[llvm] [DirectX] Set shader feature flags MinimumPrecision and NativeLowPrecision (PR #139623)
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Mon May 12 14:03:41 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-directx
Author: Deric C. (Icohedron)
<details>
<summary>Changes</summary>
Fixes #<!-- -->138997.
The shader feature flags MinimumPrecision and NativeLowPrecision were not being set, leading to validation errors.
This PR sets these shader feature flags [as in DXC](https://github.com/microsoft/DirectXShaderCompiler/blob/377c4ca6d82adb83bf2eaf978a7040443848d6fd/lib/DXIL/DxilShaderFlags.cpp#L58-L63) and adds tests for them.
---
Full diff: https://github.com/llvm/llvm-project/pull/139623.diff
4 Files Affected:
- (modified) llvm/lib/Target/DirectX/DXILShaderFlags.cpp (+8)
- (modified) llvm/test/CodeGen/DirectX/ShaderFlags/low-precision.ll (+17-3)
- (modified) llvm/test/CodeGen/DirectX/ShaderFlags/use-native-low-precision-0.ll (+14-4)
- (modified) llvm/test/CodeGen/DirectX/ShaderFlags/use-native-low-precision-1.ll (+16-3)
``````````diff
diff --git a/llvm/lib/Target/DirectX/DXILShaderFlags.cpp b/llvm/lib/Target/DirectX/DXILShaderFlags.cpp
index b50a9b5d6051c..36f909ffa6ef5 100644
--- a/llvm/lib/Target/DirectX/DXILShaderFlags.cpp
+++ b/llvm/lib/Target/DirectX/DXILShaderFlags.cpp
@@ -296,6 +296,14 @@ void ModuleShaderFlags::initialize(Module &M, DXILResourceTypeMap &DRTM,
if (NumUAVs > 8)
CombinedSFMask.Max64UAVs = true;
+ // Set the Shader Feature Info flags related to low-precision datatypes
+ if (CombinedSFMask.LowPrecisionPresent) {
+ if (CombinedSFMask.UseNativeLowPrecision)
+ CombinedSFMask.NativeLowPrecision = true;
+ else
+ CombinedSFMask.MinimumPrecision = true;
+ }
+
CombinedSFMask.UAVsAtEveryStage = hasUAVsAtEveryStage(DRM, MMDI);
}
diff --git a/llvm/test/CodeGen/DirectX/ShaderFlags/low-precision.ll b/llvm/test/CodeGen/DirectX/ShaderFlags/low-precision.ll
index 561e09bb1e9dc..bccc14d2b38cb 100644
--- a/llvm/test/CodeGen/DirectX/ShaderFlags/low-precision.ll
+++ b/llvm/test/CodeGen/DirectX/ShaderFlags/low-precision.ll
@@ -1,4 +1,10 @@
; 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
+
+; Check that when the dx.nativelowprec module flag is not specified, the
+; module-level shader flag UseNativeLowPrecision is not set, and the
+; MinimumPrecision feature flag is set due to the presence of half and i16
+; without native low precision.
target triple = "dxil-pc-shadermodel6.7-library"
@@ -6,25 +12,33 @@ target triple = "dxil-pc-shadermodel6.7-library"
;CHECK-NEXT: ; Shader Flags Value: 0x00000020
;CHECK-NEXT: ;
;CHECK-NEXT: ; Note: shader requires additional functionality:
+;CHECK-NEXT: ; Minimum-precision data types
;CHECK-NEXT: ; Note: extra DXIL module flags:
;CHECK-NEXT: ; Low-precision data types
;CHECK-NEXT: ;
;CHECK-NEXT: ; Shader Flags for Module Functions
;CHECK-LABEL: ; Function add_i16 : 0x00000020
-define i16 @add_i16(i16 %a, i16 %b) {
+define i16 @add_i16(i16 %a, i16 %b) "hlsl.export" {
%sum = add i16 %a, %b
ret i16 %sum
}
;CHECK-LABEL: ; Function add_i32 : 0x00000000
-define i32 @add_i32(i32 %a, i32 %b) {
+define i32 @add_i32(i32 %a, i32 %b) "hlsl.export" {
%sum = add i32 %a, %b
ret i32 %sum
}
;CHECK-LABEL: ; Function add_half : 0x00000020
-define half @add_half(half %a, half %b) {
+define half @add_half(half %a, half %b) "hlsl.export" {
%sum = fadd half %a, %b
ret half %sum
}
+
+; DXC: - Name: SFI0
+; DXC-NEXT: Size: 8
+; DXC-NEXT: Flags:
+; DXC: MinimumPrecision: true
+; DXC: NativeLowPrecision: false
+; DXC: ...
diff --git a/llvm/test/CodeGen/DirectX/ShaderFlags/use-native-low-precision-0.ll b/llvm/test/CodeGen/DirectX/ShaderFlags/use-native-low-precision-0.ll
index c537a01482f39..e4d55d3d89013 100644
--- a/llvm/test/CodeGen/DirectX/ShaderFlags/use-native-low-precision-0.ll
+++ b/llvm/test/CodeGen/DirectX/ShaderFlags/use-native-low-precision-0.ll
@@ -1,7 +1,9 @@
; 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
; Check that when the dx.nativelowprec module flag is set to 0, the module-level
-; shader flag UseNativeLowPrecision is not set
+; shader flag UseNativeLowPrecision is not set, and the MinimumPrecision feature
+; flag is set due to the presence of half and i16 without native low precision.
