[clang] [llvm] [HLSL] implement elementwise firstbithigh hlsl builtin (PR #111082)

via cfe-commits cfe-commits at lists.llvm.org
Thu Oct 3 18:17:36 PDT 2024


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-codegen

Author: Sarah Spall (spall)

<details>
<summary>Changes</summary>

Implements elementwise firstbithigh hlsl builtin.
Implements firstbituhigh intrinsic for spirv and directx, which handles unsigned integers
Implements firstbitshigh intrinsic for spirv and directx, which handles signed integers.
Closes #<!-- -->99115 

---

Patch is 25.59 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/111082.diff


16 Files Affected:

- (modified) clang/include/clang/Basic/Builtins.td (+6) 
- (modified) clang/lib/CodeGen/CGBuiltin.cpp (+17) 
- (modified) clang/lib/CodeGen/CGHLSLRuntime.h (+2) 
- (modified) clang/lib/Headers/hlsl/hlsl_intrinsics.h (+72) 
- (modified) clang/lib/Sema/SemaHLSL.cpp (+18) 
- (added) clang/test/CodeGenHLSL/builtins/firstbithigh.hlsl (+153) 
- (added) clang/test/SemaHLSL/BuiltIns/firstbithigh-errors.hlsl (+28) 
- (modified) llvm/include/llvm/IR/IntrinsicsDirectX.td (+2) 
- (modified) llvm/include/llvm/IR/IntrinsicsSPIRV.td (+2) 
- (modified) llvm/lib/Target/DirectX/DXIL.td (+24) 
- (modified) llvm/lib/Target/DirectX/DirectXTargetTransformInfo.cpp (+2) 
- (modified) llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp (+14) 
- (added) llvm/test/CodeGen/DirectX/firstbithigh.ll (+91) 
- (added) llvm/test/CodeGen/DirectX/firstbitshigh_error.ll (+10) 
- (added) llvm/test/CodeGen/DirectX/firstbituhigh_error.ll (+10) 
- (added) llvm/test/CodeGen/SPIRV/hlsl-intrinsics/firstbithigh.ll (+37) 


``````````diff
diff --git a/clang/include/clang/Basic/Builtins.td b/clang/include/clang/Basic/Builtins.td
index a726a0ef4b4bd2..cc4630c281052d 100644
--- a/clang/include/clang/Basic/Builtins.td
+++ b/clang/include/clang/Basic/Builtins.td
@@ -4751,6 +4751,12 @@ def HLSLDotProduct : LangBuiltin<"HLSL_LANG"> {
   let Prototype = "void(...)";
 }
 
+def HLSLFirstBitHigh : LangBuiltin<"HLSL_LANG"> {
+  let Spellings = ["__builtin_hlsl_elementwise_firstbithigh"];
+  let Attributes = [NoThrow, Const];
+  let Prototype = "void(...)";
+}
+
 def HLSLFrac : LangBuiltin<"HLSL_LANG"> {
   let Spellings = ["__builtin_hlsl_elementwise_frac"];
   let Attributes = [NoThrow, Const];
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 43700ea9dd3cfd..6033dcffb3a6da 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -18631,6 +18631,14 @@ static Intrinsic::ID getDotProductIntrinsic(CGHLSLRuntime &RT, QualType QT) {
   return RT.getUDotIntrinsic();
 }
 
+Intrinsic::ID getFirstBitHighIntrinsic(CGHLSLRuntime &RT, QualType QT) {
+  if (QT->hasSignedIntegerRepresentation()) {
+    return RT.getFirstBitSHighIntrinsic();
+  }
+
+  return RT.getFirstBitUHighIntrinsic();
+}
+
 Value *CodeGenFunction::EmitHLSLBuiltinExpr(unsigned BuiltinID,
                                             const CallExpr *E,
                                             ReturnValueSlot ReturnValue) {
@@ -18720,6 +18728,15 @@ Value *CodeGenFunction::EmitHLSLBuiltinExpr(unsigned BuiltinID,
         getDotProductIntrinsic(CGM.getHLSLRuntime(), VecTy0->getElementType()),
         ArrayRef<Value *>{Op0, Op1}, nullptr, "hlsl.dot");
   } break;
+  case Builtin::BI__builtin_hlsl_elementwise_firstbithigh: {
+    
+    Value *X = EmitScalarExpr(E->getArg(0));
+    
+    return Builder.CreateIntrinsic(
+	/*ReturnType=*/X->getType(),
