[llvm-branch-commits] [llvm] [DirectX] Add missing verifications during `validate` of `DXILRootSignature` (PR #147111)

Finn Plummer via llvm-branch-commits llvm-branch-commits at lists.llvm.org
Fri Jul 4 14:23:25 PDT 2025


https://github.com/inbelic created https://github.com/llvm/llvm-project/pull/147111

This pr resolves some discrepancies in verification during `validate` in `DXILRootSignature.cpp`.

Namely,
- `verifyDescriptorFlag` should be updated to check what flags are valid based on the root signature version, as reflected here https://github.com/llvm/wg-hlsl/pull/297.
- There is currently no verification that `numDescriptors > 0` which should be added to be compliant with DXC:  https://github.com/microsoft/DirectXShaderCompiler/blob/4fcf67f78f7d6ffd286316112694a3ae000860e2/lib/DxilRootSignature/DxilRootSignatureValidator.cpp#L197.

- Updates `verifyDescriptorFlag` to check for valid flags based on version
- Add test to demonstrate updated flag verifications
- Adds `verifyNumDescriptors` to the validation of `DescriptorRange`s
- Add a test to demonstrate `numDescriptors` verification
- Updates a number of tests that mistakenly had an invalid `numDescriptors` specified

Resolves: https://github.com/llvm/llvm-project/issues/147107

>From ab274d239bd12e39fc91d7cc2fc7e899be274e55 Mon Sep 17 00:00:00 2001
From: Finn Plummer <canadienfinn at gmail.com>
Date: Fri, 4 Jul 2025 20:54:50 +0000
Subject: [PATCH 1/3] [HLSL][DirectX] Add `verifyNumDescriptors`

---
 .../Frontend/HLSL/RootSignatureValidations.h  |  1 +
 .../HLSL/RootSignatureValidations.cpp         |  4 ++++
 llvm/lib/Target/DirectX/DXILRootSignature.cpp |  3 +++
 ...-DescriptorTable-Invalid-NumDescriptors.ll | 19 +++++++++++++++++++
 4 files changed, 27 insertions(+)
 create mode 100644 llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-NumDescriptors.ll

diff --git a/llvm/include/llvm/Frontend/HLSL/RootSignatureValidations.h b/llvm/include/llvm/Frontend/HLSL/RootSignatureValidations.h
index 9b68a524432cc..bcef20530559d 100644
--- a/llvm/include/llvm/Frontend/HLSL/RootSignatureValidations.h
+++ b/llvm/include/llvm/Frontend/HLSL/RootSignatureValidations.h
@@ -31,6 +31,7 @@ bool verifyDescriptorFlag(uint32_t Flags);
 bool verifyRangeType(uint32_t Type);
 bool verifyDescriptorRangeFlag(uint32_t Version, uint32_t Type,
                                uint32_t FlagsVal);
+bool verifyNumDescriptors(uint32_t NumDescriptors);
 bool verifySamplerFilter(uint32_t Value);
 bool verifyAddress(uint32_t Address);
 bool verifyMipLODBias(float MipLODBias);
diff --git a/llvm/lib/Frontend/HLSL/RootSignatureValidations.cpp b/llvm/lib/Frontend/HLSL/RootSignatureValidations.cpp
index b5b5fc0c74d83..6c238e0f04468 100644
--- a/llvm/lib/Frontend/HLSL/RootSignatureValidations.cpp
+++ b/llvm/lib/Frontend/HLSL/RootSignatureValidations.cpp
@@ -108,6 +108,10 @@ bool verifyDescriptorRangeFlag(uint32_t Version, uint32_t Type,
   return (Flags & ~Mask) == FlagT::None;
 }
 
+bool verifyNumDescriptors(uint32_t NumDescriptors) {
+  return NumDescriptors > 0;
+}
+
 bool verifySamplerFilter(uint32_t Value) {
   switch (Value) {
 #define FILTER(Num, Val) case llvm::to_underlying(dxbc::SamplerFilter::Val):
diff --git a/llvm/lib/Target/DirectX/DXILRootSignature.cpp b/llvm/lib/Target/DirectX/DXILRootSignature.cpp
index e46b184a353f1..edad63bfe7ea7 100644
--- a/llvm/lib/Target/DirectX/DXILRootSignature.cpp
+++ b/llvm/lib/Target/DirectX/DXILRootSignature.cpp
@@ -447,6 +447,9 @@ static bool validate(LLVMContext *Ctx, const mcdxbc::RootSignatureDesc &RSD) {
         if (!llvm::hlsl::rootsig::verifyRegisterSpace(Range.RegisterSpace))
           return reportValueError(Ctx, "RegisterSpace", Range.RegisterSpace);
 
