[HLSL] implement exp intrinsic (#83832)

This change implements: #70072

- `hlsl_intrinsics.h` - add the `exp` api
- `DXIL.td` - add the llvm intrinsic to DXIL opcode lowering mapping.
- This change reuses llvm's existing intrinsic
`__builtin_elementwise_exp` \ `int_exp` & `__builtin_elementwise_exp2` \
`int_exp2`
- This PR is part 1 of 2.
- Part 2 requires an intrinsic to instructions lowering.
Part2 will expand `int_exp` to 
```
A = Builder.CreateFMul(log2eConst, val);
int_exp2(A)
```
just like we do in
[TranslateExp](https://github.com/microsoft/DirectXShaderCompiler/blob/main/lib/HLSL/HLOperationLower.cpp#L2220C1-L2236C2)

6 files changed, 231 insertions, 0 deletions

diff --git a/clang/lib/Headers/hlsl/hlsl_intrinsics.h b/clang/lib/Headers/hlsl/hlsl_intrinsics.h
index b5bef78..ed288fa 100644
--- a/clang/lib/Headers/hlsl/hlsl_intrinsics.h
+++ b/clang/lib/Headers/hlsl/hlsl_intrinsics.h
@@ -278,6 +278,70 @@ _HLSL_BUILTIN_ALIAS(__builtin_hlsl_dot)
 uint64_t dot(uint64_t4, uint64_t4);
 
 //===----------------------------------------------------------------------===//
+// exp builtins
+//===----------------------------------------------------------------------===//
+
+/// \fn T exp(T x)
+/// \brief Returns the base-e exponential, or \a e**x, of the specified value.
+/// \param x The specified input value.
+///
+/// The return value is the base-e exponential of the \a x parameter.
+
+_HLSL_16BIT_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp)
+half exp(half);
+_HLSL_16BIT_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp)
+half2 exp(half2);
+_HLSL_16BIT_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp)
+half3 exp(half3);
+_HLSL_16BIT_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp)
+half4 exp(half4);
+
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp)
+float exp(float);
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp)
+float2 exp(float2);
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp)
+float3 exp(float3);
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp)
+float4 exp(float4);
+
+//===----------------------------------------------------------------------===//
+// exp2 builtins
+//===----------------------------------------------------------------------===//
+
+/// \fn T exp2(T x)
+/// \brief Returns the base 2 exponential, or \a 2**x, of the specified value.
+/// \param x The specified input value.
+///
+/// The base 2 exponential of the \a x parameter.
+
+_HLSL_16BIT_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp2)
+half exp2(half);
+_HLSL_16BIT_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp2)
+half2 exp2(half2);
+_HLSL_16BIT_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp2)
+half3 exp2(half3);
+_HLSL_16BIT_AVAILABILITY(shadermodel, 6.2)
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp2)
+half4 exp2(half4);
+
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp2)
+float exp2(float);
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp2)
+float2 exp2(float2);
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp2)
+float3 exp2(float3);
