[llvm] 4f48abf - [HLSL] Implement elementwise firstbitlow builtin (#116858)

via llvm-commits llvm-commits at lists.llvm.org
Wed Jan 15 14:36:54 PST 2025


Author: Ashley Coleman
Date: 2025-01-15T15:36:50-07:00
New Revision: 4f48abff0fb90ea0a05470755b799cdb1ff79d89

URL: https://github.com/llvm/llvm-project/commit/4f48abff0fb90ea0a05470755b799cdb1ff79d89
DIFF: https://github.com/llvm/llvm-project/commit/4f48abff0fb90ea0a05470755b799cdb1ff79d89.diff

LOG: [HLSL] Implement elementwise firstbitlow builtin (#116858)

Closes https://github.com/llvm/llvm-project/issues/99116

Implements `firstbitlow` by extracting common functionality from
`firstbithigh` into a shared function while also fixing a bug for an edge
case where `u64x3` and larger vectors will attempt to create vectors
larger than the SPRIV max of 4.
---------

Co-authored-by: Steven Perron <stevenperron at google.com>

Added: 
    clang/test/CodeGenHLSL/builtins/firstbitlow.hlsl
    clang/test/SemaHLSL/BuiltIns/firstbitlow-errors.hlsl
    llvm/test/CodeGen/DirectX/firstbitlow.ll
    llvm/test/CodeGen/DirectX/firstbitlow_error.ll
    llvm/test/CodeGen/SPIRV/hlsl-intrinsics/firstbitlow.ll

Modified: 
    clang/include/clang/Basic/Builtins.td
    clang/lib/CodeGen/CGBuiltin.cpp
    clang/lib/CodeGen/CGHLSLRuntime.h
    clang/lib/Headers/hlsl/hlsl_intrinsics.h
    clang/lib/Sema/SemaHLSL.cpp
    clang/test/SemaHLSL/BuiltIns/firstbithigh-errors.hlsl
    llvm/include/llvm/IR/IntrinsicsDirectX.td
    llvm/include/llvm/IR/IntrinsicsSPIRV.td
    llvm/lib/Target/DirectX/DXIL.td
    llvm/lib/Target/DirectX/DirectXTargetTransformInfo.cpp
    llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
    llvm/test/CodeGen/SPIRV/hlsl-intrinsics/firstbithigh.ll

Removed: 
    


################################################################################
diff  --git a/clang/include/clang/Basic/Builtins.td b/clang/include/clang/Basic/Builtins.td
index ea22690ce4f5cc..e903c2c000ee95 100644
--- a/clang/include/clang/Basic/Builtins.td
+++ b/clang/include/clang/Basic/Builtins.td
@@ -4855,6 +4855,12 @@ def HLSLFirstBitHigh : LangBuiltin<"HLSL_LANG"> {
   let Prototype = "void(...)";
 }
 
+def HLSLFirstBitLow : LangBuiltin<"HLSL_LANG"> {
+  let Spellings = ["__builtin_hlsl_elementwise_firstbitlow"];
+  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 1b25d365932c30..2b41a87525f19f 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -19316,7 +19316,6 @@ Value *CodeGenFunction::EmitHLSLBuiltinExpr(unsigned BuiltinID,
         "hlsl.dot4add.u8packed");
   }
   case Builtin::BI__builtin_hlsl_elementwise_firstbithigh: {
-
     Value *X = EmitScalarExpr(E->getArg(0));
 
     return Builder.CreateIntrinsic(
@@ -19324,6 +19323,14 @@ Value *CodeGenFunction::EmitHLSLBuiltinExpr(unsigned BuiltinID,
         getFirstBitHighIntrinsic(CGM.getHLSLRuntime(), E->getArg(0)->getType()),
         ArrayRef<Value *>{X}, nullptr, "hlsl.firstbithigh");
   }
+  case Builtin::BI__builtin_hlsl_elementwise_firstbitlow: {
+    Value *X = EmitScalarExpr(E->getArg(0));
+
+    return Builder.CreateIntrinsic(
+        /*ReturnType=*/ConvertType(E->getType()),
+        CGM.getHLSLRuntime().getFirstBitLowIntrinsic(), ArrayRef<Value *>{X},
+        nullptr, "hlsl.firstbitlow");
+  }
   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 00e110e8e6fa27..f9dc7b87af0e34 100644
--- a/clang/lib/CodeGen/CGHLSLRuntime.h
+++ b/clang/lib/CodeGen/CGHLSLRuntime.h
@@ -99,6 +99,7 @@ class CGHLSLRuntime {
   GENERATE_HLSL_INTRINSIC_FUNCTION(WaveReadLaneAt, wave_readlane)
   GENERATE_HLSL_INTRINSIC_FUNCTION(FirstBitUHigh, firstbituhigh)
   GENERATE_HLSL_INTRINSIC_FUNCTION(FirstBitSHigh, firstbitshigh)
+  GENERATE_HLSL_INTRINSIC_FUNCTION(FirstBitLow, firstbitlow)
   GENERATE_HLSL_INTRINSIC_FUNCTION(NClamp, nclamp)
   GENERATE_HLSL_INTRINSIC_FUNCTION(SClamp, sclamp)
   GENERATE_HLSL_INTRINSIC_FUNCTION(UClamp, uclamp)

diff  --git a/clang/lib/Headers/hlsl/hlsl_intrinsics.h b/clang/lib/Headers/hlsl/hlsl_intrinsics.h
index 378b18e18b71b6..855f4a6d8133fc 100644
--- a/clang/lib/Headers/hlsl/hlsl_intrinsics.h
+++ b/clang/lib/Headers/hlsl/hlsl_intrinsics.h
@@ -1150,6 +1150,78 @@ uint3 firstbithigh(uint64_t3);
 _HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbithigh)
 uint4 firstbithigh(uint64_t4);
 
+//===----------------------------------------------------------------------===//
+// firstbitlow builtins
+//===----------------------------------------------------------------------===//
+
+/// \fn T firstbitlow(T Val)
+/// \brief Returns the location of the first set bit starting from the lowest
+/// order bit and working upward, per component.
+/// \param Val the input value.
+
+#ifdef __HLSL_ENABLE_16_BIT
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint firstbitlow(int16_t);
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint2 firstbitlow(int16_t2);
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint3 firstbitlow(int16_t3);
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint4 firstbitlow(int16_t4);
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint firstbitlow(uint16_t);
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint2 firstbitlow(uint16_t2);
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint3 firstbitlow(uint16_t3);
+_HLSL_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint4 firstbitlow(uint16_t4);
+#endif
+
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint firstbitlow(int);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint2 firstbitlow(int2);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint3 firstbitlow(int3);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint4 firstbitlow(int4);
+
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint firstbitlow(uint);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint2 firstbitlow(uint2);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint3 firstbitlow(uint3);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint4 firstbitlow(uint4);
+
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint firstbitlow(int64_t);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint2 firstbitlow(int64_t2);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint3 firstbitlow(int64_t3);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint4 firstbitlow(int64_t4);
+
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint firstbitlow(uint64_t);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint2 firstbitlow(uint64_t2);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint3 firstbitlow(uint64_t3);
+_HLSL_BUILTIN_ALIAS(__builtin_hlsl_elementwise_firstbitlow)
+uint4 firstbitlow(uint64_t4);
+
 //===----------------------------------------------------------------------===//
 // floor builtins
 //===----------------------------------------------------------------------===//

diff  --git a/clang/lib/Sema/SemaHLSL.cpp b/clang/lib/Sema/SemaHLSL.cpp
index 65ddee05a21512..fceb4e68bb3ff3 100644
--- a/clang/lib/Sema/SemaHLSL.cpp
+++ b/clang/lib/Sema/SemaHLSL.cpp
@@ -2036,7 +2036,8 @@ bool SemaHLSL::CheckBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
       return true;
     break;
   }
-  case Builtin::BI__builtin_hlsl_elementwise_firstbithigh: {
+  case Builtin::BI__builtin_hlsl_elementwise_firstbithigh:
+  case Builtin::BI__builtin_hlsl_elementwise_firstbitlow: {
     if (SemaRef.PrepareBuiltinElementwiseMathOneArgCall(TheCall))
       return true;
 

diff  --git a/clang/test/CodeGenHLSL/builtins/firstbitlow.hlsl b/clang/test/CodeGenHLSL/builtins/firstbitlow.hlsl
new file mode 100644
index 00000000000000..5d490fabc5bc8d
--- /dev/null
+++ b/clang/test/CodeGenHLSL/builtins/firstbitlow.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_firstbitlow_ushort
+// CHECK: call i32 @llvm.[[TARGET]].firstbitlow.i16
+uint test_firstbitlow_ushort(uint16_t p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_ushort2
+// CHECK: call <2 x i32> @llvm.[[TARGET]].firstbitlow.v2i16
+uint2 test_firstbitlow_ushort2(uint16_t2 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_ushort3
+// CHECK: call <3 x i32> @llvm.[[TARGET]].firstbitlow.v3i16
+uint3 test_firstbitlow_ushort3(uint16_t3 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_ushort4
+// CHECK: call <4 x i32> @llvm.[[TARGET]].firstbitlow.v4i16
+uint4 test_firstbitlow_ushort4(uint16_t4 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_short
+// CHECK: call i32 @llvm.[[TARGET]].firstbitlow.i16
+uint test_firstbitlow_short(int16_t p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_short2
+// CHECK: call <2 x i32> @llvm.[[TARGET]].firstbitlow.v2i16
+uint2 test_firstbitlow_short2(int16_t2 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_short3
+// CHECK: call <3 x i32> @llvm.[[TARGET]].firstbitlow.v3i16
+uint3 test_firstbitlow_short3(int16_t3 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_short4
+// CHECK: call <4 x i32> @llvm.[[TARGET]].firstbitlow.v4i16
+uint4 test_firstbitlow_short4(int16_t4 p0) {
+  return firstbitlow(p0);
+}
+#endif // __HLSL_ENABLE_16_BIT
+
+// CHECK-LABEL: test_firstbitlow_uint
+// CHECK: call i32 @llvm.[[TARGET]].firstbitlow.i32
+uint test_firstbitlow_uint(uint p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_uint2
+// CHECK: call <2 x i32> @llvm.[[TARGET]].firstbitlow.v2i32
+uint2 test_firstbitlow_uint2(uint2 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_uint3
+// CHECK: call <3 x i32> @llvm.[[TARGET]].firstbitlow.v3i32
+uint3 test_firstbitlow_uint3(uint3 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_uint4
+// CHECK: call <4 x i32> @llvm.[[TARGET]].firstbitlow.v4i32
+uint4 test_firstbitlow_uint4(uint4 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_ulong
+// CHECK: call i32 @llvm.[[TARGET]].firstbitlow.i64
+uint test_firstbitlow_ulong(uint64_t p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_ulong2
+// CHECK: call <2 x i32> @llvm.[[TARGET]].firstbitlow.v2i64
+uint2 test_firstbitlow_ulong2(uint64_t2 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_ulong3
+// CHECK: call <3 x i32> @llvm.[[TARGET]].firstbitlow.v3i64
+uint3 test_firstbitlow_ulong3(uint64_t3 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_ulong4
+// CHECK: call <4 x i32> @llvm.[[TARGET]].firstbitlow.v4i64
+uint4 test_firstbitlow_ulong4(uint64_t4 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_int
+// CHECK: call i32 @llvm.[[TARGET]].firstbitlow.i32
+uint test_firstbitlow_int(int p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_int2
+// CHECK: call <2 x i32> @llvm.[[TARGET]].firstbitlow.v2i32
+uint2 test_firstbitlow_int2(int2 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_int3
+// CHECK: call <3 x i32> @llvm.[[TARGET]].firstbitlow.v3i32
+uint3 test_firstbitlow_int3(int3 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_int4
+// CHECK: call <4 x i32> @llvm.[[TARGET]].firstbitlow.v4i32
+uint4 test_firstbitlow_int4(int4 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_long
+// CHECK: call i32 @llvm.[[TARGET]].firstbitlow.i64
+uint test_firstbitlow_long(int64_t p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_long2
+// CHECK: call <2 x i32> @llvm.[[TARGET]].firstbitlow.v2i64
+uint2 test_firstbitlow_long2(int64_t2 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_long3
+// CHECK: call <3 x i32> @llvm.[[TARGET]].firstbitlow.v3i64
+uint3 test_firstbitlow_long3(int64_t3 p0) {
+  return firstbitlow(p0);
+}
+
+// CHECK-LABEL: test_firstbitlow_long4
+// CHECK: call <4 x i32> @llvm.[[TARGET]].firstbitlow.v4i64
+uint4 test_firstbitlow_long4(int64_t4 p0) {
+  return firstbitlow(p0);
+}

