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author | Jakob Stoklund Olesen <stoklund@2pi.dk> | 2009-12-04 00:16:04 +0000 |
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committer | Jakob Stoklund Olesen <stoklund@2pi.dk> | 2009-12-04 00:16:04 +0000 |
commit | 6b74e505be1016223e090a6c806f7caa3165a146 (patch) | |
tree | dcc016454a3e8332b8d9f3e22e331a4ab0073158 /lib/CodeGen/RegAllocLinearScan.cpp | |
parent | 2e65c29ac64e7b36603d1a1de3d01cdfd2e61e23 (diff) | |
download | external_llvm-6b74e505be1016223e090a6c806f7caa3165a146.zip external_llvm-6b74e505be1016223e090a6c806f7caa3165a146.tar.gz external_llvm-6b74e505be1016223e090a6c806f7caa3165a146.tar.bz2 |
Also attempt trivial coalescing for live intervals that end in a copy.
The coalescer is supposed to clean these up, but when setting up parameters
for a function call, there may be copies to physregs. If the defining
instruction has been LICM'ed far away, the coalescer won't touch it.
The register allocation hint does not always work - when the register
allocator is backtracking, it clears the hints.
This patch takes care of a few more cases that r90163 missed.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90502 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen/RegAllocLinearScan.cpp')
-rw-r--r-- | lib/CodeGen/RegAllocLinearScan.cpp | 92 |
1 files changed, 48 insertions, 44 deletions
diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp index 4ff5129..79bde16 100644 --- a/lib/CodeGen/RegAllocLinearScan.cpp +++ b/lib/CodeGen/RegAllocLinearScan.cpp @@ -390,66 +390,70 @@ void RALinScan::ComputeRelatedRegClasses() { RelatedRegClasses.unionSets(I->second, OneClassForEachPhysReg[*AS]); } -/// attemptTrivialCoalescing - If a simple interval is defined by a copy, -/// try allocate the definition the same register as the source register -/// if the register is not defined during live time of the interval. This -/// eliminate a copy. This is used to coalesce copies which were not -/// coalesced away before allocation either due to dest and src being in -/// different register classes or because the coalescer was overly -/// conservative. +/// attemptTrivialCoalescing - If a simple interval is defined by a copy, try +/// allocate the definition the same register as the source register if the +/// register is not defined during live time of the interval. If the interval is +/// killed by a copy, try to use the destination register. This eliminates a +/// copy. This is used to coalesce copies which were not coalesced away before +/// allocation either due to dest and src being in different register classes or +/// because the coalescer was overly conservative. unsigned RALinScan::attemptTrivialCoalescing(LiveInterval &cur, unsigned Reg) { unsigned Preference = vrm_->getRegAllocPref(cur.reg); if ((Preference && Preference == Reg) || !cur.containsOneValue()) return Reg; VNInfo *vni = cur.begin()->valno; - if ((vni->def == SlotIndex()) || - vni->isUnused() || !vni->isDefAccurate()) + if (vni->isUnused()) return Reg; - MachineInstr *CopyMI = li_->getInstructionFromIndex(vni->def); - unsigned SrcReg, DstReg, SrcSubReg, DstSubReg, PhysReg; - if (!CopyMI || - !tii_->isMoveInstr(*CopyMI, SrcReg, DstReg, SrcSubReg, DstSubReg)) - return Reg; - PhysReg = SrcReg; - if (TargetRegisterInfo::isVirtualRegister(SrcReg)) { - if (!vrm_->isAssignedReg(SrcReg)) + unsigned CandReg; + bool forward; // extending physreg forward + { + MachineInstr *CopyMI; + unsigned SrcReg, DstReg, SrcSubReg, DstSubReg; + if (vni->def != SlotIndex() && vni->isDefAccurate() && + (CopyMI = li_->getInstructionFromIndex(vni->def)) && + tii_->isMoveInstr(*CopyMI, SrcReg, DstReg, SrcSubReg, DstSubReg)) + // Defined by a copy, try to extend SrcReg forward + CandReg = SrcReg, forward = true; + else if (cur.ranges.size()==1 && + (CopyMI = + li_->getInstructionFromIndex(cur.begin()->end.getBaseIndex())) && + tii_->isMoveInstr(*CopyMI, SrcReg, DstReg, SrcSubReg, DstSubReg) && + cur.reg == SrcReg) + // Only used by a copy, try to extend DstReg backwards + CandReg = DstReg, forward = false; + else + return Reg; + } + + if (TargetRegisterInfo::isVirtualRegister(CandReg)) { + if (!vrm_->isAssignedReg(CandReg)) return Reg; - PhysReg = vrm_->getPhys(SrcReg); + CandReg = vrm_->getPhys(CandReg); } - if (Reg == PhysReg) + if (Reg == CandReg) return Reg; const TargetRegisterClass *RC = mri_->getRegClass(cur.reg); - if (!RC->contains(PhysReg)) + if (!RC->contains(CandReg)) return Reg; - // Try to coalesce. - if (!li_->conflictsWithPhysRegDef(cur, *vrm_, PhysReg)) { - DEBUG(errs() << "Coalescing: " << cur << " -> " << tri_->getName(PhysReg) - << '\n'); - vrm_->clearVirt(cur.reg); - vrm_->assignVirt2Phys(cur.reg, PhysReg); - - // Remove unnecessary kills since a copy does not clobber the register. - if (li_->hasInterval(SrcReg)) { - LiveInterval &SrcLI = li_->getInterval(SrcReg); - for (MachineRegisterInfo::use_iterator I = mri_->use_begin(cur.reg), - E = mri_->use_end(); I != E; ++I) { - MachineOperand &O = I.getOperand(); - if (!O.isKill()) - continue; - MachineInstr *MI = &*I; - if (SrcLI.liveAt(li_->getInstructionIndex(MI).getDefIndex())) - O.setIsKill(false); - } - } - - ++NumCoalesce; - return PhysReg; + if (forward) { + if (li_->conflictsWithPhysRegDef(cur, *vrm_, CandReg)) + return Reg; + } else { + if (li_->conflictsWithPhysRegUse(cur, *vrm_, CandReg)) + return Reg; } - return Reg; + // Try to coalesce. + DEBUG(errs() << "Coalescing: " << cur << " -> " << tri_->getName(CandReg) + << '\n'); + vrm_->clearVirt(cur.reg); + vrm_->assignVirt2Phys(cur.reg, CandReg); + + ++NumCoalesce; + return CandReg; } bool RALinScan::runOnMachineFunction(MachineFunction &fn) { |