[HLSL] error on out of bounds vector accesses #128952

spall · 2025-02-26T22:40:13Z

Add Sema checking and diagnostics to error on out of bounds vector accesses
Add tests
Closes #91640

llvmbot · 2025-02-27T00:01:05Z

@llvm/pr-subscribers-hlsl

Author: Sarah Spall (spall)

Changes

Add Sema checking and diagnostics to error on out of bounds vector accesses
Warns if language is not HLSL, adds new warning flag -Wvector-out-of-range
Add tests
Closes #91640

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

5 Files Affected:

(modified) clang/include/clang/Basic/DiagnosticGroups.td (+1)
(modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (+6)
(modified) clang/include/clang/Sema/Sema.h (+1)
(modified) clang/lib/Sema/SemaChecking.cpp (+24)
(added) clang/test/SemaHLSL/Language/VectorOutOfRange-errors.hlsl (+19)

diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index 05e39899e6f25..d36f6086edd40 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -930,6 +930,7 @@ def SuperSubClassMismatch : DiagGroup<"super-class-method-mismatch">;
 def OverridingMethodMismatch : DiagGroup<"overriding-method-mismatch">;
 def VariadicMacros : DiagGroup<"variadic-macros">;
 def VectorConversion : DiagGroup<"vector-conversion">;      // clang specific
+def VectorOutOfRange : DiagGroup<"vector-out-of-range">;
 def VexingParse : DiagGroup<"vexing-parse">;
 def VLAUseStaticAssert : DiagGroup<"vla-extension-static-assert">;
 def VLACxxExtension : DiagGroup<"vla-cxx-extension", [VLAUseStaticAssert]>;
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 51301d95e55b9..7ff37406b459a 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -10635,6 +10635,12 @@ 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">,
+  InGroup<VectorOutOfRange>, DefaultIgnore;
+
 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<
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 476abe86cb2d2..fad3cbddc555b 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/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);
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index f9926c6b4adab..1cbf428f18366 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/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());
 
diff --git a/clang/test/SemaHLSL/Language/VectorOutOfRange-errors.hlsl b/clang/test/SemaHLSL/Language/VectorOutOfRange-errors.hlsl
new file mode 100644
index 0000000000000..b4d423fb24bd2
--- /dev/null
+++ b/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}}
+}

llvmbot · 2025-02-27T00:01:06Z

@llvm/pr-subscribers-clang

Author: Sarah Spall (spall)

Changes

Add Sema checking and diagnostics to error on out of bounds vector accesses
Warns if language is not HLSL, adds new warning flag -Wvector-out-of-range
Add tests
Closes #91640

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

5 Files Affected:

(modified) clang/include/clang/Basic/DiagnosticGroups.td (+1)
(modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (+6)
(modified) clang/include/clang/Sema/Sema.h (+1)
(modified) clang/lib/Sema/SemaChecking.cpp (+24)
(added) clang/test/SemaHLSL/Language/VectorOutOfRange-errors.hlsl (+19)

diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index 05e39899e6f25..d36f6086edd40 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -930,6 +930,7 @@ def SuperSubClassMismatch : DiagGroup<"super-class-method-mismatch">;
 def OverridingMethodMismatch : DiagGroup<"overriding-method-mismatch">;
 def VariadicMacros : DiagGroup<"variadic-macros">;
 def VectorConversion : DiagGroup<"vector-conversion">;      // clang specific
+def VectorOutOfRange : DiagGroup<"vector-out-of-range">;
 def VexingParse : DiagGroup<"vexing-parse">;
 def VLAUseStaticAssert : DiagGroup<"vla-extension-static-assert">;
 def VLACxxExtension : DiagGroup<"vla-cxx-extension", [VLAUseStaticAssert]>;
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 51301d95e55b9..7ff37406b459a 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -10635,6 +10635,12 @@ 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">,
+  InGroup<VectorOutOfRange>, DefaultIgnore;
+
 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<
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 476abe86cb2d2..fad3cbddc555b 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/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);
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index f9926c6b4adab..1cbf428f18366 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/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());
 
