[SPIR-V] The result pointer storage class and base pointer storage class in OpAccessChain do not match

[Jasper-Bekkers]

Simple repro:

struct MeshPart {
	uint indexOffset;
	uint positionOffset;
	uint normalOffset;
	uint texCoord0Offset;
};

StructuredBuffer<MeshPart> g_meshParts[] : register(t2, space1);
RWStructuredBuffer<uint> g_output : register(u1, space2);

[numthreads(64, 1, 1)]
void main()
{
	MeshPart meshPart = g_meshParts[0][0];
	g_output[0] = meshPart.indexOffset;
}

Compiling with these arguments generates incorrect build output: dxc -fspv-target-env=vulkan1.2 -spirv -Tcs_6_6 <filename>

fatal error: generated SPIR-V is invalid: The result pointer storage class and base pointer storage class in OpAccessChain do not match.
  %22 = OpAccessChain %_ptr_StorageBuffer_MeshPart %g_meshParts %int_0 %int_0 %uint_0

note: please file a bug report on https://github.com/Microsoft/DirectXShaderCompiler/issues with source code if possible

However, compiling with these arguments generates valid spirv: dxc -fspv-target-env=vulkan1.1 -spirv -Tcs_6_6:

; SPIR-V
; Version: 1.3
; Generator: Google spiregg; 0
; Bound: 25
; Schema: 0
               OpCapability Shader
               OpCapability RuntimeDescriptorArray
               OpExtension "SPV_EXT_descriptor_indexing"
               OpMemoryModel Logical GLSL450
               OpEntryPoint GLCompute %main "main"
               OpExecutionMode %main LocalSize 64 1 1
               OpSource HLSL 660
               OpName %type_StructuredBuffer_MeshPart "type.StructuredBuffer.MeshPart"
               OpName %MeshPart "MeshPart"
               OpMemberName %MeshPart 0 "indexOffset"
               OpMemberName %MeshPart 1 "positionOffset"
               OpMemberName %MeshPart 2 "normalOffset"
               OpMemberName %MeshPart 3 "texCoord0Offset"
               OpName %g_meshParts "g_meshParts"
               OpName %type_RWStructuredBuffer_uint "type.RWStructuredBuffer.uint"
               OpName %g_output "g_output"
               OpName %main "main"
               OpDecorate %g_meshParts DescriptorSet 1
               OpDecorate %g_meshParts Binding 2
               OpDecorate %g_output DescriptorSet 2
               OpDecorate %g_output Binding 1
               OpMemberDecorate %MeshPart 0 Offset 0
               OpMemberDecorate %MeshPart 1 Offset 4
               OpMemberDecorate %MeshPart 2 Offset 8
               OpMemberDecorate %MeshPart 3 Offset 12
               OpDecorate %_runtimearr_MeshPart ArrayStride 16
               OpMemberDecorate %type_StructuredBuffer_MeshPart 0 Offset 0
               OpMemberDecorate %type_StructuredBuffer_MeshPart 0 NonWritable
               OpDecorate %type_StructuredBuffer_MeshPart BufferBlock
               OpDecorate %_runtimearr_uint ArrayStride 4
               OpMemberDecorate %type_RWStructuredBuffer_uint 0 Offset 0
               OpDecorate %type_RWStructuredBuffer_uint BufferBlock
        %int = OpTypeInt 32 1
      %int_0 = OpConstant %int 0
       %uint = OpTypeInt 32 0
     %uint_0 = OpConstant %uint 0
   %MeshPart = OpTypeStruct %uint %uint %uint %uint
%_runtimearr_MeshPart = OpTypeRuntimeArray %MeshPart
%type_StructuredBuffer_MeshPart = OpTypeStruct %_runtimearr_MeshPart
%_runtimearr_type_StructuredBuffer_MeshPart = OpTypeRuntimeArray %type_StructuredBuffer_MeshPart
%_ptr_Uniform__runtimearr_type_StructuredBuffer_MeshPart = OpTypePointer Uniform %_runtimearr_type_StructuredBuffer_MeshPart
%_runtimearr_uint = OpTypeRuntimeArray %uint
%type_RWStructuredBuffer_uint = OpTypeStruct %_runtimearr_uint
%_ptr_Uniform_type_RWStructuredBuffer_uint = OpTypePointer Uniform %type_RWStructuredBuffer_uint
       %void = OpTypeVoid
         %17 = OpTypeFunction %void
%_ptr_Uniform_MeshPart = OpTypePointer Uniform %MeshPart
%_ptr_Uniform_uint = OpTypePointer Uniform %uint
%g_meshParts = OpVariable %_ptr_Uniform__runtimearr_type_StructuredBuffer_MeshPart Uniform
   %g_output = OpVariable %_ptr_Uniform_type_RWStructuredBuffer_uint Uniform
       %main = OpFunction %void None %17
         %20 = OpLabel
         %21 = OpAccessChain %_ptr_Uniform_MeshPart %g_meshParts %int_0 %int_0 %uint_0
         %22 = OpAccessChain %_ptr_Uniform_uint %21 %uint_0
         %23 = OpLoad %uint %22
         %24 = OpAccessChain %_ptr_Uniform_uint %g_output %int_0 %uint_0
               OpStore %24 %23
               OpReturn
               OpFunctionEnd

