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[DirectX] Implement Shader Flag Analysis for UAVsAtEveryStage #137085

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Merged
merged 8 commits into from
Apr 29, 2025
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[DirectX] Implement Shader Flag Analysis for UAVsAtEveryStage #137085

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8342b32
Implement UAVsAtEveryStage shader flag
Icohedron Apr 23, 2025
1f11675
Change vertex shader test function name and remove hlsl.export from it
Icohedron Apr 24, 2025
5955a67
Simplify the logic for setting UAVsAtEveryStage
Icohedron Apr 25, 2025
f6410d0
Remove repeated comments among tests
Icohedron Apr 25, 2025
bd1be2a
Remove checks for no other shader flag is being set
Icohedron Apr 25, 2025
a956f03
Merge remote-tracking branch 'upstream/main' into shader-flag-UAVsAtE…
Icohedron Apr 25, 2025
88793b6
Add additional fixes to unrelated shader-flag tests to account for UA…
Icohedron Apr 25, 2025
362c442
Apply clang-format
Icohedron Apr 25, 2025
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31 changes: 31 additions & 0 deletions llvm/lib/Target/DirectX/DXILShaderFlags.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,35 @@
using namespace llvm;
using namespace llvm::dxil;

static bool hasUAVsAtEveryStage(DXILResourceMap &DRM,
const ModuleMetadataInfo &MMDI) {
if (DRM.uavs().empty())
return false;

switch (MMDI.ShaderProfile) {
default:
return false;
case Triple::EnvironmentType::Compute:
case Triple::EnvironmentType::Pixel:
return false;
case Triple::EnvironmentType::Vertex:
case Triple::EnvironmentType::Geometry:
case Triple::EnvironmentType::Hull:
case Triple::EnvironmentType::Domain:
return true;
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Shouldnt this be only if the version is greater than 1.8, based on the issue description?

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If the version is less than 1.8, they would still get the UAVsAtEveryStage flag because they are not Compute or Pixel

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@Icohedron Icohedron Apr 29, 2025 •
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I think the real potential issue is if in the future we get new shader stage, the UAVsAtEveryStage flag will not get assigned to the new shader stage when the DXIL validator version is < 1.8

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@bogner Do you think the hasUAVsAtEveryStage function should be this instead?

bool hasUAVsAtEveryStage(DXILResourceMap &DRM, const ModuleMetadataInfo &MMDI) {
  if (DRM.uavs().empty())
    return false;

  switch (MMDI.ShaderProfile) {
  default:
    return MMDI.ValidatorVersion < VersionTuple(1, 8);
  case Triple::EnvironmentType::Compute:
  case Triple::EnvironmentType::Pixel:
    return false;
  case Triple::EnvironmentType::Vertex:
  case Triple::EnvironmentType::Geometry:
  case Triple::EnvironmentType::Hull:
  case Triple::EnvironmentType::Domain:
    return true;
  }
}

This is so that we don't have to edit the switch every time a new shader stage gets added.

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This is one of the places where the fact that we're using the triple environment rather than a dedicated enum is kind of annoying. If we had a dedicated enum then we would get a -Wcovered-switch warning if that came up and my answer to this question would unambiguously be no.

However, I still don't think that this would be an improvement. Consider:

  • If we get another shader stage then by definition the validator version is greater than 1.8, since a new shader stage couldn't be added without bumping the DXIL version.
  • Whether or not UAVsAtEveryStage should be set for the new shader stage probably depends on what that stage is, so we'd probably want to modify this anyway.
  • If we have a triple that doesn't have a shader stage as its environment (ie, it isn't a dxil- triple at all), then calling this function doesn't make any sense. We could arguably make the default case llvm_unreachable() and just crash if that were to happen.