+	getFirstBitHighIntrinsic(CGM.getHLSLRuntime(), E->getArg(0)->getType()),
+	ArrayRef<Value *>{X}, nullptr, "hlsl.firstbithigh");
+  }
   case Builtin::BI__builtin_hlsl_lerp: {
     Value *X = EmitScalarExpr(E->getArg(0));
     Value *Y = EmitScalarExpr(E->getArg(1));
diff --git a/clang/lib/CodeGen/CGHLSLRuntime.h b/clang/lib/CodeGen/CGHLSLRuntime.h
index 6722d2c7c50a2b..03ddef95800e1a 100644
--- a/clang/lib/CodeGen/CGHLSLRuntime.h
+++ b/clang/lib/CodeGen/CGHLSLRuntime.h
@@ -88,6 +88,8 @@ class CGHLSLRuntime {
   GENERATE_HLSL_INTRINSIC_FUNCTION(SDot, sdot)
   GENERATE_HLSL_INTRINSIC_FUNCTION(UDot, udot)
   GENERATE_HLSL_INTRINSIC_FUNCTION(WaveIsFirstLane, wave_is_first_lane)
+  GENERATE_HLSL_INTRINSIC_FUNCTION(FirstBitUHigh, firstbituhigh)
+  GENERATE_HLSL_INTRINSIC_FUNCTION(FirstBitSHigh, firstbitshigh)
 
   //===----------------------------------------------------------------------===//
   // End of reserved area for HLSL intrinsic getters.
diff --git a/clang/lib/Headers/hlsl/hlsl_intrinsics.h b/clang/lib/Headers/hlsl/hlsl_intrinsics.h
index c3ecfc7c90d433..afb7bd33374111 100644
--- a/clang/lib/Headers/hlsl/hlsl_intrinsics.h
+++ b/clang/lib/Headers/hlsl/hlsl_intrinsics.h
@@ -928,6 +928,78 @@ float3 exp2(float3);
 _HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp2)
 float4 exp2(float4);
 
+//===----------------------------------------------------------------------===//
+// firstbithigh builtins
+//===----------------------------------------------------------------------===//
+
+/// \fn T firstbithigh(T Val)
+/// \brief Returns the location of the first set bit starting from the highest
+/// order bit and working downward, per component.
+/// \param Val the input value.
+
+#ifdef __HLSL_ENABLE_16_BIT
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+int16_t firstbithigh(int16_t);
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+int16_t2 firstbithigh(int16_t2);
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+int16_t3 firstbithigh(int16_t3);
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+int16_t4 firstbithigh(int16_t4);
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+uint16_t firstbithigh(uint16_t);
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+uint16_t2 firstbithigh(uint16_t2);
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+uint16_t3 firstbithigh(uint16_t3);
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+uint16_t4 firstbithigh(uint16_t4);
+#endif
+
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+int firstbithigh(int);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+int2 firstbithigh(int2);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+int3 firstbithigh(int3);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+int4 firstbithigh(int4);
+
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+uint firstbithigh(uint);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+uint2 firstbithigh(uint2);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+uint3 firstbithigh(uint3);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+uint4 firstbithigh(uint4);
+
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+int64_t firstbithigh(int64_t);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+int64_t2 firstbithigh(int64_t2);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+int64_t3 firstbithigh(int64_t3);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+int64_t4 firstbithigh(int64_t4);
+