target triple = "dxil-pc-shadermodel6.7-library"
@@ -9,6 +11,7 @@ target triple = "dxil-pc-shadermodel6.7-library"
;CHECK-NEXT: ; Shader Flags Value: 0x00000020
;CHECK-NEXT: ;
;CHECK-NEXT: ; Note: shader requires additional functionality:
+;CHECK-NEXT: ; Minimum-precision data types
;CHECK-NEXT: ; Note: extra DXIL module flags:
;CHECK-NEXT: ; Low-precision data types
;CHECK-NOT: ; Native 16bit types enabled
@@ -16,22 +19,29 @@ target triple = "dxil-pc-shadermodel6.7-library"
;CHECK-NEXT: ; Shader Flags for Module Functions
;CHECK-LABEL: ; Function add_i16 : 0x00000020
-define i16 @add_i16(i16 %a, i16 %b) {
+define i16 @add_i16(i16 %a, i16 %b) "hlsl.export" {
%sum = add i16 %a, %b
ret i16 %sum
}
;CHECK-LABEL: ; Function add_i32 : 0x00000000
-define i32 @add_i32(i32 %a, i32 %b) {
+define i32 @add_i32(i32 %a, i32 %b) "hlsl.export" {
%sum = add i32 %a, %b
ret i32 %sum
}
;CHECK-LABEL: ; Function add_half : 0x00000020
-define half @add_half(half %a, half %b) {
+define half @add_half(half %a, half %b) "hlsl.export" {
%sum = fadd half %a, %b
ret half %sum
}
!llvm.module.flags = !{!0}
!0 = !{i32 1, !"dx.nativelowprec", i32 0}
+
+; DXC: - Name: SFI0
+; DXC-NEXT: Size: 8
+; DXC-NEXT: Flags:
+; DXC: MinimumPrecision: true
+; DXC: NativeLowPrecision: false
+; DXC: ...
diff --git a/llvm/test/CodeGen/DirectX/ShaderFlags/use-native-low-precision-1.ll b/llvm/test/CodeGen/DirectX/ShaderFlags/use-native-low-precision-1.ll
index 07c4b9064d666..6ee592de087a6 100644
--- a/llvm/test/CodeGen/DirectX/ShaderFlags/use-native-low-precision-1.ll
+++ b/llvm/test/CodeGen/DirectX/ShaderFlags/use-native-low-precision-1.ll
@@ -1,4 +1,9 @@
; 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
+
+; Check that when the dx.nativelowprec module flag is set to 1, the module-level
+; shader flag UseNativeLowPrecision is set, and the NativeLowPrecision feature
+; flag is set
target triple = "dxil-pc-shadermodel6.7-library"
@@ -6,6 +11,7 @@ target triple = "dxil-pc-shadermodel6.7-library"
;CHECK-NEXT: ; Shader Flags Value: 0x00800020
;CHECK-NEXT: ;
;CHECK-NEXT: ; Note: shader requires additional functionality:
+;CHECK-NEXT: ; Use native low precision
;CHECK-NEXT: ; Note: extra DXIL module flags:
;CHECK-NEXT: ; Low-precision data types
;CHECK-NEXT: ; Use native low precision
@@ -13,7 +19,7 @@ target triple = "dxil-pc-shadermodel6.7-library"
;CHECK-NEXT: ; Shader Flags for Module Functions
;CHECK-LABEL: ; Function add_i16 : 0x00800020
-define i16 @add_i16(i16 %a, i16 %b) {
+define i16 @add_i16(i16 %a, i16 %b) "hlsl.export" {
%sum = add i16 %a, %b
ret i16 %sum
}
@@ -22,16 +28,23 @@ define i16 @add_i16(i16 %a, i16 %b) {
; in the module regardless of whether or not the function uses low precision
; data types (flag 0x20). This matches the behavior in DXC
;CHECK-LABEL: ; Function add_i32 : 0x00800000
-define i32 @add_i32(i32 %a, i32 %b) {
+define i32 @add_i32(i32 %a, i32 %b) "hlsl.export" {
%sum = add i32 %a, %b
ret i32 %sum
}
;CHECK-LABEL: ; Function add_half : 0x00800020
-define half @add_half(half %a, half %b) {
+define half @add_half(half %a, half %b) "hlsl.export" {
%sum = fadd half %a, %b
ret half %sum
}
!llvm.module.flags = !{!0}
!0 = !{i32 1, !"dx.nativelowprec", i32 1}
+
+; DXC: - Name: SFI0
+; DXC-NEXT: Size: 8
+; DXC-NEXT: Flags:
+; DXC: MinimumPrecision: false
+; DXC: NativeLowPrecision: true
+; DXC: ...
``````````
</details>
https://github.com/llvm/llvm-project/pull/139623
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