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Make instsimplify's analysis of icmp eq/ne use computeKnownBits to determine whether the icmp is always true or false. Patch by Suyog Sarda!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211251 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -2241,6 +2241,25 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
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}
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}
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// If a bit is known to be zero for A and known to be one for B,
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// then A and B cannot be equal.
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if (ICmpInst::isEquality(Pred)) {
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if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
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uint32_t BitWidth = CI->getBitWidth();
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APInt LHSKnownZero(BitWidth, 0);
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APInt LHSKnownOne(BitWidth, 0);
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computeKnownBits(LHS, LHSKnownZero, LHSKnownOne);
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APInt RHSKnownZero(BitWidth, 0);
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APInt RHSKnownOne(BitWidth, 0);
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computeKnownBits(RHS, RHSKnownZero, RHSKnownOne);
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if (((LHSKnownOne & RHSKnownZero) != 0) ||
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((LHSKnownZero & RHSKnownOne) != 0))
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return (Pred == ICmpInst::ICMP_EQ)
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? ConstantInt::getFalse(CI->getContext())
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: ConstantInt::getTrue(CI->getContext());
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}
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}
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// Special logic for binary operators.
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BinaryOperator *LBO = dyn_cast<BinaryOperator>(LHS);
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BinaryOperator *RBO = dyn_cast<BinaryOperator>(RHS);
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@ -31,7 +31,7 @@ bb1:
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store <2 x double><double 0.0, double 0.0>, <2 x double>* %r, align 8
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%indvar.next = add i64 %j, 2
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%exitcond = icmp eq i64 %indvar.next, 557
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%exitcond = icmp eq i64 %indvar.next, 556
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br i1 %exitcond, label %bb11, label %bb1
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bb11:
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@ -883,3 +883,22 @@ define i1 @returns_nonnull() {
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; CHECK: ret i1 false
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}
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; If a bit is known to be zero for A and known to be one for B,
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; then A and B cannot be equal.
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define i1 @icmp_eq_const(i32 %a) nounwind {
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%b = mul nsw i32 %a, -2
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%c = icmp eq i32 %b, 1
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ret i1 %c
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; CHECK-LABEL: @icmp_eq_const
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; CHECK-NEXT: ret i1 false
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}
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define i1 @icmp_ne_const(i32 %a) nounwind {
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%b = mul nsw i32 %a, -2
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%c = icmp ne i32 %b, 1
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ret i1 %c
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; CHECK-LABEL: @icmp_ne_const
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; CHECK-NEXT: ret i1 true
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}
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