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-rw-r--r--contrib/llvm/lib/Target/MSP430/MSP430BranchSelector.cpp308
1 files changed, 191 insertions, 117 deletions
diff --git a/contrib/llvm/lib/Target/MSP430/MSP430BranchSelector.cpp b/contrib/llvm/lib/Target/MSP430/MSP430BranchSelector.cpp
index 511e5bc..5fd6b63 100644
--- a/contrib/llvm/lib/Target/MSP430/MSP430BranchSelector.cpp
+++ b/contrib/llvm/lib/Target/MSP430/MSP430BranchSelector.cpp
@@ -27,63 +27,84 @@ using namespace llvm;
#define DEBUG_TYPE "msp430-branch-select"
+static cl::opt<bool>
+ BranchSelectEnabled("msp430-branch-select", cl::Hidden, cl::init(true),
+ cl::desc("Expand out of range branches"));
+
+STATISTIC(NumSplit, "Number of machine basic blocks split");
STATISTIC(NumExpanded, "Number of branches expanded to long format");
namespace {
- struct MSP430BSel : public MachineFunctionPass {
- static char ID;
- MSP430BSel() : MachineFunctionPass(ID) {}
+class MSP430BSel : public MachineFunctionPass {
- /// BlockSizes - The sizes of the basic blocks in the function.
- std::vector<unsigned> BlockSizes;
+ typedef SmallVector<int, 16> OffsetVector;
- bool runOnMachineFunction(MachineFunction &Fn) override;
+ MachineFunction *MF;
+ const MSP430InstrInfo *TII;
- MachineFunctionProperties getRequiredProperties() const override {
- return MachineFunctionProperties().set(
- MachineFunctionProperties::Property::AllVRegsAllocated);
- }
+ unsigned measureFunction(OffsetVector &BlockOffsets,
+ MachineBasicBlock *FromBB = nullptr);
+ bool expandBranches(OffsetVector &BlockOffsets);
- const char *getPassName() const override {
- return "MSP430 Branch Selector";
- }
- };
- char MSP430BSel::ID = 0;
+public:
+ static char ID;
+ MSP430BSel() : MachineFunctionPass(ID) {}
+
+ bool runOnMachineFunction(MachineFunction &MF) override;
+
+ MachineFunctionProperties getRequiredProperties() const override {
+ return MachineFunctionProperties().set(
+ MachineFunctionProperties::Property::NoVRegs);
+ }
+
+ StringRef getPassName() const override { return "MSP430 Branch Selector"; }
+};
+char MSP430BSel::ID = 0;
}
-/// createMSP430BranchSelectionPass - returns an instance of the Branch
-/// Selection Pass
-///
-FunctionPass *llvm::createMSP430BranchSelectionPass() {
- return new MSP430BSel();
+static bool isInRage(int DistanceInBytes) {
+ // According to CC430 Family User's Guide, Section 4.5.1.3, branch
+ // instructions have the signed 10-bit word offset field, so first we need to
+ // convert the distance from bytes to words, then check if it fits in 10-bit
+ // signed integer.
+ const int WordSize = 2;
+
+ assert((DistanceInBytes % WordSize == 0) &&
+ "Branch offset should be word aligned!");
+
+ int Words = DistanceInBytes / WordSize;
+ return isInt<10>(Words);
}
-bool MSP430BSel::runOnMachineFunction(MachineFunction &Fn) {
- const MSP430InstrInfo *TII =
- static_cast<const MSP430InstrInfo *>(Fn.getSubtarget().getInstrInfo());
+/// Measure each basic block, fill the BlockOffsets, and return the size of
+/// the function, starting with BB
+unsigned MSP430BSel::measureFunction(OffsetVector &BlockOffsets,
+ MachineBasicBlock *FromBB) {
// 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 (MachineBasicBlock &MBB : Fn) {
- unsigned BlockSize = 0;
- for (MachineInstr &MI : MBB)
- BlockSize += TII->GetInstSizeInBytes(MI);
-
- BlockSizes[MBB.getNumber()] = BlockSize;
- FuncSize += BlockSize;
+ MF->RenumberBlocks(FromBB);
+
+ MachineFunction::iterator Begin;
+ if (FromBB == nullptr) {
+ Begin = MF->begin();
+ } else {
+ Begin = FromBB->getIterator();
}
- // 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 << 9)) {
- BlockSizes.clear();
- return false;
+ BlockOffsets.resize(MF->getNumBlockIDs());
+
+ unsigned TotalSize = BlockOffsets[Begin->getNumber()];
+ for (auto &MBB : make_range(Begin, MF->end())) {
+ BlockOffsets[MBB.getNumber()] = TotalSize;
+ for (MachineInstr &MI : MBB) {
+ TotalSize += TII->getInstSizeInBytes(MI);
+ }
}
+ return TotalSize;
+}
+/// Do expand branches and split the basic blocks if necessary.
