| //===--------- BreakCriticalMachineEdge.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_BREAKCRITICALMACHINEEDGE_H |
| #define LLVM_CODEGEN_BREAKCRITICALMACHINEEDGE_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.isMBB() && 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).isMBB() && |
| 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 |