Fix spirv lowering logic around pointer to unsized array. (#5243)

* Fix spirv lowering logic around pointer to unsized array.

* Fix.

---------

Co-authored-by: Ellie Hermaszewska <ellieh@nvidia.com>

2 files changed, 30 insertions, 3 deletions

diff --git a/tests/bugs/gh-3825.slang b/tests/bugs/gh-3825.slang
index 1feadb588..c7c325864 100644
--- a/tests/bugs/gh-3825.slang
+++ b/tests/bugs/gh-3825.slang
@@ -4,7 +4,7 @@
 //TEST:SIMPLE(filecheck=CHECK): -entry fragment -stage fragment -emit-spirv-directly -target spirv-assembly -emit-spirv-directly
 struct Descriptors {
   uint count;
-  uint array[];
+  uint4 array[];
 }
 
 struct Context {
@@ -17,7 +17,11 @@ struct Context {
 [shader("fragment")]
 float4 fragment(): SV_Target
 {
-  return float4(float(context.descriptors[0].array[0]), 1., 1., 1.);
+  return float4(float(context.descriptors->array[0].x), 1., 1., 1.);
 }
 
-// CHECK: OpDecorate %_ptr_PhysicalStorageBuffer__runtimearr_uint ArrayStride 65535
+// CHECK: OpDecorate %_ptr_PhysicalStorageBuffer_Descriptors_natural ArrayStride 4
+// CHECK: %{{.*}} = OpPtrAccessChain %_ptr_PhysicalStorageBuffer_Descriptors_natural %{{.*}} %int_1
+// CHECK: OpBitcast %ulong
+// CHECK: OpIAdd %ulong %{{.*}} %ulong_4
+// CHECK: OpBitcast %_ptr_PhysicalStorageBuffer
\ No newline at end of file
diff --git a/tests/spirv/ptr-unsized-array.slang b/tests/spirv/ptr-unsized-array.slang
new file mode 100644
index 000000000..48added5c
--- /dev/null
+++ b/tests/spirv/ptr-unsized-array.slang
@@ -0,0 +1,23 @@
+//TEST:SIMPLE(filecheck=CHECK): -target spirv
+
+// CHECK: OpPtrAccessChain
+
+struct MeshVertex {
+    float3 Pos;
+    float2 TexCoord;
+};
+struct MeshData { 
+    float4x4 ModelMat;
+    MeshVertex Vertices[];
+};
+struct DispatchParams {
+    MeshData* Mesh;
+    float3* Dest;
+};
+
+[vk::push_constant] DispatchParams pc;
+
+[numthreads(64)]
+void ComputeMain(uint tid: SV_DispatchThreadID) {
+    pc.Dest[tid] = pc.Mesh->Vertices[tid].Pos;
+}
\ No newline at end of file