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Cross register class coalescing. Not yet enabled.

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llvm-svn: 62832
This commit is contained in:
Evan Cheng 2009-01-23 02:15:19 +00:00
parent 86e54f5636
commit 7cdc6e4f8c
3 changed files with 129 additions and 109 deletions
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6
include/llvm/Target/TargetRegisterInfo.h
View File

@ -164,6 +164,12 @@ public:
while (*I != NULL) ++I;
return I;
}
/// isASubClass - return true if this TargetRegisterClass is a sub-class of at
/// least one other TargetRegisterClass.
bool isASubClass() const {
return SuperClasses[0] != 0;
}
/// allocation_order_begin/end - These methods define a range of registers
/// which specify the registers in this class that are valid to register

209
lib/CodeGen/SimpleRegisterCoalescing.cpp
View File

@ -36,7 +36,7 @@
using namespace llvm;
STATISTIC(numJoins , "Number of interval joins performed");
STATISTIC(numSubJoins , "Number of subclass joins performed");
STATISTIC(numCrossRCs , "Number of cross class joins performed");
STATISTIC(numCommutes , "Number of instruction commuting performed");
STATISTIC(numExtends , "Number of copies extended");
STATISTIC(NumReMats , "Number of instructions re-materialized");
@ -55,8 +55,8 @@ NewHeuristic("new-coalescer-heuristic",
cl::init(false), cl::Hidden);
static cl::opt<bool>
CrossClassJoin("join-subclass-copies",
cl::desc("Coalesce copies to sub- register class"),
CrossClassJoin("join-cross-class-copies",
cl::desc("Coalesce cross register class copies"),
cl::init(false), cl::Hidden);
static RegisterPass<SimpleRegisterCoalescing>
@ -953,38 +953,24 @@ static unsigned getMatchingSuperReg(unsigned Reg, unsigned SubIdx,
return 0;
}
/// isProfitableToCoalesceToSubRC - Given that register class of DstReg is
/// a subset of the register class of SrcReg, return true if it's profitable
/// to coalesce the two registers.
/// isWinToJoinCrossClass - Return true if it's profitable to coalesce
/// two virtual registers from different register classes.
bool
SimpleRegisterCoalescing::isProfitableToCoalesceToSubRC(unsigned SrcReg,
unsigned DstReg,
MachineBasicBlock *MBB){
if (!CrossClassJoin)
return false;
// First let's make sure all uses are in the same MBB.
for (MachineRegisterInfo::reg_iterator RI = mri_->reg_begin(SrcReg),
RE = mri_->reg_end(); RI != RE; ++RI) {
MachineInstr &MI = *RI;
if (MI.getParent() != MBB)
return false;
}
for (MachineRegisterInfo::reg_iterator RI = mri_->reg_begin(DstReg),
RE = mri_->reg_end(); RI != RE; ++RI) {
MachineInstr &MI = *RI;
if (MI.getParent() != MBB)
return false;
}
SimpleRegisterCoalescing::isWinToJoinCrossClass(unsigned LargeReg,
unsigned SmallReg,
unsigned Threshold) {
// Then make sure the intervals are *short*.
LiveInterval &SrcInt = li_->getInterval(SrcReg);
LiveInterval &DstInt = li_->getInterval(DstReg);
unsigned SrcSize = li_->getApproximateInstructionCount(SrcInt);
unsigned DstSize = li_->getApproximateInstructionCount(DstInt);
const TargetRegisterClass *RC = mri_->getRegClass(DstReg);
unsigned Threshold = allocatableRCRegs_[RC].count() * 2;
return (SrcSize + DstSize) <= Threshold;
LiveInterval &LargeInt = li_->getInterval(LargeReg);
LiveInterval &SmallInt = li_->getInterval(SmallReg);
unsigned LargeSize = li_->getApproximateInstructionCount(LargeInt);
unsigned SmallSize = li_->getApproximateInstructionCount(SmallInt);
if (SmallSize > Threshold || LargeSize > Threshold)
if ((float)std::distance(mri_->use_begin(SmallReg),
mri_->use_end()) / SmallSize <
(float)std::distance(mri_->use_begin(LargeReg),
mri_->use_end()) / LargeSize)
return false;
return true;
}
/// HasIncompatibleSubRegDefUse - If we are trying to coalesce a virtual
@ -1047,15 +1033,9 @@ SimpleRegisterCoalescing::HasIncompatibleSubRegDefUse(MachineInstr *CopyMI,
/// an extract_subreg where dst is a physical register, e.g.
