[llvm] [InstCombine] Combine and->cmp->sel->or-disjoint into and->mul (PR #135274)

[Yingwei Zheng via llvm-commits]

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@@ -95,24 +95,28 @@ namespace llvm {
   /// Represents the operation icmp (X & Mask) pred C, where pred can only be
   /// eq or ne.
   struct DecomposedBitTest {
-    Value *X;
+    Value *X = nullptr;
     CmpInst::Predicate Pred;
     APInt Mask;
     APInt C;
   };
 
   /// Decompose an icmp into the form ((X & Mask) pred C) if possible.
-  /// Unless \p AllowNonZeroC is true, C will always be 0.
+  /// Unless \p AllowNonZeroC is true, C will always be 0. If \p
+  /// DecomposeBitMask is specified, then, for equality predicates, this will
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dtcxzyw wrote:

I recommend landing this change separately. Then we can remove duplicate logic in other places.
https://github.com/llvm/llvm-project/blob/3ed83630b263f667bacd1ef1a65f26d8665c282e/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp#L873-L895
https://github.com/llvm/llvm-project/blob/3ed83630b263f667bacd1ef1a65f26d8665c282e/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp#L2755-L2787
https://github.com/llvm/llvm-project/blob/3ed83630b263f667bacd1ef1a65f26d8665c282e/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp#L3732-L3765



https://github.com/llvm/llvm-project/pull/135274