diff  --git a/clang/test/SemaHLSL/BuiltIns/firstbithigh-errors.hlsl b/clang/test/SemaHLSL/BuiltIns/firstbithigh-errors.hlsl
index 1912ab3ae806b3..b4024418dbba4f 100644
--- a/clang/test/SemaHLSL/BuiltIns/firstbithigh-errors.hlsl
+++ b/clang/test/SemaHLSL/BuiltIns/firstbithigh-errors.hlsl
@@ -17,12 +17,10 @@ double test_int_builtin(double p0) {
 
 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>'))}}
+  // 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')}}
+  // expected-error at -1 {{1st argument must be a vector of integers (was 'double')}}
 }

diff  --git a/clang/test/SemaHLSL/BuiltIns/firstbitlow-errors.hlsl b/clang/test/SemaHLSL/BuiltIns/firstbitlow-errors.hlsl
new file mode 100644
index 00000000000000..95c25e9e2fb60d
--- /dev/null
+++ b/clang/test/SemaHLSL/BuiltIns/firstbitlow-errors.hlsl
@@ -0,0 +1,26 @@
+// 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 firstbitlow();
+  // expected-error at -1 {{no matching function for call to 'firstbitlow'}}
+}
+
+int test_too_many_arg(int p0) {
+  return firstbitlow(p0, p0);
+  // expected-error at -1 {{no matching function for call to 'firstbitlow'}}
+}
+
+double test_int_builtin(double p0) {
+  return firstbitlow(p0);
+  // expected-error at -1 {{call to 'firstbitlow' is ambiguous}}
+}
+
+double2 test_int_builtin_2(double2 p0) {
+  return __builtin_hlsl_elementwise_firstbitlow(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_firstbitlow(p0);
+  // expected-error at -1 {{1st argument must be a vector of integers (was 'double')}}
+}

diff  --git a/llvm/include/llvm/IR/IntrinsicsDirectX.td b/llvm/include/llvm/IR/IntrinsicsDirectX.td
index 2a56ba78ce88e8..544f9f428f41a8 100644
--- a/llvm/include/llvm/IR/IntrinsicsDirectX.td
+++ b/llvm/include/llvm/IR/IntrinsicsDirectX.td
@@ -115,6 +115,7 @@ def int_dx_radians : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>
 def int_dx_discard : DefaultAttrsIntrinsic<[], [llvm_i1_ty], []>;
 def int_dx_firstbituhigh : DefaultAttrsIntrinsic<[LLVMScalarOrSameVectorWidth<0, llvm_i32_ty>], [llvm_anyint_ty], [IntrNoMem]>;
 def int_dx_firstbitshigh : DefaultAttrsIntrinsic<[LLVMScalarOrSameVectorWidth<0, llvm_i32_ty>], [llvm_anyint_ty], [IntrNoMem]>;
+def int_dx_firstbitlow : DefaultAttrsIntrinsic<[LLVMScalarOrSameVectorWidth<0, llvm_i32_ty>], [llvm_anyint_ty], [IntrNoMem]>;
 
 def int_dx_group_memory_barrier_with_group_sync : DefaultAttrsIntrinsic<[], [], []>;
 }

diff  --git a/llvm/include/llvm/IR/IntrinsicsSPIRV.td b/llvm/include/llvm/IR/IntrinsicsSPIRV.td
index 37057271b6c284..e29415d2d9bc34 100644
--- a/llvm/include/llvm/IR/IntrinsicsSPIRV.td
+++ b/llvm/include/llvm/IR/IntrinsicsSPIRV.td
@@ -113,6 +113,7 @@ let TargetPrefix = "spv" in {
 
   def int_spv_firstbituhigh : DefaultAttrsIntrinsic<[LLVMScalarOrSameVectorWidth<0, llvm_i32_ty>], [llvm_anyint_ty], [IntrNoMem]>;
   def int_spv_firstbitshigh : DefaultAttrsIntrinsic<[LLVMScalarOrSameVectorWidth<0, llvm_i32_ty>], [llvm_anyint_ty], [IntrNoMem]>;
+  def int_spv_firstbitlow : DefaultAttrsIntrinsic<[LLVMScalarOrSameVectorWidth<0, llvm_i32_ty>], [llvm_anyint_ty], [IntrNoMem]>;
 
   def int_spv_resource_updatecounter
       : DefaultAttrsIntrinsic<[llvm_i32_ty], [llvm_any_ty, llvm_i8_ty],

diff  --git a/llvm/lib/Target/DirectX/DXIL.td b/llvm/lib/Target/DirectX/DXIL.td
index 6fdd83c4dc8778..7d1651971f340b 100644
--- a/llvm/lib/Target/DirectX/DXIL.td
+++ b/llvm/lib/Target/DirectX/DXIL.td
@@ -620,6 +620,18 @@ def CountBits :  DXILOp<31, unaryBits> {
   let attributes = [Attributes<DXIL1_0, [ReadNone]>];
 }
 
+def FirstbitLo : DXILOp<32, unaryBits> {
+  let Doc = "Returns the location of the first set bit starting from "
+            "the lowest order bit and working upward.";
+  let intrinsics = [ IntrinSelect<int_dx_firstbitlow> ];
+  let arguments = [OverloadTy];
+  let result = Int32Ty;
+  let overloads =
+      [Overloads<DXIL1_0, [Int16Ty, Int32Ty, Int64Ty]>];
+  let stages = [Stages<DXIL1_0, [all_stages]>];
+  let attributes = [Attributes<DXIL1_0, [ReadNone]>];
+}
+
 def FirstbitHi :  DXILOp<33, unaryBits> {
   let Doc = "Returns the location of the first set bit starting from "
             "the highest order bit and working downward.";

diff  --git a/llvm/lib/Target/DirectX/DirectXTargetTransformInfo.cpp b/llvm/lib/Target/DirectX/DirectXTargetTransformInfo.cpp
index 4be1326085bc02..60a9d5c257f1ca 100644
--- a/llvm/lib/Target/DirectX/DirectXTargetTransformInfo.cpp
+++ b/llvm/lib/Target/DirectX/DirectXTargetTransformInfo.cpp
@@ -45,6 +45,7 @@ bool DirectXTTIImpl::isTargetIntrinsicTriviallyScalarizable(
   case Intrinsic::dx_splitdouble:
   case Intrinsic::dx_firstbituhigh:
   case Intrinsic::dx_firstbitshigh:
+  case Intrinsic::dx_firstbitlow:
     return true;
   default:
     return false;

diff  --git a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
index 1d6be7619ecf4b..ad9f1367086397 100644
--- a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
@@ -109,15 +109,25 @@ class SPIRVInstructionSelector : public InstructionSelector {
   bool selectFirstBitHigh(Register ResVReg, const SPIRVType *ResType,
                           MachineInstr &I, bool IsSigned) const;
 
-  bool selectFirstBitHigh16(Register ResVReg, const SPIRVType *ResType,
-                            MachineInstr &I, bool IsSigned) const;
+  bool selectFirstBitLow(Register ResVReg, const SPIRVType *ResType,
+                         MachineInstr &I) const;
+
+  bool selectFirstBitSet16(Register ResVReg, const SPIRVType *ResType,
+                           MachineInstr &I, unsigned ExtendOpcode,
+                           unsigned BitSetOpcode) const;
+
+  bool selectFirstBitSet32(Register ResVReg, const SPIRVType *ResType,
+                           MachineInstr &I, Register SrcReg,
+                           unsigned BitSetOpcode) const;
 
-  bool selectFirstBitHigh32(Register ResVReg, const SPIRVType *ResType,
-                            MachineInstr &I, Register SrcReg,
-                            bool IsSigned) const;
+  bool selectFirstBitSet64(Register ResVReg, const SPIRVType *ResType,
+                           MachineInstr &I, Register SrcReg,
+                           unsigned BitSetOpcode, bool SwapPrimarySide) const;
 
-  bool selectFirstBitHigh64(Register ResVReg, const SPIRVType *ResType,
-                            MachineInstr &I, bool IsSigned) const;
+  bool selectFirstBitSet64Overflow(Register ResVReg, const SPIRVType *ResType,
+                                   MachineInstr &I, Register SrcReg,
+                                   unsigned BitSetOpcode,
+                                   bool SwapPrimarySide) const;
 
   bool selectGlobalValue(Register ResVReg, MachineInstr &I,
                          const MachineInstr *Init = nullptr) const;
@@ -2952,6 +2962,8 @@ bool SPIRVInstructionSelector::selectIntrinsic(Register ResVReg,
     return selectFirstBitHigh(ResVReg, ResType, I, /*IsSigned=*/false);
   case Intrinsic::spv_firstbitshigh: // There is no CL equivalent of FindSMsb
     return selectFirstBitHigh(ResVReg, ResType, I, /*IsSigned=*/true);
+  case Intrinsic::spv_firstbitlow: // There is no CL equivlent of FindILsb
+    return selectFirstBitLow(ResVReg, ResType, I);
   case Intrinsic::spv_group_memory_barrier_with_group_sync: {
     bool Result = true;
     auto MemSemConstant =
@@ -3208,136 +3220,249 @@ Register SPIRVInstructionSelector::buildPointerToResource(
   return AcReg;
 }
 