+        if (!llvm::hlsl::rootsig::verifyNumDescriptors(Range.NumDescriptors))
+          return reportValueError(Ctx, "NumDescriptors", Range.NumDescriptors);
+
         if (!llvm::hlsl::rootsig::verifyDescriptorRangeFlag(
                 RSD.Version, Range.RangeType, Range.Flags))
           return reportValueError(Ctx, "DescriptorFlag", Range.Flags);
diff --git a/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-NumDescriptors.ll b/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-NumDescriptors.ll
new file mode 100644
index 0000000000000..99d126ee95443
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-NumDescriptors.ll
@@ -0,0 +1,19 @@
+; RUN: not opt -passes='print<dxil-root-signature>' %s -S -o - 2>&1 | FileCheck %s
+
+target triple = "dxil-unknown-shadermodel6.0-compute"
+
+; CHECK: error: Invalid value for NumDescriptors: 0
+; CHECK-NOT: Root Signature Definitions
+
+define void @main() #0 {
+entry:
+  ret void
+}
+attributes #0 = { "hlsl.numthreads"="1,1,1" "hlsl.shader"="compute" }
+
+
+!dx.rootsignatures = !{!2} ; list of function/root signature pairs
+!2 = !{ ptr @main, !3, i32 2 } ; function, root signature
+!3 = !{ !5 } ; list of root signature elements
+!5 = !{ !"DescriptorTable", i32 0, !6}
+!6 = !{ !"SRV", i32 0, i32 0, i32 10, i32 -1, i32 4 }

>From 56ae9d9316fd02b588ba67ddf1820c9bd80bae49 Mon Sep 17 00:00:00 2001
From: Finn Plummer <canadienfinn at gmail.com>
Date: Fri, 4 Jul 2025 20:59:09 +0000
Subject: [PATCH 2/3] fix up testcases using invalid num descriptors

---
 ...ootSignature-DescriptorTable-AllValidFlagCombinationsV1.ll | 4 ++--
 .../RootSignature-DescriptorTable-Invalid-Flag.ll             | 2 +-
 .../RootSignature-DescriptorTable-Invalid-RangeType.ll        | 2 +-
 .../RootSignature-DescriptorTable-Invalid-RegisterSpace.ll    | 2 +-
 .../DirectX/ContainerData/RootSignature-DescriptorTable.ll    | 4 ++--
 .../CodeGen/DirectX/ContainerData/RootSignature-Parameters.ll | 4 ++--
 6 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-AllValidFlagCombinationsV1.ll b/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-AllValidFlagCombinationsV1.ll
index 9d89dbdd9107b..053721de1eb1f 100644
--- a/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-AllValidFlagCombinationsV1.ll
+++ b/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-AllValidFlagCombinationsV1.ll
@@ -13,7 +13,7 @@ attributes #0 = { "hlsl.numthreads"="1,1,1" "hlsl.shader"="compute" }
 !2 = !{ ptr @main, !3, i32 1 } ; function, root signature
 !3 = !{ !5 } ; list of root signature elements
 !5 = !{ !"DescriptorTable", i32 0, !6, !7 }
-!6 = !{ !"Sampler", i32 0, i32 1, i32 0, i32 -1, i32 1 }
+!6 = !{ !"Sampler", i32 1, i32 1, i32 0, i32 -1, i32 1 }
 !7 = !{ !"UAV", i32 5, i32 1, i32 10, i32 5, i32 3 }
 
