From e9615c14ce8f4f598c975bff6cfb6b5b8784a73b Mon Sep 17 00:00:00 2001
From: Chris Bieneman <cbieneman@microsoft.com>
Date: Mon, 21 Sep 2026 22:43:46 -0500
Subject: [PATCH] [202x] Fix nesting cbuffers in namespaces

This is a long-standing bug in DXC, but in HLSL 202x since we're
addressing a bunch of other issues around cbuffer/tbuffer semantics we
also will address this here.

With this change declarations placed inside a cbuffer are targeted to
the enclosing declaration context which must be either a namespace or
the top-level translation unit declaration context.
---
 docs/ReleaseNotes.md                          |  2 ++
 tools/clang/lib/Sema/SemaHLSL.cpp             |  3 ++
 .../test/CodeGenDXIL/cbuffer.namespace.hlsl   | 23 ++++++++++++
 .../test/CodeGenSPIRV/cbuffer.namespace.hlsl  | 22 ++++++++++++
 .../v202x/buffer-namespace-decl-context.hlsl  | 35 +++++++++++++++++++
 5 files changed, 85 insertions(+)
 create mode 100644 tools/clang/test/CodeGenDXIL/cbuffer.namespace.hlsl
 create mode 100644 tools/clang/test/CodeGenSPIRV/cbuffer.namespace.hlsl
 create mode 100644 tools/clang/test/SemaHLSL/v202x/buffer-namespace-decl-context.hlsl

diff --git a/docs/ReleaseNotes.md b/docs/ReleaseNotes.md
index 375d68d2fa..14e035c081 100644
--- a/docs/ReleaseNotes.md
+++ b/docs/ReleaseNotes.md
@@ -63,6 +63,8 @@ line upon naming the release. Refer to previous for appropriate section names.
 - The `shared` and `uniform` keywords are removed in HLSL 202x, with
   compatibility warnings available for earlier language versions
   [#8482](https://github.com/microsoft/DirectXShaderCompiler/issues/8482).
+- Starting with HLSL 202x, `cbuffer` and `tbuffer` declarations and their
+  members belong to their enclosing namespace.
 
 #### SPIR-V
 
diff --git a/tools/clang/lib/Sema/SemaHLSL.cpp b/tools/clang/lib/Sema/SemaHLSL.cpp
index 274adae6d7..fee88a1812 100644
--- a/tools/clang/lib/Sema/SemaHLSL.cpp
+++ b/tools/clang/lib/Sema/SemaHLSL.cpp
@@ -15446,6 +15446,9 @@ HLSLBufferDecl::Create(ASTContext &C, DeclContext *lexicalParent, bool cbuffer,
                        std::vector<hlsl::UnusualAnnotation *> &BufferAttributes,
                        SourceLocation LBrace) {
   DeclContext *DC = C.getTranslationUnitDecl();
+  // In HLSL 202x, buffers and their members belong to the enclosing namespace.
+  if (C.getLangOpts().HLSLVersion >= hlsl::LangStd::v202x)
+    DC = lexicalParent;
   HLSLBufferDecl *result = ::new (C) HLSLBufferDecl(
       DC, cbuffer, constantbuffer, KwLoc, Id, IdLoc, BufferAttributes, LBrace);
   if (DC != lexicalParent) {
diff --git a/tools/clang/test/CodeGenDXIL/cbuffer.namespace.hlsl b/tools/clang/test/CodeGenDXIL/cbuffer.namespace.hlsl
new file mode 100644
index 0000000000..ec436c2d69
--- /dev/null
+++ b/tools/clang/test/CodeGenDXIL/cbuffer.namespace.hlsl
@@ -0,0 +1,23 @@
+// RUN: %dxc -T ps_6_0 -E main -HV 202x %s | FileCheck %s
+
+// CHECK: ; cbuffer SceneConstants
+// CHECK: ; cbuffer SceneConstants
+// CHECK: ; Resource Bindings:
+// CHECK-DAG: ; SceneConstants{{ +}}cbuffer{{ +}}NA{{ +}}NA{{ +}}CB0{{ +}}cb3{{ +}}1
+// CHECK-DAG: ; SceneConstants{{ +}}cbuffer{{ +}}NA{{ +}}NA{{ +}}CB1{{ +}}cb4{{ +}}1
+
+namespace First {
+cbuffer SceneConstants : register(b3) {
+  float Value;
+}
+}
+
+namespace Second {
+cbuffer SceneConstants : register(b4) {
+  float Value;
+}
+}
+
+float4 main() : SV_Target {
+  return First::Value + Second::Value;
+}
diff --git a/tools/clang/test/CodeGenSPIRV/cbuffer.namespace.hlsl b/tools/clang/test/CodeGenSPIRV/cbuffer.namespace.hlsl
new file mode 100644
index 0000000000..8e755a2779
--- /dev/null
+++ b/tools/clang/test/CodeGenSPIRV/cbuffer.namespace.hlsl
@@ -0,0 +1,22 @@
+// RUN: %dxc -T ps_6_0 -E main -HV 202x -spirv -fcgl %s | FileCheck %s
+
+// CHECK-DAG: OpDecorate [[FIRST:%[^ ]+]] Binding 3
+// CHECK-DAG: OpDecorate [[SECOND:%[^ ]+]] Binding 4
+// CHECK-DAG: [[FIRST]] = OpVariable {{%[^ ]+}} Uniform
+// CHECK-DAG: [[SECOND]] = OpVariable {{%[^ ]+}} Uniform
+
+namespace First {
+cbuffer SceneConstants : register(b3) {
+  float Value;
+}
+}
+
+namespace Second {
+cbuffer SceneConstants : register(b4) {
+  float Value;
+}
+}
+
+float4 main() : SV_Target {
+  return First::Value + Second::Value;
+}
diff --git a/tools/clang/test/SemaHLSL/v202x/buffer-namespace-decl-context.hlsl b/tools/clang/test/SemaHLSL/v202x/buffer-namespace-decl-context.hlsl
new file mode 100644
index 0000000000..92cfff7502
--- /dev/null
+++ b/tools/clang/test/SemaHLSL/v202x/buffer-namespace-decl-context.hlsl
@@ -0,0 +1,35 @@
+// RUN: %dxc -T lib_6_3 -HV 202x -verify %s
+// RUN: %dxc -T lib_6_3 -HV 202x -ast-dump %s 2>&1 | FileCheck %s
+
+// expected-no-diagnostics
+
+namespace First {
+// CHECK: NamespaceDecl {{.*}} First
+// CHECK-NEXT: {{.*}}HLSLBufferDecl {{0x[0-9a-f]+}} <{{.*}}> {{.*}} cbuffer Constants
+cbuffer Constants {
+  float FirstValue;
+}
+
+// CHECK: HLSLBufferDecl {{0x[0-9a-f]+}} <{{.*}}> {{.*}} tbuffer Textures
+tbuffer Textures {
+  float FirstTextureValue;
+}
+}
+
+namespace Second {
+// CHECK: NamespaceDecl {{.*}} Second
+// CHECK-NEXT: {{.*}}HLSLBufferDecl {{0x[0-9a-f]+}} <{{.*}}> {{.*}} cbuffer Constants
+cbuffer Constants {
+  float SecondValue;
+}
+
+// CHECK: HLSLBufferDecl {{0x[0-9a-f]+}} <{{.*}}> {{.*}} tbuffer Textures
+tbuffer Textures {
+  float SecondTextureValue;
+}
+}
+
+float4 main() : SV_Target {
+  return First::FirstValue + First::FirstTextureValue +
+         Second::SecondValue + Second::SecondTextureValue;
+}