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Refactor. No intentional functionality change.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146187 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel 2011-12-08 21:48:01 +00:00
parent 73e08d3507
commit e265bcf1a6
1 changed files with 41 additions and 29 deletions
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70
lib/CodeGen/MachineSink.cpp
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@ -90,6 +90,8 @@ namespace {
bool AllUsesDominatedByBlock(unsigned Reg, MachineBasicBlock *MBB,
MachineBasicBlock *DefMBB,
bool &BreakPHIEdge, bool &LocalUse) const;
MachineBasicBlock *FindSuccToSinkTo(MachineInstr *MI, bool &BreakPHIEdge);
bool PerformTrivialForwardCoalescing(MachineInstr *MI,
MachineBasicBlock *MBB);
};
@ -401,25 +403,9 @@ static void collectDebugValues(MachineInstr *MI,
}
}
/// SinkInstruction - Determine whether it is safe to sink the specified machine
/// instruction out of its current block into a successor.
bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
// Don't sink insert_subreg, subreg_to_reg, reg_sequence. These are meant to
// be close to the source to make it easier to coalesce.
if (AvoidsSinking(MI, MRI))
return false;
// Check if it's safe to move the instruction.
if (!MI->isSafeToMove(TII, AA, SawStore))
return false;
// FIXME: This should include support for sinking instructions within the
// block they are currently in to shorten the live ranges. We often get
// instructions sunk into the top of a large block, but it would be better to
// also sink them down before their first use in the block. This xform has to
// be careful not to *increase* register pressure though, e.g. sinking
// "x = y + z" down if it kills y and z would increase the live ranges of y
// and z and only shrink the live range of x.
/// FindSuccToSinkTo - Find a successor to sink this instruction to.
MachineBasicBlock *MachineSinking::FindSuccToSinkTo(MachineInstr *MI,
bool &BreakPHIEdge) {
// Loop over all the operands of the specified instruction. If there is
// anything we can't handle, bail out.
@ -429,7 +415,6 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
// decide.
MachineBasicBlock *SuccToSinkTo = 0;
bool BreakPHIEdge = false;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg()) continue; // Ignore non-register operands.
@ -443,23 +428,23 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
// and we can freely move its uses. Alternatively, if it's allocatable,
// it could get allocated to something with a def during allocation.
if (!MRI->def_empty(Reg))
return false;
return NULL;
if (AllocatableSet.test(Reg))
return false;
return NULL;
// Check for a def among the register's aliases too.
for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
unsigned AliasReg = *Alias;
if (!MRI->def_empty(AliasReg))
return false;
return NULL;
if (AllocatableSet.test(AliasReg))
return false;
return NULL;
}
} else if (!MO.isDead()) {
// A def that isn't dead. We can't move it.
return false;
return NULL;
}
} else {
// Virtual register uses are always safe to sink.
@ -467,7 +452,7 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
// If it's not safe to move defs of the register class, then abort.
if (!TII->isSafeToMoveRegClassDefs(MRI->getRegClass(Reg)))
return false;
return NULL;
// FIXME: This picks a successor to sink into based on having one
// successor that dominates all the uses. However, there are cases where
@ -490,7 +475,7 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
bool LocalUse = false;
if (!AllUsesDominatedByBlock(Reg, SuccToSinkTo, ParentBlock,
BreakPHIEdge, LocalUse))
return false;
return NULL;
continue;
}
@ -518,14 +503,39 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
}
if (LocalUse)
// Def is used locally, it's never safe to move this def.
return false;
return NULL;
}
// If we couldn't find a block to sink to, ignore this instruction.
if (SuccToSinkTo == 0)
return false;
return NULL;
}
}
return SuccToSinkTo;
}
/// SinkInstruction - Determine whether it is safe to sink the specified machine
/// instruction out of its current block into a successor.
bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
// Don't sink insert_subreg, subreg_to_reg, reg_sequence. These are meant to
// be close to the source to make it easier to coalesce.
if (AvoidsSinking(MI, MRI))
return false;
// Check if it's safe to move the instruction.
if (!MI->isSafeToMove(TII, AA, SawStore))
return false;
// FIXME: This should include support for sinking instructions within the
// block they are currently in to shorten the live ranges. We often get
// instructions sunk into the top of a large block, but it would be better to
// also sink them down before their first use in the block. This xform has to
// be careful not to *increase* register pressure though, e.g. sinking
// "x = y + z" down if it kills y and z would increase the live ranges of y
// and z and only shrink the live range of x.
bool BreakPHIEdge = false;
MachineBasicBlock *SuccToSinkTo = FindSuccToSinkTo(MI, BreakPHIEdge);
// If there are no outputs, it must have side-effects.
if (SuccToSinkTo == 0)
@ -546,6 +556,8 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
DEBUG(dbgs() << "Sink instr " << *MI << "\tinto block " << *SuccToSinkTo);
MachineBasicBlock *ParentBlock = MI->getParent();
// If the block has multiple predecessors, this would introduce computation on
// a path that it doesn't already exist. We could split the critical edge,
// but for now we just punt.