 
@@ -33,7 +33,7 @@ attributes #0 = { "hlsl.numthreads"="1,1,1" "hlsl.shader"="compute" }
 ; DXC-NEXT:             RangesOffset:    44
 ; DXC-NEXT:             Ranges:
 ; DXC-NEXT:               - RangeType:       3
-; DXC-NEXT:                 NumDescriptors:  0
+; DXC-NEXT:                 NumDescriptors:  1
 ; DXC-NEXT:                 BaseShaderRegister: 1
 ; DXC-NEXT:                 RegisterSpace:   0
 ; DXC-NEXT:                 OffsetInDescriptorsFromTableStart: 4294967295
diff --git a/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-Flag.ll b/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-Flag.ll
index 41101c1f1fe8e..58056c5d4ba94 100644
--- a/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-Flag.ll
+++ b/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-Flag.ll
@@ -16,5 +16,5 @@ attributes #0 = { "hlsl.numthreads"="1,1,1" "hlsl.shader"="compute" }
 !2 = !{ ptr @main, !3, i32 2 } ; function, root signature
 !3 = !{ !5 } ; list of root signature elements
 !5 = !{ !"DescriptorTable", i32 0, !6, !7 }
-!6 = !{ !"SRV", i32 0, i32 1, i32 0, i32 -1, i32 22 }
+!6 = !{ !"SRV", i32 1, i32 1, i32 0, i32 -1, i32 22 }
 !7 = !{ !"UAV", i32 5, i32 1, i32 10, i32 5, i32 2 }
diff --git a/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-RangeType.ll b/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-RangeType.ll
index b7e99ae7cd27b..0f7116307c315 100644
--- a/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-RangeType.ll
+++ b/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-RangeType.ll
@@ -16,5 +16,5 @@ attributes #0 = { "hlsl.numthreads"="1,1,1" "hlsl.shader"="compute" }
 !2 = !{ ptr @main, !3, i32 2 } ; function, root signature
 !3 = !{ !5 } ; list of root signature elements
 !5 = !{ !"DescriptorTable", i32 0, !6, !7 }
-!6 = !{ !"Invalid", i32 0, i32 0, i32 -1, i32 -1, i32 4 }
+!6 = !{ !"Invalid", i32 1, i32 0, i32 -1, i32 -1, i32 4 }
 !7 = !{ !"UAV", i32 5, i32 1, i32 10, i32 5, i32 2 }
diff --git a/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-RegisterSpace.ll b/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-RegisterSpace.ll
index 4cef5d86a980b..94cd25b06a127 100644
--- a/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-RegisterSpace.ll
+++ b/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable-Invalid-RegisterSpace.ll
@@ -16,5 +16,5 @@ attributes #0 = { "hlsl.numthreads"="1,1,1" "hlsl.shader"="compute" }
 !2 = !{ ptr @main, !3, i32 2 } ; function, root signature
 !3 = !{ !5 } ; list of root signature elements
 !5 = !{ !"DescriptorTable", i32 0, !6, !7 }
-!6 = !{ !"SRV", i32 0, i32 0, i32 10, i32 -1, i32 4 }
+!6 = !{ !"SRV", i32 1, i32 0, i32 10, i32 -1, i32 4 }
 !7 = !{ !"UAV", i32 5, i32 1, i32 4294967280, i32 5, i32 2 }
diff --git a/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable.ll b/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable.ll
index b516d66180247..8e9b4b43b11a6 100644
--- a/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable.ll
+++ b/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-DescriptorTable.ll
@@ -16,7 +16,7 @@ attributes #0 = { "hlsl.numthreads"="1,1,1" "hlsl.shader"="compute" }
 !2 = !{ ptr @main, !3, i32 2 } ; function, root signature
 !3 = !{ !5 } ; list of root signature elements
 !5 = !{ !"DescriptorTable", i32 0, !6, !7 }
-!6 = !{ !"SRV", i32 0, i32 1, i32 0, i32 -1, i32 4 }
+!6 = !{ !"SRV", i32 1, i32 1, i32 0, i32 -1, i32 4 }
 !7 = !{ !"UAV", i32 5, i32 1, i32 10, i32 5, i32 2 }
 
 ; DXC:  - Name:            RTS0
@@ -35,7 +35,7 @@ attributes #0 = { "hlsl.numthreads"="1,1,1" "hlsl.shader"="compute" }
 ; DXC-NEXT:            RangesOffset:    44
 ; DXC-NEXT:            Ranges:
 ; DXC-NEXT:              - RangeType:       0
-; DXC-NEXT:                NumDescriptors:  0
+; DXC-NEXT:                NumDescriptors:  1
 ; DXC-NEXT:                BaseShaderRegister: 1
 ; DXC-NEXT:                RegisterSpace:   0
 ; DXC-NEXT:                OffsetInDescriptorsFromTableStart: 4294967295
diff --git a/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-Parameters.ll b/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-Parameters.ll
index d0a58bc34ffa4..a8444c6079a85 100644
--- a/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-Parameters.ll
+++ b/llvm/test/CodeGen/DirectX/ContainerData/RootSignature-Parameters.ll
@@ -17,7 +17,7 @@ attributes #0 = { "hlsl.numthreads"="1,1,1" "hlsl.shader"="compute" }
 !5 = !{ !"RootConstants", i32 0, i32 1, i32 2, i32 3 }
 !6 = !{ !"RootSRV", i32 1, i32 4, i32 5, i32 6 }
 !7 = !{ !"DescriptorTable", i32 0, !8, !9 }
-!8 = !{ !"SRV", i32 0, i32 1, i32 0, i32 -1, i32 4 }
+!8 = !{ !"SRV", i32 1, i32 1, i32 0, i32 -1, i32 4 }
 !9 = !{ !"UAV", i32 5, i32 1, i32 10, i32 5, i32 2 }
 