-bool SPIRVInstructionSelector::selectFirstBitHigh16(Register ResVReg,
-                                                    const SPIRVType *ResType,
-                                                    MachineInstr &I,
-                                                    bool IsSigned) const {
-  unsigned Opcode = IsSigned ? SPIRV::OpSConvert : SPIRV::OpUConvert;
-  // zero or sign extend
+bool SPIRVInstructionSelector::selectFirstBitSet16(
+    Register ResVReg, const SPIRVType *ResType, MachineInstr &I,
+    unsigned ExtendOpcode, unsigned BitSetOpcode) const {
   Register ExtReg = MRI->createVirtualRegister(GR.getRegClass(ResType));
-  bool Result =
-      selectOpWithSrcs(ExtReg, ResType, I, {I.getOperand(2).getReg()}, Opcode);
-  return Result && selectFirstBitHigh32(ResVReg, ResType, I, ExtReg, IsSigned);
+  bool Result = selectOpWithSrcs(ExtReg, ResType, I, {I.getOperand(2).getReg()},
+                                 ExtendOpcode);
+
+  return Result &&
+         selectFirstBitSet32(ResVReg, ResType, I, ExtReg, BitSetOpcode);
 }
 
-bool SPIRVInstructionSelector::selectFirstBitHigh32(Register ResVReg,
-                                                    const SPIRVType *ResType,
-                                                    MachineInstr &I,
-                                                    Register SrcReg,
-                                                    bool IsSigned) const {
-  unsigned Opcode = IsSigned ? GL::FindSMsb : GL::FindUMsb;
+bool SPIRVInstructionSelector::selectFirstBitSet32(
+    Register ResVReg, const SPIRVType *ResType, MachineInstr &I,
+    Register SrcReg, unsigned BitSetOpcode) const {
   return BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(SPIRV::OpExtInst))
       .addDef(ResVReg)
       .addUse(GR.getSPIRVTypeID(ResType))
       .addImm(static_cast<uint32_t>(SPIRV::InstructionSet::GLSL_std_450))
-      .addImm(Opcode)
+      .addImm(BitSetOpcode)
       .addUse(SrcReg)
       .constrainAllUses(TII, TRI, RBI);
 }
 
-bool SPIRVInstructionSelector::selectFirstBitHigh64(Register ResVReg,
-                                                    const SPIRVType *ResType,
-                                                    MachineInstr &I,
-                                                    bool IsSigned) const {
-  Register OpReg = I.getOperand(2).getReg();
-  // 1. split our int64 into 2 pieces using a bitcast
-  unsigned count = GR.getScalarOrVectorComponentCount(ResType);
-  SPIRVType *baseType = GR.retrieveScalarOrVectorIntType(ResType);
+bool SPIRVInstructionSelector::selectFirstBitSet64Overflow(
+    Register ResVReg, const SPIRVType *ResType, MachineInstr &I,
+    Register SrcReg, unsigned BitSetOpcode, bool SwapPrimarySide) const {
+
+  // SPIR-V allow vectors of size 2,3,4 only. Calling with a larger vectors
+  // requires creating a param register and return register with an invalid
+  // vector size. If that is resolved, then this function can be used for
+  // vectors of any component size.
+  unsigned ComponentCount = GR.getScalarOrVectorComponentCount(ResType);
+  assert(ComponentCount < 5 && "Vec 5+ will generate invalid SPIR-V ops");
+
   MachineIRBuilder MIRBuilder(I);
-  SPIRVType *postCastT =
-      GR.getOrCreateSPIRVVectorType(baseType, 2 * count, MIRBuilder);
-  Register bitcastReg = MRI->createVirtualRegister(GR.getRegClass(postCastT));
-  bool Result =
-      selectOpWithSrcs(bitcastReg, postCastT, I, {OpReg}, SPIRV::OpBitcast);
+  SPIRVType *BaseType = GR.retrieveScalarOrVectorIntType(ResType);
+  SPIRVType *I64Type = GR.getOrCreateSPIRVIntegerType(64, MIRBuilder);
+  SPIRVType *I64x2Type = GR.getOrCreateSPIRVVectorType(I64Type, 2, MIRBuilder);
+  SPIRVType *Vec2ResType =
+      GR.getOrCreateSPIRVVectorType(BaseType, 2, MIRBuilder);
+
+  std::vector<Register> PartialRegs;
+
+  // Loops 0, 2, 4, ... but stops one loop early when ComponentCount is odd
+  unsigned CurrentComponent = 0;
+  for (; CurrentComponent + 1 < ComponentCount; CurrentComponent += 2) {
+    // This register holds the firstbitX result for each of the i64x2 vectors
+    // extracted from SrcReg
+    Register BitSetResult =
+        MRI->createVirtualRegister(GR.getRegClass(I64x2Type));
+
+    auto MIB = BuildMI(*I.getParent(), I, I.getDebugLoc(),
+                       TII.get(SPIRV::OpVectorShuffle))
+                   .addDef(BitSetResult)
+                   .addUse(GR.getSPIRVTypeID(I64x2Type))
+                   .addUse(SrcReg)
+                   .addUse(SrcReg)
+                   .addImm(CurrentComponent)
+                   .addImm(CurrentComponent + 1);
+
+    if (!MIB.constrainAllUses(TII, TRI, RBI))
+      return false;
+
+    Register SubVecBitSetReg =
+        MRI->createVirtualRegister(GR.getRegClass(Vec2ResType));
+
+    if (!selectFirstBitSet64(SubVecBitSetReg, Vec2ResType, I, BitSetResult,
+                             BitSetOpcode, SwapPrimarySide))
+      return false;
+
+    PartialRegs.push_back(SubVecBitSetReg);
+  }
+
+  // On odd component counts we need to handle one more component
+  if (CurrentComponent != ComponentCount) {
+    bool ZeroAsNull = STI.isOpenCLEnv();
+    Register FinalElemReg = MRI->createVirtualRegister(GR.getRegClass(I64Type));
+    Register ConstIntLastIdx = GR.getOrCreateConstInt(
+        ComponentCount - 1, I, BaseType, TII, ZeroAsNull);
+
+    if (!selectOpWithSrcs(FinalElemReg, I64Type, I, {SrcReg, ConstIntLastIdx},
+                          SPIRV::OpVectorExtractDynamic))
+      return false;
+
+    Register FinalElemBitSetReg =
+        MRI->createVirtualRegister(GR.getRegClass(BaseType));
 
-  // 2. call firstbithigh
-  Register FBHReg = MRI->createVirtualRegister(GR.getRegClass(postCastT));
-  Result &= selectFirstBitHigh32(FBHReg, postCastT, I, bitcastReg, IsSigned);
+    if (!selectFirstBitSet64(FinalElemBitSetReg, BaseType, I, FinalElemReg,
+                             BitSetOpcode, SwapPrimarySide))
+      return false;
+
+    PartialRegs.push_back(FinalElemBitSetReg);
+  }
 
-  // 3. split result vector into high bits and low bits
+  // Join all the resulting registers back into the return type in order
+  // (ie i32x2, i32x2, i32x1 -> i32x5)
+  return selectOpWithSrcs(ResVReg, ResType, I, PartialRegs,
+                          SPIRV::OpCompositeConstruct);
+}
+
+bool SPIRVInstructionSelector::selectFirstBitSet64(
+    Register ResVReg, const SPIRVType *ResType, MachineInstr &I,
+    Register SrcReg, unsigned BitSetOpcode, bool SwapPrimarySide) const {
+  unsigned ComponentCount = GR.getScalarOrVectorComponentCount(ResType);
+  SPIRVType *BaseType = GR.retrieveScalarOrVectorIntType(ResType);
+  bool ZeroAsNull = STI.isOpenCLEnv();
+  Register ConstIntZero =
+      GR.getOrCreateConstInt(0, I, BaseType, TII, ZeroAsNull);
+  Register ConstIntOne =
+      GR.getOrCreateConstInt(1, I, BaseType, TII, ZeroAsNull);
+
+  // SPIRV doesn't support vectors with more than 4 components. Since the
+  // algoritm below converts i64 -> i32x2 and i64x4 -> i32x8 it can only
+  // operate on vectors with 2 or less components. When largers vectors are
+  // seen. Split them, recurse, then recombine them.
+  if (ComponentCount > 2) {
+    return selectFirstBitSet64Overflow(ResVReg, ResType, I, SrcReg,
+                                       BitSetOpcode, SwapPrimarySide);
+  }
+
+  // 1. Split int64 into 2 pieces using a bitcast
+  MachineIRBuilder MIRBuilder(I);
+  SPIRVType *PostCastType =
+      GR.getOrCreateSPIRVVectorType(BaseType, 2 * ComponentCount, MIRBuilder);
+  Register BitcastReg =
+      MRI->createVirtualRegister(GR.getRegClass(PostCastType));
+
+  if (!selectOpWithSrcs(BitcastReg, PostCastType, I, {SrcReg},
+                        SPIRV::OpBitcast))
+    return false;
+
+  // 2. Find the first set bit from the primary side for all the pieces in #1
+  Register FBSReg = MRI->createVirtualRegister(GR.getRegClass(PostCastType));
+  if (!selectFirstBitSet32(FBSReg, PostCastType, I, BitcastReg, BitSetOpcode))
+    return false;
+
+  // 3. Split result vector into high bits and low bits
   Register HighReg = MRI->createVirtualRegister(GR.getRegClass(ResType));
   Register LowReg = MRI->createVirtualRegister(GR.getRegClass(ResType));
 
-  bool ZeroAsNull = STI.isOpenCLEnv();
-  bool isScalarRes = ResType->getOpcode() != SPIRV::OpTypeVector;
-  if (isScalarRes) {
+  bool IsScalarRes = ResType->getOpcode() != SPIRV::OpTypeVector;
+  if (IsScalarRes) {
     // if scalar do a vector extract
-    Result &= selectOpWithSrcs(
-        HighReg, ResType, I,
-        {FBHReg, GR.getOrCreateConstInt(0, I, ResType, TII, ZeroAsNull)},
-        SPIRV::OpVectorExtractDynamic);
-    Result &= selectOpWithSrcs(
-        LowReg, ResType, I,
-        {FBHReg, GR.getOrCreateConstInt(1, I, ResType, TII, ZeroAsNull)},
-        SPIRV::OpVectorExtractDynamic);
-  } else { // vector case do a shufflevector
+    if (!selectOpWithSrcs(HighReg, ResType, I, {FBSReg, ConstIntZero},
+                          SPIRV::OpVectorExtractDynamic))
+      return false;
+    if (!selectOpWithSrcs(LowReg, ResType, I, {FBSReg, ConstIntOne},
+                          SPIRV::OpVectorExtractDynamic))
+      return false;
+  } else {
+    // if vector do a shufflevector
     auto MIB = BuildMI(*I.getParent(), I, I.getDebugLoc(),
                        TII.get(SPIRV::OpVectorShuffle))
                    .addDef(HighReg)
                    .addUse(GR.getSPIRVTypeID(ResType))
-                   .addUse(FBHReg)
-                   .addUse(FBHReg);
-    // ^^ this vector will not be selected from; could be empty
-    unsigned j;
-    for (j = 0; j < count * 2; j += 2) {
-      MIB.addImm(j);
+                   .addUse(FBSReg)
+                   // Per the spec, repeat the vector if only one vec is needed
+                   .addUse(FBSReg);
+
+    // high bits are stored in even indexes. Extract them from FBSReg
+    for (unsigned J = 0; J < ComponentCount * 2; J += 2) {
+      MIB.addImm(J);
     }
-    Result &= MIB.constrainAllUses(TII, TRI, RBI);
 
