- // Thumb2, 2 on Thumb1. Possible Thumb1 alignment padding is allowed for
- // inside OffsetIsInRange.
- if (BBHasFallthrough(UserMBB) &&
- OffsetIsInRange(UserOffset, OffsetOfNextBlock + (isThumb1 ? 2: 4),
- U.MaxDisp, U.NegOk, U.IsSoImm)) {
- DEBUG(errs() << "Split at end of block\n");
- if (&UserMBB->back() == UserMI)
- assert(BBHasFallthrough(UserMBB) && "Expected a fallthrough BB!");
- NewMBB = llvm::next(MachineFunction::iterator(UserMBB));
- // Add an unconditional branch from UserMBB to fallthrough block.
- // Record it for branch lengthening; this new branch will not get out of
- // range, but if the preceding conditional branch is out of range, the
- // targets will be exchanged, and the altered branch may be out of
- // range, so the machinery has to know about it.
- int UncondBr = isThumb ? ((isThumb2) ? ARM::t2B : ARM::tB) : ARM::B;
- BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB);
- unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
- ImmBranches.push_back(ImmBranch(&UserMBB->back(),
- MaxDisp, false, UncondBr));
- int delta = isThumb1 ? 2 : 4;
- BBSizes[UserMBB->getNumber()] += delta;
- AdjustBBOffsetsAfter(UserMBB, delta);
- } else {
- // What a big block. Find a place within the block to split it.
- // This is a little tricky on Thumb1 since instructions are 2 bytes
- // and constant pool entries are 4 bytes: if instruction I references
- // island CPE, and instruction I+1 references CPE', it will
- // not work well to put CPE as far forward as possible, since then
- // CPE' cannot immediately follow it (that location is 2 bytes
- // farther away from I+1 than CPE was from I) and we'd need to create
- // a new island. So, we make a first guess, then walk through the
- // instructions between the one currently being looked at and the
- // possible insertion point, and make sure any other instructions
- // that reference CPEs will be able to use the same island area;
- // if not, we back up the insertion point.
-
- // The 4 in the following is for the unconditional branch we'll be
- // inserting (allows for long branch on Thumb1). Alignment of the
- // island is handled inside OffsetIsInRange.
- unsigned BaseInsertOffset = UserOffset + U.MaxDisp -4;
- // This could point off the end of the block if we've already got
- // constant pool entries following this block; only the last one is
- // in the water list. Back past any possible branches (allow for a
- // conditional and a maximally long unconditional).
- if (BaseInsertOffset >= BBOffsets[UserMBB->getNumber()+1])
- BaseInsertOffset = BBOffsets[UserMBB->getNumber()+1] -
- (isThumb1 ? 6 : 8);
- unsigned EndInsertOffset = BaseInsertOffset +
- CPEMI->getOperand(2).getImm();
- MachineBasicBlock::iterator MI = UserMI;
- ++MI;
- unsigned CPUIndex = CPUserIndex+1;
- for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI);
- Offset < BaseInsertOffset;
- Offset += TII->GetInstSizeInBytes(MI),
- MI = llvm::next(MI)) {
- if (CPUIndex < CPUsers.size() && CPUsers[CPUIndex].MI == MI) {
- CPUser &U = CPUsers[CPUIndex];
- if (!OffsetIsInRange(Offset, EndInsertOffset,
- U.MaxDisp, U.NegOk, U.IsSoImm)) {
- BaseInsertOffset -= (isThumb1 ? 2 : 4);
- EndInsertOffset -= (isThumb1 ? 2 : 4);
- }
- // This is overly conservative, as we don't account for CPEMIs
- // being reused within the block, but it doesn't matter much.
- EndInsertOffset += CPUsers[CPUIndex].CPEMI->getOperand(2).getImm();
- CPUIndex++;
+ // Thumb2, 2 on Thumb1.
+ if (BBHasFallthrough(UserMBB)) {
+ // Size of branch to insert.
+ unsigned Delta = isThumb1 ? 2 : 4;
+ // Compute the offset where the CPE will begin.