+_HLSL_BUILTIN_ALIAS(__builtin_elementwise_exp2)
+float4 exp2(float4);
+
+//===----------------------------------------------------------------------===//
 // floor builtins
 //===----------------------------------------------------------------------===//
 
diff --git a/clang/test/CodeGenHLSL/builtins/exp.hlsl b/clang/test/CodeGenHLSL/builtins/exp.hlsl
new file mode 100644
index 0000000..773edbe
--- /dev/null
+++ b/clang/test/CodeGenHLSL/builtins/exp.hlsl
@@ -0,0 +1,53 @@
+// 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 \ 
+// RUN:   --check-prefixes=CHECK,NATIVE_HALF
+// RUN: %clang_cc1 -finclude-default-header -x hlsl -triple \
+// RUN:   dxil-pc-shadermodel6.3-library %s -emit-llvm -disable-llvm-passes \
+// RUN:   -o - | FileCheck %s --check-prefixes=CHECK,NO_HALF
+
+// NATIVE_HALF: define noundef half @
+// NATIVE_HALF: %elt.exp = call half @llvm.exp.f16(
+// NATIVE_HALF: ret half %elt.exp
+// NO_HALF: define noundef float @"?test_exp_half@@YA$halff@$halff@@Z"(
+// NO_HALF: %elt.exp = call float @llvm.exp.f32(
+// NO_HALF: ret float %elt.exp
+half test_exp_half(half p0) { return exp(p0); }
+// NATIVE_HALF: define noundef <2 x half> @
+// NATIVE_HALF: %elt.exp = call <2 x half> @llvm.exp.v2f16
+// NATIVE_HALF: ret <2 x half> %elt.exp
+// NO_HALF: define noundef <2 x float> @
+// NO_HALF: %elt.exp = call <2 x float> @llvm.exp.v2f32(
+// NO_HALF: ret <2 x float> %elt.exp
+half2 test_exp_half2(half2 p0) { return exp(p0); }
+// NATIVE_HALF: define noundef <3 x half> @
+// NATIVE_HALF: %elt.exp = call <3 x half> @llvm.exp.v3f16
+// NATIVE_HALF: ret <3 x half> %elt.exp
+// NO_HALF: define noundef <3 x float> @
+// NO_HALF: %elt.exp = call <3 x float> @llvm.exp.v3f32(
+// NO_HALF: ret <3 x float> %elt.exp
+half3 test_exp_half3(half3 p0) { return exp(p0); }
+// NATIVE_HALF: define noundef <4 x half> @
+// NATIVE_HALF: %elt.exp = call <4 x half> @llvm.exp.v4f16
+// NATIVE_HALF: ret <4 x half> %elt.exp
+// NO_HALF: define noundef <4 x float> @
+// NO_HALF: %elt.exp = call <4 x float> @llvm.exp.v4f32(
+// NO_HALF: ret <4 x float> %elt.exp
+half4 test_exp_half4(half4 p0) { return exp(p0); }
+
+// CHECK: define noundef float @
+// CHECK: %elt.exp = call float @llvm.exp.f32(
+// CHECK: ret float %elt.exp
+float test_exp_float(float p0) { return exp(p0); }
+// CHECK: define noundef <2 x float> @
+// CHECK: %elt.exp = call <2 x float> @llvm.exp.v2f32
+// CHECK: ret <2 x float> %elt.exp
+float2 test_exp_float2(float2 p0) { return exp(p0); }
+// CHECK: define noundef <3 x float> @
+// CHECK: %elt.exp = call <3 x float> @llvm.exp.v3f32
+// CHECK: ret <3 x float> %elt.exp
+float3 test_exp_float3(float3 p0) { return exp(p0); }
+// CHECK: define noundef <4 x float> @
+// CHECK: %elt.exp = call <4 x float> @llvm.exp.v4f32
+// CHECK: ret <4 x float> %elt.exp
+float4 test_exp_float4(float4 p0) { return exp(p0); }
diff --git a/clang/test/CodeGenHLSL/builtins/exp2.hlsl b/clang/test/CodeGenHLSL/builtins/exp2.hlsl
new file mode 100644
index 0000000..f21cdd9
--- /dev/null
+++ b/clang/test/CodeGenHLSL/builtins/exp2.hlsl