-    // get low bits
+    if (!MIB.constrainAllUses(TII, TRI, RBI))
+      return false;
+
     MIB = BuildMI(*I.getParent(), I, I.getDebugLoc(),
                   TII.get(SPIRV::OpVectorShuffle))
               .addDef(LowReg)
               .addUse(GR.getSPIRVTypeID(ResType))
-              .addUse(FBHReg)
-              .addUse(FBHReg);
-    // ^^ this vector will not be selected from; could be empty
-    for (j = 1; j < count * 2; j += 2) {
-      MIB.addImm(j);
+              .addUse(FBSReg)
+              // Per the spec, repeat the vector if only one vec is needed
+              .addUse(FBSReg);
+
+    // low bits are stored in odd indexes. Extract them from FBSReg
+    for (unsigned J = 1; J < ComponentCount * 2; J += 2) {
+      MIB.addImm(J);
     }
-    Result &= MIB.constrainAllUses(TII, TRI, RBI);
+    if (!MIB.constrainAllUses(TII, TRI, RBI))
+      return false;
   }
 
-  // 4. check if result of each top 32 bits is == -1
+  // 4. Check the result. When primary bits == -1 use secondary, otherwise use
+  // primary
   SPIRVType *BoolType = GR.getOrCreateSPIRVBoolType(I, TII);
   Register NegOneReg;
   Register Reg0;
   Register Reg32;
-  unsigned selectOp;
-  unsigned addOp;
-  if (isScalarRes) {
+  unsigned SelectOp;
+  unsigned AddOp;
+
+  if (IsScalarRes) {
     NegOneReg =
         GR.getOrCreateConstInt((unsigned)-1, I, ResType, TII, ZeroAsNull);
     Reg0 = GR.getOrCreateConstInt(0, I, ResType, TII, ZeroAsNull);
     Reg32 = GR.getOrCreateConstInt(32, I, ResType, TII, ZeroAsNull);
-    selectOp = SPIRV::OpSelectSISCond;
-    addOp = SPIRV::OpIAddS;
+    SelectOp = SPIRV::OpSelectSISCond;
+    AddOp = SPIRV::OpIAddS;
   } else {
-    BoolType = GR.getOrCreateSPIRVVectorType(BoolType, count, MIRBuilder);
+    BoolType =
+        GR.getOrCreateSPIRVVectorType(BoolType, ComponentCount, MIRBuilder);
     NegOneReg =
         GR.getOrCreateConstVector((unsigned)-1, I, ResType, TII, ZeroAsNull);
     Reg0 = GR.getOrCreateConstVector(0, I, ResType, TII, ZeroAsNull);
     Reg32 = GR.getOrCreateConstVector(32, I, ResType, TII, ZeroAsNull);
-    selectOp = SPIRV::OpSelectVIVCond;
-    addOp = SPIRV::OpIAddV;
+    SelectOp = SPIRV::OpSelectVIVCond;
+    AddOp = SPIRV::OpIAddV;
   }
 
-  // check if the high bits are == -1; true if -1
+  Register PrimaryReg = HighReg;
+  Register SecondaryReg = LowReg;
+  Register PrimaryShiftReg = Reg32;
+  Register SecondaryShiftReg = Reg0;
+
+  // By default the emitted opcodes check for the set bit from the MSB side.
+  // Setting SwapPrimarySide checks the set bit from the LSB side
+  if (SwapPrimarySide) {
+    PrimaryReg = LowReg;
+    SecondaryReg = HighReg;
+    PrimaryShiftReg = Reg0;
+    SecondaryShiftReg = Reg32;
+  }
+
+  // Check if the primary bits are == -1
   Register BReg = MRI->createVirtualRegister(GR.getRegClass(BoolType));
-  Result &= selectOpWithSrcs(BReg, BoolType, I, {HighReg, NegOneReg},
-                             SPIRV::OpIEqual);
+  if (!selectOpWithSrcs(BReg, BoolType, I, {PrimaryReg, NegOneReg},
+                        SPIRV::OpIEqual))
+    return false;
 
-  // Select low bits if true in BReg, otherwise high bits
+  // Select secondary bits if true in BReg, otherwise primary bits
   Register TmpReg = MRI->createVirtualRegister(GR.getRegClass(ResType));
-  Result &=
-      selectOpWithSrcs(TmpReg, ResType, I, {BReg, LowReg, HighReg}, selectOp);
+  if (!selectOpWithSrcs(TmpReg, ResType, I, {BReg, SecondaryReg, PrimaryReg},
+                        SelectOp))
+    return false;
 
-  // Add 32 for high bits, 0 for low bits
+  // 5. Add 32 when high bits are used, otherwise 0 for low bits
   Register ValReg = MRI->createVirtualRegister(GR.getRegClass(ResType));
-  Result &= selectOpWithSrcs(ValReg, ResType, I, {BReg, Reg0, Reg32}, selectOp);
+  if (!selectOpWithSrcs(ValReg, ResType, I,
+                        {BReg, SecondaryShiftReg, PrimaryShiftReg}, SelectOp))
+    return false;
 
-  return Result &&
-         selectOpWithSrcs(ResVReg, ResType, I, {ValReg, TmpReg}, addOp);
+  return selectOpWithSrcs(ResVReg, ResType, I, {ValReg, TmpReg}, AddOp);
 }
 
 bool SPIRVInstructionSelector::selectFirstBitHigh(Register ResVReg,
@@ -3347,20 +3472,49 @@ bool SPIRVInstructionSelector::selectFirstBitHigh(Register ResVReg,
   // FindUMsb and FindSMsb intrinsics only support 32 bit integers
   Register OpReg = I.getOperand(2).getReg();
   SPIRVType *OpType = GR.getSPIRVTypeForVReg(OpReg);
+  // zero or sign extend
+  unsigned ExtendOpcode = IsSigned ? SPIRV::OpSConvert : SPIRV::OpUConvert;
+  unsigned BitSetOpcode = IsSigned ? GL::FindSMsb : GL::FindUMsb;
 
   switch (GR.getScalarOrVectorBitWidth(OpType)) {
   case 16:
-    return selectFirstBitHigh16(ResVReg, ResType, I, IsSigned);
+    return selectFirstBitSet16(ResVReg, ResType, I, ExtendOpcode, BitSetOpcode);
   case 32:
-    return selectFirstBitHigh32(ResVReg, ResType, I, OpReg, IsSigned);
+    return selectFirstBitSet32(ResVReg, ResType, I, OpReg, BitSetOpcode);
   case 64:
-    return selectFirstBitHigh64(ResVReg, ResType, I, IsSigned);
+    return selectFirstBitSet64(ResVReg, ResType, I, OpReg, BitSetOpcode,
+                               /*SwapPrimarySide=*/false);
   default:
     report_fatal_error(
         "spv_firstbituhigh and spv_firstbitshigh only support 16,32,64 bits.");
   }
 }
 
+bool SPIRVInstructionSelector::selectFirstBitLow(Register ResVReg,
+                                                 const SPIRVType *ResType,
+                                                 MachineInstr &I) const {
+  // FindILsb intrinsic only supports 32 bit integers
+  Register OpReg = I.getOperand(2).getReg();
+  SPIRVType *OpType = GR.getSPIRVTypeForVReg(OpReg);
+  // OpUConvert treats the operand bits as an unsigned i16 and zero extends it
+  // to an unsigned i32. As this leaves all the least significant bits unchanged
+  // so the first set bit from the LSB side doesn't change.
+  unsigned ExtendOpcode = SPIRV::OpUConvert;
+  unsigned BitSetOpcode = GL::FindILsb;
+
+  switch (GR.getScalarOrVectorBitWidth(OpType)) {
+  case 16:
+    return selectFirstBitSet16(ResVReg, ResType, I, ExtendOpcode, BitSetOpcode);
+  case 32:
+    return selectFirstBitSet32(ResVReg, ResType, I, OpReg, BitSetOpcode);
+  case 64:
+    return selectFirstBitSet64(ResVReg, ResType, I, OpReg, BitSetOpcode,
+                               /*SwapPrimarySide=*/true);
+  default:
+    report_fatal_error("spv_firstbitlow only supports 16,32,64 bits.");
+  }
+}
+
 bool SPIRVInstructionSelector::selectAllocaArray(Register ResVReg,
                                                  const SPIRVType *ResType,
                                                  MachineInstr &I) const {

diff  --git a/llvm/test/CodeGen/DirectX/firstbitlow.ll b/llvm/test/CodeGen/DirectX/firstbitlow.ll
new file mode 100644
index 00000000000000..884ec1164fc992
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/firstbitlow.ll
@@ -0,0 +1,47 @@
+; RUN: opt -S -scalarizer -dxil-op-lower -mtriple=dxil-pc-shadermodel6.3-library %s | FileCheck %s
+
+; Make sure dxil operation function calls for firstbitlow are generated for all integer types.
+
+define noundef i32 @test_firstbitlow_short(i16 noundef %a) {
+entry:
+; CHECK: call i32 @dx.op.unaryBits.i16(i32 32, i16 %{{.*}})
+  %elt.firstbitlow = call i32 @llvm.dx.firstbitlow.i16(i16 %a)
+  ret i32 %elt.firstbitlow
+}
+
+define noundef i32 @test_firstbitlow_int(i32 noundef %a) {
+entry:
+; CHECK: call i32 @dx.op.unaryBits.i32(i32 32, i32 %{{.*}})
+  %elt.firstbitlow = call i32 @llvm.dx.firstbitlow.i32(i32 %a)
+  ret i32 %elt.firstbitlow
+}
+
+define noundef i32 @test_firstbitlow_long(i64 noundef %a) {
+entry:
+; CHECK: call i32 @dx.op.unaryBits.i64(i32 32, i64 %{{.*}})
+  %elt.firstbitlow = call i32 @llvm.dx.firstbitlow.i64(i64 %a)
+  ret i32 %elt.firstbitlow
+}
+
+define noundef <4 x i32> @test_firstbitlow_vec4_i32(<4 x i32> noundef %a)  {
+entry:
+  ; CHECK: [[ee0:%.*]] = extractelement <4 x i32> %a, i64 0
+  ; CHECK: [[ie0:%.*]] = call i32 @dx.op.unaryBits.i32(i32 32, i32 [[ee0]])
+  ; CHECK: [[ee1:%.*]] = extractelement <4 x i32> %a, i64 1
+  ; CHECK: [[ie1:%.*]] = call i32 @dx.op.unaryBits.i32(i32 32, i32 [[ee1]])
+  ; CHECK: [[ee2:%.*]] = extractelement <4 x i32> %a, i64 2
+  ; CHECK: [[ie2:%.*]] = call i32 @dx.op.unaryBits.i32(i32 32, i32 [[ee2]])
+  ; CHECK: [[ee3:%.*]] = extractelement <4 x i32> %a, i64 3
+  ; CHECK: [[ie3:%.*]] = call i32 @dx.op.unaryBits.i32(i32 32, i32 [[ee3]])
+  ; CHECK: insertelement <4 x i32> poison, i32 [[ie0]], i64 0
+  ; CHECK: insertelement <4 x i32> %{{.*}}, i32 [[ie1]], i64 1
+  ; CHECK: insertelement <4 x i32> %{{.*}}, i32 [[ie2]], i64 2
+  ; CHECK: insertelement <4 x i32> %{{.*}}, i32 [[ie3]], i64 3
+  %2 = call <4 x i32> @llvm.dx.firstbitlow.v4i32(<4 x i32> %a)
+  ret <4 x i32> %2
+}
+
+declare i32 @llvm.dx.firstbitlow.i16(i16)
+declare i32 @llvm.dx.firstbitlow.i32(i32)
+declare i32 @llvm.dx.firstbitlow.i64(i64)
+declare <4 x i32> @llvm.dx.firstbitlow.v4i32(<4 x i32>)

