[DirectX] Adding missing descriptor table validations #153276

joaosaffran · 2025-08-12T20:22:59Z

This patch adds 2 small validation to DirectX backend. First, it checks if registers in descriptor tables are not overflowing, meaning they don't try to bind registers over the maximum allowed value; second, it checks if samplers are being mixed with other resource types.
Closes: #153057, #153058

llvmbot · 2025-08-12T20:23:29Z

@llvm/pr-subscribers-hlsl

@llvm/pr-subscribers-backend-directx

Author: None (joaosaffran)

Changes

This patch adds 2 small validation to DirectX backend. First, it checks if registers in descriptor tables are not overflowing, meaning they don't try to bind registers over the maximum allowed value; second, it checks if samplers are being mixed with other resource types.
Closes: #153057, #153058

Full diff: https://github.com/llvm/llvm-project/pull/153276.diff

4 Files Affected:

(modified) llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp (+96-7)
(added) llvm/test/CodeGen/DirectX/rootsignature-validation-fail-appending-overflow.ll (+18)
(added) llvm/test/CodeGen/DirectX/rootsignature-validation-fail-register-overflow.ll (+17)
(added) llvm/test/CodeGen/DirectX/rootsignature-validation-fail-sampler-mix.ll (+18)

diff --git a/llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp b/llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp
index abcefe287d9bc..7067d6a2960e8 100644
--- a/llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp
+++ b/llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp
@@ -155,6 +155,31 @@ reportRegNotBound(Module &M, ResourceClass Class,
   M.getContext().diagnose(DiagnosticInfoGeneric(Message));
 }
 
+static void
+reportDescriptorTableMixingTypes(Module &M, uint32_t Location,
+                                 dxbc::DescriptorRangeType RangeType) {
+  SmallString<128> Message;
+  raw_svector_ostream OS(Message);
+  OS << "Samplers cannot be mixed with other "
+     << "resource types in a descriptor table, "
+     << getResourceClassName(toResourceClass(RangeType))
+     << "(location=" << Location << ")";
+
+  M.getContext().diagnose(DiagnosticInfoGeneric(Message));
+}
+
+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.";
+  M.getContext().diagnose(DiagnosticInfoGeneric(Message));
+}
+
 static void reportInvalidHandleTy(
     Module &M, const llvm::ArrayRef<dxil::ResourceInfo::ResourceBinding> &RDs,
     const iterator_range<SmallVectorImpl<dxil::ResourceInfo>::iterator>
@@ -236,10 +261,73 @@ getRootDescriptorsBindingInfo(const mcdxbc::RootSignatureDesc &RSD,
   return RDs;
 }
 
-static void validateRootSignature(Module &M,
-                                  const mcdxbc::RootSignatureDesc &RSD,
-                                  dxil::ModuleMetadataInfo &MMI,
-                                  DXILResourceMap &DRM) {
+
+
+static void validateDescriptorTables(Module &M,
+                                     const mcdxbc::RootSignatureDesc &RSD,
+                                     dxil::ModuleMetadataInfo &MMI,
+                                     DXILResourceMap &DRM) {
+  for (const mcdxbc::RootParameterInfo &ParamInfo : RSD.ParametersContainer) {
+    if (static_cast<dxbc::RootParameterType>(ParamInfo.Header.ParameterType) !=
+        dxbc::RootParameterType::DescriptorTable)
+      continue;
+
+    mcdxbc::DescriptorTable Table =
+        RSD.ParametersContainer.getDescriptorTable(ParamInfo.Location);
+
+    bool HasSampler = false;
+    bool HasOtherRangeType = false;
+    dxbc::DescriptorRangeType OtherRangeType;
+    uint32_t OtherRangeTypeLocation = 0;
+
+    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)
+        Offset = Range.OffsetInDescriptorsFromTableStart;
+      
+      if(Offset > ~0U)
+        reportOverlowingRange(M, Range);
+      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)
+          reportOverlowingRange(M, Range);
+
+        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 {
+        HasOtherRangeType = true;
+        OtherRangeType = RangeType;
+        OtherRangeTypeLocation = ParamInfo.Location;
+      }
+    }
+
+    // Samplers cannot be mixed with other resources in a descriptor table.
+    if (HasSampler && HasOtherRangeType) {
+      reportDescriptorTableMixingTypes(M, OtherRangeTypeLocation,
+                                       OtherRangeType);
+      continue;
+    }
+  }
+}
+
+static void validateRootSignatureBindings(Module &M,
+                                          const mcdxbc::RootSignatureDesc &RSD,
+                                          dxil::ModuleMetadataInfo &MMI,
+                                          DXILResourceMap &DRM) {
 
