[llvm] [SeparateConstOffsetFromGEP] Reorder trivial GEP chains to separate constants (PR #73056)

[Matt Arsenault via llvm-commits]

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@@ -987,11 +987,50 @@ bool SeparateConstOffsetFromGEP::splitGEP(GetElementPtrInst *GEP) {
   bool NeedsExtraction;
   int64_t AccumulativeByteOffset = accumulateByteOffset(GEP, NeedsExtraction);
 
-  if (!NeedsExtraction)
-    return Changed;
-
   TargetTransformInfo &TTI = GetTTI(*GEP->getFunction());
 
+  if (!NeedsExtraction) {
+    // Attempt to reassociate GEPs for better AddrMode construction.
+    if (auto PtrGEP = dyn_cast<GetElementPtrInst>(GEP->getPointerOperand())) {
+      // TODO: support reordering for non-trivial GEP chains
+      if (PtrGEP->getNumIndices() != 1 || GEP->getNumIndices() != 1)
+        return Changed;
+
+      Type *GEPType = GEP->getResultElementType();
+      Type *PtrGEPType = PtrGEP->getResultElementType();
+      // TODO: support reordering for non-trivial GEP chains
+      if ((PtrGEPType != GEPType) ||
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arsenm wrote:

Remove parentheses around the compare 

https://github.com/llvm/llvm-project/pull/73056