diff  --git a/llvm/test/CodeGen/DirectX/firstbitlow_error.ll b/llvm/test/CodeGen/DirectX/firstbitlow_error.ll
new file mode 100644
index 00000000000000..d8b9333067f4ac
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/firstbitlow_error.ll
@@ -0,0 +1,10 @@
+; RUN: not opt -S -dxil-op-lower -mtriple=dxil-pc-shadermodel6.3-library %s 2>&1 | FileCheck %s
+
+; DXIL operation firstbitshigh does not support double overload type
+; CHECK: invalid intrinsic signature
+
+define noundef double @firstbitlow_double(double noundef %a) {
+entry:
+  %1 = call double @llvm.dx.firstbitlow.f64(double %a)
+  ret double %1
+}

diff  --git a/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/firstbithigh.ll b/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/firstbithigh.ll
index 3d35e102310f50..a4dd09d84d9963 100644
--- a/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/firstbithigh.ll
+++ b/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/firstbithigh.ll
@@ -1,94 +1,261 @@
 ; RUN: llc -verify-machineinstrs -O0 -mtriple=spirv-unknown-unknown %s -o - | FileCheck %s
 ; RUN: %if spirv-tools %{ llc -O0 -mtriple=spirv-unknown-unknown %s -o - -filetype=obj | spirv-val %}
 
-; CHECK: OpMemoryModel Logical GLSL450
-; CHECK-DAG: [[Z:%.*]] = OpConstant %[[#]] 0
-; CHECK-DAG: [[X:%.*]] = OpConstant %[[#]] 1
+; CHECK-DAG: [[glsl_450_ext:%.+]] = OpExtInstImport "GLSL.std.450"
+; CHECK-DAG: OpMemoryModel Logical GLSL450
+; CHECK-DAG: [[u32_t:%.+]] = OpTypeInt 32 0
+; CHECK-DAG: [[u32x2_t:%.+]] = OpTypeVector [[u32_t]] 2
+; CHECK-DAG: [[u32x3_t:%.+]] = OpTypeVector [[u32_t]] 3
+; CHECK-DAG: [[u32x4_t:%.+]] = OpTypeVector [[u32_t]] 4
+; CHECK-DAG: [[const_0:%.*]] = OpConstant [[u32_t]] 0
+; CHECK-DAG: [[const_2:%.*]] = OpConstant [[u32_t]] 2
+; CHECK-DAG: [[const_0x2:%.*]] = OpConstantComposite [[u32x2_t]] [[const_0]] [[const_0]]
+; CHECK-DAG: [[const_1:%.*]] = OpConstant [[u32_t]] 1
+; CHECK-DAG: [[const_32:%.*]] = OpConstant [[u32_t]] 32
+; CHECK-DAG: [[const_32x2:%.*]] = OpConstantComposite [[u32x2_t]] [[const_32]] [[const_32]]
+; CHECK-DAG: [[const_neg1:%.*]] = OpConstant [[u32_t]] 4294967295
+; CHECK-DAG: [[const_neg1x2:%.*]] = OpConstantComposite [[u32x2_t]] [[const_neg1]] [[const_neg1]]
+; CHECK-DAG: [[u16_t:%.+]] = OpTypeInt 16 0
+; CHECK-DAG: [[u16x2_t:%.+]] = OpTypeVector [[u16_t]] 2
+; CHECK-DAG: [[u16x3_t:%.+]] = OpTypeVector [[u16_t]] 3
+; CHECK-DAG: [[u16x4_t:%.+]] = OpTypeVector [[u16_t]] 4
+; CHECK-DAG: [[u64_t:%.+]] = OpTypeInt 64 0
+; CHECK-DAG: [[u64x2_t:%.+]] = OpTypeVector [[u64_t]] 2
+; CHECK-DAG: [[u64x3_t:%.+]] = OpTypeVector [[u64_t]] 3
+; CHECK-DAG: [[u64x4_t:%.+]] = OpTypeVector [[u64_t]] 4
+; CHECK-DAG: [[bool_t:%.+]] = OpTypeBool
+; CHECK-DAG: [[boolx2_t:%.+]] = OpTypeVector [[bool_t]] 2
 
+; CHECK-LABEL: Begin function firstbituhigh_i32
 define noundef i32 @firstbituhigh_i32(i32 noundef %a) {
 entry:
-; CHECK: %[[#]] = OpExtInst %[[#]] %[[#]] FindUMsb %[[#]]
+; CHECK: [[a:%.+]] = OpFunctionParameter [[u32_t]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32_t]] [[glsl_450_ext]] FindUMsb [[a]]
+; CHECK: OpReturnValue [[ret]]
   %elt.firstbituhigh = call i32 @llvm.spv.firstbituhigh.i32(i32 %a)
   ret i32 %elt.firstbituhigh
 }
 
-define noundef <2 x i32> @firstbituhigh_2xi32(<2 x i32> noundef %a) {
+; CHECK-LABEL: Begin function firstbituhigh_v2xi32
+define noundef <2 x i32> @firstbituhigh_v2xi32(<2 x i32> noundef %a) {
 entry:
-; CHECK: %[[#]] = OpExtInst %[[#]] %[[#]] FindUMsb %[[#]]
+; CHECK: [[a:%.+]] = OpFunctionParameter [[u32x2_t]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32x2_t]] [[glsl_450_ext]] FindUMsb [[a]]
+; CHECK: OpReturnValue [[ret]]
   %elt.firstbituhigh = call <2 x i32> @llvm.spv.firstbituhigh.v2i32(<2 x i32> %a)
   ret <2 x i32> %elt.firstbituhigh
 }
 
+; CHECK-LABEL: Begin function firstbituhigh_v3xi32
+define noundef <3 x i32> @firstbituhigh_v3xi32(<3 x i32> noundef %a) {
+entry:
+; CHECK: [[a:%.+]] = OpFunctionParameter [[u32x3_t]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32x3_t]] [[glsl_450_ext]] FindUMsb [[a]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbituhigh = call <3 x i32> @llvm.spv.firstbituhigh.v3i32(<3 x i32> %a)
+  ret <3 x i32> %elt.firstbituhigh
+}
+
+; CHECK-LABEL: Begin function firstbituhigh_v4xi32
+define noundef <4 x i32> @firstbituhigh_v4xi32(<4 x i32> noundef %a) {
+entry:
+; CHECK: [[a:%.+]] = OpFunctionParameter [[u32x4_t]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32x4_t]] [[glsl_450_ext]] FindUMsb [[a]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbituhigh = call <4 x i32> @llvm.spv.firstbituhigh.v4i32(<4 x i32> %a)
+  ret <4 x i32> %elt.firstbituhigh
+}
+
+; CHECK-LABEL: Begin function firstbituhigh_i16
 define noundef i32 @firstbituhigh_i16(i16 noundef %a) {
 entry:
-; CHECK: [[A:%.*]] = OpUConvert %[[#]]
-; CHECK: %[[#]] = OpExtInst %[[#]] %[[#]] FindUMsb [[A]]
+; CHECK: [[a16:%.+]] = OpFunctionParameter [[u16_t]]
+; CHECK: [[a32:%.+]] = OpUConvert [[u32_t]] [[a16]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32_t]] [[glsl_450_ext]] FindUMsb [[a32]]
+; CHECK: OpReturnValue [[ret]]
   %elt.firstbituhigh = call i32 @llvm.spv.firstbituhigh.i16(i16 %a)
   ret i32 %elt.firstbituhigh
 }
 
-define noundef <2 x i32> @firstbituhigh_v2i16(<2 x i16> noundef %a) {
+; CHECK-LABEL: Begin function firstbituhigh_v2xi16
+define noundef <2 x i32> @firstbituhigh_v2xi16(<2 x i16> noundef %a) {
 entry:
-; CHECK: [[A:%.*]] = OpUConvert %[[#]]
-; CHECK: %[[#]] = OpExtInst %[[#]] %[[#]] FindUMsb [[A]]
+; CHECK: [[a16:%.+]] = OpFunctionParameter [[u16x2_t]]
+; CHECK: [[a32:%.+]] = OpUConvert [[u32x2_t]] [[a16]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32x2_t]] [[glsl_450_ext]] FindUMsb [[a32]]
+; CHECK: OpReturnValue [[ret]]
   %elt.firstbituhigh = call <2 x i32> @llvm.spv.firstbituhigh.v2i16(<2 x i16> %a)
   ret <2 x i32> %elt.firstbituhigh
 }
 
+; CHECK-LABEL: Begin function firstbituhigh_v3xi16
+define noundef <3 x i32> @firstbituhigh_v3xi16(<3 x i16> noundef %a) {
+entry:
+; CHECK: [[a16:%.+]] = OpFunctionParameter [[u16x3_t]]
+; CHECK: [[a32:%.+]] = OpUConvert [[u32x3_t]] [[a16]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32x3_t]] [[glsl_450_ext]] FindUMsb [[a32]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbituhigh = call <3 x i32> @llvm.spv.firstbituhigh.v3i16(<3 x i16> %a)
+  ret <3 x i32> %elt.firstbituhigh
+}
+
+; CHECK-LABEL: Begin function firstbituhigh_v4xi16
+define noundef <4 x i32> @firstbituhigh_v4xi16(<4 x i16> noundef %a) {
+entry:
+; CHECK: [[a16:%.+]] = OpFunctionParameter [[u16x4_t]]
+; CHECK: [[a32:%.+]] = OpUConvert [[u32x4_t]] [[a16]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32x4_t]] [[glsl_450_ext]] FindUMsb [[a32]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbituhigh = call <4 x i32> @llvm.spv.firstbituhigh.v4i16(<4 x i16> %a)
+  ret <4 x i32> %elt.firstbituhigh
+}
+
+; CHECK-LABEL: Begin function firstbituhigh_i64
 define noundef i32 @firstbituhigh_i64(i64 noundef %a) {
 entry:
-; CHECK: [[O:%.*]] = OpBitcast %[[#]] %[[#]]
-; CHECK: [[N:%.*]] = OpExtInst %[[#]] %[[#]] FindUMsb [[O]]
-; CHECK: [[M:%.*]] = OpVectorExtractDynamic %[[#]] [[N]] [[Z]]
-; CHECK: [[L:%.*]] = OpVectorExtractDynamic %[[#]] [[N]] [[X]]
-; CHECK: [[I:%.*]] = OpIEqual %[[#]] [[M]] %[[#]]
-; CHECK: [[H:%.*]] = OpSelect %[[#]] [[I]] [[L]] [[M]]
-; CHECK: [[C:%.*]] = OpSelect %[[#]] [[I]] %[[#]] %[[#]]
-; CHECK: [[B:%.*]] = OpIAdd %[[#]] [[C]] [[H]]
+; CHECK: [[a64:%.+]] = OpFunctionParameter [[u64_t]]
+; CHECK: [[a32x2:%.+]] = OpBitcast [[u32x2_t]] [[a64]]
+; CHECK: [[lsb_bits:%.+]] = OpExtInst [[u32x2_t]] [[glsl_450_ext]] FindUMsb [[a32x2]]
+; CHECK: [[high_bits:%.+]] = OpVectorExtractDynamic [[u32_t]] [[lsb_bits]] [[const_0]]
+; CHECK: [[low_bits:%.+]] = OpVectorExtractDynamic [[u32_t]] [[lsb_bits]] [[const_1]]
+; CHECK: [[should_use_low:%.+]] = OpIEqual [[bool_t]] [[high_bits]] [[const_neg1]]
+; CHECK: [[ans_bits:%.+]] = OpSelect [[u32_t]] [[should_use_low]] [[low_bits]] [[high_bits]]
+; CHECK: [[ans_offset:%.+]] = OpSelect [[u32_t]] [[should_use_low]] [[const_0]] [[const_32]]
+; CHECK: [[ret:%.+]] = OpIAdd [[u32_t]] [[ans_offset]] [[ans_bits]]
+; CHECK: OpReturnValue [[ret]]
   %elt.firstbituhigh = call i32 @llvm.spv.firstbituhigh.i64(i64 %a)
   ret i32 %elt.firstbituhigh
 }
 
