[clang] [HLSL] Desugar ConstantArrayType when calculating cbuffer field layout (PR #134683)

[Sarah Spall via cfe-commits]

https://github.com/spall updated 
https://github.com/llvm/llvm-project/pull/134683

>From 87308905daa9093caef9ffb920bf9968c0bfb597 Mon Sep 17 00:00:00 2001
From: Sarah Spall <sarahsp...@microsoft.com>
Date: Mon, 7 Apr 2025 09:31:28 -0700
Subject: [PATCH 1/2] desguar constantarraytype

---
 clang/lib/CodeGen/HLSLBufferLayoutBuilder.cpp |  3 ++-
 clang/test/CodeGenHLSL/cbuffer.hlsl           | 17 ++++++++++++++++-
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/clang/lib/CodeGen/HLSLBufferLayoutBuilder.cpp 
b/clang/lib/CodeGen/HLSLBufferLayoutBuilder.cpp
index b546b6dd574ff..20d311f3609e0 100644
--- a/clang/lib/CodeGen/HLSLBufferLayoutBuilder.cpp
+++ b/clang/lib/CodeGen/HLSLBufferLayoutBuilder.cpp
@@ -195,7 +195,8 @@ bool HLSLBufferLayoutBuilder::layoutField(const FieldDecl 
*FD,
     // Unwrap array to find the element type and get combined array size.
     QualType Ty = FieldTy;
     while (Ty->isConstantArrayType()) {
-      const ConstantArrayType *ArrayTy = cast<ConstantArrayType>(Ty);
+      const ConstantArrayType *ArrayTy =
+          cast<ConstantArrayType>(Ty.getDesugaredType(CGM.getContext()));
       ArrayCount *= ArrayTy->getSExtSize();
       Ty = ArrayTy->getElementType();
     }
diff --git a/clang/test/CodeGenHLSL/cbuffer.hlsl 
b/clang/test/CodeGenHLSL/cbuffer.hlsl
index db06cea808b62..0a0465cc44e91 100644
--- a/clang/test/CodeGenHLSL/cbuffer.hlsl
+++ b/clang/test/CodeGenHLSL/cbuffer.hlsl
@@ -99,6 +99,19 @@ cbuffer CBArrays : register(b2) {
 // CHECK: @c7 = external addrspace(2) global [2 x i64], align 8
 // CHECK: @c8 = external addrspace(2) global [4 x i32], align 4
 
+typedef uint32_t4 uint32_t8[2];
+typedef uint4 T1;
+typedef T1 T2[2]; // check a double typedef
+
+cbuffer CBTypedefArray {
+  uint32_t8 t1[2];
+  T2 t2[2];
+}
+
+// CHECK: @CBTypedefArray.cb = global target("dx.CBuffer", target("dx.Layout", 
%__cblayout_CBTypedefArray,
+// CHECK-SAME: 128, 0, 64))
+// CHECK: @t1 = external addrspace(2) global [2 x [2 x <4 x i32>]], align 16
+// CHECK: @t2 = external addrspace(2) global [2 x [2 x <4 x i32>]], align 16
 struct Empty {};
 
 struct A {
@@ -278,7 +291,7 @@ void main() {
 // CHECK-NEXT: call void @_init_resource_CBScalars.cb()
 // CHECK-NEXT: call void @_init_resource_CBArrays.cb()
 
-// CHECK: !hlsl.cbs = !{![[CBSCALARS:[0-9]+]], ![[CBVECTORS:[0-9]+]], 
![[CBARRAYS:[0-9]+]], ![[CBSTRUCTS:[0-9]+]], ![[CBCLASSES:[0-9]+]],
+// CHECK: !hlsl.cbs = !{![[CBSCALARS:[0-9]+]], ![[CBVECTORS:[0-9]+]], 
![[CBARRAYS:[0-9]+]], ![[CBTYPEDEFARRAY:[0-9]+]], ![[CBSTRUCTS:[0-9]+]], 
![[CBCLASSES:[0-9]+]],
 // CHECK-SAME: ![[CBMIX:[0-9]+]], ![[CB_A:[0-9]+]], ![[CB_B:[0-9]+]], 
![[CB_C:[0-9]+]]}
 
 // CHECK: ![[CBSCALARS]] = !{ptr @CBScalars.cb, ptr addrspace(2) @a1, ptr 
addrspace(2) @a2, ptr addrspace(2) @a3, ptr addrspace(2) @a4,
@@ -290,6 +303,8 @@ void main() {
 // CHECK: ![[CBARRAYS]] = !{ptr @CBArrays.cb, ptr addrspace(2) @c1, ptr 
addrspace(2) @c2, ptr addrspace(2) @c3, ptr addrspace(2) @c4,
 // CHECK-SAME: ptr addrspace(2) @c5, ptr addrspace(2) @c6, ptr addrspace(2) 
@c7, ptr addrspace(2) @c8}
 
+// CHECK: ![[CBTYPEDEFARRAY]] = !{ptr @CBTypedefArray.cb, ptr addrspace(2) 
@t1, ptr addrspace(2) @t2}
+
 // CHECK: ![[CBSTRUCTS]] = !{ptr @CBStructs.cb, ptr addrspace(2) @a, ptr 
addrspace(2) @b, ptr addrspace(2) @c, ptr addrspace(2) @array_of_A,
 // CHECK-SAME: ptr addrspace(2) @d, ptr addrspace(2) @e, ptr addrspace(2) @f}
 

>From eb6debf6a203f0a5f240e8d752fbfea0f0301faf Mon Sep 17 00:00:00 2001
From: Sarah Spall <sarahsp...@microsoft.com>
Date: Mon, 7 Apr 2025 11:08:42 -0700
Subject: [PATCH 2/2] make suggested change

---
 clang/lib/CodeGen/HLSLBufferLayoutBuilder.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/lib/CodeGen/HLSLBufferLayoutBuilder.cpp 
b/clang/lib/CodeGen/HLSLBufferLayoutBuilder.cpp
index 20d311f3609e0..99521ff7361bb 100644
--- a/clang/lib/CodeGen/HLSLBufferLayoutBuilder.cpp
+++ b/clang/lib/CodeGen/HLSLBufferLayoutBuilder.cpp
@@ -196,7 +196,7 @@ bool HLSLBufferLayoutBuilder::layoutField(const FieldDecl 
*FD,
     QualType Ty = FieldTy;
     while (Ty->isConstantArrayType()) {
       const ConstantArrayType *ArrayTy =
-          cast<ConstantArrayType>(Ty.getDesugaredType(CGM.getContext()));
+          cast<ConstantArrayType>(Ty->getUnqualifiedDesugaredType());
       ArrayCount *= ArrayTy->getSExtSize();
       Ty = ArrayTy->getElementType();
     }

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