[clang] [HLSL] Enable InitList code to handle zero sized structs (PR #160355)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Sarah Spall (spall)

<details>
<summary>Changes</summary>

Enable InitList code to handle zero sized structs; this includes structs with no fields and those with only unnamed bitfields.
Closes #<!-- -->157920

---
Full diff: https://github.com/llvm/llvm-project/pull/160355.diff


2 Files Affected:

- (modified) clang/lib/Sema/SemaHLSL.cpp (+2) 
- (modified) clang/test/CodeGenHLSL/BasicFeatures/InitLists.hlsl (+42) 


``````````diff
diff --git a/clang/lib/Sema/SemaHLSL.cpp b/clang/lib/Sema/SemaHLSL.cpp
index 7a61474e2a25c..7f85886f72366 100644
--- a/clang/lib/Sema/SemaHLSL.cpp
+++ b/clang/lib/Sema/SemaHLSL.cpp
@@ -4284,6 +4284,8 @@ bool SemaHLSL::transformInitList(const InitializedEntity &Entity,
   }
   size_t ExpectedSize = ILT.DestTypes.size();
   size_t ActualSize = ILT.ArgExprs.size();
+  if (ExpectedSize == 0 && ActualSize == 0)
+    return true;
   // For incomplete arrays it is completely arbitrary to choose whether we think
   // the user intended fewer or more elements. This implementation assumes that
   // the user intended more, and errors that there are too few initializers to
diff --git a/clang/test/CodeGenHLSL/BasicFeatures/InitLists.hlsl b/clang/test/CodeGenHLSL/BasicFeatures/InitLists.hlsl
index 5a5c45f686956..5fe69806b61eb 100644
--- a/clang/test/CodeGenHLSL/BasicFeatures/InitLists.hlsl
+++ b/clang/test/CodeGenHLSL/BasicFeatures/InitLists.hlsl
@@ -50,6 +50,16 @@ struct Unnamed {
   int : 8;
 };
 
+struct Empty {
+};
+
+struct UnnamedOnly {
+  int : 8;
+};
+
+// CHECK-DAG: [[ConstE:@.*]] = private unnamed_addr constant %struct.Empty undef, align 1
+// CHECK-DAG: [[ConstUO:@.*]] = private unnamed_addr constant %struct.UnnamedOnly undef, align 1
+
 // Case 1: Extraneous braces get ignored in literal instantiation.
 // CHECK-LABEL: define hidden void @_Z5case1v(
 // CHECK-SAME: ptr dead_on_unwind noalias writable sret([[STRUCT_TWOFLOATS:%.*]]) align 1 [[AGG_RESULT:%.*]]) #[[ATTR0:[0-9]+]] {
@@ -985,3 +995,35 @@ void case18() {
 void case19(Unnamed U) {
   TwoInts TI = {U, 1};
 }
+
+// InitList with Empty Struct on LHS
+// CHECK-LABEL: case20
+// CHECK: [[E:%.*]] = alloca %struct.Empty, align 1
+// CHECK-NEXT: call void @llvm.memcpy.p0.p0.i32(ptr align 1 [[E]], ptr align 1 [[ConstE]], i32 1, i1 false)
+void case20() {
+  Empty E = {};
+}
+
+// InitList with Empty Struct on RHS
+// CHECK-LABEL: case21
+// CHECK: [[TI:%.*]] = alloca %struct.TwoInts, align 1
+// CHECK-NEXT: call void @llvm.memcpy.p0.p0.i32(ptr align 1 %TI, ptr align 1 {{.*}}, i32 8, i1 false)
+void case21(Empty E) {
+  TwoInts TI = {E, 1, 2};
+}
+
+// InitList with Struct with only unnamed bitfield on LHS
+// CHECK-LABEL: case22
+// CHECK: [[UO:%.*]] = alloca %struct.UnnamedOnly, align 1
+// CHECK-NEXT: call void @llvm.memcpy.p0.p0.i32(ptr align 1 [[UO]], ptr align 1 [[ConstUO]], i32 1, i1 false)
+void case22() {
+ UnnamedOnly UO = {}; 
+}
+
+// InitList with Struct with only unnamed bitfield on RHS
+// CHECK-LABEL: case23
+// CHECK: [[TI:%.*]] = alloca %struct.TwoInts, align 1
+// CHECK-NEXT: call void @llvm.memcpy.p0.p0.i32(ptr align 1 [[TI]], ptr align 1 {{.*}}, i32 8, i1 false)
+void case23(UnnamedOnly UO) {
+  TwoInts TI = {UO, 1, 2};
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/160355