-define noundef <2 x i32> @firstbituhigh_v2i64(<2 x i64> noundef %a) {
+; CHECK-LABEL: Begin function firstbituhigh_v2xi64
+define noundef <2 x i32> @firstbituhigh_v2xi64(<2 x i64> noundef %a) {
 entry:
-; CHECK: [[O:%.*]] = OpBitcast %[[#]] %[[#]]
-; CHECK: [[N:%.*]] = OpExtInst %[[#]] %[[#]] FindUMsb [[O]]
-; CHECK: [[M:%.*]] = OpVectorShuffle %[[#]] [[N]] [[N]] 0
-; CHECK: [[L:%.*]] = OpVectorShuffle %[[#]] [[N]] [[N]] 1
-; CHECK: [[I:%.*]] = OpIEqual %[[#]] [[M]] %[[#]]
-; CHECK: [[H:%.*]] = OpSelect %[[#]] [[I]] [[L]] [[M]]
-; CHECK: [[C:%.*]] = OpSelect %[[#]] [[I]] %[[#]] %[[#]]
-; CHECK: [[B:%.*]] = OpIAdd %[[#]] [[C]] [[H]]
-; CHECK: OpReturnValue [[B]]
+; CHECK: [[a64x2:%.+]] = OpFunctionParameter [[u64x2_t]]
+; CHECK: [[a32x4:%.+]] = OpBitcast [[u32x4_t]] [[a64x2]]
+; CHECK: [[lsb_bits:%.+]] = OpExtInst [[u32x4_t]] [[glsl_450_ext]] FindUMsb [[a32x4]]
+; CHECK: [[high_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[lsb_bits]] [[lsb_bits]] 0 2
+; CHECK: [[low_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[lsb_bits]] [[lsb_bits]] 1 3
+; CHECK: [[should_use_low:%.+]] = OpIEqual [[boolx2_t]] [[high_bits]] [[const_neg1x2]]
+; CHECK: [[ans_bits:%.+]] = OpSelect [[u32x2_t]] [[should_use_low]] [[low_bits]] [[high_bits]]
+; CHECK: [[ans_offset:%.+]] = OpSelect [[u32x2_t]] [[should_use_low]] [[const_0x2]] [[const_32x2]]
+; CHECK: [[ret:%.+]] = OpIAdd [[u32x2_t]] [[ans_offset]] [[ans_bits]]
+; CHECK: OpReturnValue [[ret]]
   %elt.firstbituhigh = call <2 x i32> @llvm.spv.firstbituhigh.v2i64(<2 x i64> %a)
   ret <2 x i32> %elt.firstbituhigh
 }
 
+; CHECK-LABEL: Begin function firstbituhigh_v3xi64
+define noundef <3 x i32> @firstbituhigh_v3xi64(<3 x i64> noundef %a) {
+entry:
+; Preamble
+; CHECK: [[a:%.+]] = OpFunctionParameter [[u64x3_t]]
+
+; Extract first 2 components from %a
+; CHECK: [[pt1:%.+]] = OpVectorShuffle [[u64x2_t]] [[a]] [[a]] 0 1
+
+; Do firstbituhigh on the first 2 components
+; CHECK: [[pt1_cast:%.+]] = OpBitcast [[u32x4_t]] [[pt1]]
+; CHECK: [[pt1_lsb_bits:%.+]] = OpExtInst [[u32x4_t]] [[glsl_450_ext]] FindUMsb [[pt1_cast]]
+; CHECK: [[pt1_high_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[pt1_lsb_bits]] [[pt1_lsb_bits]] 0 2
+; CHECK: [[pt1_low_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[pt1_lsb_bits]] [[pt1_lsb_bits]] 1 3
+; CHECK: [[pt1_should_use_low:%.+]] = OpIEqual [[boolx2_t]] [[pt1_high_bits]] [[const_neg1x2]]
+; CHECK: [[pt1_ans_bits:%.+]] = OpSelect [[u32x2_t]] [[pt1_should_use_low]] [[pt1_low_bits]] [[pt1_high_bits]]
+; CHECK: [[pt1_ans_offset:%.+]] = OpSelect [[u32x2_t]] [[pt1_should_use_low]] [[const_0x2]] [[const_32x2]]
+; CHECK: [[pt1_res:%.+]] = OpIAdd [[u32x2_t]] [[pt1_ans_offset]] [[pt1_ans_bits]]
+
+; Extract the last component from %a
+; CHECK: [[pt2:%.+]] = OpVectorExtractDynamic [[u64_t]] [[a]] [[const_2]]
+
+; Do firstbituhigh on the last component
+; CHECK: [[pt2_cast:%.+]] = OpBitcast [[u32x2_t]] [[pt2]]
+; CHECK: [[pt2_lsb_bits:%.+]] = OpExtInst [[u32x2_t]] [[glsl_450_ext]] FindUMsb [[pt2_cast]]
+; CHECK: [[pt2_high_bits:%.+]] = OpVectorExtractDynamic [[u32_t]] [[pt2_lsb_bits]] [[const_0]]
+; CHECK: [[pt2_low_bits:%.+]] = OpVectorExtractDynamic [[u32_t]] [[pt2_lsb_bits]] [[const_1]]
+; CHECK: [[pt2_should_use_low:%.+]] = OpIEqual [[bool_t]] [[pt2_high_bits]] [[const_neg1]]
+; CHECK: [[pt2_ans_bits:%.+]] = OpSelect [[u32_t]] [[pt2_should_use_low]] [[pt2_low_bits]] [[pt2_high_bits]]
+; CHECK: [[pt2_ans_offset:%.+]] = OpSelect [[u32_t]] [[pt2_should_use_low]] [[const_0]] [[const_32]]
+; CHECK: [[pt2_res:%.+]] = OpIAdd [[u32_t]] [[pt2_ans_offset]] [[pt2_ans_bits]]
+
+; Merge the parts into the final i32x3 and return it
+; CHECK: [[ret:%.+]] = OpCompositeConstruct [[u32x3_t]] [[pt1_res]] [[pt2_res]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbituhigh = call <3 x i32> @llvm.spv.firstbituhigh.v3i64(<3 x i64> %a)
+  ret <3 x i32> %elt.firstbituhigh
+}
+
+; CHECK-LABEL: Begin function firstbituhigh_v4xi64
+define noundef <4 x i32> @firstbituhigh_v4xi64(<4 x i64> noundef %a) {
+entry:
+; Preamble
+; CHECK: [[a:%.+]] = OpFunctionParameter [[u64x4_t]]
+
+; Extract first 2 components from %a
+; CHECK: [[pt1:%.+]] = OpVectorShuffle [[u64x2_t]] [[a]] [[a]] 0 1
+
+; Do firstbituhigh on the first 2 components
+; CHECK: [[pt1_cast:%.+]] = OpBitcast [[u32x4_t]] [[pt1]]
+; CHECK: [[pt1_lsb_bits:%.+]] = OpExtInst [[u32x4_t]] [[glsl_450_ext]] FindUMsb [[pt1_cast]]
+; CHECK: [[pt1_high_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[pt1_lsb_bits]] [[pt1_lsb_bits]] 0 2
+; CHECK: [[pt1_low_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[pt1_lsb_bits]] [[pt1_lsb_bits]] 1 3
+; CHECK: [[pt1_should_use_low:%.+]] = OpIEqual [[boolx2_t]] [[pt1_high_bits]] [[const_neg1x2]]
+; CHECK: [[pt1_ans_bits:%.+]] = OpSelect [[u32x2_t]] [[pt1_should_use_low]] [[pt1_low_bits]] [[pt1_high_bits]]
+; CHECK: [[pt1_ans_offset:%.+]] = OpSelect [[u32x2_t]] [[pt1_should_use_low]] [[const_0x2]] [[const_32x2]]
+; CHECK: [[pt1_res:%.+]] = OpIAdd [[u32x2_t]] [[pt1_ans_offset]] [[pt1_ans_bits]]
+
+; Extract last 2 components from %a
+; CHECK: [[pt2:%.+]] = OpVectorShuffle [[u64x2_t]] [[a]] [[a]] 2 3
+
+; Do firstbituhigh on the last 2 components
+; CHECK: [[pt2_cast:%.+]] = OpBitcast [[u32x4_t]] [[pt2]]
+; CHECK: [[pt2_lsb_bits:%.+]] = OpExtInst [[u32x4_t]] [[glsl_450_ext]] FindUMsb [[pt2_cast]]
+; CHECK: [[pt2_high_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[pt2_lsb_bits]] [[pt2_lsb_bits]] 0 2
+; CHECK: [[pt2_low_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[pt2_lsb_bits]] [[pt2_lsb_bits]] 1 3
+; CHECK: [[pt2_should_use_low:%.+]] = OpIEqual [[boolx2_t]] [[pt2_high_bits]] [[const_neg1x2]]
+; CHECK: [[pt2_ans_bits:%.+]] = OpSelect [[u32x2_t]] [[pt2_should_use_low]] [[pt2_low_bits]] [[pt2_high_bits]]
+; CHECK: [[pt2_ans_offset:%.+]] = OpSelect [[u32x2_t]] [[pt2_should_use_low]] [[const_0x2]] [[const_32x2]]
+; CHECK: [[pt2_res:%.+]] = OpIAdd [[u32x2_t]] [[pt2_ans_offset]] [[pt2_ans_bits]]
+
+; Merge the parts into the final i32x4 and return it
+; CHECK: [[ret:%.+]] = OpCompositeConstruct [[u32x4_t]] [[pt1_res]] [[pt2_res]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbituhigh = call <4 x i32> @llvm.spv.firstbituhigh.v4i64(<4 x i64> %a)
+  ret <4 x i32> %elt.firstbituhigh
+}
+
+; CHECK-LABEL: Begin function firstbitshigh_i32
 define noundef i32 @firstbitshigh_i32(i32 noundef %a) {
 entry:
-; CHECK: %[[#]] = OpExtInst %[[#]] %[[#]] FindSMsb %[[#]]
+; CHECK: [[a:%.+]] = OpFunctionParameter [[u32_t]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32_t]] [[glsl_450_ext]] FindSMsb [[a]]
+; CHECK: OpReturnValue [[ret]]
   %elt.firstbitshigh = call i32 @llvm.spv.firstbitshigh.i32(i32 %a)
   ret i32 %elt.firstbitshigh
 }
 
