GlobalMerge.h

Go to the documentation of this file.

//===- llvm/CodeGen/GlobalMerge.h -------------------------------*- 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
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_CODEGEN_GLOBALMERGE_H
#define LLVM_CODEGEN_GLOBALMERGE_H
 
#include "llvm/IR/PassManager.h"
 
namespace llvm {
 
class TargetMachine;
 
struct GlobalMergeOptions {
  // FIXME: Infer the maximum possible offset depending on the actual users
  // (these max offsets are different for the users inside Thumb or ARM
  // functions), see the code that passes in the offset in the ARM backend
  // for more information.
  unsigned MaxOffset = 0;
  // The minimum size in bytes of each global that should considered in merging.
  unsigned MinSize = 0;
  bool GroupByUse = true;
  bool IgnoreSingleUse = true;
  /// Whether we should merge global variables that have external linkage.
  bool MergeExternal = true;
  /// Whether we should merge constant global variables.
  bool MergeConstantGlobals = false;
  /// Whether we should merge constant global variables aggressively without
  /// looking at use.
  bool MergeConstAggressive = false;
  /// Whether we should try to optimize for size only.
  /// Currently, this applies a dead simple heuristic: only consider globals
  /// used in minsize functions for merging.
  /// FIXME: This could learn about optsize, and be used in the cost model.
  bool SizeOnly = false;
};
 
// FIXME: This pass must run before AsmPrinterPass::doInitialization!
class GlobalMergePass : public PassInfoMixin<GlobalMergePass> {
  const TargetMachine *TM;
  GlobalMergeOptions Options;
 
public:
  GlobalMergePass(const TargetMachine *TM, GlobalMergeOptions Options)
      : TM(TM), Options(Options) {}
 
  PreservedAnalyses run(Module &M, ModuleAnalysisManager &MAM);
};
 
} // namespace llvm
 
#endif // LLVM_CODEGEN_GLOBALMERGE_H