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Remove unused constant pool entries.

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llvm-svn: 35635
This commit is contained in:
Evan Cheng 2007-04-03 23:39:48 +00:00
parent ff2c460267
commit 2cd9df6983
1 changed files with 60 additions and 32 deletions
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92
lib/Target/ARM/ARMConstantIslandPass.cpp
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@ -139,13 +139,15 @@ namespace {
MachineBasicBlock *SplitBlockBeforeInstr(MachineInstr *MI);
void UpdateForInsertedWaterBlock(MachineBasicBlock *NewBB);
void AdjustBBOffsetsAfter(MachineBasicBlock *BB, int delta);
bool DecrementOldEntry(unsigned CPI, MachineInstr* CPEMI, unsigned Size);
bool DecrementOldEntry(unsigned CPI, MachineInstr* CPEMI);
int LookForExistingCPEntry(CPUser& U, unsigned UserOffset);
bool LookForWater(CPUser&U, unsigned UserOffset, bool* PadNewWater,
MachineBasicBlock** NewMBB);
void CreateNewWater(unsigned CPUserIndex, unsigned UserOffset,
MachineBasicBlock** NewMBB);
bool HandleConstantPoolUser(MachineFunction &Fn, unsigned CPUserIndex);
void RemoveDeadCPEMI(MachineInstr *CPEMI);
bool RemoveUnusedCPEntries();
bool CPEIsInRange(MachineInstr *MI, unsigned UserOffset,
MachineInstr *CPEMI, unsigned Disp,
bool DoDump);
@ -197,6 +199,9 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &Fn) {
InitialFunctionScan(Fn, CPEMIs);
CPEMIs.clear();
/// Remove dead constant pool entries.
RemoveUnusedCPEntries();
// Iteratively place constant pool entries and fix up branches until there
// is no change.
bool MadeChange = false;
@ -210,7 +215,7 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &Fn) {
break;
MadeChange = true;
}
// If LR has been forced spilled and no far jumps (i.e. BL) has been issued.
// Undo the spill / restore of LR if possible.
if (!HasFarJump && AFI->isLRSpilledForFarJump() && isThumb)
@ -648,34 +653,13 @@ void ARMConstantIslands::AdjustBBOffsetsAfter(MachineBasicBlock *BB, int delta)
/// 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) {
bool ARMConstantIslands::DecrementOldEntry(unsigned CPI, MachineInstr *CPEMI) {
// 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;
CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
assert(CPE && "Unexpected!");
if (--CPE->RefCount == 0) {
RemoveDeadCPEMI(CPEMI);
CPE->CPEMI = NULL;
NumCPEs--;
return true;
}
@ -723,8 +707,7 @@ int ARMConstantIslands::LookForExistingCPEntry(CPUser& U, unsigned UserOffset)
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 DecrementOldEntry(CPI, CPEMI) ? 2 : 1;
}
}
return 0;
@ -910,7 +893,7 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &Fn,
UpdateForInsertedWaterBlock(NewIsland);
// Decrement the old entry, and remove it if refcount becomes 0.
DecrementOldEntry(CPI, CPEMI, Size);
DecrementOldEntry(CPI, CPEMI);
// Now that we have an island to add the CPE to, clone the original CPE and
// add it to the island.
@ -938,6 +921,51 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &Fn,
return true;
}
/// RemoveDeadCPEMI - Remove a dead constant pool entry instruction. Update
/// sizes and offsets of impacted basic blocks.
void ARMConstantIslands::RemoveDeadCPEMI(MachineInstr *CPEMI) {
MachineBasicBlock *CPEBB = CPEMI->getParent();
if (CPEBB->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[CPEBB->getNumber()] != 0) {
AdjustBBOffsetsAfter(CPEBB, -BBSizes[CPEBB->getNumber()]);
BBSizes[CPEBB->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(CPEBB) && "How did this happen?");
// FIXME: remove the empty blocks after all the work is done?
} else {
unsigned Size = CPEMI->getOperand(2).getImm();
BBSizes[CPEBB->getNumber()] -= Size;
// All succeeding offsets have the current size value added in, fix this.
AdjustBBOffsetsAfter(CPEBB, -Size);
}
CPEMI->eraseFromParent();
}
/// RemoveUnusedCPEntries - Remove constant pool entries whose refcounts
/// are zero.
bool ARMConstantIslands::RemoveUnusedCPEntries() {
unsigned MadeChange = false;
for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) {
std::vector<CPEntry> &CPEs = CPEntries[i];
for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) {
if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) {
RemoveDeadCPEMI(CPEs[j].CPEMI);
CPEs[j].CPEMI = NULL;
MadeChange = true;
}
}
}
return MadeChange;
}
/// 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,