HLSL/MSL: Passing samplers and textures to functions results in global sampler and unused parameters

[Ravbug]

The following GLSL function:

float pcfForShadow(vec3 pixelWorldPos, mat4 lightViewProj, sampler shadowSampler, texture2D t_depthshadow){
	vec4 sampledPos = vec4(pixelWorldPos,1);
	sampledPos = lightViewProj * sampledPos;    // where is this on the light
	sampledPos /= sampledPos.w; // perspective divide
	sampledPos.xy = sampledPos.xy * 0.5 + 0.5;    // transform to [0,1] 
	sampledPos.y = 1 - sampledPos.y;

    return texture(sampler2DShadow(t_depthshadow,shadowSampler), sampledPos.xyz, 0).x;
}

Becomes this when compiled to SPIRV via glslang 14.3.0 and converted to HLSL:

Texture2D<float4> t_depthshadowshadowSampler;
SamplerComparisonState _t_depthshadowshadowSampler_sampler;

float pcfForShadow(float3 pixelWorldPos, float4x4 lightViewProj, SamplerState shadowSampler_1, Texture2D<float4> t_depthshadow)
{
    float4 sampledPos = float4(pixelWorldPos, 1.0f);
    sampledPos = mul(sampledPos, lightViewProj);
    sampledPos /= sampledPos.w.xxxx;
    float4 _854 = sampledPos;
    float2 _860 = (_854.xy * 0.5f) + 0.5f.xx;
    sampledPos.x = _860.x;
    sampledPos.y = _860.y;
    sampledPos.y = 1.0f - sampledPos.y;
    return t_depthshadowshadowSampler.SampleCmp(_t_depthshadowshadowSampler_sampler, sampledPos.xyz.xy, sampledPos.xyz.z);
}

The parameters shadowSampler_1 and t_depthshadow are unused in the HLSL function body and instead the globals t_depthshadowshadowSampler and _t_depthshadowshadowSampler_sampler are created. They are not initialized anywhere in the generated HLSL.

The desired behavior is for the generated function to use the sampler and texture arguments passed in.

[HansKristian-Work]

I cannot reproduce this.

GLSL:

#version 450

layout(location = 0) out float FragColor;
layout(set = 0, binding = 0) uniform texture2D depthShadow;
layout(set = 0, binding = 1) uniform sampler depthSampler;


float pcfForShadow(vec3 pixelWorldPos, mat4 lightViewProj, sampler shadowSampler, texture2D t_depthshadow){
	vec4 sampledPos = vec4(pixelWorldPos,1);
	sampledPos = lightViewProj * sampledPos;    // where is this on the light
	sampledPos /= sampledPos.w; // perspective divide
	sampledPos.xy = sampledPos.xy * 0.5 + 0.5;    // transform to [0,1] 
	sampledPos.y = 1 - sampledPos.y;

    return texture(sampler2DShadow(t_depthshadow,shadowSampler), sampledPos.xyz, 0).x;
}

void main()
{
	FragColor = pcfForShadow(vec3(0.0), mat4(1.0), depthSampler, depthShadow);
}

SPIR-V:

; SPIR-V
; Version: 1.0
; Generator: Khronos Glslang Reference Front End; 11
; Bound: 84
; Schema: 0
               OpCapability Shader
          %1 = OpExtInstImport "GLSL.std.450"
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %main "main" %FragColor
               OpExecutionMode %main OriginUpperLeft
               OpSource GLSL 450
               OpName %main "main"
               OpName %pcfForShadow_vf3_mf44_p1_t21_ "pcfForShadow(vf3;mf44;p1;t21;"
               OpName %pixelWorldPos "pixelWorldPos"
               OpName %lightViewProj "lightViewProj"
               OpName %shadowSampler "shadowSampler"
               OpName %t_depthshadow "t_depthshadow"
               OpName %sampledPos "sampledPos"
               OpName %FragColor "FragColor"
               OpName %depthSampler "depthSampler"
               OpName %depthShadow "depthShadow"
               OpName %param "param"
               OpName %param_0 "param"
               OpDecorate %FragColor Location 0
               OpDecorate %depthSampler DescriptorSet 0
               OpDecorate %depthSampler Binding 1
               OpDecorate %depthShadow DescriptorSet 0
               OpDecorate %depthShadow Binding 0
       %void = OpTypeVoid
          %3 = OpTypeFunction %void
      %float = OpTypeFloat 32
    %v3float = OpTypeVector %float 3
%_ptr_Function_v3float = OpTypePointer Function %v3float
    %v4float = OpTypeVector %float 4
%mat4v4float = OpTypeMatrix %v4float 4
%_ptr_Function_mat4v4float = OpTypePointer Function %mat4v4float
         %12 = OpTypeSampler
%_ptr_UniformConstant_12 = OpTypePointer UniformConstant %12
         %14 = OpTypeImage %float 2D 0 0 0 1 Unknown
%_ptr_UniformConstant_14 = OpTypePointer UniformConstant %14
         %16 = OpTypeFunction %float %_ptr_Function_v3float %_ptr_Function_mat4v4float %_ptr_UniformConstant_12 %_ptr_UniformConstant_14
%_ptr_Function_v4float = OpTypePointer Function %v4float
    %float_1 = OpConstant %float 1
       %uint = OpTypeInt 32 0
     %uint_3 = OpConstant %uint 3
%_ptr_Function_float = OpTypePointer Function %float
    %v2float = OpTypeVector %float 2
  %float_0_5 = OpConstant %float 0.5
     %uint_0 = OpConstant %uint 0
     %uint_1 = OpConstant %uint 1
         %61 = OpTypeImage %float 2D 1 0 0 1 Unknown
         %62 = OpTypeSampledImage %61
    %float_0 = OpConstant %float 0
%_ptr_Output_float = OpTypePointer Output %float
  %FragColor = OpVariable %_ptr_Output_float Output
         %73 = OpConstantComposite %v3float %float_0 %float_0 %float_0
         %74 = OpConstantComposite %v4float %float_1 %float_0 %float_0 %float_0
         %75 = OpConstantComposite %v4float %float_0 %float_1 %float_0 %float_0
         %76 = OpConstantComposite %v4float %float_0 %float_0 %float_1 %float_0
         %77 = OpConstantComposite %v4float %float_0 %float_0 %float_0 %float_1
         %78 = OpConstantComposite %mat4v4float %74 %75 %76 %77
%depthSampler = OpVariable %_ptr_UniformConstant_12 UniformConstant
%depthShadow = OpVariable %_ptr_UniformConstant_14 UniformConstant
       %main = OpFunction %void None %3
          %5 = OpLabel
      %param = OpVariable %_ptr_Function_v3float Function
    %param_0 = OpVariable %_ptr_Function_mat4v4float Function
               OpStore %param %73
               OpStore %param_0 %78
         %83 = OpFunctionCall %float %pcfForShadow_vf3_mf44_p1_t21_ %param %param_0 %depthSampler %depthShadow
               OpStore %FragColor %83
               OpReturn
               OpFunctionEnd
%pcfForShadow_vf3_mf44_p1_t21_ = OpFunction %float None %16
%pixelWorldPos = OpFunctionParameter %_ptr_Function_v3float
%lightViewProj = OpFunctionParameter %_ptr_Function_mat4v4float
%shadowSampler = OpFunctionParameter %_ptr_UniformConstant_12
%t_depthshadow = OpFunctionParameter %_ptr_UniformConstant_14
         %22 = OpLabel
 %sampledPos = OpVariable %_ptr_Function_v4float Function
         %25 = OpLoad %v3float %pixelWorldPos
         %27 = OpCompositeExtract %float %25 0
         %28 = OpCompositeExtract %float %25 1
         %29 = OpCompositeExtract %float %25 2
         %30 = OpCompositeConstruct %v4float %27 %28 %29 %float_1
               OpStore %sampledPos %30
         %31 = OpLoad %mat4v4float %lightViewProj
         %32 = OpLoad %v4float %sampledPos
         %33 = OpMatrixTimesVector %v4float %31 %32
               OpStore %sampledPos %33
         %37 = OpAccessChain %_ptr_Function_float %sampledPos %uint_3
         %38 = OpLoad %float %37
         %39 = OpLoad %v4float %sampledPos
         %40 = OpCompositeConstruct %v4float %38 %38 %38 %38
         %41 = OpFDiv %v4float %39 %40
               OpStore %sampledPos %41
         %43 = OpLoad %v4float %sampledPos
         %44 = OpVectorShuffle %v2float %43 %43 0 1
         %46 = OpVectorTimesScalar %v2float %44 %float_0_5
         %47 = OpCompositeConstruct %v2float %float_0_5 %float_0_5
         %48 = OpFAdd %v2float %46 %47
         %50 = OpAccessChain %_ptr_Function_float %sampledPos %uint_0
         %51 = OpCompositeExtract %float %48 0
               OpStore %50 %51
         %53 = OpAccessChain %_ptr_Function_float %sampledPos %uint_1
         %54 = OpCompositeExtract %float %48 1
               OpStore %53 %54
         %55 = OpAccessChain %_ptr_Function_float %sampledPos %uint_1
         %56 = OpLoad %float %55
         %57 = OpFSub %float %float_1 %56
         %58 = OpAccessChain %_ptr_Function_float %sampledPos %uint_1
               OpStore %58 %57
         %59 = OpLoad %14 %t_depthshadow
         %60 = OpLoad %12 %shadowSampler
         %63 = OpSampledImage %62 %59 %60
         %64 = OpLoad %v4float %sampledPos
         %65 = OpVectorShuffle %v3float %64 %64 0 1 2
         %67 = OpCompositeExtract %float %65 2
         %68 = OpImageSampleDrefImplicitLod %float %63 %65 %67 Bias %float_0
               OpReturnValue %68
               OpFunctionEnd