case Triple::EnvironmentType::Library:
case Triple::EnvironmentType::RayGeneration:
case Triple::EnvironmentType::Intersection:
case Triple::EnvironmentType::AnyHit:
case Triple::EnvironmentType::ClosestHit:
case Triple::EnvironmentType::Miss:
case Triple::EnvironmentType::Callable:
case Triple::EnvironmentType::Mesh:
case Triple::EnvironmentType::Amplification:
return MMDI.ValidatorVersion < VersionTuple(1, 8);
}
}

static bool checkWaveOps(Intrinsic::ID IID) {
// Currently unsupported intrinsics
// case Intrinsic::dx_wave_getlanecount:
Expand Down Expand Up @@ -266,6 +295,8 @@ void ModuleShaderFlags::initialize(Module &M, DXILResourceTypeMap &DRTM,
NumUAVs += UAV.getBinding().Size;
if (NumUAVs > 8)
CombinedSFMask.Max64UAVs = true;

CombinedSFMask.UAVsAtEveryStage = hasUAVsAtEveryStage(DRM, MMDI);
}

void ComputedShaderFlags::print(raw_ostream &OS) const {
Expand Down
7 changes: 3 additions & 4 deletions llvm/test/CodeGen/DirectX/ShaderFlags/max-64-uavs-array-valver1.5.ll
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Expand Up @@ -7,9 +7,10 @@
target triple = "dxil-pc-shadermodel6.7-library"

; CHECK: Combined Shader Flags for Module
; CHECK-NEXT: Shader Flags Value: 0x00000000
; CHECK-NEXT: Shader Flags Value: 0x00010000

; CHECK-NOT: Note: shader requires additional functionality:
; CHECK: Note: shader requires additional functionality:
; CHECK: UAVs at every shader stage
; CHECK-NOT: 64 UAV slots

; CHECK: Function test : 0x00000000
Expand All @@ -26,10 +27,8 @@ define void @test() "hlsl.export" {
ret void
}

; Set validator version to 1.5
!dx.valver = !{!1}
!1 = !{i32 1, i32 5}

; Set this flag to 1 to prevent the ResMayNotAlias flag from being set
!llvm.module.flags = !{!0}
!0 = !{i32 1, !"dx.resmayalias", i32 1}
9 changes: 3 additions & 6 deletions llvm/test/CodeGen/DirectX/ShaderFlags/max-64-uavs-array-valver1.6.ll
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Expand Up @@ -8,9 +8,10 @@
target triple = "dxil-pc-shadermodel6.7-library"

; CHECK: Combined Shader Flags for Module
; CHECK-NEXT: Shader Flags Value: 0x00008000
; CHECK-NEXT: Shader Flags Value: 0x00018000

; CHECK: Note: shader requires additional functionality:
; CHECK: UAVs at every shader stage
; CHECK: 64 UAV slots

; CHECK: Function test : 0x00000000
Expand All @@ -27,19 +28,15 @@ define void @test() "hlsl.export" {
ret void
}

; Set validator version to 1.6
!dx.valver = !{!1}
!1 = !{i32 1, i32 6}

; Set this flag to 1 to prevent the ResMayNotAlias flag from being set
!llvm.module.flags = !{!0}
!0 = !{i32 1, !"dx.resmayalias", i32 1}

; DXC: - Name: SFI0
; DXC-NEXT: Size: 8
; DXC-NEXT: Flags:
; DXC-NOT: {{[A-Za-z]+: +true}}
; DXC: Max64UAVs: true
; DXC-NOT: {{[A-Za-z]+: +true}}
; DXC: Max64UAVs: true
; DXC: NextUnusedBit: false
; DXC: ...
6 changes: 3 additions & 3 deletions llvm/test/CodeGen/DirectX/ShaderFlags/max-64-uavs.ll
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Expand Up @@ -55,13 +55,13 @@ define void @test() "hlsl.export" {
}

!llvm.module.flags = !{!0}
!dx.valver = !{!1}
!0 = !{i32 1, !"dx.resmayalias", i32 1}
!1 = !{i32 1, i32 8}

; DXC: - Name: SFI0
; DXC-NEXT: Size: 8
; DXC-NEXT: Flags:
; DXC-NOT: {{[A-Za-z]+: +true}}
; DXC: Max64UAVs: true
; DXC-NOT: {{[A-Za-z]+: +true}}
; DXC: Max64UAVs: true
; DXC: NextUnusedBit: false
; DXC: ...
4 changes: 3 additions & 1 deletion llvm/test/CodeGen/DirectX/ShaderFlags/res-may-alias-1.ll
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Expand Up @@ -35,7 +35,9 @@ define float @loadSRV() #0 {
}