   hlsl::BindingInfoBuilder Builder;
   dxbc::ShaderVisibility Visibility = tripleToVisibility(MMI.ShaderProfile);
@@ -309,7 +397,6 @@ static void validateRootSignature(Module &M,
         reportOverlappingRegisters(M, ReportedBinding, Overlaping);
       });
   // Next checks require that the root signature definition is valid.
-  // Next checks require that the root signature definition is valid.
   if (!HasOverlap) {
     SmallVector<ResourceInfo::ResourceBinding> RDs =
         getRootDescriptorsBindingInfo(RSD, Visibility);
@@ -351,8 +438,10 @@ static void reportErrors(Module &M, DXILResourceMap &DRM,
   assert(!DRBI.hasImplicitBinding() && "implicit bindings should be handled in "
                                        "DXILResourceImplicitBinding pass");
 
-  if (mcdxbc::RootSignatureDesc *RSD = getRootSignature(RSBI, MMI))
-    validateRootSignature(M, *RSD, MMI, DRM);
+  if (mcdxbc::RootSignatureDesc *RSD = getRootSignature(RSBI, MMI)) {
+    validateRootSignatureBindings(M, *RSD, MMI, DRM);
+    validateDescriptorTables(M, *RSD, MMI, DRM);
+  }
 }
 
 PreservedAnalyses
diff --git a/llvm/test/CodeGen/DirectX/rootsignature-validation-fail-appending-overflow.ll b/llvm/test/CodeGen/DirectX/rootsignature-validation-fail-appending-overflow.ll
new file mode 100644
index 0000000000000..865312a43b5a8
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/rootsignature-validation-fail-appending-overflow.ll
@@ -0,0 +1,18 @@
+; RUN: not opt -S -passes='dxil-post-optimization-validation' -mtriple=dxil-pc-shadermodel6.6-compute %s 2>&1 | FileCheck %s
+; CHECK: error: Cannot append range with implicit lower bound after an unbounded range UAV(register=3, space=4) exceeds maximum allowed value.
+
+@TB.str = private unnamed_addr constant [3 x i8] c"TB\00", align 1
+
+define void @CSMain() "hlsl.shader"="compute" {
+entry:
+  ret void
+}
+
+!dx.rootsignatures = !{!0}
+
+!0 = !{ptr @CSMain, !1, i32 2}
+!1 = !{!3}
+!3 = !{!"DescriptorTable", i32 0, !4, !5}
+!4 = !{!"UAV", i32 -1, i32 1, i32 2, i32 -1, i32 0}
+!5 = !{!"UAV", i32 1, i32 3, i32 4, i32 -1, i32 0}
+
diff --git a/llvm/test/CodeGen/DirectX/rootsignature-validation-fail-register-overflow.ll b/llvm/test/CodeGen/DirectX/rootsignature-validation-fail-register-overflow.ll
new file mode 100644
index 0000000000000..ef887baf80728
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/rootsignature-validation-fail-register-overflow.ll
@@ -0,0 +1,17 @@
+; RUN: not opt -S -passes='dxil-post-optimization-validation' -mtriple=dxil-pc-shadermodel6.6-compute %s 2>&1 | FileCheck %s
+; CHECK: error: Cannot append range with implicit lower bound after an unbounded range UAV(register=4294967295, space=0) exceeds maximum allowed value. 
+
+@TB.str = private unnamed_addr constant [3 x i8] c"TB\00", align 1
+
+define void @CSMain() "hlsl.shader"="compute" {
+entry:
+  ret void
+}
+
+!dx.rootsignatures = !{!0}
+
+!0 = !{ptr @CSMain, !1, i32 2}
+!1 = !{!3}
+!3 = !{!"DescriptorTable", i32 0, !4}
+!4 = !{!"UAV", i32 100, i32 4294967295, i32 0, i32 -1, i32 0}
+
diff --git a/llvm/test/CodeGen/DirectX/rootsignature-validation-fail-sampler-mix.ll b/llvm/test/CodeGen/DirectX/rootsignature-validation-fail-sampler-mix.ll
new file mode 100644
index 0000000000000..d4caeb2675d82
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/rootsignature-validation-fail-sampler-mix.ll
@@ -0,0 +1,18 @@
+; RUN: not opt -S -passes='dxil-post-optimization-validation' -mtriple=dxil-pc-shadermodel6.6-compute %s 2>&1 | FileCheck %s
+; CHECK: error: Samplers cannot be mixed with other resource types in a descriptor table, UAV(location=0)
+
+@TB.str = private unnamed_addr constant [3 x i8] c"TB\00", align 1
+
+define void @CSMain() "hlsl.shader"="compute" {
+entry:
+  ret void
+}
+
+!dx.rootsignatures = !{!0}
+
+!0 = !{ptr @CSMain, !1, i32 2}
+!1 = !{!3}
+!3 = !{!"DescriptorTable", i32 0, !4, !5}
+!4 = !{!"UAV", i32 1, i32 0, i32 0, i32 -1, i32 0}
+!5 = !{!"Sampler", i32 2, i32 0, i32 0, i32 -1, i32 0}
+

github-actions · 2025-08-12T20:24:41Z

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github-actions · 2025-08-12T20:26:15Z

