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Merge pull request #59 from pftbest/msp430_backport
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Backport patches for MSP430 codegen.
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@alexcrichton
alexcrichton committed Dec 8, 2016
2 parents 3ec14da + 6041df6 commit d7342a9
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Showing 4 changed files with 820 additions and 117 deletions.
9 changes: 9 additions & 0 deletions lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3425,6 +3425,15 @@ bool SelectionDAGLegalize::ExpandNode(SDNode *Node) {
TopHalf = DAG.getSetCC(dl, getSetCCResultType(VT), TopHalf,
DAG.getConstant(0, dl, VT), ISD::SETNE);
}

// Truncate the result if SetCC returns a larger type than needed.
EVT RType = Node->getValueType(1);
if (RType.getSizeInBits() < TopHalf.getValueSizeInBits())
TopHalf = DAG.getNode(ISD::TRUNCATE, dl, RType, TopHalf);

assert(RType.getSizeInBits() == TopHalf.getValueSizeInBits() &&
"Unexpected result type for S/UMULO legalization");

Results.push_back(BottomHalf);
Results.push_back(TopHalf);
break;
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308 changes: 191 additions & 117 deletions lib/Target/MSP430/MSP430BranchSelector.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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::AllVRegsAllocated);
}

const char *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:
Expand All @@ -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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