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

[Sarah Spall 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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spall wrote:

There is a test which is meant to prevent new enabled by default warnings; Misc/warning-flags.c, which gives the impression that new by default warnings are not allowed. Or I'm misunderstanding what a default warning is. 

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