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+uint64_t firstbithigh(uint64_t);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+uint64_t2 firstbithigh(uint64_t2);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+uint64_t3 firstbithigh(uint64_t3);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
+uint64_t4 firstbithigh(uint64_t4);
+  
 //===----------------------------------------------------------------------===//
 // floor builtins
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/Sema/SemaHLSL.cpp b/clang/lib/Sema/SemaHLSL.cpp
index fbcba201a351a6..48ea1d4aab7a18 100644
--- a/clang/lib/Sema/SemaHLSL.cpp
+++ b/clang/lib/Sema/SemaHLSL.cpp
@@ -1874,6 +1874,24 @@ bool SemaHLSL::CheckBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
       return true;
     break;
   }
+  case Builtin::BI__builtin_hlsl_elementwise_firstbithigh: {
+    if (SemaRef.PrepareBuiltinElementwiseMathOneArgCall(TheCall))
+      return true;
+
+    const Expr *Arg = TheCall->getArg(0);
+    QualType ArgTy = Arg->getType();
+    QualType EltTy = ArgTy;
+
+    if (auto *VecTy = EltTy->getAs<VectorType>())
+      EltTy = VecTy->getElementType();
+
+    if (!EltTy->isIntegerType()) {
+      Diag(Arg->getBeginLoc(), diag::err_builtin_invalid_arg_type)
+          << 1 << /* integer ty */ 6 << ArgTy;
+      return true;
+    }
+    break;
+  }
   case Builtin::BI__builtin_hlsl_select: {
     if (SemaRef.checkArgCount(TheCall, 3))
       return true;
diff --git a/clang/test/CodeGenHLSL/builtins/firstbithigh.hlsl b/clang/test/CodeGenHLSL/builtins/firstbithigh.hlsl
new file mode 100644
index 00000000000000..9821b308e63521
--- /dev/null
+++ b/clang/test/CodeGenHLSL/builtins/firstbithigh.hlsl
@@ -0,0 +1,153 @@
+// RUN: %clang_cc1 -finclude-default-header -x hlsl -triple \
+// RUN:   dxil-pc-shadermodel6.3-library %s -fnative-half-type \
+// RUN:   -emit-llvm -disable-llvm-passes -o - | FileCheck %s -DTARGET=dx
+// RUN: %clang_cc1 -finclude-default-header -x hlsl -triple \
+// RUN:   spirv-unknown-vulkan-compute %s -fnative-half-type \
+// RUN: -emit-llvm -disable-llvm-passes \
+// RUN:   -o - | FileCheck %s -DTARGET=spv
+
+#ifdef __HLSL_ENABLE_16_BIT
+// CHECK-LABEL: test_firstbithigh_ushort
+// CHECK: call i16 @llvm.[[TARGET]].firstbituhigh.i16
+int test_firstbithigh_ushort(uint16_t p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_ushort2
+// CHECK: call <2 x i16> @llvm.[[TARGET]].firstbituhigh.v2i16
+uint16_t2 test_firstbithigh_ushort2(uint16_t2 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_ushort3
+// CHECK: call <3 x i16> @llvm.[[TARGET]].firstbituhigh.v3i16
+uint16_t3 test_firstbithigh_ushort3(uint16_t3 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_ushort4
+// CHECK: call <4 x i16> @llvm.[[TARGET]].firstbituhigh.v4i16
+uint16_t4 test_firstbithigh_ushort4(uint16_t4 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_short
+// CHECK: call i16 @llvm.[[TARGET]].firstbitshigh.i16
+int16_t test_firstbithigh_short(int16_t p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_short2
+// CHECK: call <2 x i16> @llvm.[[TARGET]].firstbitshigh.v2i16
+int16_t2 test_firstbithigh_short2(int16_t2 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_short3
+// CHECK: call <3 x i16> @llvm.[[TARGET]].firstbitshigh.v3i16
+int16_t3 test_firstbithigh_short3(int16_t3 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_short4
+// CHECK: call <4 x i16> @llvm.[[TARGET]].firstbitshigh.v4i16
+int16_t4 test_firstbithigh_short4(int16_t4 p0) {
+  return firstbithigh(p0);
+}
+#endif // __HLSL_ENABLE_16_BIT
+
