[clang] [Clang][HLSL] Start emitting structured GEP instruction (PR #177332)

[Nathan Gauër via cfe-commits]

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@@ -5521,6 +5545,14 @@ static Address emitAddrOfFieldStorage(CodeGenFunction &CGF, Address base,
 
   unsigned idx =
     CGF.CGM.getTypes().getCGRecordLayout(rec).getLLVMFieldNo(field);
+  llvm::Type *StructType =
+      CGF.CGM.getTypes().getCGRecordLayout(rec).getLLVMType();
+
+  if (CGF.getLangOpts().HLSL && CGF.getLangOpts().EmitStructuredGEP)
+    return RawAddress(
+        CGF.Builder.CreateStructuredGEP(StructType, base.emitRawPointer(CGF),
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Keenuts wrote:

I'm afraid doing this would cause issues on more complex codes: the SGEP gives us some guarantees around what optimizations can do. Emitting a GEP instead will allow optimizations to merge those and do normal pointer arithmetic. Seems to me that the simplest approach is to always emit. But maybe we'll see in the future that in some cases we can emit a GEP.

https://github.com/llvm/llvm-project/pull/177332