HLSL with --shader-model 50

SamplerComparisonState depthSampler : register(s1);
Texture2D<float4> depthShadow : register(t0);

static float FragColor;

struct SPIRV_Cross_Output
{
    float FragColor : SV_Target0;
};

float pcfForShadow(float3 pixelWorldPos, float4x4 lightViewProj, SamplerComparisonState shadowSampler, Texture2D<float4> t_depthshadow)
{
    float4 sampledPos = float4(pixelWorldPos, 1.0f);
    sampledPos = mul(sampledPos, lightViewProj);
    sampledPos /= sampledPos.w.xxxx;
    float4 _43 = sampledPos;
    float2 _48 = (_43.xy * 0.5f) + 0.5f.xx;
    sampledPos.x = _48.x;
    sampledPos.y = _48.y;
    sampledPos.y = 1.0f - sampledPos.y;
    return t_depthshadow.SampleCmp(shadowSampler, sampledPos.xyz.xy, sampledPos.xyz.z);
}

void frag_main()
{
    float3 param = 0.0f.xxx;
    float4x4 param_1 = float4x4(float4(1.0f, 0.0f, 0.0f, 0.0f), float4(0.0f, 1.0f, 0.0f, 0.0f), float4(0.0f, 0.0f, 1.0f, 0.0f), float4(0.0f, 0.0f, 0.0f, 1.0f));
    FragColor = pcfForShadow(param, param_1, depthSampler, depthShadow);
}

SPIRV_Cross_Output main()
{
    frag_main();
    SPIRV_Cross_Output stage_output;
    stage_output.FragColor = FragColor;
    return stage_output;
}

MSL:

#pragma clang diagnostic ignored "-Wmissing-prototypes"

#include <metal_stdlib>
#include <simd/simd.h>

using namespace metal;

struct main0_out
{
    float FragColor [[color(0)]];
};

static inline __attribute__((always_inline))
float pcfForShadow(thread const float3& pixelWorldPos, thread const float4x4& lightViewProj, sampler shadowSampler, depth2d<float> t_depthshadow)
{
    float4 sampledPos = float4(pixelWorldPos, 1.0);
    sampledPos = lightViewProj * sampledPos;
    sampledPos /= float4(sampledPos.w);
    float4 _43 = sampledPos;
    float2 _48 = (_43.xy * 0.5) + float2(0.5);
    sampledPos.x = _48.x;
    sampledPos.y = _48.y;
    sampledPos.y = 1.0 - sampledPos.y;
    return t_depthshadow.sample_compare(shadowSampler, sampledPos.xyz.xy, sampledPos.xyz.z);
}

fragment main0_out main0(depth2d<float> depthShadow [[texture(0)]], sampler depthSampler [[sampler(0)]])
{
    main0_out out = {};
    float3 param = float3(0.0);
    float4x4 param_1 = float4x4(float4(1.0, 0.0, 0.0, 0.0), float4(0.0, 1.0, 0.0, 0.0), float4(0.0, 0.0, 1.0, 0.0), float4(0.0, 0.0, 0.0, 1.0));
    out.FragColor = pcfForShadow(param, param_1, depthSampler, depthShadow);
    return out;
}

[Ravbug]

Apologies for the late response. Here is my full shader and the intermediate SPIR-V that glslang generated. Does this reproduce for you? I updated to the latest glslang ToT and it's still happening. On my older glslang version the issue does not occur (same spirv-cross version).

full_shader.frag.txt
full_shader.spv.txt

I am using the glslang and spirv-cross C++ APIs to perform the conversions. I used spvBinaryToText to get the textual SPIR-V representation.