[DirectX] Validating Root flags are denying shader stage #153287

joaosaffran · 2025-08-12T20:40:27Z

Root Signature Flags, allow flags to block compilation of certain shader stages. This PR implements a validation and notify the user if they compile a root signature that is denying such shader stage.
Closes: #153062

llvmbot · 2025-08-12T20:41:00Z

@llvm/pr-subscribers-backend-directx

Author: None (joaosaffran)

Changes

Root Signature Flags, allow flags to block compilation of certain shader stages. This PR implements a validation and notify the user if they compile a root signature that is denying such shader stage.
Closes: #153062

Full diff: https://github.com/llvm/llvm-project/pull/153287.diff

4 Files Affected:

(modified) llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp (+71-24)
(added) llvm/test/CodeGen/DirectX/rootsignature-validation-deny-shader.ll (+16)
(added) llvm/test/CodeGen/DirectX/rootsignature-validation-fail-deny-multiple-shader.ll (+17)
(added) llvm/test/CodeGen/DirectX/rootsignature-validation-fail-deny-single-shader.ll (+17)

diff --git a/llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp b/llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp
index 3721b5f539b8c..3897056d5081a 100644
--- a/llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp
+++ b/llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp
@@ -21,7 +21,6 @@
 #include "llvm/InitializePasses.h"
 #include "llvm/MC/DXContainerRootSignature.h"
 #include "llvm/Support/DXILABI.h"
-#include <cstdint>
 
 #define DEBUG_TYPE "dxil-post-optimization-validation"
 
@@ -169,15 +168,16 @@ reportDescriptorTableMixingTypes(Module &M, uint32_t Location,
   M.getContext().diagnose(DiagnosticInfoGeneric(Message));
 }
 
-static void reportOverlowingRange(Module &M, const dxbc::RTS0::v2::DescriptorRange &Range) {
+static void
+reportOverlowingRange(Module &M, const dxbc::RTS0::v2::DescriptorRange &Range) {
   SmallString<128> Message;
   raw_svector_ostream OS(Message);
-  OS << "Cannot append range with implicit lower " 
-      << "bound after an unbounded range "
-      << getResourceClassName(toResourceClass(static_cast<dxbc::DescriptorRangeType>(Range.RangeType)))
-      << "(register=" << Range.BaseShaderRegister << ", space=" << 
-      Range.RegisterSpace
-      << ") exceeds maximum allowed value.";
+  OS << "Cannot append range with implicit lower "
+     << "bound after an unbounded range "
+     << getResourceClassName(toResourceClass(
+            static_cast<dxbc::DescriptorRangeType>(Range.RangeType)))
+     << "(register=" << Range.BaseShaderRegister
+     << ", space=" << Range.RegisterSpace << ") exceeds maximum allowed value.";
   M.getContext().diagnose(DiagnosticInfoGeneric(Message));
 }
 
@@ -262,12 +262,57 @@ getRootDescriptorsBindingInfo(const mcdxbc::RootSignatureDesc &RSD,
   return RDs;
 }
 
+static void reportIfDeniedShaderStageAccess(Module &M, dxbc::RootFlags Flags,
+                                            dxbc::RootFlags Mask) {
+  if ((Flags & Mask) == Mask) {
+    SmallString<128> Message;
+    raw_svector_ostream OS(Message);
+    OS << "Shader has root bindings but root signature uses a DENY flag to "
+          "disallow root binding access to the shader stage.";
+    M.getContext().diagnose(DiagnosticInfoGeneric(Message));
+  }
+}
+
+static void validateRootFlags(Module &M, const mcdxbc::RootSignatureDesc &RSD,
+                              const dxil::ModuleMetadataInfo &MMI) {
+  dxbc::RootFlags Flags = dxbc::RootFlags(RSD.Flags);
 
