[llvm-branch-commits] [clang] [HLSL] Global resource arrays element access (PR #152454)

[Joshua Batista via llvm-branch-commits]

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@@ -701,3 +808,95 @@ void CGHLSLRuntime::emitInitListOpaqueValues(CodeGenFunction &CGF,
     }
   }
 }
+
+std::optional<LValue> CGHLSLRuntime::emitResourceArraySubscriptExpr(
+    const ArraySubscriptExpr *ArraySubsExpr, CodeGenFunction &CGF) {
+  assert(ArraySubsExpr->getType()->isHLSLResourceRecord() ||
+         ArraySubsExpr->getType()->isHLSLResourceRecordArray() &&
+             "expected resource array subscript expression");
+
+  // let clang codegen handle local resource array subscrips
+  const VarDecl *ArrayDecl = dyn_cast<VarDecl>(getArrayDecl(ArraySubsExpr));
+  if (!ArrayDecl || !ArrayDecl->hasGlobalStorage())
+    return std::nullopt;
+
+  // FIXME: this is not yet implemented (llvm/llvm-project#145426)
+  assert(!ArraySubsExpr->getType()->isArrayType() &&
+         "indexing of array subsets it not supported yet");
+
+  // get total array size (= range size)
+  const Type *ResArrayTy = ArrayDecl->getType().getTypePtr();
+  assert(ResArrayTy->isHLSLResourceRecordArray() &&
+         "expected array of resource classes");
+  llvm::Value *Range =
+      llvm::ConstantInt::get(CGM.IntTy, getTotalArraySize(ResArrayTy));
+
+  // Iterate through all nested array subscript expressions to calculate
+  // the index in the flattened resource array (if this is a multi-
+  // dimensional array). The index is calculated as a sum of all indices
+  // multiplied by the total size of the array at that level.
+  Value *Index = nullptr;
+  Value *Multiplier = nullptr;
+  const ArraySubscriptExpr *ASE = ArraySubsExpr;
+  while (ASE != nullptr) {
+    Value *SubIndex = CGF.EmitScalarExpr(ASE->getIdx());
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bob80905 wrote:

Could SubIndex ever be null?

https://github.com/llvm/llvm-project/pull/152454