[llvm] [SROA][Target] Add requiresStructuredGEP to TTI (PR #183296)

[Jameson Nash via llvm-commits]

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@@ -4103,18 +4113,25 @@ class AggLoadStoreRewriter : public InstVisitor<AggLoadStoreRewriter, bool> {
 
     LoadOpSplitter(Instruction *InsertionPoint, Value *Ptr, Type *BaseTy,
                    AAMDNodes AATags, Align BaseAlign, const DataLayout &DL,
-                   IRBuilderTy &IRB)
+                   const TargetTransformInfo &TTI, IRBuilderTy &IRB)
         : OpSplitter<LoadOpSplitter>(InsertionPoint, Ptr, BaseTy, BaseAlign, DL,
-                                     IRB),
+                                     TTI, IRB),
           AATags(AATags) {}
 
     /// Emit a leaf load of a single value. This is called at the leaves of the
     /// recursive emission to actually load values.
     void emitFunc(Type *Ty, Value *&Agg, Align Alignment, const Twine &Name) {
       assert(Ty->isSingleValueType());
       // Load the single value and insert it using the indices.
-      Value *GEP =
-          IRB.CreateInBoundsGEP(BaseTy, Ptr, GEPIndices, Name + ".gep");
+      Value *GEP = nullptr;
+      if (TTI.requiresStructuredGEP()) {
+        assert(GEPIndices.size() > 0);
+        llvm::ArrayRef<Value *> SGEPIndices =
+            llvm::ArrayRef<Value *>(GEPIndices).drop_front(1);
+        GEP = IRB.CreateStructuredGEP(BaseTy, Ptr, SGEPIndices, Name + ".gep");
+      } else {
+        GEP = IRB.CreateInBoundsGEP(BaseTy, Ptr, GEPIndices, Name + ".gep");
+      }
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vtjnash wrote:

Since this feels like it will be a fairly common operation, I wonder if this pattern should be added as a helper in IRBuilderBase, if the user explicitly provides both values? With the availability of DataLayout, it is also trivial for IRBuilder to convert a GEP to ptradd and a ptradd to GEP using getElementOffset and getElementContainingOffset (for ptradd with known BaseTy), respectively

https://github.com/llvm/llvm-project/pull/183296