+  switch (MMI.ShaderProfile) {
+  case Triple::Pixel:
+    reportIfDeniedShaderStageAccess(M, Flags,
+                                    dxbc::RootFlags::DenyPixelShaderRootAccess);
+    break;
+  case Triple::Vertex:
+    reportIfDeniedShaderStageAccess(
+        M, Flags, dxbc::RootFlags::DenyVertexShaderRootAccess);
+    break;
+  case Triple::Geometry:
+    reportIfDeniedShaderStageAccess(
+        M, Flags, dxbc::RootFlags::DenyGeometryShaderRootAccess);
+    break;
+  case Triple::Hull:
+    reportIfDeniedShaderStageAccess(M, Flags,
+                                    dxbc::RootFlags::DenyHullShaderRootAccess);
+    break;
+  case Triple::Domain:
+    reportIfDeniedShaderStageAccess(
+        M, Flags, dxbc::RootFlags::DenyDomainShaderRootAccess);
+    break;
+  case Triple::Mesh:
+    reportIfDeniedShaderStageAccess(M, Flags,
+                                    dxbc::RootFlags::DenyMeshShaderRootAccess);
+    break;
+  case Triple::Amplification:
+    reportIfDeniedShaderStageAccess(
+        M, Flags, dxbc::RootFlags::DenyAmplificationShaderRootAccess);
+    break;
+  default:
+    break;
+  }
+}
 
 static void validateDescriptorTables(Module &M,
-                                     const mcdxbc::RootSignatureDesc &RSD,
-                                     dxil::ModuleMetadataInfo &MMI,
-                                     DXILResourceMap &DRM) {
+                                     const mcdxbc::RootSignatureDesc &RSD) {
   for (const mcdxbc::RootParameterInfo &ParamInfo : RSD.ParametersContainer) {
     if (static_cast<dxbc::RootParameterType>(ParamInfo.Header.ParameterType) !=
         dxbc::RootParameterType::DescriptorTable)
@@ -283,30 +328,31 @@ static void validateDescriptorTables(Module &M,
 
     uint64_t AppendingOffset = 0;
 
-
     for (const dxbc::RTS0::v2::DescriptorRange &Range : Table.Ranges) {
       dxbc::DescriptorRangeType RangeType =
           static_cast<dxbc::DescriptorRangeType>(Range.RangeType);
-      
+
       uint64_t Offset = AppendingOffset;
-      if(Range.OffsetInDescriptorsFromTableStart != ~0U)
+      if (Range.OffsetInDescriptorsFromTableStart != ~0U)
         Offset = Range.OffsetInDescriptorsFromTableStart;
-      
-      if(Offset > ~0U)
+
+      if (Offset > ~0U)
         reportOverlowingRange(M, Range);
-      if(Range.NumDescriptors == ~0U) {
+      if (Range.NumDescriptors == ~0U) {
         AppendingOffset = (uint64_t)~0U + (uint64_t)1ULL;
-      } else { 
-        uint64_t UpperBound = (uint64_t)Range.BaseShaderRegister + (uint64_t)Range.NumDescriptors - (uint64_t)1U;
-        if(UpperBound > ~0U)
+      } else {
+        uint64_t UpperBound = (uint64_t)Range.BaseShaderRegister +
+                              (uint64_t)Range.NumDescriptors - (uint64_t)1U;
+        if (UpperBound > ~0U)
           reportOverlowingRange(M, Range);
 
-        uint64_t AppendingUpperBound = (uint64_t)Offset + (uint64_t)Range.NumDescriptors - (uint64_t)1U;
-        if(AppendingUpperBound > ~0U)
+        uint64_t AppendingUpperBound =
+            (uint64_t)Offset + (uint64_t)Range.NumDescriptors - (uint64_t)1U;
+        if (AppendingUpperBound > ~0U)
           reportOverlowingRange(M, Range);
         AppendingOffset = Offset + Range.NumDescriptors;
       }
-      
+
       if (RangeType == dxbc::DescriptorRangeType::Sampler) {
         HasSampler = true;
       } else {
@@ -441,7 +487,8 @@ static void reportErrors(Module &M, DXILResourceMap &DRM,
 
   if (mcdxbc::RootSignatureDesc *RSD = getRootSignature(RSBI, MMI)) {
     validateRootSignatureBindings(M, *RSD, MMI, DRM);
-    validateDescriptorTables(M, *RSD, MMI, DRM);
+    validateDescriptorTables(M, *RSD);
+    validateRootFlags(M, *RSD, MMI);
   }
 }
 
