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llvm-mirror/lib/Transforms/Utils/CanonicalizeAliases.cpp
Reid Kleckner 68092989f3 Sink all InitializePasses.h includes
This file lists every pass in LLVM, and is included by Pass.h, which is
very popular. Every time we add, remove, or rename a pass in LLVM, it
caused lots of recompilation.

I found this fact by looking at this table, which is sorted by the
number of times a file was changed over the last 100,000 git commits
multiplied by the number of object files that depend on it in the
current checkout:
  recompiles    touches affected_files  header
  342380        95      3604    llvm/include/llvm/ADT/STLExtras.h
  314730        234     1345    llvm/include/llvm/InitializePasses.h
  307036        118     2602    llvm/include/llvm/ADT/APInt.h
  213049        59      3611    llvm/include/llvm/Support/MathExtras.h
  170422        47      3626    llvm/include/llvm/Support/Compiler.h
  162225        45      3605    llvm/include/llvm/ADT/Optional.h
  158319        63      2513    llvm/include/llvm/ADT/Triple.h
  140322        39      3598    llvm/include/llvm/ADT/StringRef.h
  137647        59      2333    llvm/include/llvm/Support/Error.h
  131619        73      1803    llvm/include/llvm/Support/FileSystem.h

Before this change, touching InitializePasses.h would cause 1345 files
to recompile. After this change, touching it only causes 550 compiles in
an incremental rebuild.

Reviewers: bkramer, asbirlea, bollu, jdoerfert

Differential Revision: https://reviews.llvm.org/D70211
2019-11-13 16:34:37 -08:00

106 lines
3.2 KiB
C++

//===- CanonicalizeAliases.cpp - ThinLTO Support: Canonicalize Aliases ----===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Currently this file implements partial alias canonicalization, to
// flatten chains of aliases (also done by GlobalOpt, but not on for
// O0 compiles). E.g.
// @a = alias i8, i8 *@b
// @b = alias i8, i8 *@g
//
// will be converted to:
// @a = alias i8, i8 *@g <-- @a is now an alias to base object @g
// @b = alias i8, i8 *@g
//
// Eventually this file will implement full alias canonicalation, so that
// all aliasees are private anonymous values. E.g.
// @a = alias i8, i8 *@g
// @g = global i8 0
//
// will be converted to:
// @0 = private global
// @a = alias i8, i8* @0
// @g = alias i8, i8* @0
//
// This simplifies optimization and ThinLTO linking of the original symbols.
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/CanonicalizeAliases.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
using namespace llvm;
namespace {
static Constant *canonicalizeAlias(Constant *C, bool &Changed) {
if (auto *GA = dyn_cast<GlobalAlias>(C)) {
auto *NewAliasee = canonicalizeAlias(GA->getAliasee(), Changed);
if (NewAliasee != GA->getAliasee()) {
GA->setAliasee(NewAliasee);
Changed = true;
}
return NewAliasee;
}
auto *CE = dyn_cast<ConstantExpr>(C);
if (!CE)
return C;
std::vector<Constant *> Ops;
for (Use &U : CE->operands())
Ops.push_back(canonicalizeAlias(cast<Constant>(U), Changed));
return CE->getWithOperands(Ops);
}
/// Convert aliases to canonical form.
static bool canonicalizeAliases(Module &M) {
bool Changed = false;
for (auto &GA : M.aliases())
canonicalizeAlias(&GA, Changed);
return Changed;
}
// Legacy pass that canonicalizes aliases.
class CanonicalizeAliasesLegacyPass : public ModulePass {
public:
/// Pass identification, replacement for typeid
static char ID;
/// Specify pass name for debug output
StringRef getPassName() const override { return "Canonicalize Aliases"; }
explicit CanonicalizeAliasesLegacyPass() : ModulePass(ID) {}
bool runOnModule(Module &M) override { return canonicalizeAliases(M); }
};
char CanonicalizeAliasesLegacyPass::ID = 0;
} // anonymous namespace
PreservedAnalyses CanonicalizeAliasesPass::run(Module &M,
ModuleAnalysisManager &AM) {
if (!canonicalizeAliases(M))
return PreservedAnalyses::all();
return PreservedAnalyses::none();
}
INITIALIZE_PASS_BEGIN(CanonicalizeAliasesLegacyPass, "canonicalize-aliases",
"Canonicalize aliases", false, false)
INITIALIZE_PASS_END(CanonicalizeAliasesLegacyPass, "canonicalize-aliases",
"Canonicalize aliases", false, false)
namespace llvm {
ModulePass *createCanonicalizeAliasesPass() {
return new CanonicalizeAliasesLegacyPass();
}
} // namespace llvm