MI->eraseFromParent(); // The pseudo instruction is gone now.
return BB;
}
-
- case ARM::ABS:
- case ARM::t2ABS: {
- // To insert an ABS instruction, we have to insert the
- // diamond control-flow pattern. The incoming instruction knows the
- // source vreg to test against 0, the destination vreg to set,
- // the condition code register to branch on, the
- // true/false values to select between, and a branch opcode to use.
- // It transforms
- // V1 = ABS V0
- // into
- // V2 = MOVS V0
- // BCC (branch to SinkBB if V0 >= 0)
- // RSBBB: V3 = RSBri V2, 0 (compute ABS if V2 < 0)
- // SinkBB: V1 = PHI(V2, V3)
- const BasicBlock *LLVM_BB = BB->getBasicBlock();
- MachineFunction::iterator BBI = BB;
- ++BBI;
- MachineFunction *Fn = BB->getParent();
- MachineBasicBlock *RSBBB = Fn->CreateMachineBasicBlock(LLVM_BB);
- MachineBasicBlock *SinkBB = Fn->CreateMachineBasicBlock(LLVM_BB);
- Fn->insert(BBI, RSBBB);
- Fn->insert(BBI, SinkBB);
-
- unsigned int ABSSrcReg = MI->getOperand(1).getReg();
- unsigned int ABSDstReg = MI->getOperand(0).getReg();
- bool isThumb2 = Subtarget->isThumb2();
- MachineRegisterInfo &MRI = Fn->getRegInfo();
- // In Thumb mode S must not be specified if source register is the SP or
- // PC and if destination register is the SP, so restrict register class
- unsigned NewMovDstReg = MRI.createVirtualRegister(
- isThumb2 ? ARM::rGPRRegisterClass : ARM::GPRRegisterClass);
- unsigned NewRsbDstReg = MRI.createVirtualRegister(
- isThumb2 ? ARM::rGPRRegisterClass : ARM::GPRRegisterClass);
-
- // Transfer the remainder of BB and its successor edges to sinkMBB.
- SinkBB->splice(SinkBB->begin(), BB,
- llvm::next(MachineBasicBlock::iterator(MI)),
- BB->end());
- SinkBB->transferSuccessorsAndUpdatePHIs(BB);
-
- BB->addSuccessor(RSBBB);
- BB->addSuccessor(SinkBB);
-
- // fall through to SinkMBB
- RSBBB->addSuccessor(SinkBB);
-
- // insert a movs at the end of BB
- BuildMI(BB, dl, TII->get(isThumb2 ? ARM::t2MOVr : ARM::MOVr),
- NewMovDstReg)
- .addReg(ABSSrcReg, RegState::Kill)
- .addImm((unsigned)ARMCC::AL).addReg(0)
- .addReg(ARM::CPSR, RegState::Define);
-
- // insert a bcc with opposite CC to ARMCC::MI at the end of BB
- BuildMI(BB, dl,
- TII->get(isThumb2 ? ARM::t2Bcc : ARM::Bcc)).addMBB(SinkBB)
- .addImm(ARMCC::getOppositeCondition(ARMCC::MI)).addReg(ARM::CPSR);
-
- // insert rsbri in RSBBB
- // Note: BCC and rsbri will be converted into predicated rsbmi
- // by if-conversion pass
- BuildMI(*RSBBB, RSBBB->begin(), dl,
- TII->get(isThumb2 ? ARM::t2RSBri : ARM::RSBri), NewRsbDstReg)
- .addReg(NewMovDstReg, RegState::Kill)
- .addImm(0).addImm((unsigned)ARMCC::AL).addReg(0).addReg(0);
-
- // insert PHI in SinkBB,
- // reuse ABSDstReg to not change uses of ABS instruction
- BuildMI(*SinkBB, SinkBB->begin(), dl,
- TII->get(ARM::PHI), ABSDstReg)
- .addReg(NewRsbDstReg).addMBB(RSBBB)
- .addReg(NewMovDstReg).addMBB(BB);
-
- // remove ABS instruction
- MI->eraseFromParent();
-
- // return last added BB
- return SinkBB;
- }
}
}