diff --git a/llvm/test/CodeGen/DirectX/rootsignature-validation-deny-shader.ll b/llvm/test/CodeGen/DirectX/rootsignature-validation-deny-shader.ll
new file mode 100644
index 0000000000000..234909e82b792
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/rootsignature-validation-deny-shader.ll
@@ -0,0 +1,16 @@
+; RUN: opt -S -passes='dxil-post-optimization-validation' %s 2>&1 
+; expected-no-diagnostics
+target triple = "dxil-pc-shadermodel6.6-geometry"
+
+define void @CSMain() #0 {
+entry:
+  ret void
+}
+attributes #0 = { noinline nounwind "exp-shader"="cs" "hlsl.numthreads"="1,2,1" "hlsl.shader"="geometry" }
+
+!dx.rootsignatures = !{!0}
+
+!0 = !{ptr @CSMain, !1, i32 2}
+!1 = !{!2}
+!2 = !{ !"RootFlags", i32 294 } ; 32 = deny_pixel/hull/vertex/amplification_shader_root_access
+
diff --git a/llvm/test/CodeGen/DirectX/rootsignature-validation-fail-deny-multiple-shader.ll b/llvm/test/CodeGen/DirectX/rootsignature-validation-fail-deny-multiple-shader.ll
new file mode 100644
index 0000000000000..9286c31db2de0
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/rootsignature-validation-fail-deny-multiple-shader.ll
@@ -0,0 +1,17 @@
+; RUN: not opt -S -passes='dxil-post-optimization-validation' %s 2>&1 | FileCheck %s
+
+; CHECK: error: Shader has root bindings but root signature uses a DENY flag to disallow root binding access to the shader stage.
+target triple = "dxil-pc-shadermodel6.6-hull"
+
+define void @CSMain() #0 {
+entry:
+  ret void
+}
+attributes #0 = { noinline nounwind "exp-shader"="cs" "hlsl.numthreads"="1,2,1" "hlsl.shader"="hull" }
+
+!dx.rootsignatures = !{!0}
+
+!0 = !{ptr @CSMain, !1, i32 2}
+!1 = !{!2}
+!2 = !{ !"RootFlags", i32 294 } ; 32 = deny_pixel/hull/vertex/amplification_shader_root_access
+
diff --git a/llvm/test/CodeGen/DirectX/rootsignature-validation-fail-deny-single-shader.ll b/llvm/test/CodeGen/DirectX/rootsignature-validation-fail-deny-single-shader.ll
new file mode 100644
index 0000000000000..7294346900415
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/rootsignature-validation-fail-deny-single-shader.ll
@@ -0,0 +1,17 @@
+; RUN: not opt -S -passes='dxil-post-optimization-validation' %s 2>&1 | FileCheck %s
+
+; CHECK: error: Shader has root bindings but root signature uses a DENY flag to disallow root binding access to the shader stage.
+target triple = "dxil-pc-shadermodel6.6-pixel"
+
+define void @CSMain() #0 {
+entry:
+  ret void
+}
+attributes #0 = { noinline nounwind "exp-shader"="cs" "hlsl.numthreads"="1,2,1" "hlsl.shader"="pixel" }
+
+!dx.rootsignatures = !{!0}
+
+!0 = !{ptr @CSMain, !1, i32 2}
+!1 = !{!2}
+!2 = !{ !"RootFlags", i32 32 } ; 32 = deny_pixel_shader_root_access
+

github-actions · 2025-08-12T20:45:20Z

✅ With the latest revision this PR passed the C/C++ code formatter.

joaosaffran · 2025-09-15T20:06:42Z

llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp

+      if (RK != ResourceKind::RawBuffer &&
+          RK != ResourceKind::StructuredBuffer) {


Formatter trigger that, since it gets linger than 80 columns

joaosaffran · 2025-09-15T20:07:02Z

llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp

            Builder.findOverlapping(ReportedBinding);
        reportOverlappingRegisters(M, ReportedBinding, Overlaping);
      });
+


That is intentional, I think it improves readability.

joaosaffran · 2025-09-15T20:10:39Z

llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp

+  if ((Flags & Mask) != Mask)
+    return;


I added this check here, because I think it simplifies the code. If this is not here, I need to make the same check in all statements of the switch with slightly different masks.

joaosaffran · 2025-09-15T20:19:44Z

llvm/test/CodeGen/DirectX/rootsignature-validation-fail-deny-single-shader-root-descriptor.ll