/// cl = EXTRACT_SUBREG reg1024, 1
bool
SimpleRegisterCoalescing::CanJoinExtractSubRegToPhysReg(MachineInstr *CopyMI,
unsigned DstReg, unsigned SrcReg,
unsigned SubIdx, unsigned &RealDstReg) {
if (CopyMI->getOperand(1).getSubReg()) {
DOUT << "\tSrc of extract_subreg already coalesced with reg"
<< " of a super-class.\n";
return false; // Not coalescable.
}
SimpleRegisterCoalescing::CanJoinExtractSubRegToPhysReg(unsigned DstReg,
unsigned SrcReg, unsigned SubIdx,
unsigned &RealDstReg) {
const TargetRegisterClass *RC = mri_->getRegClass(SrcReg);
RealDstReg = getMatchingSuperReg(DstReg, SubIdx, RC, tri_);
assert(RealDstReg && "Invalid extract_subreg instruction!");
@ -1083,14 +1063,9 @@ SimpleRegisterCoalescing::CanJoinExtractSubRegToPhysReg(MachineInstr *CopyMI,
/// an insert_subreg where src is a physical register, e.g.
/// reg1024 = INSERT_SUBREG reg1024, c1, 0
bool
SimpleRegisterCoalescing::CanJoinInsertSubRegToPhysReg(MachineInstr *CopyMI,
unsigned DstReg, unsigned SrcReg,
unsigned SubIdx, unsigned &RealSrcReg) {
if (CopyMI->getOperand(1).getSubReg()) {
DOUT << "\tSrc of insert_subreg already coalesced with reg"
<< " of a super-class.\n";
return false; // Not coalescable.
}
SimpleRegisterCoalescing::CanJoinInsertSubRegToPhysReg(unsigned DstReg,
unsigned SrcReg, unsigned SubIdx,
unsigned &RealSrcReg) {
const TargetRegisterClass *RC = mri_->getRegClass(DstReg);
RealSrcReg = getMatchingSuperReg(SrcReg, SubIdx, RC, tri_);
assert(RealSrcReg && "Invalid extract_subreg instruction!");
@ -1111,7 +1086,6 @@ SimpleRegisterCoalescing::CanJoinInsertSubRegToPhysReg(MachineInstr *CopyMI,
return true;
}
/// JoinCopy - Attempt to join intervals corresponding to SrcReg/DstReg,
/// which are the src/dst of the copy instruction CopyMI. This returns true
/// if the copy was successfully coalesced away. If it is not currently
@ -1172,7 +1146,8 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
}
// Should be non-null only when coalescing to a sub-register class.
const TargetRegisterClass *SubRC = NULL;
bool CrossRC = false;
const TargetRegisterClass *NewRC = NULL;
MachineBasicBlock *CopyMBB = CopyMI->getParent();
unsigned RealDstReg = 0;
unsigned RealSrcReg = 0;
@ -1206,13 +1181,17 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
DstReg = tri_->getSubReg(DstReg, SubIdx);
SubIdx = 0;
} else if ((DstIsPhys && isExtSubReg) || (SrcIsPhys && isInsSubReg)) {
if (CopyMI->getOperand(1).getSubReg()) {
DOUT << "\tSrc of extract_subreg already coalesced with reg"
<< " of a super-class.\n";
return false; // Not coalescable.
}
if (isExtSubReg) {
if (!CanJoinExtractSubRegToPhysReg(CopyMI, DstReg, SrcReg, SubIdx,
RealDstReg))
if (!CanJoinExtractSubRegToPhysReg(DstReg, SrcReg, SubIdx, RealDstReg))
return false; // Not coalescable
} else {
if (!CanJoinInsertSubRegToPhysReg(CopyMI, DstReg, SrcReg, SubIdx,
RealSrcReg))
if (!CanJoinInsertSubRegToPhysReg(DstReg, SrcReg, SubIdx, RealSrcReg))
return false; // Not coalescable
}
SubIdx = 0;
@ -1220,8 +1199,7 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
unsigned OldSubIdx = isExtSubReg ? CopyMI->getOperand(0).getSubReg()
: CopyMI->getOperand(2).getSubReg();
if (OldSubIdx) {
if (OldSubIdx == SubIdx &&
!differingRegisterClasses(SrcReg, DstReg, SubRC))
if (OldSubIdx == SubIdx && !differingRegisterClasses(SrcReg, DstReg))
// r1024<2> = EXTRACT_SUBREG r1025, 2. Then r1024 has already been
// coalesced to a larger register so the subreg indices cancel out.
