error on out of bounds vector accesses

Author: spall

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -10635,6 +10635,11 @@ def err_block_on_vm : Error<
 def err_sizeless_nonlocal : Error<
   "non-local variable with sizeless type %0">;
 
+def err_vector_index_out_of_range : Error<
+  "vector element index %0 is out of bounds">;
+def warn_vector_index_out_of_range : Warning<
+  "vector element index %0 is out of bounds">;
+
 def err_vec_builtin_non_vector : Error<
  "%select{first two|all}1 arguments to %0 must be vectors">;
 def err_vec_builtin_incompatible_vector : Error<

clang/include/clang/Sema/Sema.h

@@ -2468,6 +2468,7 @@ class Sema final : public SemaBase {
                         const ArraySubscriptExpr *ASE = nullptr,
                         bool AllowOnePastEnd = true, bool IndexNegated = false);
   void CheckArrayAccess(const Expr *E);
+  void CheckVectorAccess(const Expr *BaseExpr, const Expr *IndexExpr);
 
   bool CheckPointerCall(NamedDecl *NDecl, CallExpr *TheCall,
                         const FunctionProtoType *Proto);

clang/lib/Sema/SemaChecking.cpp

@@ -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;
+
+  llvm::APSInt index = Result.Val.getInt();
+  if (index.isNegative() || index >= VTy->getNumElements())
+    Diag(BaseExpr->getBeginLoc(), DiagID) << toString(index, 10, true);
+  return;
+}
+
 void Sema::CheckArrayAccess(const Expr *BaseExpr, const Expr *IndexExpr,
                             const ArraySubscriptExpr *ASE,
                             bool AllowOnePastEnd, bool IndexNegated) {
@@ -14031,6 +14049,12 @@ void Sema::CheckArrayAccess(const Expr *BaseExpr, const Expr *IndexExpr,
   const Type *EffectiveType =
       BaseExpr->getType()->getPointeeOrArrayElementType();
   BaseExpr = BaseExpr->IgnoreParenCasts();
+
+  if (BaseExpr->getType()->isVectorType()) {
+    CheckVectorAccess(BaseExpr, IndexExpr);
+    return;
+  }
+
   const ConstantArrayType *ArrayTy =
       Context.getAsConstantArrayType(BaseExpr->getType());
 

clang/test/SemaHLSL/Language/VectorOutOfRange-errors.hlsl

@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -finclude-default-header -triple dxil-pc-shadermodel6.6-library %s -verify
+
+export void fn1() {
+  int2 A = {1,2};
+  int X = A[-1];
+  // expected-error@-1 {{vector element index '-1' is out of bounds}}
+}
+
+export void fn2() {
+  int4 A = {1,2,3,4};
+  int X = A[4];
+  // expected-error@-1 {{vector element index '4' is out of bounds}}
+}
+
+export void fn3() {
+  bool2 A = {true,true};
+  bool X = A[-1];
+  // expected-error@-1 {{vector element index '-1' is out of bounds}}
+}