diff --git a/clang/test/SemaHLSL/Language/VectorOutOfRange-errors.hlsl b/clang/test/SemaHLSL/Language/VectorOutOfRange-errors.hlsl
new file mode 100644
index 0000000000000..b4d423fb24bd2
--- /dev/null
+++ b/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}}
+}

clang/include/clang/Basic/DiagnosticSemaKinds.td

clang/lib/Sema/SemaChecking.cpp

clang/include/clang/Basic/DiagnosticSemaKinds.td

Co-authored-by: Chris B <[email protected]>

hekota

LGTM!

AaronBallman

Please also add a release note to clang/docs/ReleaseNotes.rst so users know about the improvement.

clang/lib/Sema/SemaChecking.cpp

Co-authored-by: Aaron Ballman <[email protected]>

spall · 2025-03-10T16:56:36Z

The latest commits make it an error for all, add a release note, and modify a test which had an out of bounds vector access.

llvm-beanz

One suggestion of different wording on the release note, but otherwise LGTM.

clang/docs/ReleaseNotes.rst

Co-authored-by: Chris B <[email protected]>

hekota

LGTM!

zmodem · 2025-03-12T11:31:06Z

This broke our builds. Here's a small repro:

$ cat /tmp/a.cc
#include <immintrin.h>
__m256i parens;
int f() {
  return ((__v32qi)parens)[31];
}
$ build/bin/clang -c /tmp/a.cc
/tmp/a.cc:4:20: error: vector element index 31 is out of bounds
    4 |   return ((__v32qi)parens)[31];
      |                    ^
1 error generated.

__v32qi is a 32-element vector of char.

I'll revert to green for now.

This caused false-positive errors, see comment on the PR. > Add Sema checking and diagnostics to error on out of bounds vector > accesses > Add tests > Closes #91640 This reverts commit f1e3675.

efriedma-quic · 2025-03-19T21:06:26Z

clang/lib/Sema/SemaChecking.cpp

+    return;
+
+  Expr::EvalResult Result;
+  if (!IndexExpr->EvaluateAsInt(Result, Context, Expr::SE_AllowSideEffects))


Generally, if a value is not required to be a constant, we don't want different semantic rules depending on whether the value is in fact constant. (There are a few places that do in fact work like this, like array bounds, but it causes weird results. Especially when people do stuff with macros.) So I don't think we want to reject here.

A DiagRuntimeBehavior() is probably appropriate, though.

spall added 2 commits February 26, 2025 14:38

error on out of bounds vector accesses

656d6e8

add warning flag for vector out of bounds warning. fix test

f44e697

spall marked this pull request as ready for review February 27, 2025 00:00

llvmbot added clang Clang issues not falling into any other category clang:frontend Language frontend issues, e.g. anything involving "Sema" HLSL HLSL Language Support labels Feb 27, 2025

joaosaffran reviewed Feb 27, 2025

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spall and others added 2 commits February 27, 2025 07:36

Update clang/include/clang/Basic/DiagnosticSemaKinds.td

8449ac1

Co-authored-by: Chris B <[email protected]>

make new warning not ignored by default

14f60af

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spall and others added 3 commits March 4, 2025 14:19

Update clang/lib/Sema/SemaChecking.cpp

8488243

Co-authored-by: Aaron Ballman <[email protected]>

remove warning and always error

2fa2c72

release note

7ef3654

llvm-beanz approved these changes Mar 10, 2025

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spall and others added 2 commits March 10, 2025 13:01

Update clang/docs/ReleaseNotes.rst

d49eb7c

Co-authored-by: Chris B <[email protected]>

Merge branch 'main' into issue-91640

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spall merged commit f1e3675 into llvm:main Mar 11, 2025
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[HLSL] error on out of bounds vector accesses #128952

[HLSL] error on out of bounds vector accesses #128952

spall commented Feb 26, 2025 •

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[HLSL] error on out of bounds vector accesses #128952

[HLSL] error on out of bounds vector accesses #128952

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