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//===- TailDuplication.cpp - Duplicate blocks into predecessors' tails ----===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass duplicates basic blocks ending in unconditional branches into
// the tails of their predecessors, using the TailDuplicator utility class.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/TailDuplicator.h"
#include "llvm/Pass.h"
using namespace llvm;
#define DEBUG_TYPE "tailduplication"
namespace {
/// Perform tail duplication. Delegates to TailDuplicator
class TailDuplicatePass : public MachineFunctionPass {
TailDuplicator Duplicator;
public:
static char ID;
explicit TailDuplicatePass() : MachineFunctionPass(ID) {}
bool runOnMachineFunction(MachineFunction &MF) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
};
} // end anonymous namespace
char TailDuplicatePass::ID = 0;
char &llvm::TailDuplicateID = TailDuplicatePass::ID;
INITIALIZE_PASS(TailDuplicatePass, DEBUG_TYPE, "Tail Duplication", false, false)
bool TailDuplicatePass::runOnMachineFunction(MachineFunction &MF) {
if (skipFunction(MF.getFunction()))
return false;
auto MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
// TODO: Querying isSSA() to determine pre-/post-regalloc is fragile, better
// split this into two passes instead.
bool PreRegAlloc = MF.getRegInfo().isSSA();
Duplicator.initMF(MF, PreRegAlloc, MBPI, /* LayoutMode */ false);
bool MadeChange = false;
while (Duplicator.tailDuplicateBlocks())
MadeChange = true;
return MadeChange;
}
void TailDuplicatePass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<MachineBranchProbabilityInfo>();
MachineFunctionPass::getAnalysisUsage(AU);
}
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