// Also check if the other larger register is of the same register
@ -1235,41 +1213,90 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
if (SubIdx) {
unsigned LargeReg = isExtSubReg ? SrcReg : DstReg;
unsigned SmallReg = isExtSubReg ? DstReg : SrcReg;
unsigned LargeRegSize =
li_->getApproximateInstructionCount(li_->getInterval(LargeReg));
unsigned SmallRegSize =
li_->getApproximateInstructionCount(li_->getInterval(SmallReg));
const TargetRegisterClass *RC = mri_->getRegClass(SmallReg);
unsigned Threshold = allocatableRCRegs_[RC].count();
// Be conservative. If both sides are virtual registers, do not coalesce
// if this will cause a high use density interval to target a smaller
// set of registers.
if (SmallRegSize > Threshold || LargeRegSize > Threshold) {
if ((float)std::distance(mri_->use_begin(SmallReg),
mri_->use_end()) / SmallRegSize <
(float)std::distance(mri_->use_begin(LargeReg),
mri_->use_end()) / LargeRegSize) {
Again = true; // May be possible to coalesce later.
return false;
}
unsigned Limit= allocatableRCRegs_[mri_->getRegClass(SmallReg)].count();
if (!isWinToJoinCrossClass(LargeReg, SmallReg, Limit)) {
Again = true; // May be possible to coalesce later.
return false;
}
}
}
} else if (differingRegisterClasses(SrcReg, DstReg, SubRC)) {
// FIXME: What if the resul of a EXTRACT_SUBREG is then coalesced
} else if (differingRegisterClasses(SrcReg, DstReg)) {
if (!CrossClassJoin)
return false;
CrossRC = true;
// FIXME: What if the result of a EXTRACT_SUBREG is then coalesced
// with another? If it's the resulting destination register, then
// the subidx must be propagated to uses (but only those defined
// by the EXTRACT_SUBREG). If it's being coalesced into another
// register, it should be safe because register is assumed to have
// the register class of the super-register.
if (!SubRC || !isProfitableToCoalesceToSubRC(SrcReg, DstReg, CopyMBB)) {
// If they are not of the same register class, we cannot join them.
// Process moves where one of the registers have a sub-register index.
MachineOperand *DstMO = CopyMI->findRegisterDefOperand(DstReg);
if (DstMO->getSubReg())
// FIXME: Can we handle this?
return false;
MachineOperand *SrcMO = CopyMI->findRegisterUseOperand(SrcReg);
SubIdx = SrcMO->getSubReg();
if (SubIdx) {
// This is not a extract_subreg but it looks like one.
// e.g. %cl = MOV16rr %reg1024:2
isExtSubReg = true;
if (DstIsPhys) {
if (!CanJoinExtractSubRegToPhysReg(DstReg, SrcReg, SubIdx,RealDstReg))
return false; // Not coalescable
SubIdx = 0;
}
}
const TargetRegisterClass *SrcRC= SrcIsPhys ? 0 : mri_->getRegClass(SrcReg);
const TargetRegisterClass *DstRC= DstIsPhys ? 0 : mri_->getRegClass(DstReg);
unsigned LargeReg = SrcReg;
unsigned SmallReg = DstReg;
unsigned Limit = 0;
// Now determine the register class of the joined register.
if (isExtSubReg) {
if (SubIdx && DstRC && DstRC->isASubClass()) {
// This is a move to a sub-register class. However, the source is a
// sub-register of a larger register class. We don't know what should
// the register class be. FIXME.
Again = true;
return false;
}
Limit = allocatableRCRegs_[DstRC].count();
} else if (!SrcIsPhys && !SrcIsPhys) {
unsigned SrcSize = SrcRC->getSize();
unsigned DstSize = DstRC->getSize();
if (SrcSize < DstSize)
// For example X86::MOVSD2PDrr copies from FR64 to VR128.
NewRC = DstRC;
else if (DstSize > SrcSize) {
NewRC = SrcRC;
std::swap(LargeReg, SmallReg);
} else {
unsigned SrcNumRegs = SrcRC->getNumRegs();
unsigned DstNumRegs = DstRC->getNumRegs();
if (DstNumRegs < SrcNumRegs)
// Sub-register class?
NewRC = DstRC;
else if (SrcNumRegs < DstNumRegs) {
NewRC = SrcRC;
std::swap(LargeReg, SmallReg);
} else
// No idea what's the right register class to use.
return false;
}
}
if (!SrcIsPhys && !DstIsPhys &&
!isWinToJoinCrossClass(LargeReg, SmallReg, Limit)) {
DOUT << "\tSrc/Dest are different register classes.\n";
// Allow the coalescer to try again in case either side gets coalesced to
// a physical register that's compatible with the other side. e.g.
// r1024 = MOV32to32_ r1025
// but later r1024 is assigned EAX then r1025 may be coalesced with EAX.
// But later r1024 is assigned EAX then r1025 may be coalesced with EAX.