+// CHECK-LABEL: test_firstbithigh_uint
+// CHECK: call i32 @llvm.[[TARGET]].firstbituhigh.i32
+uint test_firstbithigh_uint(uint p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_uint2
+// CHECK: call <2 x i32> @llvm.[[TARGET]].firstbituhigh.v2i32
+uint2 test_firstbithigh_uint2(uint2 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_uint3
+// CHECK: call <3 x i32> @llvm.[[TARGET]].firstbituhigh.v3i32
+uint3 test_firstbithigh_uint3(uint3 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_uint4
+// CHECK: call <4 x i32> @llvm.[[TARGET]].firstbituhigh.v4i32
+uint4 test_firstbithigh_uint4(uint4 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_ulong
+// CHECK: call i64 @llvm.[[TARGET]].firstbituhigh.i64
+uint64_t test_firstbithigh_ulong(uint64_t p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_ulong2
+// CHECK: call <2 x i64> @llvm.[[TARGET]].firstbituhigh.v2i64
+uint64_t2 test_firstbithigh_ulong2(uint64_t2 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_ulong3
+// CHECK: call <3 x i64> @llvm.[[TARGET]].firstbituhigh.v3i64
+uint64_t3 test_firstbithigh_ulong3(uint64_t3 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_ulong4
+// CHECK: call <4 x i64> @llvm.[[TARGET]].firstbituhigh.v4i64
+uint64_t4 test_firstbithigh_ulong4(uint64_t4 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_int
+// CHECK: call i32 @llvm.[[TARGET]].firstbitshigh.i32
+int test_firstbithigh_int(int p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_int2
+// CHECK: call <2 x i32> @llvm.[[TARGET]].firstbitshigh.v2i32
+int2 test_firstbithigh_int2(int2 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_int3
+// CHECK: call <3 x i32> @llvm.[[TARGET]].firstbitshigh.v3i32
+int3 test_firstbithigh_int3(int3 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_int4
+// CHECK: call <4 x i32> @llvm.[[TARGET]].firstbitshigh.v4i32
+int4 test_firstbithigh_int4(int4 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_long
+// CHECK: call i64 @llvm.[[TARGET]].firstbitshigh.i64
+int64_t test_firstbithigh_long(int64_t p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_long2
+// CHECK: call <2 x i64> @llvm.[[TARGET]].firstbitshigh.v2i64
+int64_t2 test_firstbithigh_long2(int64_t2 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_long3
+// CHECK: call <3 x i64> @llvm.[[TARGET]].firstbitshigh.v3i64
+int64_t3 test_firstbithigh_long3(int64_t3 p0) {
+  return firstbithigh(p0);
+}
+
+// CHECK-LABEL: test_firstbithigh_long4
+// CHECK: call <4 x i64> @llvm.[[TARGET]].firstbitshigh.v4i64
+int64_t4 test_firstbithigh_long4(int64_t4 p0) {
+  return firstbithigh(p0);
+}
\ No newline at end of file
diff --git a/clang/test/SemaHLSL/BuiltIns/firstbithigh-errors.hlsl b/clang/test/SemaHLSL/BuiltIns/firstbithigh-errors.hlsl
new file mode 100644
index 00000000000000..1912ab3ae806b3
--- /dev/null
+++ b/clang/test/SemaHLSL/BuiltIns/firstbithigh-errors.hlsl
@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 -finclude-default-header -triple dxil-pc-shadermodel6.6-library %s -fnative-half-type -emit-llvm-only -disable-llvm-passes -verify -verify-ignore-unexpected
+
+int test_too_few_arg() {
+  return firstbithigh();
+  // expected-error at -1 {{no matching function for call to 'firstbithigh'}}
+}
+
+int test_too_many_arg(int p0) {
+  return firstbithigh(p0, p0);
+  // expected-error at -1 {{no matching function for call to 'firstbithigh'}}
+}
+
+double test_int_builtin(double p0) {
+  return firstbithigh(p0);
+  // expected-error at -1 {{call to 'firstbithigh' is ambiguous}}
