#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
+#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Statistic.h"
-#include <iostream>
using namespace llvm;
+STATISTIC(NumCPEs, "Number of constpool entries");
STATISTIC(NumSplit, "Number of uncond branches inserted");
STATISTIC(NumCBrFixed, "Number of cond branches fixed");
STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
namespace {
- /// ARMConstantIslands - Due to limited pc-relative displacements, ARM
+ /// ARMConstantIslands - Due to limited PC-relative displacements, ARM
/// requires constant pool entries to be scattered among the instructions
/// inside a function. To do this, it completely ignores the normal LLVM
- /// constant pool, instead, it places constants where-ever it feels like with
+ /// constant pool; instead, it places constants wherever it feels like with
/// special instructions.
///
/// The terminology used in this pass includes:
class VISIBILITY_HIDDEN ARMConstantIslands : public MachineFunctionPass {
/// NextUID - Assign unique ID's to CPE's.
unsigned NextUID;
-
+
/// BBSizes - The size of each MachineBasicBlock in bytes of code, indexed
/// by MBB Number.
std::vector<unsigned> BBSizes;
+ /// BBOffsets - the offset of each MBB in bytes, starting from 0.
+ std::vector<unsigned> BBOffsets;
+
/// WaterList - A sorted list of basic blocks where islands could be placed
/// (i.e. blocks that don't fall through to the following block, due
/// to a return, unreachable, or unconditional branch).
std::vector<MachineBasicBlock*> WaterList;
-
+
/// CPUser - One user of a constant pool, keeping the machine instruction
/// pointer, the constant pool being referenced, and the max displacement
/// allowed from the instruction to the CP.
/// constant pools and their max displacement.
std::vector<CPUser> CPUsers;
+ /// CPEntry - One per constant pool entry, keeping the machine instruction
+ /// pointer, the constpool index, and the number of CPUser's which
+ /// reference this entry.
+ struct CPEntry {
+ MachineInstr *CPEMI;
+ unsigned CPI;
+ unsigned RefCount;
+ CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
+ : CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
+ };
+
+ /// CPEntries - Keep track of all of the constant pool entry machine
+ /// instructions. For each original constpool index (i.e. those that
+ /// existed upon entry to this pass), it keeps a vector of entries.
+ /// Original elements are cloned as we go along; the clones are
+ /// put in the vector of the original element, but have distinct CPIs.
+ std::vector<std::vector<CPEntry> > CPEntries;
+
/// ImmBranch - One per immediate branch, keeping the machine instruction
/// pointer, conditional or unconditional, the max displacement,
/// and (if isCond is true) the corresponding unconditional branch
/// PushPopMIs - Keep track of all the Thumb push / pop instructions.
///
- std::vector<MachineInstr*> PushPopMIs;
+ SmallVector<MachineInstr*, 4> PushPopMIs;
/// HasFarJump - True if any far jump instruction has been emitted during
/// the branch fix up pass.
private:
void DoInitialPlacement(MachineFunction &Fn,
std::vector<MachineInstr*> &CPEMIs);
+ CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
void InitialFunctionScan(MachineFunction &Fn,
const std::vector<MachineInstr*> &CPEMIs);
MachineBasicBlock *SplitBlockBeforeInstr(MachineInstr *MI);
void UpdateForInsertedWaterBlock(MachineBasicBlock *NewBB);
+ void AdjustBBOffsetsAfter(MachineBasicBlock *BB, int delta);
+ bool DecrementOldEntry(unsigned CPI, MachineInstr* CPEMI, unsigned Size);
+ int LookForExistingCPEntry(CPUser& U, unsigned UserOffset);
bool HandleConstantPoolUser(MachineFunction &Fn, CPUser &U);
- bool CPEIsInRange(MachineInstr *MI, MachineInstr *CPEMI, unsigned Disp);
+ bool CPEIsInRange(MachineInstr *MI, unsigned UserOffset,
+ MachineInstr *CPEMI, unsigned Disp,
+ bool DoDump);
+ bool WaterIsInRange(unsigned UserOffset, MachineBasicBlock *Water,
+ unsigned Disp);
+ bool OffsetIsInRange(unsigned UserOffset, unsigned TrialOffset,
+ unsigned Disp, bool NegativeOK);
bool BBIsInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp);
bool FixUpImmediateBr(MachineFunction &Fn, ImmBranch &Br);
bool FixUpConditionalBr(MachineFunction &Fn, ImmBranch &Br);
bool UndoLRSpillRestore();
unsigned GetOffsetOf(MachineInstr *MI) const;
- unsigned GetOffsetOf(MachineBasicBlock *MBB) const;
};
}
MadeChange |= UndoLRSpillRestore();
BBSizes.clear();
+ BBOffsets.clear();
WaterList.clear();
CPUsers.clear();
+ CPEntries.clear();
ImmBranches.clear();
+ PushPopMIs.clear();
return MadeChange;
}
/// DoInitialPlacement - Perform the initial placement of the constant pool
/// entries. To start with, we put them all at the end of the function.