+/// Returns true if made any change.
+bool MSP430BSel::expandBranches(OffsetVector &BlockOffsets) {
// 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:
@@ -93,91 +114,144 @@ bool MSP430BSel::runOnMachineFunction(MachineFunction &Fn) {
// b!CC $PC+6
// 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) {
- if ((I->getOpcode() != MSP430::JCC || I->getOperand(0).isImm()) &&
- I->getOpcode() != MSP430::JMP) {
- MBBStartOffset += TII->GetInstSizeInBytes(*I);
- continue;
- }
+ bool MadeChange = false;
+ for (auto MBB = MF->begin(), E = MF->end(); MBB != E; ++MBB) {
+ unsigned MBBStartOffset = 0;
+ for (auto MI = MBB->begin(), EE = MBB->end(); MI != EE; ++MI) {
+ MBBStartOffset += TII->getInstSizeInBytes(*MI);
- // Determine the offset from the current branch to the destination
- // block.
- MachineBasicBlock *Dest = I->getOperand(0).getMBB();
-
- 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 instruction is not a short branch then skip it.
+ if (MI->getOpcode() != MSP430::JCC && MI->getOpcode() != MSP430::JMP) {
+ continue;
+ }
- // If this branch is in range, ignore it.
- if (isInt<10>(BranchSize)) {
- MBBStartOffset += 2;
- continue;
- }
+ MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
+ // Determine the distance from the current branch to the destination
+ // block. MBBStartOffset already includes the size of the current branch
+ // instruction.
+ int BlockDistance =
+ BlockOffsets[DestBB->getNumber()] - BlockOffsets[MBB->getNumber()];
+ int BranchDistance = BlockDistance - MBBStartOffset;
+
+ // If this branch is in range, ignore it.
+ if (isInRage(BranchDistance)) {
+ continue;
+ }
+
+ DEBUG(dbgs() << " Found a branch that needs expanding, BB#"
+ << DestBB->getNumber() << ", Distance " << BranchDistance
+ << "\n");
+
+ // If JCC is not the last instruction we need to split the MBB.
+ if (MI->getOpcode() == MSP430::JCC && std::next(MI) != EE) {
+
+ DEBUG(dbgs() << " Found a basic block that needs to be split, BB#"
+ << MBB->getNumber() << "\n");
+
+ // Create a new basic block.
+ MachineBasicBlock *NewBB =
+ MF->CreateMachineBasicBlock(MBB->getBasicBlock());
+ MF->insert(std::next(MBB), NewBB);
- // Otherwise, we have to expand it to a long branch.
- unsigned NewSize;
- MachineInstr &OldBranch = *I;
- DebugLoc dl = OldBranch.getDebugLoc();
-
- if (I->getOpcode() == MSP430::JMP) {
- NewSize = 4;
- } else {
- // The BCC operands are:
- // 0. MSP430 branch predicate
- // 1. Target MBB
- SmallVector<MachineOperand, 1> Cond;
- Cond.push_back(I->getOperand(1));
-
- // Jump over the uncond branch inst (i.e. $+6) on opposite condition.
- TII->ReverseBranchCondition(Cond);
- BuildMI(MBB, I, dl, TII->get(MSP430::JCC))
- .addImm(4).addOperand(Cond[0]);
-
- NewSize = 6;
+ // Splice the instructions following MI over to the NewBB.
+ NewBB->splice(NewBB->end(), &*MBB, std::next(MI), MBB->end());
+
+ // Update the successor lists.
