[clang] [HLSL] error on out of bounds vector accesses (PR #128952)

[Chris B via cfe-commits]

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@@ -14017,6 +14017,24 @@ void Sema::CheckCastAlign(Expr *Op, QualType T, SourceRange TRange) {
     << TRange << Op->getSourceRange();
 }
 
+void Sema::CheckVectorAccess(const Expr *BaseExpr, const Expr *IndexExpr) {
+  const VectorType *VTy = BaseExpr->getType()->getAs<VectorType>();
+  if (!VTy)
+    return;
+
+  Expr::EvalResult Result;
+  if (!IndexExpr->EvaluateAsInt(Result, Context, Expr::SE_AllowSideEffects))
+    return;
+
+  unsigned DiagID = getLangOpts().HLSL ? diag::err_vector_index_out_of_range
+                                       : diag::warn_vector_index_out_of_range;
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llvm-beanz wrote:

@svenvh are you okay with this becoming an error for OpenCL?

If we make it an error everywhere that would simplify this patch. I had mostly thought to make it a warning to avoid disrupting users, but this is a case where it would 100% be an out-of-bounds access unless the generated code happens to get optimized away.

The vector element access expressions already error on out of bounds element accessors for all languages, so this probably isn't too far out of reasonable expectations.

https://github.com/llvm/llvm-project/pull/128952