@@ -0,0 +1,20 @@
+; RUN: not opt -S -passes='dxil-post-optimization-validation' %s 2>&1 | FileCheck %s


This test checks an edge case, where root descriptors can be bound with non textures, but if they are denied, it should fail

inbelic

Mostly LGTM, just some clean ups I think we should do

inbelic · 2025-09-15T20:37:27Z

llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp

  }
+
+  if (HasBindings && MMI.ShaderProfile != Triple::Compute) {
+    dxbc::RootFlags Flags = dxbc::RootFlags(RSD.Flags);


nit: it may be nicer if we define a separate function like getEnvironmentDenyFlag and then just invoked reportIfDeniedShaderStageAccess once. Might prevent a copy of this switch table appearing elsewhere

llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp

bogner · 2025-09-17T16:59:32Z

llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp

+  if (HasBindings && MMI.ShaderProfile != Triple::Compute) {
+    const dxbc::RootFlags Flags = dxbc::RootFlags(RSD.Flags);
+    const dxbc::RootFlags Mask = getEnvironmentDenyFlagMask(MMI.ShaderProfile);


Does this do the right thing for Library shaders? What about the various raytracing profiles (RayGeneration, Intersection, AnyHit, etc)? Is there some reason we can't get here for those?

inbelic · 2025-09-17T21:18:17Z

llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp

+        ParamInfo->Type == dxbc::RootParameterType::DescriptorTable;
+    const bool IsRawOrStructuredBuffer =
+        RK != ResourceKind::RawBuffer && RK != ResourceKind::StructuredBuffer;
+    if (IsRootSRVOrUAV && !IsDescriptorTable && IsRawOrStructuredBuffer) {


Why is the !IsDescriptorTable needed? I would've assumed that IsRootSRVOrUAV would imply that.

IsRootSRVOrUAV only check if the resource being bound is SRV or UAV, is not checking what kind of resource is being bounded to. In this validation, you can bound to a DescriptorTable but not with a RootSRV or RootUAV.

Here is a godbolt link with this example:
https://hlsl.godbolt.org/z/WW4qTs4hf

llvm/test/CodeGen/DirectX/rootsignature-validation-fail-deny-multiple-shader.ll

bogner

Looks mostly good. A few minor comments yet.

bogner · 2025-09-23T16:36:03Z

llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp

+  const std::optional<dxbc::RootFlags> Mask =
+      getEnvironmentDenyFlagMask(MMI.ShaderProfile);


While it isn't wrong, const on variables with value types like bool and std::optional doesn't gain us a lot (since the memory is local anyway) so it's somewhat uncommon. I would probably not bother with them here as a matter of style and clarity.

bogner · 2025-09-23T16:42:31Z

llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp

+  if (!Mask.has_value() || !HasBindings)
+    return;


I think it's slightly clearer to check !HasBindings and return early before calling getEnvironmentalDenyFlagMask. This makes it obvious that the Mask doesn't matter if we don't have any bindings. This could also let you nest the declaration of Mask in the if () condition if you think it reads better:

if (std::optional<dxbc::RootFlags> Mask = getEnvironmentDenyFlagMask(MMI.ShaderProfile)) reportIfDeniedShaderStageAccess(M, dxbc::RootFlags(RSD.Flags), *Mask);

bogner · 2025-09-23T16:43:02Z

llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp

+  if (!Mask.has_value() || !HasBindings)
+    return;
+
+  const dxbc::RootFlags Flags = dxbc::RootFlags(RSD.Flags);


We know that RSD.Flags is valid at this point and that's why this cast is okay, correct?

Yeah, RSD.Flags is validated when we read from the metadata, this data is not changed after such validation, so is valid.

…3287)" This reverts commit d7dd8f0.