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

inbelic · 2025-08-12T21:20:03Z

llvm/test/CodeGen/DirectX/rootsignature-validation-fail-register-overflow.ll

@@ -0,0 +1,17 @@
+; RUN: not opt -S -passes='dxil-post-optimization-validation' -mtriple=dxil-pc-shadermodel6.6-compute %s 2>&1 | FileCheck %s
+; CHECK: error: Cannot append range with implicit lower bound after an unbounded range UAV(register=4294967295, space=0) exceeds maximum allowed value. 


This error message is incorrect, this case does have an explicit binding

That is the same error message as DXC. It has nothing to do with implicit binding. It means that you cannot bind if the lower bound is, implicit, exceeding the maximum allowed value. This happens when you append a range after an unbounded range.

Thant being said, I change the error message to fix this confusion.

inbelic · 2025-08-12T21:25:11Z

llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp

+static void validateDescriptorTables(Module &M,
+                                     const mcdxbc::RootSignatureDesc &RSD) {


Suggested change

static void validateDescriptorTables(Module &M,

const mcdxbc::RootSignatureDesc &RSD) {

static void validateDescriptorTable(Module &M,

const mcdxbc::DescriptorTable &Table) {

Does it make more sense to call validateDescriptorTable when we encounter a descriptor table while iterating in validateRootSignature?

inbelic · 2025-08-12T21:27:27Z

llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp

+    // Samplers cannot be mixed with other resources in a descriptor table.
+    if (HasSampler && HasOtherRangeType) {
+      reportDescriptorTableMixingTypes(M, OtherRangeTypeLocation,
+                                       OtherRangeType);
+      continue;
+    }


Suggested change

// Samplers cannot be mixed with other resources in a descriptor table.

if (HasSampler && HasOtherRangeType) {

reportDescriptorTableMixingTypes(M, OtherRangeTypeLocation,

OtherRangeType);

continue;

}

// Samplers cannot be mixed with other resources in a descriptor table.

if (HasSampler && HasOtherRangeType)

reportDescriptorTableMixingTypes(M, OtherRangeTypeLocation,

OtherRangeType);

inbelic · 2025-08-12T21:39:26Z

llvm/lib/Target/DirectX/DXILPostOptimizationValidation.cpp

+      dxbc::DescriptorRangeType RangeType =
+          static_cast<dxbc::DescriptorRangeType>(Range.RangeType);
+
+      uint64_t Offset = AppendingOffset;


I am having a really hard time trying to figure what it happening here to validate it is correct. Can you add some comments to describe how this checks for an overflow

…osaffran/llvm-project into validation/descriptor-tables

inbelic · 2025-08-18T15:23:46Z

Given we want to use these for the frontend as well. Would it be possible to do these validations with an HLSLBinding instead? Both the front and backend will create the bindings I believe and could be a common interface?

Joao Saffran added 3 commits August 12, 2025 11:21

check if table mix samplers with others

50e78d2

validating register not overflow in table

aee4c56

clean

7d1c13e

llvmbot added the backend:DirectX label Aug 12, 2025

format

85719af

Joao Saffran added 3 commits August 12, 2025 13:30

format

cc304fd

fix typo

3c28142

clean

81261ff

inbelic reviewed Aug 12, 2025

View reviewed changes

address comments

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llvmbot added the HLSL HLSL Language Support label Aug 12, 2025

Joao Saffran added 7 commits August 12, 2025 17:04

address comments

ad0e1f3

Merge branch 'validation/descriptor-tables' of https://github.com/joa…

d97eb7c

…osaffran/llvm-project into validation/descriptor-tables

fix comment

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addressing comment

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Merge

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clean up

d3349ce

moving code to where I think make sense

bf5714d

This was linked to issues Aug 18, 2025

[DirectX] Descriptor table registers can only allocate up to MAX_UINT register #153058

Open

[DirectX] validate Samples are not being mixed with other resources types in descriptor table #153057

Open

moving offset logic into shared validations

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		@@ -0,0 +1,17 @@
		; RUN: not opt -S -passes='dxil-post-optimization-validation' -mtriple=dxil-pc-shadermodel6.6-compute %s 2>&1 \| FileCheck %s
		; CHECK: error: Cannot append range with implicit lower bound after an unbounded range UAV(register=4294967295, space=0) exceeds maximum allowed value.

		static void validateDescriptorTables(Module &M,
		const mcdxbc::RootSignatureDesc &RSD) {

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