[llvm] [InstCombine] fold `sub(zext(ptrtoint), zext(ptrtoint))` (PR #115369)

[Yingwei Zheng via llvm-commits]

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@@ -2631,6 +2631,21 @@ Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) {
                                                /* IsNUW */ false))
       return replaceInstUsesWith(I, Res);
 
+  if (match(Op0, m_ZExt(m_PtrToInt(m_Value(LHSOp)))) &&
+      match(Op1, m_ZExtOrSelf(m_PtrToInt(m_Value(RHSOp))))) {
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dtcxzyw wrote:

> The pattern-matching replaces only subtract with an offset

`EmitGEPOffset` generates additional instructions.


https://github.com/llvm/llvm-project/pull/115369