1 //===- TailDuplication.cpp - Duplicate blocks into predecessors' tails ----===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass duplicates basic blocks ending in unconditional branches into
11 // the tails of their predecessors, using the TailDuplicator utility class.
13 //===----------------------------------------------------------------------===//
15 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
16 #include "llvm/CodeGen/MachineFunction.h"
17 #include "llvm/CodeGen/MachineFunctionPass.h"
18 #include "llvm/CodeGen/MachineRegisterInfo.h"
19 #include "llvm/CodeGen/Passes.h"
20 #include "llvm/CodeGen/TailDuplicator.h"
21 #include "llvm/Pass.h"
25 #define DEBUG_TYPE "tailduplication"
29 /// Perform tail duplication. Delegates to TailDuplicator
30 class TailDuplicatePass : public MachineFunctionPass {
31 TailDuplicator Duplicator;
36 explicit TailDuplicatePass() : MachineFunctionPass(ID) {}
38 bool runOnMachineFunction(MachineFunction &MF) override;
40 void getAnalysisUsage(AnalysisUsage &AU) const override;
43 } // end anonymous namespace
45 char TailDuplicatePass::ID = 0;
47 char &llvm::TailDuplicateID = TailDuplicatePass::ID;
49 INITIALIZE_PASS(TailDuplicatePass, DEBUG_TYPE, "Tail Duplication", false, false)
51 bool TailDuplicatePass::runOnMachineFunction(MachineFunction &MF) {
52 if (skipFunction(MF.getFunction()))
55 auto MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
57 // TODO: Querying isSSA() to determine pre-/post-regalloc is fragile, better
58 // split this into two passes instead.
59 bool PreRegAlloc = MF.getRegInfo().isSSA();
60 Duplicator.initMF(MF, PreRegAlloc, MBPI, /* LayoutMode */ false);
62 bool MadeChange = false;
63 while (Duplicator.tailDuplicateBlocks())
69 void TailDuplicatePass::getAnalysisUsage(AnalysisUsage &AU) const {
70 AU.addRequired<MachineBranchProbabilityInfo>();
71 MachineFunctionPass::getAnalysisUsage(AU);