void ARMConstantIslands::DoInitialPlacement(MachineFunction &Fn,
- std::vector<MachineInstr*> &CPEMIs){
+ std::vector<MachineInstr*> &CPEMIs){
// Create the basic block to hold the CPE's.
MachineBasicBlock *BB = new MachineBasicBlock();
Fn.getBasicBlockList().push_back(BB);
BuildMI(BB, TII->get(ARM::CONSTPOOL_ENTRY))
.addImm(i).addConstantPoolIndex(i).addImm(Size);
CPEMIs.push_back(CPEMI);
- DEBUG(std::cerr << "Moved CPI#" << i << " to end of function as #"
- << i << "\n");
+
+ // Add a new CPEntry, but no corresponding CPUser yet.
+ std::vector<CPEntry> CPEs;
+ CPEs.push_back(CPEntry(CPEMI, i));
+ CPEntries.push_back(CPEs);
+ NumCPEs++;
+ DOUT << "Moved CPI#" << i << " to end of function as #" << i << "\n";
}
}
-/// BBHasFallthrough - Return true of the specified basic block can fallthrough
+/// BBHasFallthrough - Return true if the specified basic block can fallthrough
/// into the block immediately after it.
static bool BBHasFallthrough(MachineBasicBlock *MBB) {
// Get the next machine basic block in the function.
return false;
}
+/// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
+/// look up the corresponding CPEntry.
+ARMConstantIslands::CPEntry
+*ARMConstantIslands::findConstPoolEntry(unsigned CPI,
+ const MachineInstr *CPEMI) {
+ std::vector<CPEntry> &CPEs = CPEntries[CPI];
+ // Number of entries per constpool index should be small, just do a
+ // linear search.
+ for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
+ if (CPEs[i].CPEMI == CPEMI)
+ return &CPEs[i];
+ }
+ return NULL;
+}
+
/// InitialFunctionScan - Do the initial scan of the function, building up
/// information about the sizes of each block, the location of all the water,
/// and finding all of the constant pool users.
void ARMConstantIslands::InitialFunctionScan(MachineFunction &Fn,
- const std::vector<MachineInstr*> &CPEMIs) {
+ const std::vector<MachineInstr*> &CPEMIs) {
+ unsigned Offset = 0;
for (MachineFunction::iterator MBBI = Fn.begin(), E = Fn.end();
MBBI != E; ++MBBI) {
MachineBasicBlock &MBB = *MBBI;
Scale = 2;
break;
}
- unsigned MaxDisp = (1 << (Bits-1)) * Scale;
- ImmBranches.push_back(ImmBranch(I, MaxDisp, isCond, UOpc));
+
+ // Record this immediate branch.
+ unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
+ ImmBranches.push_back(ImmBranch(I, MaxOffs, isCond, UOpc));
}
if (Opc == ARM::tPUSH || Opc == ARM::tPOP_RET)
if (I->getOperand(op).isConstantPoolIndex()) {
// We found one. The addressing mode tells us the max displacement
// from the PC that this instruction permits.
- unsigned MaxOffs = 0;
// Basic size info comes from the TSFlags field.
+ unsigned Bits = 0;
+ unsigned Scale = 1;
unsigned TSFlags = I->getInstrDescriptor()->TSFlags;
switch (TSFlags & ARMII::AddrModeMask) {
default:
continue;
assert(0 && "Unknown addressing mode for CP reference!");
case ARMII::AddrMode1: // AM1: 8 bits << 2
- MaxOffs = 1 << (8+2); // Taking the address of a CP entry.
