llvm-6502/include/llvm/CodeGen/BreakCriticalMachineEdge.h

110 lines
3.5 KiB
C
Raw Normal View History

//===--------- BreakCriticalMachineEdges.h - Break critical edges ---------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===---------------------------------------------------------------------===//
//
// Helper function to break a critical machine edge.
//
//===---------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_ASMPRINTER_H
#define LLVM_CODEGEN_ASMPRINTER_H
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
namespace llvm {
MachineBasicBlock* SplitCriticalMachineEdge(MachineBasicBlock* src,
MachineBasicBlock* dst) {
MachineFunction &MF = *src->getParent();
const BasicBlock* srcBB = src->getBasicBlock();
MachineBasicBlock* crit_mbb = MF.CreateMachineBasicBlock(srcBB);
// modify the llvm control flow graph
src->removeSuccessor(dst);
src->addSuccessor(crit_mbb);
crit_mbb->addSuccessor(dst);
// insert the new block into the machine function.
MF.push_back(crit_mbb);
// insert a unconditional branch linking the new block to dst
const TargetMachine& TM = MF.getTarget();
const TargetInstrInfo* TII = TM.getInstrInfo();
std::vector<MachineOperand> emptyConditions;
TII->InsertBranch(*crit_mbb, dst, (MachineBasicBlock*)0,
emptyConditions);
// modify every branch in src that points to dst to point to the new
// machine basic block instead:
MachineBasicBlock::iterator mii = src->end();
bool found_branch = false;
while (mii != src->begin()) {
mii--;
// if there are no more branches, finish the loop
if (!mii->getDesc().isTerminator()) {
break;
}
// Scan the operands of this branch, replacing any uses of dst with
// crit_mbb.
for (unsigned i = 0, e = mii->getNumOperands(); i != e; ++i) {
MachineOperand & mo = mii->getOperand(i);
if (mo.isMachineBasicBlock() &&
mo.getMBB() == dst) {
found_branch = true;
mo.setMBB(crit_mbb);
}
}
}
// TODO: This is tentative. It may be necessary to fix this code. Maybe
// I am inserting too many gotos, but I am trusting that the asm printer
// will optimize the unnecessary gotos.
if(!found_branch) {
TII->InsertBranch(*src, crit_mbb, (MachineBasicBlock*)0,
emptyConditions);
}
/// Change all the phi functions in dst, so that the incoming block be
/// crit_mbb, instead of src
for(mii = dst->begin(); mii != dst->end(); mii++) {
/// the first instructions are always phi functions.
if(mii->getOpcode() != TargetInstrInfo::PHI)
break;
// Find the operands corresponding to the source block
std::vector<unsigned> toRemove;
unsigned reg = 0;
for (unsigned u = 0; u != mii->getNumOperands(); ++u)
if (mii->getOperand(u).isMachineBasicBlock() &&
mii->getOperand(u).getMBB() == src) {
reg = mii->getOperand(u-1).getReg();
toRemove.push_back(u-1);
}
// Remove all uses of this MBB
for (std::vector<unsigned>::reverse_iterator I = toRemove.rbegin(),
E = toRemove.rend(); I != E; ++I) {
mii->RemoveOperand(*I+1);
mii->RemoveOperand(*I);
}
// Add a single use corresponding to the new MBB
mii->addOperand(MachineOperand::CreateReg(reg, false));
mii->addOperand(MachineOperand::CreateMBB(crit_mbb));
}
return crit_mbb;
}
}
#endif