…60917) Reverts #153287

Root Signature Flags, allow flags to block compilation of certain shader stages. This PR implements a validation and notify the user if they compile a root signature that is denying such shader stage. Closes: #153062 Previously approved: #153287 --------- Co-authored-by: joaosaffran <[email protected]> Co-authored-by: Joao Saffran <{ID}+{username}@users.noreply.github.com> Co-authored-by: Joao Saffran <[email protected]>

…#160919) Root Signature Flags, allow flags to block compilation of certain shader stages. This PR implements a validation and notify the user if they compile a root signature that is denying such shader stage. Closes: llvm/llvm-project#153062 Previously approved: llvm/llvm-project#153287 --------- Co-authored-by: joaosaffran <[email protected]> Co-authored-by: Joao Saffran <{ID}+{username}@users.noreply.github.com> Co-authored-by: Joao Saffran <[email protected]>

Root Signature Flags, allow flags to block compilation of certain shader stages. This PR implements a validation and notify the user if they compile a root signature that is denying such shader stage. Closes: llvm#153062 Previously approved: llvm#153287 --------- Co-authored-by: joaosaffran <[email protected]> Co-authored-by: Joao Saffran <{ID}+{username}@users.noreply.github.com> Co-authored-by: Joao Saffran <[email protected]>

Joao Saffran added 2 commits August 12, 2025 13:07

adding validaiton and tests

b1e34ff

fix?

90c2578

llvmbot added the backend:DirectX label Aug 12, 2025

Merge branch 'users/joaosaffran/153276' into validation/root-flags

6e20bdf

Joao Saffran added 4 commits August 12, 2025 13:46

format

84a4c4b

format

4400e2e

making validation function according to spec

eb425c5

merge

ffcff83

joaosaffran requested review from DeinAlptraum, JDevlieghere, daniel-grumberg, QuietMisdreavus, cyndyishida, aaupov, maksfb, rafaelauler, ayermolo, yota9, paschalis-mpeis, yozhu, lanza, bcardosolopes, xlauko, andykaylor, Endilll, nikic and a team as code owners August 15, 2025 01:06

joaosaffran marked this pull request as draft August 15, 2025 01:07

joaosaffran added 5 commits September 15, 2025 13:09

clean up

901bd1d

fix test

aba77f9

rename test

22319f9

rename test

4c86232

rename test

6641d66

joaosaffran commented Sep 15, 2025

View reviewed changes

joaosaffran marked this pull request as ready for review September 15, 2025 20:22

inbelic reviewed Sep 15, 2025

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joaosaffran added 4 commits September 15, 2025 14:32

refactoring follow inbelic suggestion

c9986ed

formating

a0916e1

adding getEnvironmentDenyFlagMask

1f8e5b6

format

1c2a864

bogner reviewed Sep 17, 2025

View reviewed changes

making getEnvironmentDenyFlagMask return optional

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inbelic reviewed Sep 17, 2025

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joaosaffran added 2 commits September 17, 2025 16:45

renaming SRVorUAV flag

b3bc8b8

Merge branch 'validation/descriptor-tables' into validation/root-flags

18f9e9c

bogner reviewed Sep 23, 2025

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addressing comments from bogner

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joaosaffran requested a review from bogner September 24, 2025 17:33

bogner approved these changes Sep 24, 2025

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removing consts

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joaosaffran merged commit d7dd8f0 into llvm:users/joaosaffran/153276 Sep 26, 2025
8 of 9 checks passed

joaosaffran added a commit that referenced this pull request Sep 26, 2025

Revert "[DirectX] Validating Root flags are denying shader stage (#15…

ac34c5a

…3287)" This reverts commit d7dd8f0.

joaosaffran mentioned this pull request Sep 26, 2025

Revert "[DirectX] Validating Root flags are denying shader stage" #160917

Merged

joaosaffran added a commit that referenced this pull request Sep 26, 2025

Revert "[DirectX] Validating Root flags are denying shader stage" (#1…

5a48b24

…60917) Reverts #153287

joaosaffran mentioned this pull request Sep 26, 2025

[DirectX] Validating Root flags are denying shader stage #160919

Merged

		if (RK != ResourceKind::RawBuffer &&
		RK != ResourceKind::StructuredBuffer) {

		@@ -0,0 +1,20 @@
		; RUN: not opt -S -passes='dxil-post-optimization-validation' %s 2>&1 \| FileCheck %s

		const std::optional<dxbc::RootFlags> Mask =
		getEnvironmentDenyFlagMask(MMI.ShaderProfile);

[DirectX] Validating Root flags are denying shader stage #153287

[DirectX] Validating Root flags are denying shader stage #153287

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