Again = true; // May be possible to coalesce later.
return false;
}
@ -1417,9 +1444,10 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
// Coalescing to a virtual register that is of a sub-register class of the
// other. Make sure the resulting register is set to the right register class.
if (SubRC) {
mri_->setRegClass(DstReg, SubRC);
++numSubJoins;
if (CrossRC) {
++numCrossRCs;
if (NewRC)
mri_->setRegClass(DstReg, NewRC);
}
if (NewHeuristic) {
@ -2208,14 +2236,10 @@ void SimpleRegisterCoalescing::joinIntervals() {
}
/// Return true if the two specified registers belong to different register
/// classes. The registers may be either phys or virt regs. In the
/// case where both registers are virtual registers, it would also returns
/// true by reference the RegB register class in SubRC if it is a subset of
/// RegA's register class.
/// classes. The registers may be either phys or virt regs.
bool
SimpleRegisterCoalescing::differingRegisterClasses(unsigned RegA, unsigned RegB,
const TargetRegisterClass *&SubRC) const {
SimpleRegisterCoalescing::differingRegisterClasses(unsigned RegA,
unsigned RegB) const {
// Get the register classes for the first reg.
if (TargetRegisterInfo::isPhysicalRegister(RegA)) {
assert(TargetRegisterInfo::isVirtualRegister(RegB) &&
@ -2227,10 +2251,7 @@ SimpleRegisterCoalescing::differingRegisterClasses(unsigned RegA, unsigned RegB,
const TargetRegisterClass *RegClassA = mri_->getRegClass(RegA);
if (TargetRegisterInfo::isVirtualRegister(RegB)) {
const TargetRegisterClass *RegClassB = mri_->getRegClass(RegB);
if (RegClassA == RegClassB)
return false;
SubRC = (RegClassA->hasSubClass(RegClassB)) ? RegClassB : NULL;
return true;
return RegClassA != RegClassB;
}
return !RegClassA->contains(RegB);
}

23
lib/CodeGen/SimpleRegisterCoalescing.h
View File

@ -173,12 +173,8 @@ namespace llvm {
bool SimpleJoin(LiveInterval &LHS, LiveInterval &RHS);
/// Return true if the two specified registers belong to different register
/// classes. The registers may be either phys or virt regs. In the
/// case where both registers are virtual registers, it would also returns
/// true by reference the RegB register class in SubRC if it is a subset of
/// RegA's register class.
bool differingRegisterClasses(unsigned RegA, unsigned RegB,
const TargetRegisterClass *&SubRC) const;
/// classes. The registers may be either phys or virt regs.
bool differingRegisterClasses(unsigned RegA, unsigned RegB) const;
/// AdjustCopiesBackFrom - We found a non-trivially-coalescable copy. If
@ -219,11 +215,10 @@ namespace llvm {
/// identity copies so they will be removed.
void RemoveCopiesFromValNo(LiveInterval &li, VNInfo *VNI);
/// isProfitableToCoalesceToSubRC - Given that register class of DstReg is
/// a subset of the register class of SrcReg, return true if it's profitable
/// to coalesce the two registers.
bool isProfitableToCoalesceToSubRC(unsigned SrcReg, unsigned DstReg,
MachineBasicBlock *MBB);
/// isWinToJoinCrossClass - Return true if it's profitable to coalesce
/// two virtual registers from different register classes.
bool isWinToJoinCrossClass(unsigned LargeReg, unsigned SmallReg,
unsigned Threshold);
/// HasIncompatibleSubRegDefUse - If we are trying to coalesce a virtual
/// register with a physical register, check if any of the virtual register
@ -235,15 +230,13 @@ namespace llvm {
/// CanJoinExtractSubRegToPhysReg - Return true if it's possible to coalesce
/// an extract_subreg where dst is a physical register, e.g.
/// cl = EXTRACT_SUBREG reg1024, 1
bool CanJoinExtractSubRegToPhysReg(MachineInstr *CopyMI,
unsigned DstReg, unsigned SrcReg,
bool CanJoinExtractSubRegToPhysReg(unsigned DstReg, unsigned SrcReg,
unsigned SubIdx, unsigned &RealDstReg);
/// CanJoinInsertSubRegToPhysReg - Return true if it's possible to coalesce
/// an insert_subreg where src is a physical register, e.g.
/// reg1024 = INSERT_SUBREG reg1024, c1, 0
bool CanJoinInsertSubRegToPhysReg(MachineInstr *CopyMI,
unsigned DstReg, unsigned SrcReg,
bool CanJoinInsertSubRegToPhysReg(unsigned DstReg, unsigned SrcReg,
unsigned SubIdx, unsigned &RealDstReg);
/// RangeIsDefinedByCopyFromReg - Return true if the specified live range of