+ return new PPCBSel();
+}
+
+bool PPCBSel::runOnMachineFunction(MachineFunction &Fn) {
+ const PPCInstrInfo *TII =
+ static_cast<const PPCInstrInfo*>(Fn.getTarget().getInstrInfo());
+ // Give the blocks of the function a dense, in-order, numbering.
+ Fn.RenumberBlocks();
+ BlockSizes.resize(Fn.getNumBlockIDs());
+
+ // Measure each MBB and compute a size for the entire function.
+ unsigned FuncSize = 0;
+ for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
+ ++MFI) {
+ MachineBasicBlock *MBB = MFI;
+
+ unsigned BlockSize = 0;
+ for (MachineBasicBlock::iterator MBBI = MBB->begin(), EE = MBB->end();
+ MBBI != EE; ++MBBI)
+ BlockSize += TII->GetInstSizeInBytes(MBBI);
+
+ BlockSizes[MBB->getNumber()] = BlockSize;
+ FuncSize += BlockSize;
+ }
+
+ // If the entire function is smaller than the displacement of a branch field,
+ // we know we don't need to shrink any branches in this function. This is a
+ // common case.
+ if (FuncSize < (1 << 15)) {
+ BlockSizes.clear();
+ return false;
+ }
+
+ // For each conditional branch, if the offset to its destination is larger
+ // than the offset field allows, transform it into a long branch sequence
+ // like this:
+ // short branch:
+ // bCC MBB
+ // long branch:
+ // b!CC $PC+8
+ // b MBB
+ //
+ bool MadeChange = true;
+ bool EverMadeChange = false;
+ while (MadeChange) {
+ // Iteratively expand branches until we reach a fixed point.
+ MadeChange = false;
+
+ for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
+ ++MFI) {
+ MachineBasicBlock &MBB = *MFI;
+ unsigned MBBStartOffset = 0;
+ for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
+ I != E; ++I) {
+ MachineBasicBlock *Dest = 0;
+ if (I->getOpcode() == PPC::BCC && !I->getOperand(2).isImm())
+ Dest = I->getOperand(2).getMBB();
+ else if ((I->getOpcode() == PPC::BDNZ8 || I->getOpcode() == PPC::BDNZ ||
+ I->getOpcode() == PPC::BDZ8 || I->getOpcode() == PPC::BDZ) &&
+ !I->getOperand(0).isImm())
+ Dest = I->getOperand(0).getMBB();
+
+ if (!Dest) {
+ MBBStartOffset += TII->GetInstSizeInBytes(I);
+ continue;
+ }
+
+ // Determine the offset from the current branch to the destination
+ // block.
+ int BranchSize;
+ if (Dest->getNumber() <= MBB.getNumber()) {
+ // If this is a backwards branch, the delta is the offset from the
+ // start of this block to this branch, plus the sizes of all blocks
+ // from this block to the dest.
+ BranchSize = MBBStartOffset;
+
+ for (unsigned i = Dest->getNumber(), e = MBB.getNumber(); i != e; ++i)
+ BranchSize += BlockSizes[i];
+ } else {
+ // Otherwise, add the size of the blocks between this block and the
+ // dest to the number of bytes left in this block.
+ BranchSize = -MBBStartOffset;
+
+ for (unsigned i = MBB.getNumber(), e = Dest->getNumber(); i != e; ++i)
+ BranchSize += BlockSizes[i];
+ }
+
+ // If this branch is in range, ignore it.
+ if (isInt<16>(BranchSize)) {
+ MBBStartOffset += 4;
+ continue;
+ }
+
+ // Otherwise, we have to expand it to a long branch.
+ MachineInstr *OldBranch = I;
+ DebugLoc dl = OldBranch->getDebugLoc();
+
+ if (I->getOpcode() == PPC::BCC) {
+ // The BCC operands are:
+ // 0. PPC branch predicate
+ // 1. CR register
+ // 2. Target MBB
+ PPC::Predicate Pred = (PPC::Predicate)I->getOperand(0).getImm();
+ unsigned CRReg = I->getOperand(1).getReg();
+
+ // Jump over the uncond branch inst (i.e. $PC+8) on opposite condition.
+ BuildMI(MBB, I, dl, TII->get(PPC::BCC))
+ .addImm(PPC::InvertPredicate(Pred)).addReg(CRReg).addImm(2);
+ } else if (I->getOpcode() == PPC::BDNZ) {
+ BuildMI(MBB, I, dl, TII->get(PPC::BDZ)).addImm(2);
+ } else if (I->getOpcode() == PPC::BDNZ8) {
+ BuildMI(MBB, I, dl, TII->get(PPC::BDZ8)).addImm(2);
+ } else if (I->getOpcode() == PPC::BDZ) {
+ BuildMI(MBB, I, dl, TII->get(PPC::BDNZ)).addImm(2);
+ } else if (I->getOpcode() == PPC::BDZ8) {
+ BuildMI(MBB, I, dl, TII->get(PPC::BDNZ8)).addImm(2);
+ } else {
+ llvm_unreachable("Unhandled branch type!");
+ }
+
+ // Uncond branch to the real destination.
+ I = BuildMI(MBB, I, dl, TII->get(PPC::B)).addMBB(Dest);
+
+ // Remove the old branch from the function.
+ OldBranch->eraseFromParent();
+
+ // Remember that this instruction is 8-bytes, increase the size of the
+ // block by 4, remember to iterate.
+ BlockSizes[MBB.getNumber()] += 4;
+ MBBStartOffset += 8;
+ ++NumExpanded;
+ MadeChange = true;
+ }
+ }
+ EverMadeChange |= MadeChange;
+ }
+
+ BlockSizes.clear();
+ return true;