 ;CHECK-LABEL: Definition for 'main':
@@ -41,7 +41,7 @@ attributes #0 = { "hlsl.numthreads"="1,1,1" "hlsl.shader"="compute" }
 ;CHECK-NEXT:     - Range Type: 0
 ;CHECK-NEXT:       Register Space: 0
 ;CHECK-NEXT:       Base Shader Register: 1
-;CHECK-NEXT:       Num Descriptors: 0
+;CHECK-NEXT:       Num Descriptors: 1
 ;CHECK-NEXT:       Offset In Descriptors From Table Start: 4294967295
 ;CHECK-NEXT:       Flags: 4
 ;CHECK-NEXT:     - Range Type: 1

>From b6ac185f96beb673660f68e22ffd16bdcf023e46 Mon Sep 17 00:00:00 2001
From: Finn Plummer <canadienfinn at gmail.com>
Date: Fri, 4 Jul 2025 21:11:47 +0000
Subject: [PATCH 3/3] [HLSL][DirectX] update `verifyRootDescriptorFlag` to
 match the spec

---
 .../Frontend/HLSL/RootSignatureValidations.h  |  2 +-
 .../HLSL/RootSignatureValidations.cpp         | 19 ++++++++++++++++++-
 llvm/lib/Target/DirectX/DXILRootSignature.cpp |  3 ++-
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/llvm/include/llvm/Frontend/HLSL/RootSignatureValidations.h b/llvm/include/llvm/Frontend/HLSL/RootSignatureValidations.h
index bcef20530559d..03f4e2cf5bb8f 100644
--- a/llvm/include/llvm/Frontend/HLSL/RootSignatureValidations.h
+++ b/llvm/include/llvm/Frontend/HLSL/RootSignatureValidations.h
@@ -27,7 +27,7 @@ bool verifyRootFlag(uint32_t Flags);
 bool verifyVersion(uint32_t Version);
 bool verifyRegisterValue(uint32_t RegisterValue);
 bool verifyRegisterSpace(uint32_t RegisterSpace);
-bool verifyDescriptorFlag(uint32_t Flags);
+bool verifyRootDescriptorFlag(uint32_t Version, uint32_t FlagsVal);
 bool verifyRangeType(uint32_t Type);
 bool verifyDescriptorRangeFlag(uint32_t Version, uint32_t Type,
                                uint32_t FlagsVal);
diff --git a/llvm/lib/Frontend/HLSL/RootSignatureValidations.cpp b/llvm/lib/Frontend/HLSL/RootSignatureValidations.cpp
index 6c238e0f04468..48d6b8639b2dc 100644
--- a/llvm/lib/Frontend/HLSL/RootSignatureValidations.cpp
+++ b/llvm/lib/Frontend/HLSL/RootSignatureValidations.cpp
@@ -32,7 +32,24 @@ bool verifyRegisterSpace(uint32_t RegisterSpace) {
   return !(RegisterSpace >= 0xFFFFFFF0 && RegisterSpace <= 0xFFFFFFFF);
 }
 
-bool verifyDescriptorFlag(uint32_t Flags) { return (Flags & ~0xE) == 0; }
+bool verifyRootDescriptorFlag(uint32_t Version, uint32_t FlagsVal) {
+  using FlagT = dxbc::RootDescriptorFlags;
+  FlagT Flags = FlagT(FlagsVal);
+  if (Version == 1)
+    return FlagsVal == FlagT::DataVolatile;
+
+  assert(Version == 2 && "Provided invalid root signature version");
+
+  // The data-specific flags are mutually exclusive.
+  FlagT DataFlags = FlagT::DataVolatile | FlagT::DataStatic |
+                    FlagT::DataStaticWhileSetAtExecute;
+
+  if (popcount(llvm::to_underlying(Flags & DataFlags)) > 1)
+    return false;
+
+  // Only a data flag or no flags is valid
+  return (FlagsVal & ~0xE) == 0;
+}
 
 bool verifyRangeType(uint32_t Type) {
   switch (Type) {
diff --git a/llvm/lib/Target/DirectX/DXILRootSignature.cpp b/llvm/lib/Target/DirectX/DXILRootSignature.cpp
index edad63bfe7ea7..37a60075514ef 100644
--- a/llvm/lib/Target/DirectX/DXILRootSignature.cpp
+++ b/llvm/lib/Target/DirectX/DXILRootSignature.cpp
@@ -432,7 +432,8 @@ static bool validate(LLVMContext *Ctx, const mcdxbc::RootSignatureDesc &RSD) {
         return reportValueError(Ctx, "RegisterSpace", Descriptor.RegisterSpace);
 
       if (RSD.Version > 1) {
-        if (!llvm::hlsl::rootsig::verifyDescriptorFlag(Descriptor.Flags))
+        if (!llvm::hlsl::rootsig::verifyRootDescriptorFlag(RSD.Version,
+                                                           Descriptor.Flags))
           return reportValueError(Ctx, "DescriptorRangeFlag", Descriptor.Flags);
       }
       break;



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