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-rw-r--r--lib/CodeGen/CriticalAntiDepBreaker.cpp158
1 files changed, 104 insertions, 54 deletions
diff --git a/lib/CodeGen/CriticalAntiDepBreaker.cpp b/lib/CodeGen/CriticalAntiDepBreaker.cpp
index fd957b1..e3746a9 100644
--- a/lib/CodeGen/CriticalAntiDepBreaker.cpp
+++ b/lib/CodeGen/CriticalAntiDepBreaker.cpp
@@ -18,6 +18,7 @@
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
@@ -29,6 +30,7 @@ CriticalAntiDepBreaker::
CriticalAntiDepBreaker(MachineFunction& MFi) :
AntiDepBreaker(), MF(MFi),
MRI(MF.getRegInfo()),
+ TII(MF.getTarget().getInstrInfo()),
TRI(MF.getTarget().getRegisterInfo()),
AllocatableSet(TRI->getAllocatableSet(MF))
{
@@ -71,25 +73,27 @@ void CriticalAntiDepBreaker::StartBlock(MachineBasicBlock *BB) {
DefIndices[AliasReg] = ~0u;
}
}
- } else {
- // In a non-return block, examine the live-in regs of all successors.
- for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
+ }
+
+ // In a non-return block, examine the live-in regs of all successors.
+ // Note a return block can have successors if the return instruction is
+ // predicated.
+ for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
SE = BB->succ_end(); SI != SE; ++SI)
- for (MachineBasicBlock::livein_iterator I = (*SI)->livein_begin(),
+ for (MachineBasicBlock::livein_iterator I = (*SI)->livein_begin(),
E = (*SI)->livein_end(); I != E; ++I) {
- unsigned Reg = *I;
- Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
- KillIndices[Reg] = BB->size();
- DefIndices[Reg] = ~0u;
- // Repeat, for all aliases.
- for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
- unsigned AliasReg = *Alias;
- Classes[AliasReg] = reinterpret_cast<TargetRegisterClass *>(-1);
- KillIndices[AliasReg] = BB->size();
- DefIndices[AliasReg] = ~0u;
- }
+ unsigned Reg = *I;
+ Classes[Reg] = reinterpret_cast<TargetRegisterClass *>(-1);
+ KillIndices[Reg] = BB->size();
+ DefIndices[Reg] = ~0u;
+ // Repeat, for all aliases.
+ for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
+ unsigned AliasReg = *Alias;
+ Classes[AliasReg] = reinterpret_cast<TargetRegisterClass *>(-1);
+ KillIndices[AliasReg] = BB->size();
+ DefIndices[AliasReg] = ~0u;
}
- }
+ }
// Mark live-out callee-saved registers. In a return block this is
// all callee-saved registers. In non-return this is any
@@ -164,6 +168,26 @@ static const SDep *CriticalPathStep(const SUnit *SU) {
}
void CriticalAntiDepBreaker::PrescanInstruction(MachineInstr *MI) {
+ // It's not safe to change register allocation for source operands of
+ // that have special allocation requirements. Also assume all registers
+ // used in a call must not be changed (ABI).
+ // FIXME: The issue with predicated instruction is more complex. We are being
+ // conservatively here because the kill markers cannot be trusted after
+ // if-conversion:
+ // %R6<def> = LDR %SP, %reg0, 92, pred:14, pred:%reg0; mem:LD4[FixedStack14]
+ // ...
+ // STR %R0, %R6<kill>, %reg0, 0, pred:0, pred:%CPSR; mem:ST4[%395]
+ // %R6<def> = LDR %SP, %reg0, 100, pred:0, pred:%CPSR; mem:LD4[FixedStack12]
+ // STR %R0, %R6<kill>, %reg0, 0, pred:14, pred:%reg0; mem:ST4[%396](align=8)
+ //
+ // The first R6 kill is not really a kill since it's killed by a predicated
+ // instruction which may not be executed. The second R6 def may or may not
+ // re-define R6 so it's not safe to change it since the last R6 use cannot be
+ // changed.
+ bool Special = MI->getDesc().isCall() ||
+ MI->getDesc().hasExtraSrcRegAllocReq() ||
+ TII->isPredicated(MI);
+
// Scan the register operands for this instruction and update
// Classes and RegRefs.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
@@ -199,9 +223,7 @@ void CriticalAntiDepBreaker::PrescanInstruction(MachineInstr *MI) {
if (Classes[Reg] != reinterpret_cast<TargetRegisterClass *>(-1))
RegRefs.insert(std::make_pair(Reg, &MO));
- // It's not safe to change register allocation for source operands of
- // that have special allocation requirements.
- if (MO.isUse() && MI->getDesc().hasExtraSrcRegAllocReq()) {
+ if (MO.isUse() && Special) {
if (KeepRegs.insert(Reg)) {
for (const unsigned *Subreg = TRI->getSubRegisters(Reg);
*Subreg; ++Subreg)
@@ -216,38 +238,43 @@ void CriticalAntiDepBreaker::ScanInstruction(MachineInstr *MI,
// Update liveness.
// Proceding upwards, registers that are defed but not used in this
// instruction are now dead.
- for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
- MachineOperand &MO = MI->getOperand(i);
- if (!MO.isReg()) continue;
- unsigned Reg = MO.getReg();
- if (Reg == 0) continue;
- if (!MO.isDef()) continue;
- // Ignore two-addr defs.
