================
@@ -6309,7 +6309,69 @@ Instruction
*InstCombinerImpl::foldICmpUsingBoolRange(ICmpInst &I) {
Y->getType()->isIntOrIntVectorTy(1) && Pred == ICmpInst::ICMP_ULE)
return BinaryOperator::CreateOr(Builder.CreateIsNull(X), Y);
+ ICmpInst::Predicate Pred1, Pred2;
const APInt *C;
+ // icmp eq/ne X, (zext (icmp eq/ne X, C))
+ if (match(&I, m_c_ICmp(Pred1, m_Value(X),
+ m_ZExt(m_ICmp(Pred2, m_Deferred(X), m_APInt(C))))) &&
+ ICmpInst::isEquality(Pred1) && ICmpInst::isEquality(Pred2)) {
+ if (C->isZero()) {
+ if (Pred2 == ICmpInst::ICMP_EQ) {
+ // icmp eq X, (zext (icmp eq X, 0)) --> false
+ // icmp ne X, (zext (icmp eq X, 0)) --> true
+ return replaceInstUsesWith(
+ I,
+ Constant::getIntegerValue(
+ I.getType(),
+ APInt(1U, static_cast<uint64_t>(Pred1 == ICmpInst::ICMP_NE))));
+ } else {
+ // icmp eq X, (zext (icmp ne X, 0)) --> icmp ult X, 2
+ // icmp ne X, (zext (icmp ne X, 0)) --> icmp ugt X, 1
+ return ICmpInst::Create(
+ Instruction::ICmp,
+ Pred1 == ICmpInst::ICMP_NE ? ICmpInst::ICMP_UGT
+ : ICmpInst::ICMP_ULT,
+ X,
+ Constant::getIntegerValue(
+ X->getType(), APInt(X->getType()->getScalarSizeInBits(),
+ Pred1 == ICmpInst::ICMP_NE ? 1 : 2)));
+ }
+ } else if (C->isOne()) {
+ if (Pred2 == ICmpInst::ICMP_NE) {
+ // icmp eq X, (zext (icmp ne X, 1)) --> false
+ // icmp ne X, (zext (icmp ne X, 1)) --> true
+ return replaceInstUsesWith(
+ I,
+ Constant::getIntegerValue(
+ I.getType(),
+ APInt(1U, static_cast<uint64_t>(Pred1 == ICmpInst::ICMP_NE))));
+ } else {
+ // icmp eq X, (zext (icmp eq X, 1)) --> icmp ult X, 2
+ // icmp ne X, (zext (icmp eq X, 1)) --> icmp ugt X, 1
+ return ICmpInst::Create(
+ Instruction::ICmp,
+ Pred1 == ICmpInst::ICMP_NE ? ICmpInst::ICMP_UGT
+ : ICmpInst::ICMP_ULT,
+ X,
+ Constant::getIntegerValue(
+ X->getType(), APInt(X->getType()->getScalarSizeInBits(),
+ Pred1 == ICmpInst::ICMP_NE ? 1 : 2)));
+ }
+ } else {
+ // C != 0 && C != 1
+ // icmp eq X, (zext (icmp eq X, C)) --> icmp eq X, 0
+ // icmp eq X, (zext (icmp ne X, C)) --> icmp eq X, 1
+ // icmp ne X, (zext (icmp eq X, C)) --> icmp ne X, 0
+ // icmp ne X, (zext (icmp ne X, C)) --> icmp ne X, 1
+ return ICmpInst::Create(
+ Instruction::ICmp, Pred1, X,
+ Constant::getIntegerValue(
+ X->getType(),
+ APInt(X->getType()->getScalarSizeInBits(),
+ static_cast<uint64_t>(Pred2 == ICmpInst::ICMP_NE))));
+ }
+ }
+
----------------
nikic wrote:
My thought here was to do something along the lines of `a pred1 zext(a pred2
c)` to `a pred2 c ? (a pred1 1) : (a pred1 0)` and then check whether `a pred2
c` implies `a pred1 1` is true/false or `a !pred2 c` implies `a pred1 0` is
true/false. The remaining two comparisons will then get simplified based on
and/or of icmps.
But I don't know whether this will handle all cases, and maybe the code will be
more complex overall than listing all special cases.
https://github.com/llvm/llvm-project/pull/65852
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