+}
+
+double2 test_int_builtin_2(double2 p0) {
+  return __builtin_hlsl_elementwise_firstbithigh(p0);
+  // expected-error at -1 {{1st argument must be a vector of integers
+  // (was 'double2' (aka 'vector<double, 2>'))}}
+}
+
+float test_int_builtin_3(float p0) {
+  return __builtin_hlsl_elementwise_firstbithigh(p0);
+  // expected-error at -1 {{1st argument must be a vector of integers
+  // (was 'float')}}
+}
diff --git a/llvm/include/llvm/IR/IntrinsicsDirectX.td b/llvm/include/llvm/IR/IntrinsicsDirectX.td
index 1adfcdc9a1ed2f..ed46d88645f043 100644
--- a/llvm/include/llvm/IR/IntrinsicsDirectX.td
+++ b/llvm/include/llvm/IR/IntrinsicsDirectX.td
@@ -86,4 +86,6 @@ def int_dx_rsqrt  : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>]
 def int_dx_wave_is_first_lane : DefaultAttrsIntrinsic<[llvm_i1_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_firstbituhigh : DefaultAttrsIntrinsic<[llvm_anyint_ty], [LLVMMatchType<0>], [IntrNoMem]>;
+def int_dx_firstbitshigh : DefaultAttrsIntrinsic<[llvm_anyint_ty], [LLVMMatchType<0>], [IntrNoMem]>;
 }
diff --git a/llvm/include/llvm/IR/IntrinsicsSPIRV.td b/llvm/include/llvm/IR/IntrinsicsSPIRV.td
index 0567efd8a5d7af..3ca5e0e2046289 100644
--- a/llvm/include/llvm/IR/IntrinsicsSPIRV.td
+++ b/llvm/include/llvm/IR/IntrinsicsSPIRV.td
@@ -84,4 +84,6 @@ let TargetPrefix = "spv" in {
     [IntrNoMem, Commutative] >;
   def int_spv_wave_is_first_lane : DefaultAttrsIntrinsic<[llvm_i1_ty], [], [IntrConvergent]>;
   def int_spv_sign : DefaultAttrsIntrinsic<[LLVMScalarOrSameVectorWidth<0, llvm_i32_ty>], [llvm_any_ty], [IntrNoMem]>;
+  def int_spv_firstbituhigh : DefaultAttrsIntrinsic<[llvm_anyint_ty], [LLVMMatchType<0>], [IntrNoMem]>;
+  def int_spv_firstbitshigh : DefaultAttrsIntrinsic<[llvm_anyint_ty], [LLVMMatchType<0>], [IntrNoMem]>;
 }
diff --git a/llvm/lib/Target/DirectX/DXIL.td b/llvm/lib/Target/DirectX/DXIL.td
index 9aa0af3e3a6b17..4b315d53894174 100644
--- a/llvm/lib/Target/DirectX/DXIL.td
+++ b/llvm/lib/Target/DirectX/DXIL.td
@@ -564,6 +564,30 @@ def CBits :  DXILOp<31, unary> {
   let attributes = [Attributes<DXIL1_0, [ReadNone]>];
 }
 
+def FBH :  DXILOp<33, unary> {
+  let Doc = "Returns the location of the first set bit starting from "
+            "the highest order bit and working downward.";
+  let LLVMIntrinsic = int_dx_firstbituhigh;
+  let arguments = [OverloadTy];
+  let result = OverloadTy;
+  let overloads =
+      [Overloads<DXIL1_0, [Int16Ty, Int32Ty, Int64Ty]>];
+  let stages = [Stages<DXIL1_0, [all_stages]>];
+  let attributes = [Attributes<DXIL1_0, [ReadNone]>];
+}
+
+def FBSH :  DXILOp<34, unary> {
+  let Doc = "Returns the location of the first set bit from "
+            "the highest order bit based on the sign.";
+  let LLVMIntrinsic = int_dx_firstbitshigh;
+  let arguments = [OverloadTy];
+  let result = OverloadTy;
+  let overloads =
+      [Overloads<DXIL1_0, [Int16Ty, Int32Ty, Int64Ty]>];
+  let stages = [Stages<DXIL1_0, [all_stages]>];
+  let attributes = [Attributes<DXIL1_0, [ReadNone]>];
+}
+
 def FMax :  DXILOp<35, binary> {
   let Doc = "Float maximum. FMax(a,b) = a > b ? a : b";
   let LLVMIntrinsic = int_maxnum;
diff --git a/llvm/lib/Target/DirectX/DirectXTargetTransformInfo.cpp b/llvm/lib/Target/DirectX/DirectXTargetTransformInfo.cpp
index 1a59f04b214042..21a4daf2cde6d8 100644
--- a/llvm/lib/Target/DirectX/DirectXTargetTransformInfo.cpp
+++ b/llvm/lib/Target/DirectX/DirectXTargetTransformInfo.cpp
