[llvm] [InstCombine] Fold `ceil(X / (2 ^ C)) == 0` -> `X == 0` (PR #143683)
Yingwei Zheng via llvm-commits
llvm-commits at lists.llvm.org
Fri Jun 13 03:26:07 PDT 2025
================
@@ -1298,6 +1299,23 @@ Instruction *InstCombinerImpl::foldICmpWithZero(ICmpInst &Cmp) {
// eq/ne (mul X, Y)) with (icmp eq/ne X/Y) and if X/Y is known non-zero that
// will fold to a constant elsewhere.
}
+
+ // (X >> C) + ((X & ((1 << C) - 1)) != 0) == 0 -> X == 0
+ if (Pred == ICmpInst::ICMP_EQ) {
+ Value *X;
+ const APInt *C1, *C2;
+ CmpPredicate PredNE;
+ if (match(Cmp.getOperand(0),
+ m_OneUse(
+ m_Add(m_LShr(m_Value(X), m_APInt(C1)),
+ m_ZExt(m_ICmp(PredNE, m_And(m_Deferred(X), m_APInt(C2)),
----------------
dtcxzyw wrote:
```suggestion
m_ZExt(m_SpecificICmp(ICmpInst::ICMP_NE, m_And(m_Deferred(X), m_APInt(C2)),
```
https://github.com/llvm/llvm-project/pull/143683
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