
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; @test16
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; CHECK: ret i64 undef
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define i64 @test16(i64 %a) {
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%r = select i1 undef, i64 %a, i64 undef
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ret i64 %r
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}
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; @test17
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; CHECK: ret i64 undef
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define i64 @test17(i64 %a) {
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%r = select i1 undef, i64 undef, i64 %a
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ret i64 %r
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}
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