@@ -18,6 +18,8 @@ bool llvm::DirectXTTIImpl::isTargetIntrinsicTriviallyScalarizable(
   switch (ID) {
   case Intrinsic::dx_frac:
   case Intrinsic::dx_rsqrt:
+  case Intrinsic::dx_firstbituhigh:
+  case Intrinsic::dx_firstbitshigh:
     return true;
   default:
     return false;
diff --git a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
index 3917ad180b87fc..85602a8b4f6f7a 100644
--- a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
@@ -213,6 +213,8 @@ class SPIRVInstructionSelector : public InstructionSelector {
   bool selectPhi(Register ResVReg, const SPIRVType *ResType,
                  MachineInstr &I) const;
 
+  bool selectExtInst(Register ResVReg, const SPIRVType *RestType,
+		     MachineInstr &I, GL::GLSLExtInst GLInst) const;
   bool selectExtInst(Register ResVReg, const SPIRVType *ResType,
                      MachineInstr &I, CL::OpenCLExtInst CLInst) const;
   bool selectExtInst(Register ResVReg, const SPIRVType *ResType,
@@ -751,6 +753,14 @@ bool SPIRVInstructionSelector::spvSelect(Register ResVReg,
   }
 }
 
+bool SPIRVInstructionSelector::selectExtInst(Register ResVReg,
+					     const SPIRVType *ResType,
+					     MachineInstr &I,
+					     GL::GLSLExtInst GLInst) const {
+  return selectExtInst(ResVReg, ResType, I,
+		       {{SPIRV::InstructionSet::GLSL_std_450, GLInst}});
+}
+
 bool SPIRVInstructionSelector::selectExtInst(Register ResVReg,
                                              const SPIRVType *ResType,
                                              MachineInstr &I,
@@ -2515,6 +2525,10 @@ bool SPIRVInstructionSelector::selectIntrinsic(Register ResVReg,
     return selectExtInst(ResVReg, ResType, I, CL::rsqrt, GL::InverseSqrt);
   case Intrinsic::spv_sign:
     return selectSign(ResVReg, ResType, I);
+  case Intrinsic::spv_firstbituhigh:
+    return selectExtInst(ResVReg, ResType, I, GL::FindUMsb);
+  case Intrinsic::spv_firstbitshigh:
+    return selectExtInst(ResVReg, ResType, I, GL::FindSMsb);
   case Intrinsic::spv_lifetime_start:
   case Intrinsic::spv_lifetime_end: {
     unsigned Op = IID == Intrinsic::spv_lifetime_start ? SPIRV::OpLifetimeStart
diff --git a/llvm/test/CodeGen/DirectX/firstbithigh.ll b/llvm/test/CodeGen/DirectX/firstbithigh.ll
new file mode 100644
index 00000000000000..4a97ad6226149f
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/firstbithigh.ll
@@ -0,0 +1,91 @@
+; RUN: opt -S -scalarizer -dxil-op-lower -mtriple=dxil-pc-shadermodel6.3-library %s | FileCheck %s
+
+; Make sure dxil operation function calls for firstbithigh are generated for all integer types.
+
+define noundef i16 @test_firstbithigh_ushort(i16 noundef %a) {
+entry:
+; CHECK: call i16 @dx.op.unary.i16(i32 33, i16 %{{.*}})
+  %elt.firstbithigh = call i16 @llvm.dx.firstbituhigh.i16(i16 %a)
+  ret i16 %elt.firstbithigh
+}
+
+define noundef i16 @test_firstbithigh_short(i16 noundef %a) {
+entry:
+; CHECK: call i16 @dx.op.unary.i16(i32 34, i16 %{{.*}})
+  %elt.firstbithigh = call i16 @llvm.dx.firstbitshigh.i16(i16 %a)
+  ret i16 %elt.firstbithigh
+}
+
+define noundef i32 @test_firstbithigh_uint(i32 noundef %a) {
+entry:
+; CHECK: call i32 @dx.op.unary.i32(i32 33, i32 %{{.*}})
+  %elt.firstbithigh = call i32 @llvm.dx.firstbituhigh.i32(i32 %a)
+  ret i32 %elt.firstbithigh
+}
+
+define noundef i32 @test_firstbithigh_int(i32 noundef %a) {
+entry:
+; CHECK: call i32 @dx.op.unary.i32(i32 34, i32 %{{.*}})
+  %elt.firs...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/111082


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