[llvm] [InstCombine] Fold `min(X+1, Y) - min(X, Y) --> zext X < Y` (PR #157782)

via llvm-commits llvm-commits at lists.llvm.org
Thu Sep 11 11:48:04 PDT 2025


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@@ -2731,6 +2731,24 @@ Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) {
     return BinaryOperator::CreateSub(X, Not);
   }
 
+  // min(X+1, Y) - min(X, Y) --> zext X < Y
+  // Replacing a sub and at least one min with an icmp
+  // and a zext is a potential improvement.
+  if (match(Op0, m_c_SMin(m_c_NSWAdd(m_Value(X), m_One()), m_Value(Y))) &&
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benwu25 wrote:

Updated to use `m_NSWAddLike` and added a test.

https://github.com/llvm/llvm-project/pull/157782


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