+; CHECK-LABEL: Begin function firstbitshigh_i16
 define noundef i32 @firstbitshigh_i16(i16 noundef %a) {
 entry:
-; CHECK: [[A:%.*]] = OpSConvert %[[#]]
-; CHECK: %[[#]] = OpExtInst %[[#]] %[[#]] FindSMsb %[[#]]
+; CHECK: [[a16:%.+]] = OpFunctionParameter [[u16_t]]
+; CHECK: [[a32:%.+]] = OpSConvert [[u32_t]] [[a16]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32_t]] [[glsl_450_ext]] FindSMsb [[a32]]
+; CHECK: OpReturnValue [[ret]]
   %elt.firstbitshigh = call i32 @llvm.spv.firstbitshigh.i16(i16 %a)
   ret i32 %elt.firstbitshigh
 }
 
+; CHECK-LABEL: Begin function firstbitshigh_i64
 define noundef i32 @firstbitshigh_i64(i64 noundef %a) {
 entry:
-; CHECK: [[O:%.*]] = OpBitcast %[[#]] %[[#]]
-; CHECK: [[N:%.*]] = OpExtInst %[[#]] %[[#]] FindSMsb [[O]]
-; CHECK: [[M:%.*]] = OpVectorExtractDynamic %[[#]] [[N]] [[Z]]
-; CHECK: [[L:%.*]] = OpVectorExtractDynamic %[[#]] [[N]] [[X]]
-; CHECK: [[I:%.*]] = OpIEqual %[[#]] [[M]] %[[#]]
-; CHECK: [[H:%.*]] = OpSelect %[[#]] [[I]] [[L]] [[M]]
-; CHECK: [[C:%.*]] = OpSelect %[[#]] [[I]] %[[#]] %[[#]]
-; CHECK: [[B:%.*]] = OpIAdd %[[#]] [[C]] [[H]]
+; CHECK: [[a64:%.+]] = OpFunctionParameter [[u64_t]]
+; CHECK: [[a32x2:%.+]] = OpBitcast [[u32x2_t]] [[a64]]
+; CHECK: [[lsb_bits:%.+]] = OpExtInst [[u32x2_t]] [[glsl_450_ext]] FindSMsb [[a32x2]]
+; CHECK: [[high_bits:%.+]] = OpVectorExtractDynamic [[u32_t]] [[lsb_bits]] [[const_0]]
+; CHECK: [[low_bits:%.+]] = OpVectorExtractDynamic [[u32_t]] [[lsb_bits]] [[const_1]]
+; CHECK: [[should_use_low:%.+]] = OpIEqual [[bool_t]] [[high_bits]] [[const_neg1]]
+; CHECK: [[ans_bits:%.+]] = OpSelect [[u32_t]] [[should_use_low]] [[low_bits]] [[high_bits]]
+; CHECK: [[ans_offset:%.+]] = OpSelect [[u32_t]] [[should_use_low]] [[const_0]] [[const_32]]
+; CHECK: [[ret:%.+]] = OpIAdd [[u32_t]] [[ans_offset]] [[ans_bits]]
+; CHECK: OpReturnValue [[ret]]
   %elt.firstbitshigh = call i32 @llvm.spv.firstbitshigh.i64(i64 %a)
   ret i32 %elt.firstbitshigh
 }

