return NewOpc;
}
+/// True when condition code could be modified on the instruction
+/// trace starting at from and ending at to.
+static bool modifiesConditionCode(MachineInstr *From, MachineInstr *To,
+ const bool CheckOnlyCCWrites,
+ const TargetRegisterInfo *TRI) {
+ // We iterate backward starting \p To until we hit \p From
+ MachineBasicBlock::iterator I = To, E = From, B = To->getParent()->begin();
+
+ // Early exit if To is at the beginning of the BB.
+ if (I == B)
+ return true;
+
+ // Check whether the definition of SrcReg is in the same basic block as
+ // Compare. If not, assume the condition code gets modified on some path.
+ if (To->getParent() != From->getParent())
+ return true;
+
+ // Check that NZCV isn't set on the trace.
+ for (--I; I != E; --I) {
+ const MachineInstr &Instr = *I;
+
+ if (Instr.modifiesRegister(AArch64::NZCV, TRI) ||
+ (!CheckOnlyCCWrites && Instr.readsRegister(AArch64::NZCV, TRI)))
+ // This instruction modifies or uses NZCV after the one we want to
+ // change.
+ return true;
+ if (I == B)
+ // We currently don't allow the instruction trace to cross basic
+ // block boundaries
+ return true;
+ }
+ return false;
+}
/// optimizeCompareInstr - Convert the instruction supplying the argument to the
/// comparison into one that sets the zero bit in the flags register.
bool AArch64InstrInfo::optimizeCompareInstr(
if (!MI)
return false;
- // We iterate backward, starting from the instruction before CmpInstr and
- // stop when reaching the definition of the source register or done with the
- // basic block, to check whether NZCV is used or modified in between.
- MachineBasicBlock::iterator I = CmpInstr, E = MI,
- B = CmpInstr->getParent()->begin();
-
- // Early exit if CmpInstr is at the beginning of the BB.
- if (I == B)
- return false;
-
- // Check whether the definition of SrcReg is in the same basic block as
- // Compare. If not, we can't optimize away the Compare.
- if (MI->getParent() != CmpInstr->getParent())
- return false;
-
- // Check that NZCV isn't set between the comparison instruction and the one we
- // want to change.
+ bool CheckOnlyCCWrites = false;
const TargetRegisterInfo *TRI = &getRegisterInfo();
- for (--I; I != E; --I) {
- const MachineInstr &Instr = *I;
-
- if (Instr.modifiesRegister(AArch64::NZCV, TRI) ||
- Instr.readsRegister(AArch64::NZCV, TRI))
- // This instruction modifies or uses NZCV after the one we want to
- // change. We can't do this transformation.
- return false;
- if (I == B)
- // The 'and' is below the comparison instruction.
- return false;
- }
+ if (modifiesConditionCode(MI, CmpInstr, CheckOnlyCCWrites, TRI))
+ return false;
unsigned NewOpc = MI->getOpcode();
switch (MI->getOpcode()) {
return;
}
+
+/// \brief Replace csincr-branch sequence by simple conditional branch
+///
+/// Examples:
+/// 1.
+/// csinc w9, wzr, wzr, <condition code>
+/// tbnz w9, #0, 0x44
+/// to
+/// b.<inverted condition code>
+///
+/// 2.
+/// csinc w9, wzr, wzr, <condition code>
+/// tbz w9, #0, 0x44
+/// to
+/// b.<condition code>
+///
+/// \param MI Conditional Branch
+/// \return True when the simple conditional branch is generated
+///
+bool AArch64InstrInfo::optimizeCondBranch(MachineInstr *MI) const {
+ bool IsNegativeBranch = false;
+ bool IsTestAndBranch = false;
+ unsigned TargetBBInMI = 0;
+ unsigned CCInMI = 0;
+ switch (MI->getOpcode()) {
+ default:
+ llvm_unreachable("Unknown branch instruction?");
+ case AArch64::Bcc:
+ return false;
+ case AArch64::CBZW:
+ case AArch64::CBZX:
+ TargetBBInMI = 1;
+ CCInMI = 2;
+ break;
+ case AArch64::CBNZW:
+ case AArch64::CBNZX:
+ TargetBBInMI = 1;
+ CCInMI = 2;
+ IsNegativeBranch = true;
+ break;
+ case AArch64::TBZW:
+ case AArch64::TBZX:
+ TargetBBInMI = 2;
+ CCInMI = 3;
+ IsTestAndBranch = true;
+ break;
+ case AArch64::TBNZW:
+ case AArch64::TBNZX:
+ TargetBBInMI = 2;
+ CCInMI = 3;
+ IsNegativeBranch = true;
+ IsTestAndBranch = true;
+ break;
+ }
+ // So we increment a zero register and test for bits other
+ // than bit 0? Conservatively bail out in case the verifier
+ // missed this case.
+ if (IsTestAndBranch && MI->getOperand(1).getImm())
+ return false;
+
+ // Find Definition.
+ assert(MI->getParent() && "Incomplete machine instruciton\n");
+ MachineBasicBlock *MBB = MI->getParent();
+ MachineFunction *MF = MBB->getParent();
+ MachineRegisterInfo *MRI = &MF->getRegInfo();
+ unsigned VReg = MI->getOperand(0).getReg();
+ if (!TargetRegisterInfo::isVirtualRegister(VReg))
+ return false;
+
+ MachineInstr *DefMI = MRI->getVRegDef(VReg);
+
+ // Look for CSINC
+ if (!(DefMI->getOpcode() == AArch64::CSINCWr &&
+ DefMI->getOperand(1).getReg() == AArch64::WZR &&
+ DefMI->getOperand(2).getReg() == AArch64::WZR) &&
+ !(DefMI->getOpcode() == AArch64::CSINCXr &&
+ DefMI->getOperand(1).getReg() == AArch64::XZR &&
+ DefMI->getOperand(2).getReg() == AArch64::XZR))
+ return false;
+
+ if (DefMI->findRegisterDefOperandIdx(AArch64::NZCV, true) != -1)
+ return false;
+
+ AArch64CC::CondCode CC =
+ (AArch64CC::CondCode)DefMI->getOperand(CCInMI).getImm();
+ bool CheckOnlyCCWrites = true;
+ // Convert only when the condition code is not modified between
+ // the CSINC and the branch. The CC may be used by other
+ // instructions in between.
+ if (modifiesConditionCode(DefMI, MI, CheckOnlyCCWrites, &getRegisterInfo()))
+ return false;
+ MachineBasicBlock &RefToMBB = *MBB;
+ MachineBasicBlock *TBB = MI->getOperand(TargetBBInMI).getMBB();
+ DebugLoc DL = MI->getDebugLoc();
+ if (IsNegativeBranch)
+ CC = AArch64CC::getInvertedCondCode(CC);
+ BuildMI(RefToMBB, MI, DL, get(AArch64::Bcc)).addImm(CC).addMBB(TBB);
+ MI->eraseFromParent();
+ return true;
+}
projects / oota-llvm.git / blobdiff