Allow PPC B and BLR to be if-converted into some predicated forms
This enables us to form predicated branches (which are the same conditional
branches we had before) and also a larger set of predicated returns (including
instructions like bdnzlr which is a conditional return and loop-counter
decrement all in one).
At the moment, if conversion does not capture all possible opportunities. A
simple example is provided in early-ret2.ll, where if conversion forms one
predicated return, and then the PPCEarlyReturn pass picks up the other one. So,
at least for now, we'll keep both mechanisms.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179134 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/PowerPC/PPCInstrInfo.cpp b/lib/Target/PowerPC/PPCInstrInfo.cpp
index 219d893..51bc4f2 100644
--- a/lib/Target/PowerPC/PPCInstrInfo.cpp
+++ b/lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -876,6 +876,143 @@
return true;
}
+bool PPCInstrInfo::isPredicated(const MachineInstr *MI) const {
+ unsigned OpC = MI->getOpcode();
+ switch (OpC) {
+ default:
+ return false;
+ case PPC::BCC:
+ case PPC::BCLR:
+ case PPC::BDZLR:
+ case PPC::BDZLR8:
+ case PPC::BDNZLR:
+ case PPC::BDNZLR8:
+ return true;
+ }
+}
+
+bool PPCInstrInfo::isUnpredicatedTerminator(const MachineInstr *MI) const {
+ if (!MI->isTerminator())
+ return false;
+
+ // Conditional branch is a special case.
+ if (MI->isBranch() && !MI->isBarrier())
+ return true;
+
+ return !isPredicated(MI);
+}
+
+bool PPCInstrInfo::PredicateInstruction(
+ MachineInstr *MI,
+ const SmallVectorImpl<MachineOperand> &Pred) const {
+ unsigned OpC = MI->getOpcode();
+ if (OpC == PPC::BLR) {
+ if (Pred[1].getReg() == PPC::CTR8 || Pred[1].getReg() == PPC::CTR) {
+ bool isPPC64 = TM.getSubtargetImpl()->isPPC64();
+ MI->setDesc(get(Pred[0].getImm() ?
+ (isPPC64 ? PPC::BDNZLR8 : PPC::BDNZLR) :
+ (isPPC64 ? PPC::BDZLR8 : PPC::BDZLR)));
+ } else {
+ MI->setDesc(get(PPC::BCLR));
+ MachineInstrBuilder(*MI->getParent()->getParent(), MI)
+ .addImm(Pred[0].getImm())
+ .addReg(Pred[1].getReg());
+ }
+
+ return true;
+ } else if (OpC == PPC::B) {
+ if (Pred[1].getReg() == PPC::CTR8 || Pred[1].getReg() == PPC::CTR) {
+ bool isPPC64 = TM.getSubtargetImpl()->isPPC64();
+ MI->setDesc(get(Pred[0].getImm() ?
+ (isPPC64 ? PPC::BDNZ8 : PPC::BDNZ) :
+ (isPPC64 ? PPC::BDZ8 : PPC::BDZ)));
+ } else {
+ MachineBasicBlock *MBB = MI->getOperand(0).getMBB();
+ MI->RemoveOperand(0);
+
+ MI->setDesc(get(PPC::BCC));
+ MachineInstrBuilder(*MI->getParent()->getParent(), MI)
+ .addImm(Pred[0].getImm())
+ .addReg(Pred[1].getReg())
+ .addMBB(MBB);
+ }
+
+ return true;
+ }
+
+ return false;
+}
+
+bool PPCInstrInfo::SubsumesPredicate(
+ const SmallVectorImpl<MachineOperand> &Pred1,
+ const SmallVectorImpl<MachineOperand> &Pred2) const {
+ assert(Pred1.size() == 2 && "Invalid PPC first predicate");
+ assert(Pred2.size() == 2 && "Invalid PPC second predicate");
+
+ if (Pred1[1].getReg() == PPC::CTR8 || Pred1[1].getReg() == PPC::CTR)
+ return false;
+ if (Pred2[1].getReg() == PPC::CTR8 || Pred2[1].getReg() == PPC::CTR)
+ return false;
+
+ PPC::Predicate P1 = (PPC::Predicate) Pred1[0].getImm();
+ PPC::Predicate P2 = (PPC::Predicate) Pred2[0].getImm();
+
+ if (P1 == P2)
+ return true;
+
+ // Does P1 subsume P2, e.g. GE subsumes GT.
+ if (P1 == PPC::PRED_LE &&
+ (P2 == PPC::PRED_LT || P2 == PPC::PRED_EQ))
+ return true;
+ if (P1 == PPC::PRED_GE &&
+ (P2 == PPC::PRED_GT || P2 == PPC::PRED_EQ))
+ return true;
+
+ return false;
+}
+
+bool PPCInstrInfo::DefinesPredicate(MachineInstr *MI,
+ std::vector<MachineOperand> &Pred) const {
+ // Note: At the present time, the contents of Pred from this function is
+ // unused by IfConversion. This implementation follows ARM by pushing the
+ // CR-defining operand. Because the 'DZ' and 'DNZ' count as types of
+ // predicate, instructions defining CTR or CTR8 are also included as
+ // predicate-defining instructions.
+
+ const TargetRegisterClass *RCs[] =
+ { &PPC::CRRCRegClass, &PPC::CRBITRCRegClass,
+ &PPC::CTRRCRegClass, &PPC::CTRRC8RegClass };
+
+ bool Found = false;
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = MI->getOperand(i);
+ for (int c = 0; c < 2 && !Found; ++c) {
+ const TargetRegisterClass *RC = RCs[c];
+ for (TargetRegisterClass::iterator I = RC->begin(),
+ IE = RC->end(); I != IE; ++I) {
+ if ((MO.isRegMask() && MO.clobbersPhysReg(*I)) ||
+ (MO.isReg() && MO.isDef() && MO.getReg() == *I)) {
+ Pred.push_back(MO);
+ Found = true;
+ }
+ }
+ }
+ }
+
+ return Found;
+}
+
+bool PPCInstrInfo::isPredicable(MachineInstr *MI) const {
+ unsigned OpC = MI->getOpcode();
+ switch (OpC) {
+ default:
+ return false;
+ case PPC::B:
+ case PPC::BLR:
+ return true;
+ }
+}
+
/// GetInstSize - Return the number of bytes of code the specified
/// instruction may be. This returns the maximum number of bytes.
///