[DXIL] `exp`, `any`, `lerp`, & `rcp` Intrinsic Lowering (#84526)

This change implements lowering for #70076, #70100, #70072, & #70102 
`CGBuiltin.cpp` - - simplify `lerp` intrinsic
`IntrinsicsDirectX.td` - simplify `lerp` intrinsic
`SemaChecking.cpp` - remove unnecessary check
`DXILIntrinsicExpansion.*` - add intrinsic to instruction expansion
cases
`DXILOpLowering.cpp` - make sure `DXILIntrinsicExpansion` happens first
`DirectX.h` - changes to support new pass
`DirectXTargetMachine.cpp` - changes to support new pass

Why `any`, and `lerp` as instruction expansion just for DXIL?
- SPIR-V there is an
[OpAny](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#OpAny)
- SPIR-V has a GLSL lerp extension via
[Fmix](https://registry.khronos.org/SPIR-V/specs/1.0/GLSL.std.450.html#FMix)

Why `exp` instruction expansion?
- We have an `exp2` opcode and `exp` reuses that opcode. So instruction
expansion is a convenient way to do preprocessing.
- Further SPIR-V has a GLSL exp extension via
[Exp](https://registry.khronos.org/SPIR-V/specs/1.0/GLSL.std.450.html#Exp)
and
[Exp2](https://registry.khronos.org/SPIR-V/specs/1.0/GLSL.std.450.html#Exp2)

Why `rcp` as instruction expansion?
This one is a bit of the odd man out and might have to move to
`cgbuiltins` when we better understand SPIRV requirements. However I
included it because it seems like [fast math mode has an AllowRecip
flag](https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#_fp_fast_math_mode)
which lets you compute the reciprocal without performing the division.
We don't have that in DXIL so thought to include it.

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp b/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp
index 06938f8..03c825b 100644
--- a/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp
+++ b/llvm/lib/Target/DirectX/DirectXTargetMachine.cpp
@@ -39,6 +39,7 @@ using namespace llvm;
 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeDirectXTarget() {
   RegisterTargetMachine<DirectXTargetMachine> X(getTheDirectXTarget());
   auto *PR = PassRegistry::getPassRegistry();
+  initializeDXILIntrinsicExpansionLegacyPass(*PR);
   initializeDXILPrepareModulePass(*PR);
   initializeEmbedDXILPassPass(*PR);
   initializeWriteDXILPassPass(*PR);
@@ -76,6 +77,7 @@ public:
 
   FunctionPass *createTargetRegisterAllocator(bool) override { return nullptr; }
   void addCodeGenPrepare() override {
+    addPass(createDXILIntrinsicExpansionLegacyPass());
     addPass(createDXILOpLoweringLegacyPass());
     addPass(createDXILPrepareModulePass());
     addPass(createDXILTranslateMetadataPass());