Tested with the AppVeyor build from f78b10c

[Jasper-Bekkers]

Compiling with dxc -Vd -fspv-target-env=vulkan1.2 -spirv -Tcs_6_6 (validation disabled) clearly shows what's going wrong:

; SPIR-V
; Version: 1.5
; Generator: Google spiregg; 0
; Bound: 26
; Schema: 0
               OpCapability Shader
               OpCapability RuntimeDescriptorArray
               OpExtension "SPV_EXT_descriptor_indexing"
               OpMemoryModel Logical GLSL450
               OpEntryPoint GLCompute %main "main" %g_meshParts %g_output
               OpExecutionMode %main LocalSize 64 1 1
               OpSource HLSL 660
               OpName %type_StructuredBuffer_MeshPart "type.StructuredBuffer.MeshPart"
               OpName %MeshPart "MeshPart"
               OpMemberName %MeshPart 0 "indexOffset"
               OpMemberName %MeshPart 1 "positionOffset"
               OpMemberName %MeshPart 2 "normalOffset"
               OpMemberName %MeshPart 3 "texCoord0Offset"
               OpName %g_meshParts "g_meshParts"
               OpName %type_RWStructuredBuffer_uint "type.RWStructuredBuffer.uint"
               OpName %g_output "g_output"
               OpName %main "main"
               OpDecorate %g_meshParts DescriptorSet 1
               OpDecorate %g_meshParts Binding 2
               OpDecorate %g_output DescriptorSet 2
               OpDecorate %g_output Binding 1
               OpMemberDecorate %MeshPart 0 Offset 0
               OpMemberDecorate %MeshPart 1 Offset 4
               OpMemberDecorate %MeshPart 2 Offset 8
               OpMemberDecorate %MeshPart 3 Offset 12
               OpDecorate %_runtimearr_MeshPart ArrayStride 16
               OpMemberDecorate %type_StructuredBuffer_MeshPart 0 Offset 0
               OpMemberDecorate %type_StructuredBuffer_MeshPart 0 NonWritable
               OpDecorate %type_StructuredBuffer_MeshPart Block
               OpDecorate %_runtimearr_uint ArrayStride 4
               OpMemberDecorate %type_RWStructuredBuffer_uint 0 Offset 0
               OpDecorate %type_RWStructuredBuffer_uint Block
        %int = OpTypeInt 32 1
      %int_0 = OpConstant %int 0
       %uint = OpTypeInt 32 0
     %uint_0 = OpConstant %uint 0
   %MeshPart = OpTypeStruct %uint %uint %uint %uint
%_runtimearr_MeshPart = OpTypeRuntimeArray %MeshPart
%type_StructuredBuffer_MeshPart = OpTypeStruct %_runtimearr_MeshPart
%_runtimearr_type_StructuredBuffer_MeshPart = OpTypeRuntimeArray %type_StructuredBuffer_MeshPart
%_ptr_Uniform__runtimearr_type_StructuredBuffer_MeshPart = OpTypePointer Uniform %_runtimearr_type_StructuredBuffer_MeshPart
%_runtimearr_uint = OpTypeRuntimeArray %uint
%type_RWStructuredBuffer_uint = OpTypeStruct %_runtimearr_uint
%_ptr_StorageBuffer_type_RWStructuredBuffer_uint = OpTypePointer StorageBuffer %type_RWStructuredBuffer_uint
       %void = OpTypeVoid
         %17 = OpTypeFunction %void
%_ptr_StorageBuffer_MeshPart = OpTypePointer StorageBuffer %MeshPart
%_ptr_StorageBuffer_uint = OpTypePointer StorageBuffer %uint
%g_meshParts = OpVariable %_ptr_Uniform__runtimearr_type_StructuredBuffer_MeshPart Uniform
   %g_output = OpVariable %_ptr_StorageBuffer_type_RWStructuredBuffer_uint StorageBuffer
%_ptr_Uniform_uint = OpTypePointer Uniform %uint
       %main = OpFunction %void None %17
         %21 = OpLabel
         %22 = OpAccessChain %_ptr_StorageBuffer_MeshPart %g_meshParts %int_0 %int_0 %uint_0
         %23 = OpAccessChain %_ptr_Uniform_uint %22 %uint_0
         %24 = OpLoad %uint %23
         %25 = OpAccessChain %_ptr_StorageBuffer_uint %g_output %int_0 %uint_0
               OpStore %25 %24
               OpReturn
               OpFunctionEnd

For %22 the OpAccessChain has a mismatching Storage Class - the OpTypePointer has a Storage Class of StorageBuffer and the OpVariable has a Storage Class of Uniform whereas before, both were Uniform in this case.

[Jasper-Bekkers]

@ehsannas These errors usually seems to be in your street, right? :-)

[ehsannas]

Hi @Jasper-Bekkers , Yup, Thanks for reporting! We'll take a look.

[ehsannas]

@jaebaek will investigate.

[Jasper-Bekkers]

Thanks @ehsannas and @jaebaek #3039 fixes the issue for us.