diff  --git a/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/firstbitlow.ll b/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/firstbitlow.ll
new file mode 100644
index 00000000000000..6de6cdc60ea9ce
--- /dev/null
+++ b/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/firstbitlow.ll
@@ -0,0 +1,230 @@
+; RUN: llc -verify-machineinstrs -O0 -mtriple=spirv-unknown-unknown %s -o - | FileCheck %s
+; RUN: %if spirv-tools %{ llc -O0 -mtriple=spirv-unknown-unknown %s -o - -filetype=obj | spirv-val %}
+
+; CHECK-DAG: [[glsl_450_ext:%.+]] = OpExtInstImport "GLSL.std.450"
+; CHECK-DAG: OpMemoryModel Logical GLSL450
+; CHECK-DAG: [[u32_t:%.+]] = OpTypeInt 32 0
+; CHECK-DAG: [[u32x2_t:%.+]] = OpTypeVector [[u32_t]] 2
+; CHECK-DAG: [[u32x3_t:%.+]] = OpTypeVector [[u32_t]] 3
+; CHECK-DAG: [[u32x4_t:%.+]] = OpTypeVector [[u32_t]] 4
+; CHECK-DAG: [[const_0:%.*]] = OpConstant [[u32_t]] 0
+; CHECK-DAG: [[const_0x2:%.*]] = OpConstantComposite [[u32x2_t]] [[const_0]] [[const_0]]
+; CHECK-DAG: [[const_1:%.*]] = OpConstant [[u32_t]] 1
+; CHECK-DAG: [[const_2:%.*]] = OpConstant [[u32_t]] 2
+; CHECK-DAG: [[const_32:%.*]] = OpConstant [[u32_t]] 32
+; CHECK-DAG: [[const_32x2:%.*]] = OpConstantComposite [[u32x2_t]] [[const_32]] [[const_32]]
+; CHECK-DAG: [[const_neg1:%.*]] = OpConstant [[u32_t]] 4294967295
+; CHECK-DAG: [[const_neg1x2:%.*]] = OpConstantComposite [[u32x2_t]] [[const_neg1]] [[const_neg1]]
+; CHECK-DAG: [[u16_t:%.+]] = OpTypeInt 16 0
+; CHECK-DAG: [[u16x2_t:%.+]] = OpTypeVector [[u16_t]] 2
+; CHECK-DAG: [[u16x3_t:%.+]] = OpTypeVector [[u16_t]] 3
+; CHECK-DAG: [[u16x4_t:%.+]] = OpTypeVector [[u16_t]] 4
+; CHECK-DAG: [[u64_t:%.+]] = OpTypeInt 64 0
+; CHECK-DAG: [[u64x2_t:%.+]] = OpTypeVector [[u64_t]] 2
+; CHECK-DAG: [[u64x3_t:%.+]] = OpTypeVector [[u64_t]] 3
+; CHECK-DAG: [[u64x4_t:%.+]] = OpTypeVector [[u64_t]] 4
+; CHECK-DAG: [[bool_t:%.+]] = OpTypeBool
+; CHECK-DAG: [[boolx2_t:%.+]] = OpTypeVector [[bool_t]] 2
+
+; CHECK-LABEL: Begin function firstbitlow_i32
+define noundef i32 @firstbitlow_i32(i32 noundef %a) {
+entry:
+; CHECK: [[a:%.+]] = OpFunctionParameter [[u32_t]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32_t]] [[glsl_450_ext]] FindILsb [[a]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbitlow = call i32 @llvm.spv.firstbitlow.i32(i32 %a)
+  ret i32 %elt.firstbitlow
+}
+
+; CHECK-LABEL: Begin function firstbitlow_v2xi32
+define noundef <2 x i32> @firstbitlow_v2xi32(<2 x i32> noundef %a) {
+entry:
+; CHECK: [[a:%.+]] = OpFunctionParameter [[u32x2_t]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32x2_t]] [[glsl_450_ext]] FindILsb [[a]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbitlow = call <2 x i32> @llvm.spv.firstbitlow.v2i32(<2 x i32> %a)
+  ret <2 x i32> %elt.firstbitlow
+}
+
+; CHECK-LABEL: Begin function firstbitlow_v3xi32
+define noundef <3 x i32> @firstbitlow_v3xi32(<3 x i32> noundef %a) {
+entry:
+; CHECK: [[a:%.+]] = OpFunctionParameter [[u32x3_t]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32x3_t]] [[glsl_450_ext]] FindILsb [[a]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbitlow = call <3 x i32> @llvm.spv.firstbitlow.v3i32(<3 x i32> %a)
+  ret <3 x i32> %elt.firstbitlow
+}
+
+; CHECK-LABEL: Begin function firstbitlow_v4xi32
+define noundef <4 x i32> @firstbitlow_v4xi32(<4 x i32> noundef %a) {
+entry:
+; CHECK: [[a:%.+]] = OpFunctionParameter [[u32x4_t]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32x4_t]] [[glsl_450_ext]] FindILsb [[a]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbitlow = call <4 x i32> @llvm.spv.firstbitlow.v4i32(<4 x i32> %a)
+  ret <4 x i32> %elt.firstbitlow
+}
+
+; CHECK-LABEL: Begin function firstbitlow_i16
+define noundef i32 @firstbitlow_i16(i16 noundef %a) {
+entry:
+; CHECK: [[a16:%.+]] = OpFunctionParameter [[u16_t]]
+; CHECK: [[a32:%.+]] = OpUConvert [[u32_t]] [[a16]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32_t]] [[glsl_450_ext]] FindILsb [[a32]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbitlow = call i32 @llvm.spv.firstbitlow.i16(i16 %a)
+  ret i32 %elt.firstbitlow
+}
+
+; CHECK-LABEL: Begin function firstbitlow_v2xi16
+define noundef <2 x i32> @firstbitlow_v2xi16(<2 x i16> noundef %a) {
+entry:
+; CHECK: [[a16:%.+]] = OpFunctionParameter [[u16x2_t]]
+; CHECK: [[a32:%.+]] = OpUConvert [[u32x2_t]] [[a16]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32x2_t]] [[glsl_450_ext]] FindILsb [[a32]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbitlow = call <2 x i32> @llvm.spv.firstbitlow.v2i16(<2 x i16> %a)
+  ret <2 x i32> %elt.firstbitlow
+}
+
+; CHECK-LABEL: Begin function firstbitlow_v3xi16
+define noundef <3 x i32> @firstbitlow_v3xi16(<3 x i16> noundef %a) {
+entry:
+; CHECK: [[a16:%.+]] = OpFunctionParameter [[u16x3_t]]
+; CHECK: [[a32:%.+]] = OpUConvert [[u32x3_t]] [[a16]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32x3_t]] [[glsl_450_ext]] FindILsb [[a32]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbitlow = call <3 x i32> @llvm.spv.firstbitlow.v3i16(<3 x i16> %a)
+  ret <3 x i32> %elt.firstbitlow
+}
+
+; CHECK-LABEL: Begin function firstbitlow_v4xi16
+define noundef <4 x i32> @firstbitlow_v4xi16(<4 x i16> noundef %a) {
+entry:
+; CHECK: [[a16:%.+]] = OpFunctionParameter [[u16x4_t]]
+; CHECK: [[a32:%.+]] = OpUConvert [[u32x4_t]] [[a16]]
+; CHECK: [[ret:%.+]] = OpExtInst [[u32x4_t]] [[glsl_450_ext]] FindILsb [[a32]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbitlow = call <4 x i32> @llvm.spv.firstbitlow.v4i16(<4 x i16> %a)
+  ret <4 x i32> %elt.firstbitlow
+}
+
+; CHECK-LABEL: Begin function firstbitlow_i64
+define noundef i32 @firstbitlow_i64(i64 noundef %a) {
+entry:
+; CHECK: [[a64:%.+]] = OpFunctionParameter [[u64_t]]
+; CHECK: [[a32x2:%.+]] = OpBitcast [[u32x2_t]] [[a64]]
+; CHECK: [[lsb_bits:%.+]] = OpExtInst [[u32x2_t]] [[glsl_450_ext]] FindILsb [[a32x2]]
+; CHECK: [[high_bits:%.+]] = OpVectorExtractDynamic [[u32_t]] [[lsb_bits]] [[const_0]]
+; CHECK: [[low_bits:%.+]] = OpVectorExtractDynamic [[u32_t]] [[lsb_bits]] [[const_1]]
+; CHECK: [[should_use_high:%.+]] = OpIEqual [[bool_t]] [[low_bits]] [[const_neg1]]
+; CHECK: [[ans_bits:%.+]] = OpSelect [[u32_t]] [[should_use_high]] [[high_bits]] [[low_bits]]
+; CHECK: [[ans_offset:%.+]] = OpSelect [[u32_t]] [[should_use_high]] [[const_32]] [[const_0]]
+; CHECK: [[ret:%.+]] = OpIAdd [[u32_t]] [[ans_offset]] [[ans_bits]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbitlow = call i32 @llvm.spv.firstbitlow.i64(i64 %a)
+  ret i32 %elt.firstbitlow
+}
+
+; CHECK-LABEL: Begin function firstbitlow_v2xi64
+define noundef <2 x i32> @firstbitlow_v2xi64(<2 x i64> noundef %a) {
+entry:
+; CHECK: [[a64x2:%.+]] = OpFunctionParameter [[u64x2_t]]
+; CHECK: [[a32x4:%.+]] = OpBitcast [[u32x4_t]] [[a64x2]]
+; CHECK: [[lsb_bits:%.+]] = OpExtInst [[u32x4_t]] [[glsl_450_ext]] FindILsb [[a32x4]]
+; CHECK: [[high_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[lsb_bits]] [[lsb_bits]] 0 2
+; CHECK: [[low_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[lsb_bits]] [[lsb_bits]] 1 3
+; CHECK: [[should_use_high:%.+]] = OpIEqual [[boolx2_t]] [[low_bits]] [[const_neg1x2]]
+; CHECK: [[ans_bits:%.+]] = OpSelect [[u32x2_t]] [[should_use_high]] [[high_bits]] [[low_bits]]
+; CHECK: [[ans_offset:%.+]] = OpSelect [[u32x2_t]] [[should_use_high]] [[const_32x2]] [[const_0x2]]
+; CHECK: [[ret:%.+]] = OpIAdd [[u32x2_t]] [[ans_offset]] [[ans_bits]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbitlow = call <2 x i32> @llvm.spv.firstbitlow.v2i64(<2 x i64> %a)
+  ret <2 x i32> %elt.firstbitlow
+}
+
+; CHECK-LABEL: Begin function firstbitlow_v3xi64
+define noundef <3 x i32> @firstbitlow_v3xi64(<3 x i64> noundef %a) {
+entry:
+; Preamble
+; CHECK: [[a:%.+]] = OpFunctionParameter [[u64x3_t]]
+
+; Extract first 2 components from %a
+; CHECK: [[pt1:%.+]] = OpVectorShuffle [[u64x2_t]] [[a]] [[a]] 0 1
+
+; Do firstbitlow on the first 2 components
+; CHECK: [[pt1_cast:%.+]] = OpBitcast [[u32x4_t]] [[pt1]]
+; CHECK: [[pt1_lsb_bits:%.+]] = OpExtInst [[u32x4_t]] [[glsl_450_ext]] FindILsb [[pt1_cast]]
+; CHECK: [[pt1_high_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[pt1_lsb_bits]] [[pt1_lsb_bits]] 0 2
+; CHECK: [[pt1_low_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[pt1_lsb_bits]] [[pt1_lsb_bits]] 1 3
+; CHECK: [[pt1_should_use_high:%.+]] = OpIEqual [[boolx2_t]] [[pt1_low_bits]] [[const_neg1x2]]
+; CHECK: [[pt1_ans_bits:%.+]] = OpSelect [[u32x2_t]] [[pt1_should_use_high]] [[pt1_high_bits]] [[pt1_low_bits]]
+; CHECK: [[pt1_ans_offset:%.+]] = OpSelect [[u32x2_t]] [[pt1_should_use_high]] [[const_32x2]] [[const_0x2]]
+; CHECK: [[pt1_res:%.+]] = OpIAdd [[u32x2_t]] [[pt1_ans_offset]] [[pt1_ans_bits]]
+
+; Extract the last component from %a
+; CHECK: [[pt2:%.+]] = OpVectorExtractDynamic [[u64_t]] [[a]] [[const_2]]
+
+; Do firstbitlow on the last component
+; CHECK: [[pt2_cast:%.+]] = OpBitcast [[u32x2_t]] [[pt2]]
+; CHECK: [[pt2_lsb_bits:%.+]] = OpExtInst [[u32x2_t]] [[glsl_450_ext]] FindILsb [[pt2_cast]]
+; CHECK: [[pt2_high_bits:%.+]] = OpVectorExtractDynamic [[u32_t]] [[pt2_lsb_bits]] [[const_0]]
+; CHECK: [[pt2_low_bits:%.+]] = OpVectorExtractDynamic [[u32_t]] [[pt2_lsb_bits]] [[const_1]]
+; CHECK: [[pt2_should_use_high:%.+]] = OpIEqual [[bool_t]] [[pt2_low_bits]] [[const_neg1]]
+; CHECK: [[pt2_ans_bits:%.+]] = OpSelect [[u32_t]] [[pt2_should_use_high]] [[pt2_high_bits]] [[pt2_low_bits]]
+; CHECK: [[pt2_ans_offset:%.+]] = OpSelect [[u32_t]] [[pt2_should_use_high]] [[const_32]] [[const_0]]
+; CHECK: [[pt2_res:%.+]] = OpIAdd [[u32_t]] [[pt2_ans_offset]] [[pt2_ans_bits]]
+
+; Merge the parts into the final i32x3 and return it
+; CHECK: [[ret:%.+]] = OpCompositeConstruct [[u32x3_t]] [[pt1_res]] [[pt2_res]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbitlow = call <3 x i32> @llvm.spv.firstbitlow.v3i64(<3 x i64> %a)
+  ret <3 x i32> %elt.firstbitlow
+}
+
+; CHECK-LABEL: Begin function firstbitlow_v4xi64
+define noundef <4 x i32> @firstbitlow_v4xi64(<4 x i64> noundef %a) {
+entry:
+; Preamble
+; CHECK: [[a:%.+]] = OpFunctionParameter [[u64x4_t]]
+
+; Extract first 2 components from %a
+; CHECK: [[pt1:%.+]] = OpVectorShuffle [[u64x2_t]] [[a]] [[a]] 0 1
+
+; Do firstbitlow on the first 2 components
+; CHECK: [[pt1_cast:%.+]] = OpBitcast [[u32x4_t]] [[pt1]]
+; CHECK: [[pt1_lsb_bits:%.+]] = OpExtInst [[u32x4_t]] [[glsl_450_ext]] FindILsb [[pt1_cast]]
+; CHECK: [[pt1_high_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[pt1_lsb_bits]] [[pt1_lsb_bits]] 0 2
+; CHECK: [[pt1_low_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[pt1_lsb_bits]] [[pt1_lsb_bits]] 1 3
+; CHECK: [[pt1_should_use_high:%.+]] = OpIEqual [[boolx2_t]] [[pt1_low_bits]] [[const_neg1x2]]
+; CHECK: [[pt1_ans_bits:%.+]] = OpSelect [[u32x2_t]] [[pt1_should_use_high]] [[pt1_high_bits]] [[pt1_low_bits]]
+; CHECK: [[pt1_ans_offset:%.+]] = OpSelect [[u32x2_t]] [[pt1_should_use_high]] [[const_32x2]] [[const_0x2]]
+; CHECK: [[pt1_res:%.+]] = OpIAdd [[u32x2_t]] [[pt1_ans_offset]] [[pt1_ans_bits]]
+
+; Extract last 2 components from %a
+; CHECK: [[pt2:%.+]] = OpVectorShuffle [[u64x2_t]] [[a]] [[a]] 2 3
+
+; Do firstbituhigh on the last 2 components
+; CHECK: [[pt2_cast:%.+]] = OpBitcast [[u32x4_t]] [[pt2]]
+; CHECK: [[pt2_lsb_bits:%.+]] = OpExtInst [[u32x4_t]] [[glsl_450_ext]] FindILsb [[pt2_cast]]
+; CHECK: [[pt2_high_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[pt2_lsb_bits]] [[pt2_lsb_bits]] 0 2
+; CHECK: [[pt2_low_bits:%.+]] = OpVectorShuffle [[u32x2_t]] [[pt2_lsb_bits]] [[pt2_lsb_bits]] 1 3
+; CHECK: [[pt2_should_use_high:%.+]] = OpIEqual [[boolx2_t]] [[pt2_low_bits]] [[const_neg1x2]]
+; CHECK: [[pt2_ans_bits:%.+]] = OpSelect [[u32x2_t]] [[pt2_should_use_high]] [[pt2_high_bits]] [[pt2_low_bits]]
+; CHECK: [[pt2_ans_offset:%.+]] = OpSelect [[u32x2_t]] [[pt2_should_use_high]] [[const_32x2]] [[const_0x2]]
+; CHECK: [[pt2_res:%.+]] = OpIAdd [[u32x2_t]] [[pt2_ans_offset]] [[pt2_ans_bits]]
+
+; Merge the parts into the final i32x4 and return it
+; CHECK: [[ret:%.+]] = OpCompositeConstruct [[u32x4_t]] [[pt1_res]] [[pt2_res]]
+; CHECK: OpReturnValue [[ret]]
+  %elt.firstbitlow = call <4 x i32> @llvm.spv.firstbitlow.v4i64(<4 x i64> %a)
+  ret <4 x i32> %elt.firstbitlow
+}
+
+;declare i16 @llvm.spv.firstbitlow.i16(i16)
+;declare i32 @llvm.spv.firstbitlow.i32(i32)
+;declare i64 @llvm.spv.firstbitlow.i64(i64)
+;declare i16 @llvm.spv.firstbitlow.v2i16(<2 x i16>)
+;declare i32 @llvm.spv.firstbitlow.v2i32(<2 x i32>)
+;declare i64 @llvm.spv.firstbitlow.v2i64(<2 x i64>)


        


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