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

[Justin Bogner via cfe-commits]

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@@ -0,0 +1,187 @@
+//===- DXILIntrinsicExpansion.cpp - Prepare LLVM Module for DXIL encoding--===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file This file contains DXIL intrinsic expansions for those that don't have
+//  opcodes in DirectX Intermediate Language (DXIL).
+//===----------------------------------------------------------------------===//
+
+#include "DXILIntrinsicExpansion.h"
+#include "DirectX.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Instruction.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/IntrinsicsDirectX.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/IR/Type.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/ErrorHandling.h"
+
+#define DEBUG_TYPE "dxil-intrinsic-expansion"
+#define M_LOG2E_F 1.44269504088896340735992468100189214f
+
+using namespace llvm;
+
+static bool isIntrinsicExpansion(Function &F) {
+  switch (F.getIntrinsicID()) {
+  case Intrinsic::exp:
+  case Intrinsic::dx_any:
+  case Intrinsic::dx_lerp:
+  case Intrinsic::dx_rcp:
+    return true;
+  }
+  return false;
+}
+
+static bool expandExpIntrinsic(CallInst *Orig) {
+  Value *X = Orig->getOperand(0);
+  IRBuilder<> Builder(Orig->getParent());
+  Builder.SetInsertPoint(Orig);
+  Type *Ty = X->getType();
+  Type *EltTy = Ty->getScalarType();
+  Constant *Log2eConst =
+      Ty->isVectorTy()
+          ? ConstantVector::getSplat(
+                ElementCount::getFixed(
+                    dyn_cast<FixedVectorType>(Ty)->getNumElements()),
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bogner wrote:

If we aren't checking for null this should be `cast` not `dyn_cast`. Does this do something bad if we somehow get here with scalable vectors?

https://github.com/llvm/llvm-project/pull/84526