+ for (MachineBasicBlock *Succ : MBB->successors()) {
+ if (Succ == DestBB) {
+ continue;
+ }
+ MBB->replaceSuccessor(Succ, NewBB);
+ NewBB->addSuccessor(Succ);
}
- // Uncond branch to the real destination.
- I = BuildMI(MBB, I, dl, TII->get(MSP430::Bi)).addMBB(Dest);
- // Remove the old branch from the function.
- OldBranch.eraseFromParent();
+ // We introduced a new MBB so all following blocks should be numbered
+ // and measured again.
+ measureFunction(BlockOffsets, &*MBB);
- // Remember that this instruction is NewSize bytes, increase the size of the
- // block by NewSize-2, remember to iterate.
- BlockSizes[MBB.getNumber()] += NewSize-2;
- MBBStartOffset += NewSize;
+ ++NumSplit;
- ++NumExpanded;
- MadeChange = true;
+ // It may be not necessary to start all over at this point, but it's
+ // safer do this anyway.
+ return true;
}
+
+ MachineInstr &OldBranch = *MI;
+ DebugLoc dl = OldBranch.getDebugLoc();
+ int InstrSizeDiff = -TII->getInstSizeInBytes(OldBranch);
+
+ if (MI->getOpcode() == MSP430::JCC) {
+ MachineBasicBlock *NextMBB = &*std::next(MBB);
+ assert(MBB->isSuccessor(NextMBB) &&
+ "This block must have a layout successor!");
+
+ // The BCC operands are:
+ // 0. Target MBB
+ // 1. MSP430 branch predicate
+ SmallVector<MachineOperand, 1> Cond;
+ Cond.push_back(MI->getOperand(1));
+
+ // Jump over the long branch on the opposite condition
+ TII->reverseBranchCondition(Cond);
+ MI = BuildMI(*MBB, MI, dl, TII->get(MSP430::JCC))
+ .addMBB(NextMBB)
+ .addOperand(Cond[0]);
+ InstrSizeDiff += TII->getInstSizeInBytes(*MI);
+ ++MI;
+ }
+
+ // Unconditional branch to the real destination.
+ MI = BuildMI(*MBB, MI, dl, TII->get(MSP430::Bi)).addMBB(DestBB);
+ InstrSizeDiff += TII->getInstSizeInBytes(*MI);
+
+ // Remove the old branch from the function.
+ OldBranch.eraseFromParent();
+
+ // The size of a new instruction is different from the old one, so we need
+ // to correct all block offsets.
+ for (int i = MBB->getNumber() + 1, e = BlockOffsets.size(); i < e; ++i) {
+ BlockOffsets[i] += InstrSizeDiff;
+ }
+ MBBStartOffset += InstrSizeDiff;
+
+ ++NumExpanded;
+ MadeChange = true;
}
- EverMadeChange |= MadeChange;
}
+ return MadeChange;
+}
+
+bool MSP430BSel::runOnMachineFunction(MachineFunction &mf) {
+ MF = &mf;
+ TII = static_cast<const MSP430InstrInfo *>(MF->getSubtarget().getInstrInfo());
+
+ // If the pass is disabled, just bail early.
+ if (!BranchSelectEnabled)
+ return false;
+
+ DEBUG(dbgs() << "\n********** " << getPassName() << " **********\n");
+
+ // BlockOffsets - Contains the distance from the beginning of the function to
+ // the beginning of each basic block.
+ OffsetVector BlockOffsets;
+
+ unsigned FunctionSize = measureFunction(BlockOffsets);
+ // If the entire function is smaller than the displacement of a branch field,
+ // we know we don't need to expand any branches in this
+ // function. This is a common case.
+ if (isInRage(FunctionSize)) {
+ return false;
+ }
+
+ // Iteratively expand branches until we reach a fixed point.
+ bool MadeChange = false;
+ while (expandBranches(BlockOffsets))
+ MadeChange = true;
+
+ return MadeChange;
+}
- BlockSizes.clear();
- return true;
+/// Returns an instance of the Branch Selection Pass
+FunctionPass *llvm::createMSP430BranchSelectionPass() {
+ return new MSP430BSel();
}
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