[llvm] [DirectX] Start the creation of a DXIL Instruction legalizer (PR #131221)

[Chris B via llvm-commits]

================
@@ -0,0 +1,209 @@
+//===- DXILLegalizePass.cpp - Legalizes llvm IR for DXIL ------------------===//
+//
+// 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 a pass to remove i8 truncations and i64 extract
+/// and insert elements.
+///
+//===----------------------------------------------------------------------===//
+#include "DXILLegalizePass.h"
+#include "DirectX.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/InstIterator.h"
+#include "llvm/IR/Instruction.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include <functional>
+#include <map>
+#include <stack>
+#include <vector>
+
+#define DEBUG_TYPE "dxil-legalize"
+
+using namespace llvm;
+namespace {
+
+static void fixI8TruncUseChain(Instruction &I,
+                               std::stack<Instruction *> &ToRemove,
+                               std::map<Value *, Value *> &ReplacedValues) {
----------------
llvm-beanz wrote:

llvm::DenseMap should almost always be used instead of std::map.
see: https://llvm.org/docs/CodingStandards.html#c-standard-library

https://github.com/llvm/llvm-project/pull/131221