[SPIR-V] fatal error: generated SPIR-V is invalid: The Base <id> '35[%35]' in OpAccessChain instruction must be a pointer

[EugeneGribovich]

Hello

Have an error when compiling into SPIR-V:

dxc.exe ps.hlsl -spirv -T ps_6_6 -E ps_main -fvk-use-dx-layout -fspv-target-env=vulkan1.1 -Fo ps.out

fatal error: generated SPIR-V is invalid: The Base '35[%35]' in OpAccessChain instruction must be a pointer.
%36 = OpAccessChain %_ptr_Function_type_2d_image %35 %int_0

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

Repro Code:

SamplerState SS_OVERLAY;

Texture2D<float4> g_albedo0;
Texture2D<float4> g_albedo1;
Texture2D<float4> g_albedo2;
Texture2D<float4> g_albedo3;


float4 ps_main() : SV_Target
{
  Texture2D<float4> amTextures[4] = { g_albedo0, g_albedo1, g_albedo2, g_albedo3 };

  float4 result = 0;
  [unroll] for (int layerId = 0; layerId < 4; ++layerId)
  {
    result +=  amTextures[layerId].Sample(SS_OVERLAY, float2(0.0, 0.0));
  }

  return result;
}

Thank you

[jaebaek]

@EugeneGribovich Thank you for reporting this issue. We will take a look.

[EugeneGribovich]

@EugeneGribovich Thank you for reporting this issue. We will take a look.

Hello

Have got any updates about this issue?

Thank you

[IvanZinkevich]

Hi, @jaebaek. Did you have a chance to take a look? I've got some more insight of the issue. It reproes even with this code:

Texture2D<float4> g_albedo0;

float4 ps_main() : SV_Target
{
	Texture2D<float4> amTextures[1] = { g_albedo0 };
	return amTextures[0].Load(uint3(0, 0, 0));
}

And here's the SPIR-V output that you can get with the validator turned off:

; SPIR-V
; Version: 1.0
; Generator: Google spiregg; 0
; Bound: 31
; Schema: 0
               OpCapability Shader
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %ps_main "ps_main" %out_var_SV_Target
               OpExecutionMode %ps_main OriginUpperLeft
               OpSource HLSL 600
               OpName %type_2d_image "type.2d.image"
               OpName %g_albedo0 "g_albedo0"
               OpName %out_var_SV_Target "out.var.SV_Target"
               OpName %ps_main "ps_main"
               OpDecorate %out_var_SV_Target Location 0
               OpDecorate %g_albedo0 DescriptorSet 0
               OpDecorate %g_albedo0 Binding 0
        %int = OpTypeInt 32 1
      %int_0 = OpConstant %int 0
       %uint = OpTypeInt 32 0
     %uint_0 = OpConstant %uint 0
     %v3uint = OpTypeVector %uint 3
         %10 = OpConstantComposite %v3uint %uint_0 %uint_0 %uint_0
      %float = OpTypeFloat 32
%type_2d_image = OpTypeImage %float 2D 2 0 0 1 Unknown
%_ptr_UniformConstant_type_2d_image = OpTypePointer UniformConstant %type_2d_image
    %v4float = OpTypeVector %float 4
%_ptr_Output_v4float = OpTypePointer Output %v4float
       %void = OpTypeVoid
         %16 = OpTypeFunction %void
     %uint_1 = OpConstant %uint 1
%_arr_type_2d_image_uint_1 = OpTypeArray %type_2d_image %uint_1
%_ptr_Function_type_2d_image = OpTypePointer Function %type_2d_image
      %v3int = OpTypeVector %int 3
      %v2int = OpTypeVector %int 2
  %g_albedo0 = OpVariable %_ptr_UniformConstant_type_2d_image UniformConstant
%out_var_SV_Target = OpVariable %_ptr_Output_v4float Output
    %ps_main = OpFunction %void None %16
         %22 = OpLabel
         %23 = OpLoad %type_2d_image %g_albedo0
         %24 = OpCompositeConstruct %_arr_type_2d_image_uint_1 %23
         %25 = OpAccessChain %_ptr_Function_type_2d_image %24 %int_0
         %26 = OpLoad %type_2d_image %25
         %27 = OpBitcast %v3int %10
         %28 = OpVectorShuffle %v2int %27 %27 0 1
         %29 = OpCompositeExtract %int %27 2
         %30 = OpImageFetch %v4float %26 %28 Lod %29
               OpStore %out_var_SV_Target %30
               OpReturn
               OpFunctionEnd

As you can see in line

%25 = OpAccessChain %_ptr_Function_type_2d_image %24 %int_0

OpAccessChain expects a pointer, but gets an array.

If I pass this version of the shader:

Texture2D<float4> g_albedo0;
Texture2D<float4> amTextures[1] = { g_albedo0 };

float4 ps_main() : SV_Target
{

  return amTextures[0].Load(uint3(0, 0, 0));
}

I get this:

; SPIR-V
; Version: 1.3
; Generator: Google spiregg; 0
; Bound: 29
; Schema: 0
               OpCapability Shader
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %ps_main "ps_main" %out_var_SV_Target
               OpExecutionMode %ps_main OriginUpperLeft
               OpSource HLSL 600
               OpName %type_2d_image "type.2d.image"
               OpName %amTextures "amTextures"
               OpName %out_var_SV_Target "out.var.SV_Target"
               OpName %ps_main "ps_main"
               OpDecorate %out_var_SV_Target Location 0
               OpDecorate %amTextures DescriptorSet 0
               OpDecorate %amTextures Binding 1
       %uint = OpTypeInt 32 0
     %uint_0 = OpConstant %uint 0
     %v3uint = OpTypeVector %uint 3
          %8 = OpConstantComposite %v3uint %uint_0 %uint_0 %uint_0
        %int = OpTypeInt 32 1
      %int_0 = OpConstant %int 0
      %float = OpTypeFloat 32
%type_2d_image = OpTypeImage %float 2D 2 0 0 1 Unknown
%_ptr_UniformConstant_type_2d_image = OpTypePointer UniformConstant %type_2d_image
     %uint_1 = OpConstant %uint 1
%_arr_type_2d_image_uint_1 = OpTypeArray %type_2d_image %uint_1
%_ptr_UniformConstant__arr_type_2d_image_uint_1 = OpTypePointer UniformConstant %_arr_type_2d_image_uint_1
    %v4float = OpTypeVector %float 4
%_ptr_Output_v4float = OpTypePointer Output %v4float
       %void = OpTypeVoid
         %19 = OpTypeFunction %void
      %v3int = OpTypeVector %int 3
      %v2int = OpTypeVector %int 2
 %amTextures = OpVariable %_ptr_UniformConstant__arr_type_2d_image_uint_1 UniformConstant
%out_var_SV_Target = OpVariable %_ptr_Output_v4float Output
    %ps_main = OpFunction %void None %19
         %22 = OpLabel
         %23 = OpBitcast %v3int %8
         %24 = OpVectorShuffle %v2int %23 %23 0 1
         %25 = OpCompositeExtract %int %23 2
         %26 = OpAccessChain %_ptr_UniformConstant_type_2d_image %amTextures %int_0
         %27 = OpLoad %type_2d_image %26
         %28 = OpImageFetch %v4float %27 %24 Lod %25
               OpStore %out_var_SV_Target %28
               OpReturn
               OpFunctionEnd

I assume that the bug is somewhere in the HLSL legalization code. What do you think?

Thanks,
Ivan