@@ -0,0 +1,53 @@
+// 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 \ 
+// RUN:   --check-prefixes=CHECK,NATIVE_HALF
+// RUN: %clang_cc1 -finclude-default-header -x hlsl -triple \
+// RUN:   dxil-pc-shadermodel6.3-library %s -emit-llvm -disable-llvm-passes \
+// RUN:   -o - | FileCheck %s --check-prefixes=CHECK,NO_HALF
+
+// NATIVE_HALF: define noundef half @
+// NATIVE_HALF: %elt.exp2 = call half @llvm.exp2.f16(
+// NATIVE_HALF: ret half %elt.exp2
+// NO_HALF: define noundef float @"?test_exp2_half@@YA$halff@$halff@@Z"(
+// NO_HALF: %elt.exp2 = call float @llvm.exp2.f32(
+// NO_HALF: ret float %elt.exp2
+half test_exp2_half(half p0) { return exp2(p0); }
+// NATIVE_HALF: define noundef <2 x half> @
+// NATIVE_HALF: %elt.exp2 = call <2 x half> @llvm.exp2.v2f16
+// NATIVE_HALF: ret <2 x half> %elt.exp2
+// NO_HALF: define noundef <2 x float> @
+// NO_HALF: %elt.exp2 = call <2 x float> @llvm.exp2.v2f32(
+// NO_HALF: ret <2 x float> %elt.exp2
+half2 test_exp2_half2(half2 p0) { return exp2(p0); }
+// NATIVE_HALF: define noundef <3 x half> @
+// NATIVE_HALF: %elt.exp2 = call <3 x half> @llvm.exp2.v3f16
+// NATIVE_HALF: ret <3 x half> %elt.exp2
+// NO_HALF: define noundef <3 x float> @
+// NO_HALF: %elt.exp2 = call <3 x float> @llvm.exp2.v3f32(
+// NO_HALF: ret <3 x float> %elt.exp2
+half3 test_exp2_half3(half3 p0) { return exp2(p0); }
+// NATIVE_HALF: define noundef <4 x half> @
+// NATIVE_HALF: %elt.exp2 = call <4 x half> @llvm.exp2.v4f16
+// NATIVE_HALF: ret <4 x half> %elt.exp2
+// NO_HALF: define noundef <4 x float> @
+// NO_HALF: %elt.exp2 = call <4 x float> @llvm.exp2.v4f32(
+// NO_HALF: ret <4 x float> %elt.exp2
+half4 test_exp2_half4(half4 p0) { return exp2(p0); }
+
+// CHECK: define noundef float @
+// CHECK: %elt.exp2 = call float @llvm.exp2.f32(
+// CHECK: ret float %elt.exp2
+float test_exp2_float(float p0) { return exp2(p0); }
+// CHECK: define noundef <2 x float> @
+// CHECK: %elt.exp2 = call <2 x float> @llvm.exp2.v2f32
+// CHECK: ret <2 x float> %elt.exp2
+float2 test_exp2_float2(float2 p0) { return exp2(p0); }
+// CHECK: define noundef <3 x float> @
+// CHECK: %elt.exp2 = call <3 x float> @llvm.exp2.v3f32
+// CHECK: ret <3 x float> %elt.exp2
+float3 test_exp2_float3(float3 p0) { return exp2(p0); }
+// CHECK: define noundef <4 x float> @
+// CHECK: %elt.exp2 = call <4 x float> @llvm.exp2.v4f32
+// CHECK: ret <4 x float> %elt.exp2
+float4 test_exp2_float4(float4 p0) { return exp2(p0); }
diff --git a/clang/test/SemaHLSL/BuiltIns/exp-errors.hlsl b/clang/test/SemaHLSL/BuiltIns/exp-errors.hlsl
new file mode 100644
index 0000000..e2e79ab
--- /dev/null
+++ b/clang/test/SemaHLSL/BuiltIns/exp-errors.hlsl
@@ -0,0 +1,27 @@
+
+// RUN: %clang_cc1 -finclude-default-header -triple dxil-pc-shadermodel6.6-library %s -fnative-half-type -emit-llvm -disable-llvm-passes -verify -verify-ignore-unexpected -DTEST_FUNC=__builtin_elementwise_exp
+// RUN: %clang_cc1 -finclude-default-header -triple dxil-pc-shadermodel6.6-library %s -fnative-half-type -emit-llvm -disable-llvm-passes -verify -verify-ignore-unexpected -DTEST_FUNC=__builtin_elementwise_exp2
