[llvm] [InstCombine] Make the `(icmp eq/ne (and X, Y), X)` canonicalization work for non-const operands (PR #84688)

[Yingwei Zheng via llvm-commits]

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@@ -4709,6 +4709,26 @@ static Instruction *foldICmpAndXX(ICmpInst &I, const SimplifyQuery &Q,
   if (Pred == ICmpInst::ICMP_UGE)
     return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
 
+  if (ICmpInst::isEquality(Pred) && Op0->hasOneUse()) {
+    // icmp (X & Y) eq/ne Y --> (X | ~Y) eq/ne -1 if Y is freely invertible and
+    // Y is non-constant. If Y is constant this form is preferable (and
+    // canonicalize too it elsewhere).
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dtcxzyw wrote:

Can you explain this?


https://github.com/llvm/llvm-project/pull/84688