!llvm.module.flags = !{!0}

!0 = !{i32 1, !"dx.resmayalias", i32 1}

!dx.valver = !{!1}
!1 = !{i32 1, i32 8}

attributes #0 = { convergent norecurse nounwind "hlsl.export"}
3 changes: 3 additions & 0 deletions llvm/test/CodeGen/DirectX/ShaderFlags/res-may-not-alias-sm6.6.ll
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Expand Up @@ -34,4 +34,7 @@ define float @loadSRV() #0 {
ret float %val
}

!dx.valver = !{!0}
!0 = !{i32 1, i32 8}

attributes #0 = { convergent norecurse nounwind "hlsl.export"}
15 changes: 11 additions & 4 deletions llvm/test/CodeGen/DirectX/ShaderFlags/res-may-not-alias-sm6.7.ll
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@@ -1,14 +1,18 @@
; RUN: opt -S --passes="print-dx-shader-flags" 2>&1 %s | FileCheck %s

; This test checks to ensure the behavior of the DXIL shader flag analysis
; for the flag ResMayNotAlias is correct when the DXIL Version is >= 1.7. The
; ResMayNotAlias flag (0x20000000) should be set on all functions if there are
; one or more UAVs present globally in the module.
; for the flag ResMayNotAlias is correct when the DXIL Version is >= 1.7 and the
; DXIL Validator Version < 1.8. The ResMayNotAlias flag (0x20000000) should be
; set on all functions if there are one or more UAVs present globally in the
; module.

target triple = "dxil-pc-shadermodel6.7-library"

; CHECK: Combined Shader Flags for Module
; CHECK-NEXT: Shader Flags Value: 0x200000010
; CHECK-NEXT: Shader Flags Value: 0x200010010

; CHECK: Note: shader requires additional functionality:
; CHECK: UAVs at every shader stage

; CHECK: Note: extra DXIL module flags:
; CHECK: Raw and Structured buffers
Expand All @@ -35,4 +39,7 @@ define float @loadSRV() #0 {
ret float %val
}

!dx.valver = !{!0}
!0 = !{i32 1, i32 7}

attributes #0 = { convergent norecurse nounwind "hlsl.export"}
4 changes: 2 additions & 2 deletions llvm/test/CodeGen/DirectX/ShaderFlags/res-may-not-alias-valver1.8.ll
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Expand Up @@ -35,7 +35,7 @@ define float @loadSRV() #0 {
ret float %val
}

!dx.valver = !{!1}
!1 = !{i32 1, i32 8}
!dx.valver = !{!0}
!0 = !{i32 1, i32 8}

attributes #0 = { convergent norecurse nounwind "hlsl.export"}
2 changes: 2 additions & 0 deletions llvm/test/CodeGen/DirectX/ShaderFlags/typed-uav-load-additional-formats.ll
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Expand Up @@ -44,7 +44,9 @@ define void @noload(<4 x float> %val) #0 {
}

!llvm.module.flags = !{!0}
!dx.valver = !{!1}
!0 = !{i32 1, !"dx.resmayalias", i32 1}
!1 = !{i32 1, i32 8}

attributes #0 = { convergent norecurse nounwind "hlsl.export"}

35 changes: 35 additions & 0 deletions llvm/test/CodeGen/DirectX/ShaderFlags/uavs-at-every-stage-lib-valver1.7.ll
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@@ -0,0 +1,35 @@
; RUN: opt -S --passes="print-dx-shader-flags" 2>&1 %s | FileCheck %s
; RUN: llc %s --filetype=obj -o - | obj2yaml | FileCheck %s --check-prefix=DXC

; This test ensures that a library shader with a UAV gets the module and
; shader feature flag UAVsAtEveryStage when the DXIL validator version is < 1.8

target triple = "dxil-pc-shadermodel6.5-library"