- if (MI->isRegTiedToUseOperand(i)) continue;
-
- DefIndices[Reg] = Count;
- KillIndices[Reg] = ~0u;
- assert(((KillIndices[Reg] == ~0u) !=
- (DefIndices[Reg] == ~0u)) &&
- "Kill and Def maps aren't consistent for Reg!");
- KeepRegs.erase(Reg);
- Classes[Reg] = 0;
- RegRefs.erase(Reg);
- // Repeat, for all subregs.
- for (const unsigned *Subreg = TRI->getSubRegisters(Reg);
- *Subreg; ++Subreg) {
- unsigned SubregReg = *Subreg;
- DefIndices[SubregReg] = Count;
- KillIndices[SubregReg] = ~0u;
- KeepRegs.erase(SubregReg);
- Classes[SubregReg] = 0;
- RegRefs.erase(SubregReg);
- }
- // Conservatively mark super-registers as unusable.
- for (const unsigned *Super = TRI->getSuperRegisters(Reg);
- *Super; ++Super) {
- unsigned SuperReg = *Super;
- Classes[SuperReg] = reinterpret_cast<TargetRegisterClass *>(-1);
+
+ if (!TII->isPredicated(MI)) {
+ // Predicated defs are modeled as read + write, i.e. similar to two
+ // address updates.
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg()) continue;
+ unsigned Reg = MO.getReg();
+ if (Reg == 0) continue;
+ if (!MO.isDef()) continue;
+ // Ignore two-addr defs.
+ if (MI->isRegTiedToUseOperand(i)) continue;
+
+ DefIndices[Reg] = Count;
+ KillIndices[Reg] = ~0u;
+ assert(((KillIndices[Reg] == ~0u) !=
+ (DefIndices[Reg] == ~0u)) &&
+ "Kill and Def maps aren't consistent for Reg!");
+ KeepRegs.erase(Reg);
+ Classes[Reg] = 0;
+ RegRefs.erase(Reg);
+ // Repeat, for all subregs.
+ for (const unsigned *Subreg = TRI->getSubRegisters(Reg);
+ *Subreg; ++Subreg) {
+ unsigned SubregReg = *Subreg;
+ DefIndices[SubregReg] = Count;
+ KillIndices[SubregReg] = ~0u;
+ KeepRegs.erase(SubregReg);
+ Classes[SubregReg] = 0;
+ RegRefs.erase(SubregReg);
+ }
+ // Conservatively mark super-registers as unusable.
+ for (const unsigned *Super = TRI->getSuperRegisters(Reg);
+ *Super; ++Super) {
+ unsigned SuperReg = *Super;
+ Classes[SuperReg] = reinterpret_cast<TargetRegisterClass *>(-1);
+ }
}
}
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
@@ -334,10 +361,15 @@ BreakAntiDependencies(const std::vector<SUnit>& SUnits,
// so just duck out immediately if the block is empty.
if (SUnits.empty()) return 0;
+ // Keep a map of the MachineInstr*'s back to the SUnit representing them.
+ // This is used for updating debug information.
+ DenseMap<MachineInstr*,const SUnit*> MISUnitMap;
+
// Find the node at the bottom of the critical path.
const SUnit *Max = 0;
for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
const SUnit *SU = &SUnits[i];
+ MISUnitMap[SU->getInstr()] = SU;
if (!Max || SU->getDepth() + SU->Latency > Max->getDepth() + Max->Latency)
Max = SU;
}
@@ -473,7 +505,11 @@ BreakAntiDependencies(const std::vector<SUnit>& SUnits,
PrescanInstruction(MI);
- if (MI->getDesc().hasExtraDefRegAllocReq())
+ // If MI's defs have a special allocation requirement, don't allow
+ // any def registers to be changed. Also assume all registers
+ // defined in a call must not be changed (ABI).
+ if (MI->getDesc().isCall() || MI->getDesc().hasExtraDefRegAllocReq() ||
+ TII->isPredicated(MI))
// If this instruction's defs have special allocation requirement, don't
// break this anti-dependency.
AntiDepReg = 0;
@@ -485,7 +521,7 @@ BreakAntiDependencies(const std::vector<SUnit>& SUnits,
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (Reg == 0) continue;
- if (MO.isUse() && AntiDepReg == Reg) {
+ if (MO.isUse() && TRI->regsOverlap(AntiDepReg, Reg)) {
AntiDepReg = 0;
break;
}
@@ -519,8 +555,22 @@ BreakAntiDependencies(const std::vector<SUnit>& SUnits,
std::multimap<unsigned, MachineOperand *>::iterator>
Range = RegRefs.equal_range(AntiDepReg);
for (std::multimap<unsigned, MachineOperand *>::iterator
- Q = Range.first, QE = Range.second; Q != QE; ++Q)
+ Q = Range.first, QE = Range.second; Q != QE; ++Q) {
Q->second->setReg(NewReg);
+ // If the SU for the instruction being updated has debug information
+ // related to the anti-dependency register, make sure to update that
+ // as well.
+ const SUnit *SU = MISUnitMap[Q->second->getParent()];
+ if (!SU) continue;
+ for (unsigned i = 0, e = SU->DbgInstrList.size() ; i < e ; ++i) {
+ MachineInstr *DI = SU->DbgInstrList[i];
+ assert (DI->getNumOperands()==3 && DI->getOperand(0).isReg() &&
+ DI->getOperand(0).getReg()
+ && "Non register dbg_value attached to SUnit!");
+ if (DI->getOperand(0).getReg() == AntiDepReg)
+ DI->getOperand(0).setReg(NewReg);
+ }
+ }
// We just went back in time and modified history; the
// liveness information for the anti-depenence reg is now
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