+ Bits = 8;
+ Scale = 4; // Taking the address of a CP entry.
break;
case ARMII::AddrMode2:
- MaxOffs = 1 << 12; // +-offset_12
+ Bits = 12; // +-offset_12
break;
case ARMII::AddrMode3:
- MaxOffs = 1 << 8; // +-offset_8
+ Bits = 8; // +-offset_8
break;
// addrmode4 has no immediate offset.
case ARMII::AddrMode5:
- MaxOffs = 1 << (8+2); // +-(offset_8*4)
+ Bits = 8;
+ Scale = 4; // +-(offset_8*4)
break;
case ARMII::AddrModeT1:
- MaxOffs = 1 << 5;
+ Bits = 5; // +offset_5
break;
case ARMII::AddrModeT2:
- MaxOffs = 1 << (5+1);
+ Bits = 5;
+ Scale = 2; // +(offset_5*2)
break;
case ARMII::AddrModeT4:
- MaxOffs = 1 << (5+2);
+ Bits = 5;
+ Scale = 4; // +(offset_5*4)
break;
case ARMII::AddrModeTs:
- MaxOffs = 1 << (8+2);
+ Bits = 8;
+ Scale = 4; // +(offset_8*4)
break;
}
-
+
// Remember that this is a user of a CP entry.
- MachineInstr *CPEMI =CPEMIs[I->getOperand(op).getConstantPoolIndex()];
+ unsigned CPI = I->getOperand(op).getConstantPoolIndex();
+ MachineInstr *CPEMI = CPEMIs[CPI];
+ unsigned MaxOffs = ((1 << Bits)-1) * Scale;
CPUsers.push_back(CPUser(I, CPEMI, MaxOffs));
+
+ // Increment corresponding CPEntry reference count.
+ CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
+ assert(CPE && "Cannot find a corresponding CPEntry!");
+ CPE->RefCount++;
// Instructions can only use one CP entry, don't bother scanning the
// rest of the operands.
}
}
- // In thumb mode, if this block is a constpool island, pessmisticly assume
- // it needs to be padded by two byte so it's aligned on 4 byte boundary.
+ // In thumb mode, if this block is a constpool island, pessimistically
+ // assume it needs to be padded by two byte so it's aligned on 4 byte
+ // boundary.
if (AFI->isThumbFunction() &&
+ !MBB.empty() &&
MBB.begin()->getOpcode() == ARM::CONSTPOOL_ENTRY)
MBBSize += 2;
BBSizes.push_back(MBBSize);
+ BBOffsets.push_back(Offset);
+ Offset += MBBSize;
}
}
// The offset is composed of two things: the sum of the sizes of all MBB's
// before this instruction's block, and the offset from the start of the block
// it is in.
- unsigned Offset = 0;
-
- // Sum block sizes before MBB.
- for (unsigned BB = 0, e = MBB->getNumber(); BB != e; ++BB)
- Offset += BBSizes[BB];
+ unsigned Offset = BBOffsets[MBB->getNumber()];
// Sum instructions before MI in MBB.
for (MachineBasicBlock::iterator I = MBB->begin(); ; ++I) {
}
}
-/// GetOffsetOf - Return the current offset of the specified machine BB
-/// from the start of the function. This offset changes as stuff is moved
-/// around inside the function.
-unsigned ARMConstantIslands::GetOffsetOf(MachineBasicBlock *MBB) const {
- // Sum block sizes before MBB.
- unsigned Offset = 0;
- for (unsigned BB = 0, e = MBB->getNumber(); BB != e; ++BB)
- Offset += BBSizes[BB];
-
- return Offset;
-}
-
/// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB
/// ID.
static bool CompareMBBNumbers(const MachineBasicBlock *LHS,
// Insert a size into BBSizes to align it properly with the (newly
// renumbered) block numbers.
BBSizes.insert(BBSizes.begin()+NewBB->getNumber(), 0);
+
+ // Likewise for BBOffsets.
+ BBOffsets.insert(BBOffsets.begin()+NewBB->getNumber(), 0);
// Next, update WaterList. Specifically, we need to add NewMBB as having
// available water after it.
OrigBB->addSuccessor(NewBB);
// Update internal data structures to account for the newly inserted MBB.
- UpdateForInsertedWaterBlock(NewBB);
+ // This is almost the same as UpdateForInsertedWaterBlock, except that
+ // the Water goes after OrigBB, not NewBB.
+ NewBB->getParent()->RenumberBlocks(NewBB);
+ // Insert a size into BBSizes to align it properly with the (newly
+ // renumbered) block numbers.
+ BBSizes.insert(BBSizes.begin()+NewBB->getNumber(), 0);
+
+ // Likewise for BBOffsets.
+ BBOffsets.insert(BBOffsets.begin()+NewBB->getNumber(), 0);
+
+ // Next, update WaterList. Specifically, we need to add OrigMBB as having
+ // available water after it (but not if it's already there, which happens
+ // when splitting before a conditional branch that is followed by an
+ // unconditional branch - in that case we want to insert NewBB).
