[polly] [InstCombine] Canonicalise SextADD + GEP (PR #69581)

[Nikita Popov via llvm-commits]

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@@ -2335,6 +2335,28 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
       return GetElementPtrInst::Create(GEP.getResultElementType(), NewPtr,
                                        Idx2);
     }
+
+    Value *SIdx;
+    if (auto *SextInst = dyn_cast<SExtInst>(GEP.getOperand(1))) {
+      if (auto *AddInst = dyn_cast<BinaryOperator>(SextInst->getOperand(0))) {
+        if (match(GEP.getOperand(1), m_OneUse(m_SExt(m_Value(SIdx)))) &&
+            match(SextInst->getOperand(0),
+                  m_OneUse(m_Add(m_Value(Idx1), m_Value(Idx2)))) &&
+            hasNoSignedWrap(*AddInst)) {
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nikic wrote:

Should do something like `if (match(GEP.getOperand(1), m_OneUse(m_SExt(m_OneUse(m_NSWAdd(m_Value(Idx1), m_Value(Idx2))))))` here.

https://github.com/llvm/llvm-project/pull/69581