; CHECK: Combined Shader Flags for Module
; CHECK-NEXT: Shader Flags Value: 0x00010000

; CHECK: Note: shader requires additional functionality:
; CHECK: UAVs at every shader stage

; CHECK: Function test : 0x00000000
define void @test() "hlsl.export" {
; RWBuffer<float> Buf : register(u0, space0)
%buf0 = call target("dx.TypedBuffer", float, 1, 0, 1)
@llvm.dx.resource.handlefrombinding.tdx.TypedBuffer_f32_1_0t(
i32 0, i32 0, i32 1, i32 0, i1 false)
ret void
}

!dx.valver = !{!1}
!1 = !{i32 1, i32 7}

!llvm.module.flags = !{!0}
!0 = !{i32 1, !"dx.resmayalias", i32 1}

; DXC: - Name: SFI0
; DXC-NEXT: Size: 8
; DXC-NEXT: Flags:
; DXC: UAVsAtEveryStage: true
; DXC: NextUnusedBit: false
; DXC: ...
27 changes: 27 additions & 0 deletions llvm/test/CodeGen/DirectX/ShaderFlags/uavs-at-every-stage-lib-valver1.8.ll
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@@ -0,0 +1,27 @@
; RUN: opt -S --passes="print-dx-shader-flags" 2>&1 %s | FileCheck %s

; This test ensures that a library shader with a UAV does not get the module and
; shader feature flag UAVsAtEveryStage when the DXIL validator version is >= 1.8

target triple = "dxil-pc-shadermodel6.5-library"

; CHECK: Combined Shader Flags for Module
; CHECK-NEXT: Shader Flags Value: 0x00000000

; CHECK-NOT: Note: shader requires additional functionality:
; CHECK-NOT: UAVs at every shader stage

; CHECK: Function test : 0x00000000
define void @test() "hlsl.export" {
; RWBuffer<float> Buf : register(u0, space0)
%buf0 = call target("dx.TypedBuffer", float, 1, 0, 1)
@llvm.dx.resource.handlefrombinding.tdx.TypedBuffer_f32_1_0t(
i32 0, i32 0, i32 1, i32 0, i1 false)
ret void
}

!dx.valver = !{!1}
!1 = !{i32 1, i32 8}

!llvm.module.flags = !{!0}
!0 = !{i32 1, !"dx.resmayalias", i32 1}
36 changes: 36 additions & 0 deletions llvm/test/CodeGen/DirectX/ShaderFlags/uavs-at-every-stage-vs.ll
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@@ -0,0 +1,36 @@
; RUN: opt -S --passes="print-dx-shader-flags" 2>&1 %s | FileCheck %s
; TODO: Remove this comment and add 'RUN' to the line below once vertex shaders are supported by llc
; llc %s --filetype=obj -o - | obj2yaml | FileCheck %s --check-prefix=DXC

; This test ensures that a Vertex shader with a UAV gets the module and
; shader feature flag UAVsAtEveryStage

target triple = "dxil-pc-shadermodel6.5-vertex"

; CHECK: Combined Shader Flags for Module
; CHECK-NEXT: Shader Flags Value: 0x00010000

; CHECK: Note: shader requires additional functionality:
; CHECK: UAVs at every shader stage

; CHECK: Function VSMain : 0x00000000
define void @VSMain() {
; RWBuffer<float> Buf : register(u0, space0)
%buf0 = call target("dx.TypedBuffer", float, 1, 0, 1)
@llvm.dx.resource.handlefrombinding.tdx.TypedBuffer_f32_1_0t(
i32 0, i32 0, i32 1, i32 0, i1 false)
ret void
}

!dx.valver = !{!1}
!1 = !{i32 1, i32 8}

!llvm.module.flags = !{!0}
!0 = !{i32 1, !"dx.resmayalias", i32 1}

; DXC: - Name: SFI0
; DXC-NEXT: Size: 8
; DXC-NEXT: Flags:
; DXC: UAVsAtEveryStage: true
; DXC: NextUnusedBit: false
; DXC: ...
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