[clang] [llvm] [HLSL] Add WaveGetLaneCount() intrinsic to FE (PR #143127)
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Fri Jun 6 05:38:19 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-directx
Author: Nathan Gauër (Keenuts)
<details>
<summary>Changes</summary>
This commit adds code to lower WaveGetLaneCount() into the SPV or DXIL intrinsic. The backends will then need to lower the intrinsic into proper SPIR-V/DXIL.
Related to #<!-- -->99159
---
Full diff: https://github.com/llvm/llvm-project/pull/143127.diff
7 Files Affected:
- (modified) clang/include/clang/Basic/Builtins.td (+6)
- (modified) clang/lib/CodeGen/CGHLSLBuiltins.cpp (+5)
- (modified) clang/lib/CodeGen/CGHLSLRuntime.h (+1)
- (modified) clang/lib/Headers/hlsl/hlsl_alias_intrinsics.h (+4)
- (added) clang/test/CodeGenHLSL/builtins/wave_get_lane_count.hlsl (+32)
- (modified) llvm/include/llvm/IR/IntrinsicsDirectX.td (+2)
- (modified) llvm/include/llvm/IR/IntrinsicsSPIRV.td (+2)
``````````diff
diff --git a/clang/include/clang/Basic/Builtins.td b/clang/include/clang/Basic/Builtins.td
index b15cde05410ab..68cd3d790e78a 100644
--- a/clang/include/clang/Basic/Builtins.td
+++ b/clang/include/clang/Basic/Builtins.td
@@ -4909,6 +4909,12 @@ def HLSLWaveReadLaneAt : LangBuiltin<"HLSL_LANG"> {
let Prototype = "void(...)";
}
+def HLSLWaveGetLaneCount : LangBuiltin<"HLSL_LANG"> {
+ let Spellings = ["__builtin_hlsl_wave_get_lane_count"];
+ let Attributes = [NoThrow, Const];
+ let Prototype = "unsigned int()";
+}
+
def HLSLClamp : LangBuiltin<"HLSL_LANG"> {
let Spellings = ["__builtin_hlsl_elementwise_clamp"];
let Attributes = [NoThrow, Const, CustomTypeChecking];
diff --git a/clang/lib/CodeGen/CGHLSLBuiltins.cpp b/clang/lib/CodeGen/CGHLSLBuiltins.cpp
index 10dd9fd04eb9e..abebc201808b0 100644
--- a/clang/lib/CodeGen/CGHLSLBuiltins.cpp
+++ b/clang/lib/CodeGen/CGHLSLBuiltins.cpp
@@ -691,6 +691,11 @@ Value *CodeGenFunction::EmitHLSLBuiltinExpr(unsigned BuiltinID,
return EmitRuntimeCall(
Intrinsic::getOrInsertDeclaration(&CGM.getModule(), ID));
}
+ case Builtin::BI__builtin_hlsl_wave_get_lane_count: {
+ Intrinsic::ID ID = CGM.getHLSLRuntime().getWaveGetLaneCountIntrinsic();
+ return EmitRuntimeCall(
+ Intrinsic::getOrInsertDeclaration(&CGM.getModule(), ID));
+ }
case Builtin::BI__builtin_hlsl_wave_read_lane_at: {
// Due to the use of variadic arguments we must explicitly retreive them and
// create our function type.
diff --git a/clang/lib/CodeGen/CGHLSLRuntime.h b/clang/lib/CodeGen/CGHLSLRuntime.h
index f7ca2077a576b..bb2b82fa1f5aa 100644
--- a/clang/lib/CodeGen/CGHLSLRuntime.h
+++ b/clang/lib/CodeGen/CGHLSLRuntime.h
@@ -107,6 +107,7 @@ class CGHLSLRuntime {
GENERATE_HLSL_INTRINSIC_FUNCTION(WaveActiveAnyTrue, wave_any)
GENERATE_HLSL_INTRINSIC_FUNCTION(WaveActiveCountBits, wave_active_countbits)
GENERATE_HLSL_INTRINSIC_FUNCTION(WaveIsFirstLane, wave_is_first_lane)
+ GENERATE_HLSL_INTRINSIC_FUNCTION(WaveGetLaneCount, wave_get_lane_count)
GENERATE_HLSL_INTRINSIC_FUNCTION(WaveReadLaneAt, wave_readlane)
GENERATE_HLSL_INTRINSIC_FUNCTION(FirstBitUHigh, firstbituhigh)
GENERATE_HLSL_INTRINSIC_FUNCTION(FirstBitSHigh, firstbitshigh)
diff --git a/clang/lib/Headers/hlsl/hlsl_alias_intrinsics.h b/clang/lib/Headers/hlsl/hlsl_alias_intrinsics.h
index 3835eb78cec50..74aabbdaad266 100644
--- a/clang/lib/Headers/hlsl/hlsl_alias_intrinsics.h
+++ b/clang/lib/Headers/hlsl/hlsl_alias_intrinsics.h
@@ -2350,6 +2350,10 @@ _HLSL_AVAILABILITY(shadermodel, 6.0)
_HLSL_BUILTIN_ALIAS(__builtin_hlsl_wave_is_first_lane)
__attribute__((convergent)) bool WaveIsFirstLane();
+_HLSL_AVAILABILITY(shadermodel, 6.0)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_wave_get_lane_count)
+__attribute__((convergent)) bool WaveGetLaneCount();
+
//===----------------------------------------------------------------------===//
// WaveReadLaneAt builtins
//===----------------------------------------------------------------------===//