+ std::vector<MachineBasicBlock*>::iterator IP =
+ std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB,
+ CompareMBBNumbers);
+ MachineBasicBlock* WaterBB = *IP;
+ if (WaterBB == OrigBB)
+ WaterList.insert(next(IP), NewBB);
+ else
+ WaterList.insert(IP, OrigBB);
+
// Figure out how large the first NewMBB is.
unsigned NewBBSize = 0;
for (MachineBasicBlock::iterator I = NewBB->begin(), E = NewBB->end();
I != E; ++I)
NewBBSize += ARM::GetInstSize(I);
+ unsigned OrigBBI = OrigBB->getNumber();
+ unsigned NewBBI = NewBB->getNumber();
// Set the size of NewBB in BBSizes.
- BBSizes[NewBB->getNumber()] = NewBBSize;
+ BBSizes[NewBBI] = NewBBSize;
// We removed instructions from UserMBB, subtract that off from its size.
// Add 2 or 4 to the block to count the unconditional branch we added to it.
- BBSizes[OrigBB->getNumber()] -= NewBBSize - (isThumb ? 2 : 4);
+ unsigned delta = isThumb ? 2 : 4;
+ BBSizes[OrigBBI] -= NewBBSize - delta;
+
+ // ...and adjust BBOffsets for NewBB accordingly.
+ BBOffsets[NewBBI] = BBOffsets[OrigBBI] + BBSizes[OrigBBI];
+
+ // All BBOffsets following these blocks must be modified.
+ AdjustBBOffsetsAfter(NewBB, delta);
return NewBB;
}
-/// CPEIsInRange - Returns true is the distance between specific MI and
+//// OffsetIsInRange - Checks whether UserOffset is within MaxDisp of
+/// TrialOffset.
+bool ARMConstantIslands::OffsetIsInRange(unsigned UserOffset,
+ unsigned TrialOffset, unsigned MaxDisp, bool NegativeOK) {
+ if (UserOffset <= TrialOffset) {
+ // User before the Trial.
+ if (TrialOffset-UserOffset <= MaxDisp)
+ return true;
+ } else if (NegativeOK) {
+ if (UserOffset-TrialOffset <= MaxDisp)
+ return true;
+ }
+ return false;
+}
+
+/// WaterIsInRange - Returns true if a CPE placed after the specified
+/// Water (a basic block) will be in range for the specific MI.
+
+bool ARMConstantIslands::WaterIsInRange(unsigned UserOffset,
+ MachineBasicBlock* Water, unsigned MaxDisp)
+{
+ bool isThumb = AFI->isThumbFunction();
+ unsigned CPEOffset = BBOffsets[Water->getNumber()] +
+ BBSizes[Water->getNumber()];
+ // If the Water is a constpool island, it has already been aligned.
+ // If not, align it.
+ if (isThumb &&
+ (Water->empty() ||
+ Water->begin()->getOpcode() != ARM::CONSTPOOL_ENTRY))
+ CPEOffset += 2;
+
+ return OffsetIsInRange (UserOffset, CPEOffset, MaxDisp, !isThumb);
+}
+
+/// CPEIsInRange - Returns true if the distance between specific MI and
/// specific ConstPool entry instruction can fit in MI's displacement field.
-bool ARMConstantIslands::CPEIsInRange(MachineInstr *MI, MachineInstr *CPEMI,
- unsigned MaxDisp) {
- unsigned PCAdj = AFI->isThumbFunction() ? 4 : 8;
- unsigned UserOffset = GetOffsetOf(MI) + PCAdj;
- // In thumb mode, pessmisticly assumes the .align 2 before the first CPE
+bool ARMConstantIslands::CPEIsInRange(MachineInstr *MI, unsigned UserOffset,
+ MachineInstr *CPEMI,
+ unsigned MaxDisp, bool DoDump) {
+ // In thumb mode, pessimistically assumes the .align 2 before the first CPE
// in the island adds two byte padding.
- unsigned AlignAdj = AFI->isThumbFunction() ? 2 : 0;
+ bool isThumb = AFI->isThumbFunction();
+ unsigned AlignAdj = isThumb ? 2 : 0;
unsigned CPEOffset = GetOffsetOf(CPEMI) + AlignAdj;
- DEBUG(std::cerr << "User of CPE#" << CPEMI->getOperand(0).getImm()
- << " max delta=" << MaxDisp
- << " at offset " << int(UserOffset-CPEOffset) << "\t"
- << *MI);
+ if (DoDump) {
+ DOUT << "User of CPE#" << CPEMI->getOperand(0).getImm()
+ << " max delta=" << MaxDisp
+ << " insn address=" << UserOffset
+ << " CPE address=" << CPEOffset
+ << " offset=" << int(CPEOffset-UserOffset) << "\t" << *MI;
+ }
- if (UserOffset <= CPEOffset) {
- // User before the CPE.
