[llvm] [InstCombine] Implemented missed optimization in muldivrem (PR #140916)

[Nikita Popov via llvm-commits]

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@@ -1316,6 +1316,15 @@ Instruction *InstCombinerImpl::commonIDivTransforms(BinaryOperator &I) {
     Value *X;
     const APInt *C1;
 
+    // (X mod(C1 *C2)/C2) -> (X/C2) mod(C1)
+    if ((IsSigned && match(Op0, m_SRem(m_Value(X), m_NSWMul(m_APInt(C1), m_APInt(C2))))) ||
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nikic wrote:

This is never going to match anything: The multiply of C1*C2 will fold to a constant. You need to match a constant and then separately check whether that constant is a multiple of the other constant.

https://github.com/llvm/llvm-project/pull/140916