[llvm] [SPIR-V] Add support for HLSL SV_GroupIndex (PR #130670)
Cassandra Beckley via llvm-commits
llvm-commits at lists.llvm.org
Fri Mar 14 15:24:32 PDT 2025
https://github.com/cassiebeckley updated https://github.com/llvm/llvm-project/pull/130670
>From 76245d410e39761ce9ccd39e222a77da50c8199a Mon Sep 17 00:00:00 2001
From: Cassandra Beckley <cbeckley at google.com>
Date: Mon, 10 Mar 2025 14:08:23 -0700
Subject: [PATCH] [SPIR-V] Add support for HLSL SV_GroupIndex
This PR lowers the llvm.spv.flattened.thread.id.in.group intrinsic as a
`LocalInvocationIndex` builtin variable.
---
llvm/docs/SPIRVUsage.rst | 4 ++
llvm/include/llvm/IR/IntrinsicsSPIRV.td | 1 +
.../Target/SPIRV/SPIRVInstructionSelector.cpp | 44 +++++++++++++++++++
.../SPIRV/hlsl-intrinsics/SV_GroupIndex.ll | 32 ++++++++++++++
4 files changed, 81 insertions(+)
create mode 100644 llvm/test/CodeGen/SPIRV/hlsl-intrinsics/SV_GroupIndex.ll
diff --git a/llvm/docs/SPIRVUsage.rst b/llvm/docs/SPIRVUsage.rst
index 3e19ff881dffc..ec842db586f77 100644
--- a/llvm/docs/SPIRVUsage.rst
+++ b/llvm/docs/SPIRVUsage.rst
@@ -405,6 +405,10 @@ SPIR-V backend, along with their descriptions and argument details.
- 32-bit Integer
- `[32-bit Integer]`
- Retrieves the thread ID within a workgroup. Essential for identifying execution context in parallel compute operations.
+ * - `int_spv_flattened_thread_id_in_group`
+ - 32-bit Integer
+ - `[32-bit Integer]`
+ - Provides a flattened index for a given thread within a given group (SV_GroupIndex)
* - `int_spv_create_handle`
- Pointer
- `[8-bit Integer]`
diff --git a/llvm/include/llvm/IR/IntrinsicsSPIRV.td b/llvm/include/llvm/IR/IntrinsicsSPIRV.td
index df3e137c80980..4a0e10db2f1e4 100644
--- a/llvm/include/llvm/IR/IntrinsicsSPIRV.td
+++ b/llvm/include/llvm/IR/IntrinsicsSPIRV.td
@@ -61,6 +61,7 @@ let TargetPrefix = "spv" in {
def int_spv_thread_id : Intrinsic<[llvm_i32_ty], [llvm_i32_ty], [IntrNoMem, IntrWillReturn]>;
def int_spv_group_id : Intrinsic<[llvm_i32_ty], [llvm_i32_ty], [IntrNoMem, IntrWillReturn]>;
def int_spv_thread_id_in_group : Intrinsic<[llvm_i32_ty], [llvm_i32_ty], [IntrNoMem, IntrWillReturn]>;
+ def int_spv_flattened_thread_id_in_group : Intrinsic<[llvm_i32_ty], [], [IntrNoMem, IntrWillReturn]>;
def int_spv_all : DefaultAttrsIntrinsic<[llvm_i1_ty], [llvm_any_ty], [IntrNoMem]>;
def int_spv_any : DefaultAttrsIntrinsic<[llvm_i1_ty], [llvm_any_ty], [IntrNoMem]>;
def int_spv_cross : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>, LLVMMatchType<0>], [IntrNoMem]>;
diff --git a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
index b188f36ca9a9e..94c6b1960a02b 100644
--- a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
@@ -341,6 +341,9 @@ class SPIRVInstructionSelector : public InstructionSelector {
bool loadVec3BuiltinInputID(SPIRV::BuiltIn::BuiltIn BuiltInValue,
Register ResVReg, const SPIRVType *ResType,
MachineInstr &I) const;
+ bool loadBuiltinInputID(SPIRV::BuiltIn::BuiltIn BuiltInValue,
+ Register ResVReg, const SPIRVType *ResType,
+ MachineInstr &I) const;
bool loadHandleBeforePosition(Register &HandleReg, const SPIRVType *ResType,
GIntrinsic &HandleDef, MachineInstr &Pos) const;
};
@@ -3059,6 +3062,15 @@ bool SPIRVInstructionSelector::selectIntrinsic(Register ResVReg,
// builtin variable
return loadVec3BuiltinInputID(SPIRV::BuiltIn::WorkgroupId, ResVReg, ResType,
I);
+ case Intrinsic::spv_flattened_thread_id_in_group:
+ // The HLSL SV_GroupIndex semantic is lowered to
+ // llvm.spv.flattened.thread.id.in.group() intrinsic in LLVM IR for SPIR-V
+ // backend.
