[llvm] [InstCombine] Add support for ptrtoaddr in pointer difference folds (PR #164428)

[Nikita Popov via llvm-commits]

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@@ -2760,21 +2760,21 @@ Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) {
   // Optimize pointer differences into the same array into a size.  Consider:
   //  &A[10] - &A[0]: we should compile this to "10".
   Value *LHSOp, *RHSOp;
-  if (match(Op0, m_PtrToInt(m_Value(LHSOp))) &&
-      match(Op1, m_PtrToInt(m_Value(RHSOp))))
+  if (match(Op0, m_PtrToIntOrAddr(m_Value(LHSOp))) &&
+      match(Op1, m_PtrToIntOrAddr(m_Value(RHSOp))))
     if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType(),
                                                I.hasNoUnsignedWrap()))
       return replaceInstUsesWith(I, Res);
 
   // trunc(p)-trunc(q) -> trunc(p-q)
-  if (match(Op0, m_Trunc(m_PtrToInt(m_Value(LHSOp)))) &&
-      match(Op1, m_Trunc(m_PtrToInt(m_Value(RHSOp)))))
+  if (match(Op0, m_Trunc(m_PtrToIntOrAddr(m_Value(LHSOp)))) &&
+      match(Op1, m_Trunc(m_PtrToIntOrAddr(m_Value(RHSOp)))))
     if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType(),
                                                /* IsNUW */ false))
       return replaceInstUsesWith(I, Res);
 
-  if (match(Op0, m_ZExt(m_PtrToIntSameSize(DL, m_Value(LHSOp)))) &&
-      match(Op1, m_ZExtOrSelf(m_PtrToInt(m_Value(RHSOp))))) {
+  if (match(Op0, m_ZExt(m_PtrToIntOrAddr_GEAddrSize(DL, m_Value(LHSOp)))) &&
+      match(Op1, m_ZExtOrSelf(m_PtrToIntOrAddr(m_Value(RHSOp))))) {
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nikic wrote:

No, there was a pre-existing correctness issue here. I've decided to drop the m_PtrToIntOrAddr_GEAddrSize matcher for this patch and instead match the three cases explicitly.

This transform handles an annoying special case with constant expression ptrtoints, and it's best to match it separately, because it's the only case where the we're actually interested in a non-canonical ptrtoint.

https://github.com/llvm/llvm-project/pull/164428