diff --git a/clang/test/CodeGenHLSL/builtins/wave_get_lane_count.hlsl b/clang/test/CodeGenHLSL/builtins/wave_get_lane_count.hlsl
new file mode 100644
index 0000000000000..8072f6d4ea206
--- /dev/null
+++ b/clang/test/CodeGenHLSL/builtins/wave_get_lane_count.hlsl
@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -std=hlsl2021 -finclude-default-header -x hlsl -triple \
+// RUN: spirv-pc-vulkan-compute %s -emit-llvm -disable-llvm-passes -o - | \
+// RUN: FileCheck %s --check-prefixes=CHECK,CHECK-SPIRV
+// RUN: %clang_cc1 -std=hlsl2021 -finclude-default-header -x hlsl -triple \
+// RUN: dxil-pc-shadermodel6.3-compute %s -emit-llvm -disable-llvm-passes -o - | \
+// RUN: FileCheck %s --check-prefixes=CHECK,CHECK-DXIL
+
+[numthreads(1, 1, 1)]
+void main() {
+ uint a, b;
+// CHECK-SPIRV: %[[#entry_tok:]] = call token @llvm.experimental.convergence.entry()
+
+// CHECK-SPIRV: %[[#loop_tok:]] = call token @llvm.experimental.convergence.loop() [ "convergencectrl"(token %[[#entry_tok]]) ]
+ while (a) {
+
+// CHECK-DXIL: %[[#]] = call i32 @llvm.dx.wave.get.lane.count()
+// CHECK-SPIRV: %[[#]] = call spir_func i32 @llvm.spv.wave.get.lane.count()
+// CHECK-SPIRV-SAME: [ "convergencectrl"(token %[[#loop_tok]]) ]
+ a = WaveGetLaneCount();
+ }
+
+// CHECK-DXIL: %[[#]] = call i32 @llvm.dx.wave.get.lane.count()
+// CHECK-SPIRV: %[[#]] = call spir_func i32 @llvm.spv.wave.get.lane.count()
+// CHECK-SPIRV-SAME: [ "convergencectrl"(token %[[#entry_tok]]) ]
+ b = WaveGetLaneCount();
+}
+
+// CHECK-DXIL: i32 @llvm.dx.wave.get.lane.count() #[[#attr:]]
+// CHECK-SPIRV: i32 @llvm.spv.wave.get.lane.count() #[[#attr:]]
+
+// CHECK: attributes #[[#attr]] = {{{.*}} convergent {{.*}}}
+
diff --git a/llvm/include/llvm/IR/IntrinsicsDirectX.td b/llvm/include/llvm/IR/IntrinsicsDirectX.td
index 0f73084f88c5e..68b31a899003b 100644
--- a/llvm/include/llvm/IR/IntrinsicsDirectX.td
+++ b/llvm/include/llvm/IR/IntrinsicsDirectX.td
@@ -148,6 +148,8 @@ def int_dx_wave_reduce_sum : DefaultAttrsIntrinsic<[llvm_any_ty], [LLVMMatchType
def int_dx_wave_reduce_usum : DefaultAttrsIntrinsic<[llvm_anyint_ty], [LLVMMatchType<0>], [IntrConvergent, IntrNoMem]>;
def int_dx_wave_is_first_lane : DefaultAttrsIntrinsic<[llvm_i1_ty], [], [IntrConvergent]>;
def int_dx_wave_readlane : DefaultAttrsIntrinsic<[llvm_any_ty], [LLVMMatchType<0>, llvm_i32_ty], [IntrConvergent, IntrNoMem]>;
+def int_dx_wave_get_lane_count
+ : DefaultAttrsIntrinsic<[llvm_i32_ty], [], [IntrConvergent]>;
def int_dx_sign : DefaultAttrsIntrinsic<[LLVMScalarOrSameVectorWidth<0, llvm_i32_ty>], [llvm_any_ty], [IntrNoMem]>;
def int_dx_step : DefaultAttrsIntrinsic<[LLVMMatchType<0>], [llvm_anyfloat_ty, LLVMMatchType<0>], [IntrNoMem]>;
def int_dx_splitdouble : DefaultAttrsIntrinsic<[llvm_anyint_ty, LLVMMatchType<0>],
diff --git a/llvm/include/llvm/IR/IntrinsicsSPIRV.td b/llvm/include/llvm/IR/IntrinsicsSPIRV.td
index 8d984d6ce58df..e1c4a7aaf5a2f 100644
--- a/llvm/include/llvm/IR/IntrinsicsSPIRV.td
+++ b/llvm/include/llvm/IR/IntrinsicsSPIRV.td
@@ -102,6 +102,8 @@ let TargetPrefix = "spv" in {
def int_spv_wave_reduce_sum : DefaultAttrsIntrinsic<[llvm_any_ty], [LLVMMatchType<0>], [IntrConvergent, IntrNoMem]>;
def int_spv_wave_is_first_lane : DefaultAttrsIntrinsic<[llvm_i1_ty], [], [IntrConvergent]>;
def int_spv_wave_readlane : DefaultAttrsIntrinsic<[llvm_any_ty], [LLVMMatchType<0>, llvm_i32_ty], [IntrConvergent, IntrNoMem]>;
+ def int_spv_wave_get_lane_count
+ : DefaultAttrsIntrinsic<[llvm_i32_ty], [], [IntrConvergent]>;
def int_spv_sign : DefaultAttrsIntrinsic<[LLVMScalarOrSameVectorWidth<0, llvm_i32_ty>], [llvm_any_ty], [IntrNoMem]>;
def int_spv_radians : DefaultAttrsIntrinsic<[LLVMMatchType<0>], [llvm_anyfloat_ty], [IntrNoMem]>;
def int_spv_group_memory_barrier_with_group_sync : DefaultAttrsIntrinsic<[], [], []>;
``````````
</details>
https://github.com/llvm/llvm-project/pull/143127
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