- if (CPEOffset-UserOffset <= MaxDisp)
- return true;
- } else if (!AFI->isThumbFunction()) {
- // Thumb LDR cannot encode negative offset.
- if (UserOffset-CPEOffset <= MaxDisp)
- return true;
+ return OffsetIsInRange(UserOffset, CPEOffset, MaxDisp, !isThumb);
+}
+
+/// BBIsJumpedOver - Return true of the specified basic block's only predecessor
+/// unconditionally branches to its only successor.
+static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
+ if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
+ return false;
+
+ MachineBasicBlock *Succ = *MBB->succ_begin();
+ MachineBasicBlock *Pred = *MBB->pred_begin();
+ MachineInstr *PredMI = &Pred->back();
+ if (PredMI->getOpcode() == ARM::B || PredMI->getOpcode() == ARM::tB)
+ return PredMI->getOperand(0).getMBB() == Succ;
+ return false;
+}
+
+void ARMConstantIslands::AdjustBBOffsetsAfter(MachineBasicBlock *BB, int delta)
+{
+ MachineFunction::iterator MBBI = BB->getParent()->end();
+ for(int i=BB->getNumber()+1; i<=prior(MBBI)->getNumber(); i++)
+ BBOffsets[i] += delta;
+}
+
+/// DecrementOldEntry - find the constant pool entry with index CPI
+/// and instruction CPEMI, and decrement its refcount. If the refcount
+/// becomes 0 remove the entry and instruction. Returns true if we removed
+/// the entry, false if we didn't.
+
+bool ARMConstantIslands::DecrementOldEntry(unsigned CPI, MachineInstr *CPEMI,
+ unsigned Size) {
+ // Find the old entry. Eliminate it if it is no longer used.
+ CPEntry *OldCPE = findConstPoolEntry(CPI, CPEMI);
+ assert(OldCPE && "Unexpected!");
+ if (--OldCPE->RefCount == 0) {
+ MachineBasicBlock *OldCPEBB = OldCPE->CPEMI->getParent();
+ if (OldCPEBB->empty()) {
+ // In thumb mode, the size of island is padded by two to compensate for
+ // the alignment requirement. Thus it will now be 2 when the block is
+ // empty, so fix this.
+ // All succeeding offsets have the current size value added in, fix this.
+ if (BBSizes[OldCPEBB->getNumber()] != 0) {
+ AdjustBBOffsetsAfter(OldCPEBB, -BBSizes[OldCPEBB->getNumber()]);
+ BBSizes[OldCPEBB->getNumber()] = 0;
+ }
+ // An island has only one predecessor BB and one successor BB. Check if
+ // this BB's predecessor jumps directly to this BB's successor. This
+ // shouldn't happen currently.
+ assert(!BBIsJumpedOver(OldCPEBB) && "How did this happen?");
+ // FIXME: remove the empty blocks after all the work is done?
+ } else {
+ BBSizes[OldCPEBB->getNumber()] -= Size;
+ // All succeeding offsets have the current size value added in, fix this.
+ AdjustBBOffsetsAfter(OldCPEBB, -Size);
+ }
+ OldCPE->CPEMI->eraseFromParent();
+ OldCPE->CPEMI = NULL;
+ NumCPEs--;
+ return true;
}
return false;
}
-/// HandleConstantPoolUser - Analyze the specified user, checking to see if it
-/// is out-of-range. If so, pick it up the constant pool value and move it some
-/// place in-range.
-bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &Fn, CPUser &U){
+/// LookForCPEntryInRange - see if the currently referenced CPE is in range;
+/// if not, see if an in-range clone of the CPE is in range, and if so,
+/// change the data structures so the user references the clone. Returns:
+/// 0 = no existing entry found
+/// 1 = entry found, and there were no code insertions or deletions
+/// 2 = entry found, and there were code insertions or deletions
+int ARMConstantIslands::LookForExistingCPEntry(CPUser& U, unsigned UserOffset)
+{
MachineInstr *UserMI = U.MI;
MachineInstr *CPEMI = U.CPEMI;
// Check to see if the CPE is already in-range.
- if (CPEIsInRange(UserMI, CPEMI, U.MaxDisp))
- return false;
+ if (CPEIsInRange(UserMI, UserOffset, CPEMI, U.MaxDisp, true)) {
+ DOUT << "In range\n";
+ return 1;
+ }
- // Solution guaranteed to work: split the user's MBB right after the user and
- // insert a clone the CPE into the newly created water.
