[clang] [HLSL] Add internal linkage attribute to resources (PR #166844)

[Helena Kotas via cfe-commits]

https://github.com/hekota created https://github.com/llvm/llvm-project/pull/166844

HLSL resources should not be externally visible from the module. We made sure of this by marking them `static` as soon as they were declared. However, this prevents us fixing issue #166458 because there is no way to know if a resource has been explicitly marked `static` by the user, and can therefore be assigned to.

This change is moves from making all resources `static` to adding Clang internal linkage attribute to all non-static resource declarations as a global scope.

No explicit test added this change. There is a number of existing HLSL codegen tests that already verify that the resource globals are emitted as `internal global`.

>From 883df7bce01ddaedd133813b7e79397b974e6835 Mon Sep 17 00:00:00 2001
From: Helena Kotas <hekotas at microsoft.com>
Date: Thu, 6 Nov 2025 12:37:29 -0800
Subject: [PATCH] [HLSL] Add internal linkage attribute to resources

HLSL resources should not be externally visible from the module.
We made sure of this by marking them `static` as soon as they were declared.
However, this prevents us fixing issue #166458 because there is no way
to know if a resource has been explicitly marked `static`
by the user, and can therefore be assigned to.

This change is moves from making all resources `static` to adding Clang internal
linkage attribute to all non-static resource declarations as a global scope.
Existing tests verify that there is no change in how the resource globals are
emitted: `internal global`.
---
 clang/lib/Sema/SemaHLSL.cpp      | 13 ++++++++-----
 clang/test/AST/HLSL/cbuffer.hlsl |  2 +-
 clang/test/AST/HLSL/private.hlsl |  2 +-
 3 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/clang/lib/Sema/SemaHLSL.cpp b/clang/lib/Sema/SemaHLSL.cpp
index a06c57b15c585..e95fe16e6cb6c 100644
--- a/clang/lib/Sema/SemaHLSL.cpp
+++ b/clang/lib/Sema/SemaHLSL.cpp
@@ -3910,12 +3910,15 @@ void SemaHLSL::ActOnVariableDeclarator(VarDecl *VD) {
     if (VD->getType()->isHLSLIntangibleType())
       collectResourceBindingsOnVarDecl(VD);
 
-    if (isResourceRecordTypeOrArrayOf(VD) ||
-        VD->hasAttr<HLSLVkConstantIdAttr>()) {
-      // Make the variable for resources static. The global externally visible
-      // storage is accessed through the handle, which is a member. The variable
-      // itself is not externally visible.
+    if (VD->hasAttr<HLSLVkConstantIdAttr>())
       VD->setStorageClass(StorageClass::SC_Static);
+
+    if (isResourceRecordTypeOrArrayOf(VD) &&
+        VD->getStorageClass() != SC_Static) {
+      // Add internal linkage attribute to non-static resource variables. The
+      // global externally visible storage is accessed through the handle, which
+      // is a member. The variable itself is not externally visible.
+      VD->addAttr(InternalLinkageAttr::CreateImplicit(getASTContext()));
     }
 
     // process explicit bindings
diff --git a/clang/test/AST/HLSL/cbuffer.hlsl b/clang/test/AST/HLSL/cbuffer.hlsl
index f3c6636232798..b0b5b989e36c2 100644
--- a/clang/test/AST/HLSL/cbuffer.hlsl
+++ b/clang/test/AST/HLSL/cbuffer.hlsl
@@ -153,7 +153,7 @@ cbuffer CB {
   static float SV;
   // CHECK: VarDecl {{.*}} s7 'EmptyStruct' callinit
   EmptyStruct s7;
-  // CHECK: VarDecl {{.*}} Buf 'RWBuffer<float>':'hlsl::RWBuffer<float>' static callinit
+  // CHECK: VarDecl {{.*}} Buf 'RWBuffer<float>':'hlsl::RWBuffer<float>' callinit
   RWBuffer<float> Buf;
   // CHECK: VarDecl {{.*}} ea 'EmptyArrayTypedef':'float[10][0]'
   EmptyArrayTypedef ea;
diff --git a/clang/test/AST/HLSL/private.hlsl b/clang/test/AST/HLSL/private.hlsl
index e00afb8f5cbd8..ba7380ec3cfda 100644
--- a/clang/test/AST/HLSL/private.hlsl
+++ b/clang/test/AST/HLSL/private.hlsl
@@ -3,7 +3,7 @@
 // CHECK: VarDecl {{.*}} global_scalar 'hlsl_private int' static cinit
 static int global_scalar = 0;
 
-// CHECK: VarDecl {{.*}} global_buffer 'RWBuffer<float>':'hlsl::RWBuffer<float>' static callinit
+// CHECK: VarDecl {{.*}} global_buffer 'RWBuffer<float>':'hlsl::RWBuffer<float>' callinit
 RWBuffer<float> global_buffer;
 
 class A {