+float test_too_few_arg() {
+  return TEST_FUNC();
+  // expected-error@-1 {{too few arguments to function call, expected 1, have 0}}
+}
+
+float2 test_too_many_arg(float2 p0) {
+  return TEST_FUNC(p0, p0);
+  // expected-error@-1 {{too many arguments to function call, expected 1, have 2}}
+}
+
+float builtin_bool_to_float_type_promotion(bool p1) {
+  return TEST_FUNC(p1);
+  // expected-error@-1 {{1st argument must be a vector, integer or floating point type (was 'bool')}}
+}
+
+float builtin_exp_int_to_float_promotion(int p1) {
+  return TEST_FUNC(p1);
+  // expected-error@-1 {{1st argument must be a floating point type (was 'int')}}
+}
+
+float2 builtin_exp_int2_to_float2_promotion(int2 p1) {
+  return TEST_FUNC(p1);
+  // expected-error@-1 {{1st argument must be a floating point type (was 'int2' (aka 'vector<int, 2>'))}}
+}
diff --git a/llvm/lib/Target/DirectX/DXIL.td b/llvm/lib/Target/DirectX/DXIL.td
index 8f73c08..9536a01 100644
--- a/llvm/lib/Target/DirectX/DXIL.td
+++ b/llvm/lib/Target/DirectX/DXIL.td
@@ -218,6 +218,9 @@ class DXILOpMapping<int opCode, DXILOpClass opClass, Intrinsic intrinsic, string
 // Concrete definition of DXIL Operation mapping to corresponding LLVM intrinsic
 def Sin  : DXILOpMapping<13, unary, int_sin,
                          "Returns sine(theta) for theta in radians.">;
+def Exp2 : DXILOpMapping<21, unary, int_exp2,
+                         "Returns the base 2 exponential, or 2**x, of the specified value."
+                         "exp2(x) = 2**x.">;
 def Frac : DXILOpMapping<22, unary, int_dx_frac,
                          "Returns a fraction from 0 to 1 that represents the "
                          "decimal part of the input.">;
diff --git a/llvm/test/CodeGen/DirectX/exp2.ll b/llvm/test/CodeGen/DirectX/exp2.ll
new file mode 100644
index 0000000..b70b87d
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/exp2.ll
@@ -0,0 +1,31 @@
+; RUN: opt -S -dxil-op-lower < %s | FileCheck %s
+
+; Make sure dxil operation function calls for exp2 are generated for float and half.
+; CHECK:call float @dx.op.unary.f32(i32 21, float %{{.*}})
+; CHECK:call half @dx.op.unary.f16(i32 21, half %{{.*}})
+
+target datalayout = "e-m:e-p:32:32-i1:32-i8:8-i16:16-i32:32-i64:64-f16:16-f32:32-f64:64-n8:16:32:64"
+target triple = "dxil-pc-shadermodel6.7-library"
+
+; Function Attrs: noinline nounwind optnone
+define noundef float @exp2_float(float noundef %a) #0 {
+entry:
+  %a.addr = alloca float, align 4
+  store float %a, ptr %a.addr, align 4
+  %0 = load float, ptr %a.addr, align 4
+  %elt.exp2 = call float @llvm.exp2.f32(float %0)
+  ret float %elt.exp2
+}
+
+; Function Attrs: nocallback nofree nosync nounwind readnone speculatable willreturn
+declare float @llvm.exp2.f32(float) #1
+
+; Function Attrs: noinline nounwind optnone
+define noundef half @exp2_half(half noundef %a) #0 {
+entry:
+  %a.addr = alloca half, align 2
+  store half %a, ptr %a.addr, align 2
+  %0 = load half, ptr %a.addr, align 2
+  %elt.exp2 = call half @llvm.exp2.f16(half %0)
+  ret half %elt.exp2
+}