+ // No. Look for previously created clones of the CPE that are in range.
+ unsigned CPI = CPEMI->getOperand(1).getConstantPoolIndex();
+ std::vector<CPEntry> &CPEs = CPEntries[CPI];
+ for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
+ // We already tried this one
+ if (CPEs[i].CPEMI == CPEMI)
+ continue;
+ // Removing CPEs can leave empty entries, skip
+ if (CPEs[i].CPEMI == NULL)
+ continue;
+ if (CPEIsInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.MaxDisp, false)) {
+ DOUT << "Replacing CPE#" << CPI << " with CPE#" << CPEs[i].CPI << "\n";
+ // Point the CPUser node to the replacement
+ U.CPEMI = CPEs[i].CPEMI;
+ // Change the CPI in the instruction operand to refer to the clone.
+ for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
+ if (UserMI->getOperand(j).isConstantPoolIndex()) {
+ UserMI->getOperand(j).setConstantPoolIndex(CPEs[i].CPI);
+ break;
+ }
+ // Adjust the refcount of the clone...
+ CPEs[i].RefCount++;
+ // ...and the original. If we didn't remove the old entry, none of the
+ // addresses changed, so we don't need another pass.
+ unsigned Size = CPEMI->getOperand(2).getImm();
+ return DecrementOldEntry(CPI, CPEMI, Size) ? 2 : 1;
+ }
+ }
+ return 0;
+}
- MachineBasicBlock *UserMBB = UserMI->getParent();
+/// HandleConstantPoolUser - Analyze the specified user, checking to see if it
+/// is out-of-range. If so, pick it up the constant pool value and move it some
+/// place in-range. Return true if we changed any addresses (thus must run
+/// another pass of branch lengthening), false otherwise.
+bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &Fn, CPUser &U){
+ MachineInstr *UserMI = U.MI;
+ MachineInstr *CPEMI = U.CPEMI;
+ unsigned CPI = CPEMI->getOperand(1).getConstantPoolIndex();
+ unsigned Size = CPEMI->getOperand(2).getImm();
+ bool isThumb = AFI->isThumbFunction();
MachineBasicBlock *NewMBB;
+ // Compute this only once, it's expensive
+ unsigned UserOffset = GetOffsetOf(UserMI) + (isThumb ? 4 : 8);
+
+ // See if the current entry is within range, or there is a clone of it
+ // in range.
+ int result = LookForExistingCPEntry(U, UserOffset);
+ if (result==1) return false;
+ else if (result==2) return true;
+
+ // No existing clone of this CPE is within range.
+ // We will be generating a new clone. Get a UID for it.
+ unsigned ID = NextUID++;
- // TODO: Search for the best place to split the code. In practice, using
- // loop nesting information to insert these guys outside of loops would be
- // sufficient.
- if (&UserMBB->back() == UserMI) {
- assert(BBHasFallthrough(UserMBB) && "Expected a fallthrough BB!");
- NewMBB = next(MachineFunction::iterator(UserMBB));
- // Add an unconditional branch from UserMBB to fallthrough block.
- // Note the new unconditional branch is not being recorded.
- bool isThumb = AFI->isThumbFunction();
- BuildMI(UserMBB, TII->get(isThumb ? ARM::tB : ARM::B)).addMBB(NewMBB);
- BBSizes[UserMBB->getNumber()] += isThumb ? 2 : 4;
- } else {
- MachineInstr *NextMI = next(MachineBasicBlock::iterator(UserMI));
- NewMBB = SplitBlockBeforeInstr(NextMI);
+ // Look for water where we can place this CPE. We look for the farthest one
+ // away that will work. Forward references only for now (although later
+ // we might find some that are backwards).
+ bool WaterFound = false;
+ if (!WaterList.empty()) {
+ for (std::vector<MachineBasicBlock*>::iterator IP = prior(WaterList.end()),
+ B = WaterList.begin();; --IP) {
+ MachineBasicBlock* WaterBB = *IP;
+ if (WaterIsInRange(UserOffset, WaterBB, U.MaxDisp)) {
+ WaterFound = true;
+ DOUT << "found water in range\n";
+ // CPE goes before following block (NewMBB).
+ NewMBB = next(MachineFunction::iterator(WaterBB));
+ // Remove the original WaterList entry; we want subsequent
+ // insertions in this vicinity to go after the one we're
+ // about to insert. This considerably reduces the number
+ // of times we have to move the same CPE more than once.
