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diff --git a/llvm/tools/llvm-mca/CodeRegionGenerator.cpp b/llvm/tools/llvm-mca/CodeRegionGenerator.cpp
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+++ b/llvm/tools/llvm-mca/CodeRegionGenerator.cpp
@@ -0,0 +1,140 @@
+//===----------------------- CodeRegionGenerator.cpp ------------*- C++ -*-===//
+//
+// 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 defines classes responsible for generating llvm-mca
+/// CodeRegions from various types of input. llvm-mca only analyzes CodeRegions,
+/// so the classes here provide the input-to-CodeRegions translation.
+//
+//===----------------------------------------------------------------------===//
+
+#include "CodeRegionGenerator.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/MC/MCParser/MCTargetAsmParser.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCTargetOptions.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/SMLoc.h"
+#include <memory>
+
+namespace llvm {
+namespace mca {
+
+// This virtual dtor serves as the anchor for the CodeRegionGenerator class.
+CodeRegionGenerator::~CodeRegionGenerator() {}
+
+// A comment consumer that parses strings.  The only valid tokens are strings.
+class MCACommentConsumer : public AsmCommentConsumer {
+public:
+  CodeRegions &Regions;
+
+  MCACommentConsumer(CodeRegions &R) : Regions(R) {}
+  void HandleComment(SMLoc Loc, StringRef CommentText) override;
+};
+
+// This class provides the callbacks that occur when parsing input assembly.
+class MCStreamerWrapper final : public MCStreamer {
+  CodeRegions &Regions;
+
+public:
+  MCStreamerWrapper(MCContext &Context, mca::CodeRegions &R)
+      : MCStreamer(Context), Regions(R) {}
+
+  // We only want to intercept the emission of new instructions.
+  virtual void EmitInstruction(const MCInst &Inst,
+                               const MCSubtargetInfo &/* unused */) override {
+    Regions.addInstruction(Inst);
+  }
+
+  bool EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) override {
+    return true;
+  }
+
+  void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
+                        unsigned ByteAlignment) override {}
+  void EmitZerofill(MCSection *Section, MCSymbol *Symbol = nullptr,
+                    uint64_t Size = 0, unsigned ByteAlignment = 0,
+                    SMLoc Loc = SMLoc()) override {}
+  void EmitGPRel32Value(const MCExpr *Value) override {}
+  void BeginCOFFSymbolDef(const MCSymbol *Symbol) override {}
+  void EmitCOFFSymbolStorageClass(int StorageClass) override {}
+  void EmitCOFFSymbolType(int Type) override {}
+  void EndCOFFSymbolDef() override {}
+
+  ArrayRef<MCInst> GetInstructionSequence(unsigned Index) const {
+    return Regions.getInstructionSequence(Index);
+  }
+};
+
+void MCACommentConsumer::HandleComment(SMLoc Loc, StringRef CommentText) {
+  // Skip empty comments.
+  StringRef Comment(CommentText);
+  if (Comment.empty())
+    return;
+
+  // Skip spaces and tabs.
+  unsigned Position = Comment.find_first_not_of(" \t");
+  if (Position >= Comment.size())
+    // We reached the end of the comment. Bail out.
+    return;
+
+  Comment = Comment.drop_front(Position);
+  if (Comment.consume_front("LLVM-MCA-END")) {
+    // Skip spaces and tabs.
+    Position = Comment.find_first_not_of(" \t");
+    if (Position < Comment.size())
+      Comment = Comment.drop_front(Position);
+    Regions.endRegion(Comment, Loc);
+    return;
+  }
+
+  // Try to parse the LLVM-MCA-BEGIN comment.
+  if (!Comment.consume_front("LLVM-MCA-BEGIN"))
+    return;
+
+  // Skip spaces and tabs.
+  Position = Comment.find_first_not_of(" \t");
+  if (Position < Comment.size())
+    Comment = Comment.drop_front(Position);
+  // Use the rest of the string as a descriptor for this code snippet.
+  Regions.beginRegion(Comment, Loc);
+}
+
+Expected<const CodeRegions &> AsmCodeRegionGenerator::parseCodeRegions() {
+  MCTargetOptions Opts;
+  Opts.PreserveAsmComments = false;
+  MCStreamerWrapper Str(Ctx, Regions);
+
+  // Create a MCAsmParser and setup the lexer to recognize llvm-mca ASM
+  // comments.
+  std::unique_ptr<MCAsmParser> Parser(
+      createMCAsmParser(Regions.getSourceMgr(), Ctx, Str, MAI));
+  MCAsmLexer &Lexer = Parser->getLexer();
+  MCACommentConsumer CC(Regions);
+  Lexer.setCommentConsumer(&CC);
+  // Enable support for MASM literal numbers (example: 05h, 101b).
+  Lexer.setLexMasmIntegers(true);
+
+  std::unique_ptr<MCTargetAsmParser> TAP(
+      TheTarget.createMCAsmParser(STI, *Parser, MCII, Opts));
+  if (!TAP)
+    return make_error<StringError>(
+        "This target does not support assembly parsing.",
+        inconvertibleErrorCode());
+  Parser->setTargetParser(*TAP);
+  Parser->Run(false);
+
+  // Set the assembler dialect from the input. llvm-mca will use this as the
+  // default dialect when printing reports.
+  AssemblerDialect = Parser->getAssemblerDialect();
+  return Regions;
+}
+
+} // namespace mca
+} // namespace llvm