+ unsigned CPEOffset = UserBBI.postOffset(CPELogAlign) + Delta;
+
+ if (isOffsetInRange(UserOffset, CPEOffset, U)) {
+ DEBUG(dbgs() << "Split at end of BB#" << UserMBB->getNumber()
+ << format(", expected CPE offset %#x\n", CPEOffset));
+ NewMBB = llvm::next(MachineFunction::iterator(UserMBB));
+ // Add an unconditional branch from UserMBB to fallthrough block. Record
+ // it for branch lengthening; this new branch will not get out of range,
+ // but if the preceding conditional branch is out of range, the targets
+ // will be exchanged, and the altered branch may be out of range, so the
+ // machinery has to know about it.
+ int UncondBr = isThumb ? ((isThumb2) ? ARM::t2B : ARM::tB) : ARM::B;
+ if (!isThumb)
+ BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB);
+ else
+ BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB)
+ .addImm(ARMCC::AL).addReg(0);
+ unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
+ ImmBranches.push_back(ImmBranch(&UserMBB->back(),
+ MaxDisp, false, UncondBr));
+ BBInfo[UserMBB->getNumber()].Size += Delta;
+ adjustBBOffsetsAfter(UserMBB);
+ return;
+ }
+ }
+
+ // What a big block. Find a place within the block to split it. This is a
+ // little tricky on Thumb1 since instructions are 2 bytes and constant pool
+ // entries are 4 bytes: if instruction I references island CPE, and
+ // instruction I+1 references CPE', it will not work well to put CPE as far
+ // forward as possible, since then CPE' cannot immediately follow it (that
+ // location is 2 bytes farther away from I+1 than CPE was from I) and we'd
+ // need to create a new island. So, we make a first guess, then walk through
+ // the instructions between the one currently being looked at and the
+ // possible insertion point, and make sure any other instructions that
+ // reference CPEs will be able to use the same island area; if not, we back
+ // up the insertion point.
+
+ // Try to split the block so it's fully aligned. Compute the latest split
+ // point where we can add a 4-byte branch instruction, and then align to
+ // LogAlign which is the largest possible alignment in the function.
+ unsigned LogAlign = MF->getAlignment();
+ assert(LogAlign >= CPELogAlign && "Over-aligned constant pool entry");
+ unsigned KnownBits = UserBBI.internalKnownBits();
+ unsigned UPad = UnknownPadding(LogAlign, KnownBits);
+ unsigned BaseInsertOffset = UserOffset + U.getMaxDisp() - UPad;
+ DEBUG(dbgs() << format("Split in middle of big block before %#x",
+ BaseInsertOffset));
+
+ // The 4 in the following is for the unconditional branch we'll be inserting
+ // (allows for long branch on Thumb1). Alignment of the island is handled
+ // inside isOffsetInRange.
+ BaseInsertOffset -= 4;
+
+ DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset)
+ << " la=" << LogAlign
+ << " kb=" << KnownBits
+ << " up=" << UPad << '\n');
+
+ // This could point off the end of the block if we've already got constant
+ // pool entries following this block; only the last one is in the water list.
+ // Back past any possible branches (allow for a conditional and a maximally
+ // long unconditional).
+ if (BaseInsertOffset + 8 >= UserBBI.postOffset()) {
+ BaseInsertOffset = UserBBI.postOffset() - UPad - 8;
+ DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset));
+ }
+ unsigned EndInsertOffset = BaseInsertOffset + 4 + UPad +
+ CPEMI->getOperand(2).getImm();
+ MachineBasicBlock::iterator MI = UserMI;
+ ++MI;
+ unsigned CPUIndex = CPUserIndex+1;
+ unsigned NumCPUsers = CPUsers.size();
+ MachineInstr *LastIT = 0;
+ for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI);
+ Offset < BaseInsertOffset;
+ Offset += TII->GetInstSizeInBytes(MI),
+ MI = llvm::next(MI)) {
+ assert(MI != UserMBB->end() && "Fell off end of block");
+ if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) {
+ CPUser &U = CPUsers[CPUIndex];
+ if (!isOffsetInRange(Offset, EndInsertOffset, U)) {
+ // Shift intertion point by one unit of alignment so it is within reach.
+ BaseInsertOffset -= 1u << LogAlign;
+ EndInsertOffset -= 1u << LogAlign;