+ //
+ // In SPIR-V backend, llvm.spv.flattened.thread.id.in.group is translated to
+ // a `LocalInvocationIndex` builtin variable
+ return loadBuiltinInputID(SPIRV::BuiltIn::LocalInvocationIndex, ResVReg,
+ ResType, I);
case Intrinsic::spv_fdot:
return selectFloatDot(ResVReg, ResType, I);
case Intrinsic::spv_udot:
@@ -4005,6 +4017,38 @@ bool SPIRVInstructionSelector::loadVec3BuiltinInputID(
return Result && MIB.constrainAllUses(TII, TRI, RBI);
}
+// Generate the instructions to load 32-bit integer builtin input IDs/Indices.
+// Like LocalInvocationIndex
+bool SPIRVInstructionSelector::loadBuiltinInputID(
+ SPIRV::BuiltIn::BuiltIn BuiltInValue, Register ResVReg,
+ const SPIRVType *ResType, MachineInstr &I) const {
+ MachineIRBuilder MIRBuilder(I);
+ const SPIRVType *U32Type = GR.getOrCreateSPIRVIntegerType(32, MIRBuilder);
+ const SPIRVType *PtrType = GR.getOrCreateSPIRVPointerType(
+ U32Type, MIRBuilder, SPIRV::StorageClass::Input);
+
+ // Create new register for the input ID builtin variable.
+ Register NewRegister =
+ MIRBuilder.getMRI()->createVirtualRegister(&SPIRV::iIDRegClass);
+ MIRBuilder.getMRI()->setType(NewRegister, LLT::pointer(0, 64));
+ GR.assignSPIRVTypeToVReg(PtrType, NewRegister, MIRBuilder.getMF());
+
+ // Build global variable with the necessary decorations for the input ID
+ // builtin variable.
+ Register Variable = GR.buildGlobalVariable(
+ NewRegister, PtrType, getLinkStringForBuiltIn(BuiltInValue), nullptr,
+ SPIRV::StorageClass::Input, nullptr, true, true,
+ SPIRV::LinkageType::Import, MIRBuilder, false);
+
+ // Load uint value from the global variable.
+ auto MIB = BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(SPIRV::OpLoad))
+ .addDef(ResVReg)
+ .addUse(GR.getSPIRVTypeID(U32Type))
+ .addUse(Variable);
+
+ return MIB.constrainAllUses(TII, TRI, RBI);
+}
+
SPIRVType *SPIRVInstructionSelector::widenTypeToVec4(const SPIRVType *Type,
MachineInstr &I) const {
MachineIRBuilder MIRBuilder(I);
diff --git a/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/SV_GroupIndex.ll b/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/SV_GroupIndex.ll
new file mode 100644
index 0000000000000..f21780c7576ca
--- /dev/null
+++ b/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/SV_GroupIndex.ll
@@ -0,0 +1,32 @@
+; RUN: llc -O0 -verify-machineinstrs -mtriple=spirv-vulkan-unknown %s -o - | FileCheck %s
+; RUN: %if spirv-tools %{ llc -O0 -mtriple=spirv-vulkan-unknown %s -o - -filetype=obj | spirv-val %}
+
+; CHECK-DAG: %[[#int:]] = OpTypeInt 32 0
+; CHECK-DAG: %[[#ptr_Input_int:]] = OpTypePointer Input %[[#int]]
+; CHECK-DAG: %[[#LocalInvocationIndex:]] = OpVariable %[[#ptr_Input_int]] Input
+
+; CHECK-DAG: OpEntryPoint GLCompute {{.*}} %[[#LocalInvocationIndex]]
+; CHECK-DAG: OpName %[[#LocalInvocationIndex]] "__spirv_BuiltInLocalInvocationIndex"
+; CHECK-DAG: OpDecorate %[[#LocalInvocationIndex]] LinkageAttributes "__spirv_BuiltInLocalInvocationIndex" Import
+; CHECK-DAG: OpDecorate %[[#LocalInvocationIndex]] BuiltIn LocalInvocationIndex
+
+target triple = "spirv-unknown-vulkan-library"
+
+declare void @local_index_user(i32)
+
+; Function Attrs: convergent noinline norecurse
+define void @main() #1 {
+entry:
+
+; CHECK: %[[#load:]] = OpLoad %[[#int]] %[[#LocalInvocationIndex]]
+ %1 = call i32 @llvm.spv.flattened.thread.id.in.group()
+
+ call spir_func void @local_index_user(i32 %1)
+ ret void
+}
+
+; Function Attrs: nounwind willreturn memory(none)
+declare i32 @llvm.spv.flattened.thread.id.in.group() #3
+
+attributes #1 = { convergent noinline norecurse "hlsl.numthreads"="1,1,1" "hlsl.shader"="compute" "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
+attributes #3 = { nounwind willreturn memory(none) }
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