+ WaterList.erase(IP);
+ break;
+ }
+ if (IP == B)
+ break;
+ }
+ }
+
+ if (!WaterFound) {
+ // No water found.
+
+ DOUT << "No water found\n";
+ MachineBasicBlock *UserMBB = UserMI->getParent();
+ unsigned TrialOffset = BBOffsets[UserMBB->getNumber()] +
+ BBSizes[UserMBB->getNumber()] +
+ isThumb ? 2 : 4; /* for branch to be added */
+
+ // If the use is at the end of the block, or the end of the block
+ // is within range, make new water there. (If the block ends in
+ // an unconditional branch already, it is water, and is known to
+ // be out of range; so it's OK to assume above we'll be adding a Br.)
+ if (&UserMBB->back() == UserMI ||
+ OffsetIsInRange(UserOffset, TrialOffset, U.MaxDisp, !isThumb)) {
+ if (&UserMBB->back() == UserMI)
+ assert(BBHasFallthrough(UserMBB) && "Expected a fallthrough BB!");
+ NewMBB = next(MachineFunction::iterator(UserMBB));
+ // Add an unconditional branch from UserMBB to fallthrough block.
+ // Note the new unconditional branch is not being recorded.
+ BuildMI(UserMBB, TII->get(isThumb ? ARM::tB : ARM::B)).addMBB(NewMBB);
+ int delta = isThumb ? 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 Thumb 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.
+
+ // Solution of last resort: split the user's MBB right after the user
+ // and insert a clone of the CPE into the newly created water.
+ MachineInstr *NextMI = next(MachineBasicBlock::iterator(UserMI));
+ NewMBB = SplitBlockBeforeInstr(NextMI);
+ }
}
- // Okay, we know we can put an island before UserMBB now, do it!
+ // Okay, we know we can put an island before NewMBB now, do it!
MachineBasicBlock *NewIsland = new MachineBasicBlock();
Fn.getBasicBlockList().insert(NewMBB, NewIsland);
// Update internal data structures to account for the newly inserted MBB.
UpdateForInsertedWaterBlock(NewIsland);
+ // Decrement the old entry, and remove it if refcount becomes 0.
+ DecrementOldEntry(CPI, CPEMI, Size);
+
// Now that we have an island to add the CPE to, clone the original CPE and
// add it to the island.
- unsigned ID = NextUID++;
- unsigned CPI = CPEMI->getOperand(1).getConstantPoolIndex();
- unsigned Size = CPEMI->getOperand(2).getImm();
-
- // Build a new CPE for this user.
U.CPEMI = BuildMI(NewIsland, TII->get(ARM::CONSTPOOL_ENTRY))
.addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
-
+ CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1));
+ NumCPEs++;
+
+ // Compensate for .align 2 in thumb mode.
+ if (isThumb) Size += 2;
// Increase the size of the island block to account for the new entry.
BBSizes[NewIsland->getNumber()] += Size;
+ BBOffsets[NewIsland->getNumber()] = BBOffsets[NewMBB->getNumber()];
+ AdjustBBOffsetsAfter(NewIsland, Size);
// Finally, change the CPI in the instruction operand to be ID.
for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i)
break;
}
- DEBUG(std::cerr << " Moved CPE to #" << ID << " CPI=" << CPI << "\t"
- << *UserMI);
+ DOUT << " Moved CPE to #" << ID << " CPI=" << CPI << "\t" << *UserMI;
return true;
}
-/// BBIsInRange - Returns true is the distance between specific MI and
+/// BBIsInRange - Returns true if the distance between specific MI and
/// specific BB can fit in MI's displacement field.
bool ARMConstantIslands::BBIsInRange(MachineInstr *MI,MachineBasicBlock *DestBB,
unsigned MaxDisp) {
unsigned PCAdj = AFI->isThumbFunction() ? 4 : 8;
unsigned BrOffset = GetOffsetOf(MI) + PCAdj;
- unsigned DestOffset = GetOffsetOf(DestBB);
+ unsigned DestOffset = BBOffsets[DestBB->getNumber()];
- DEBUG(std::cerr << "Branch of destination BB#" << DestBB->getNumber()
- << " max delta=" << MaxDisp
- << " at offset " << int(BrOffset-DestOffset) << "\t"
- << *MI);
+ DOUT << "Branch of destination BB#" << DestBB->getNumber()
+ << " from BB#" << MI->getParent()->getNumber()
+ << " max delta=" << MaxDisp
+ << " at offset " << int(DestOffset-BrOffset) << "\t" << *MI;
- if (BrOffset <= DestOffset) {
- if (DestOffset - BrOffset < MaxDisp)
- return true;
- } else {
- if (BrOffset - DestOffset <= MaxDisp)
- return true;
- }
- return false;
+ return OffsetIsInRange(BrOffset, DestOffset, MaxDisp, true);
}
/// FixUpImmediateBr - Fix up an immediate branch whose destination is too far
return FixUpConditionalBr(Fn, Br);
}
-/// FixUpUnconditionalBr - Fix up an unconditional branches whose destination is
-/// too far away to fit in its displacement field. If LR register has been
+/// FixUpUnconditionalBr - Fix up an unconditional branch whose destination is
+/// too far away to fit in its displacement field. If the LR register has been
/// spilled in the epilogue, then we can use BL to implement a far jump.
-/// Otherwise, add a intermediate branch instruction to to a branch.
+/// Otherwise, add an intermediate branch instruction to to a branch.
bool
ARMConstantIslands::FixUpUnconditionalBr(MachineFunction &Fn, ImmBranch &Br) {
MachineInstr *MI = Br.MI;
Br.MaxDisp = (1 << 21) * 2;
MI->setInstrDescriptor(TII->get(ARM::tBfar));
BBSizes[MBB->getNumber()] += 2;
+ AdjustBBOffsetsAfter(MBB, 2);
HasFarJump = true;
NumUBrFixed++;
+
+ DOUT << " Changed B to long jump " << *MI;
+
return true;
}
-/// getUnconditionalBrDisp - Returns the maximum displacement that can fit in the
-/// specific unconditional branch instruction.
+/// getUnconditionalBrDisp - Returns the maximum displacement that can fit in
+/// the specific unconditional branch instruction.
static inline unsigned getUnconditionalBrDisp(int Opc) {
return (Opc == ARM::tB) ? (1<<10)*2 : (1<<23)*4;
}
-/// FixUpConditionalBr - Fix up a conditional branches whose destination is too
+/// FixUpConditionalBr - Fix up a conditional branch whose destination is too
/// far away to fit in its displacement field. It is converted to an inverse
/// conditional branch + an unconditional branch to the destination.
bool
// direct the updated conditional branch to the fall-through block. Otherwise,
// split the MBB before the next instruction.
MachineBasicBlock *MBB = MI->getParent();
- MachineInstr *BackMI = &MBB->back();
- bool NeedSplit = (BackMI != MI) || !BBHasFallthrough(MBB);
+ MachineInstr *BMI = &MBB->back();
+ bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB);
NumCBrFixed++;
- if (BackMI != MI) {
+ if (BMI != MI) {
if (next(MachineBasicBlock::iterator(MI)) == MBB->back() &&
- BackMI->getOpcode() == Br.UncondBr) {
+ BMI->getOpcode() == Br.UncondBr) {
// Last MI in the BB is a unconditional branch. Can we simply invert the
// condition and swap destinations:
// beq L1
// =>
// bne L2
// b L1
- MachineBasicBlock *NewDest = BackMI->getOperand(0).getMachineBasicBlock();
+ MachineBasicBlock *NewDest = BMI->getOperand(0).getMachineBasicBlock();
if (BBIsInRange(MI, NewDest, Br.MaxDisp)) {
- BackMI->getOperand(0).setMachineBasicBlock(DestBB);
+ DOUT << " Invert Bcc condition and swap its destination with " << *BMI;
+ BMI->getOperand(0).setMachineBasicBlock(DestBB);
MI->getOperand(0).setMachineBasicBlock(NewDest);
MI->getOperand(1).setImm(CC);
return true;
MBB->back().eraseFromParent();
}
MachineBasicBlock *NextBB = next(MachineFunction::iterator(MBB));
+
+ DOUT << " Insert B to BB#" << DestBB->getNumber()
+ << " also invert condition and change dest. to BB#"
+ << NextBB->getNumber() << "\n";
// Insert a unconditional branch and replace the conditional branch.
// Also update the ImmBranch as well as adding a new entry for the new branch.
MI->eraseFromParent();
// Increase the size of MBB to account for the new unconditional branch.
- BBSizes[MBB->getNumber()] += ARM::GetInstSize(&MBB->back());
+ int delta = ARM::GetInstSize(&MBB->back());
+ BBSizes[MBB->getNumber()] += delta;
+ AdjustBBOffsetsAfter(MBB, delta);
return true;
}
-
/// UndoLRSpillRestore - Remove Thumb push / pop instructions that only spills
/// LR / restores LR to pc.
bool ARMConstantIslands::UndoLRSpillRestore() {
projects / oota-llvm.git / blobdiff