Fix for PR1306.
- A register def / use now implicitly affects sub-register liveness but does
not affect liveness information of super-registers.
- Def of a larger register (if followed by a use later) is treated as
read/mod/write of a smaller register.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36434 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 6521d97..e936158 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -675,8 +675,12 @@
exit:
assert(start < end && "did not find end of interval?");
- LiveRange LR(start, end, interval.getNextValue(SrcReg != 0 ? start : ~0U,
- SrcReg));
+ // Already exists? Extend old live interval.
+ LiveInterval::iterator OldLR = interval.FindLiveRangeContaining(start);
+ unsigned Id = (OldLR != interval.end())
+ ? OldLR->ValId
+ : interval.getNextValue(SrcReg != 0 ? start : ~0U, SrcReg);
+ LiveRange LR(start, end, Id);
interval.addRange(LR);
DOUT << " +" << LR << '\n';
}
@@ -692,14 +696,17 @@
if (!tii_->isMoveInstr(*MI, SrcReg, DstReg))
SrcReg = 0;
handlePhysicalRegisterDef(MBB, MI, MIIdx, getOrCreateInterval(reg), SrcReg);
- for (const unsigned* AS = mri_->getAliasSet(reg); *AS; ++AS)
- handlePhysicalRegisterDef(MBB, MI, MIIdx, getOrCreateInterval(*AS), 0);
+ // Def of a register also defines its sub-registers.
+ for (const unsigned* AS = mri_->getSubRegisters(reg); *AS; ++AS)
+ // Avoid processing some defs more than once.
+ if (!MI->findRegisterDefOperand(*AS))
+ handlePhysicalRegisterDef(MBB, MI, MIIdx, getOrCreateInterval(*AS), 0);
}
}
void LiveIntervals::handleLiveInRegister(MachineBasicBlock *MBB,
unsigned MIIdx,
- LiveInterval &interval) {
+ LiveInterval &interval, bool isAlias) {
DOUT << "\t\tlivein register: "; DEBUG(printRegName(interval.reg));
// Look for kills, if it reaches a def before it's killed, then it shouldn't
@@ -728,6 +735,12 @@
}
exit:
+ // Alias of a live-in register might not be used at all.
+ if (isAlias && end == 0) {
+ DOUT << " dead";
+ end = getDefIndex(start) + 1;
+ }
+
assert(start < end && "did not find end of interval?");
LiveRange LR(start, end, interval.getNextValue(~0U, 0));
@@ -757,8 +770,10 @@
for (MachineBasicBlock::const_livein_iterator LI = MBB->livein_begin(),
LE = MBB->livein_end(); LI != LE; ++LI) {
handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*LI));
- for (const unsigned* AS = mri_->getAliasSet(*LI); *AS; ++AS)
- handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*AS));
+ // Multiple live-ins can alias the same register.
+ for (const unsigned* AS = mri_->getSubRegisters(*LI); *AS; ++AS)
+ if (!hasInterval(*AS))
+ handleLiveInRegister(MBB, MIIndex, getOrCreateInterval(*AS), true);
}
}
@@ -856,7 +871,8 @@
// If the IntB live range is assigned to a physical register, and if that
// physreg has aliases,
if (MRegisterInfo::isPhysicalRegister(IntB.reg)) {
- for (const unsigned *AS = mri_->getAliasSet(IntB.reg); *AS; ++AS) {
+ // Update the liveintervals of sub-registers.
+ for (const unsigned *AS = mri_->getSubRegisters(IntB.reg); *AS; ++AS) {
LiveInterval &AliasLI = getInterval(*AS);
AliasLI.addRange(LiveRange(FillerStart, FillerEnd,
AliasLI.getNextValue(~0U, 0)));
@@ -1055,8 +1071,9 @@
// we have to update any aliased register's live ranges to indicate that they
// have clobbered values for this range.
if (MRegisterInfo::isPhysicalRegister(repDstReg)) {
- for (const unsigned *AS = mri_->getAliasSet(repDstReg); *AS; ++AS)
- getInterval(*AS).MergeInClobberRanges(SrcInt);
+ // Update the liveintervals of sub-registers.
+ for (const unsigned *AS = mri_->getSubRegisters(repDstReg); *AS; ++AS)
+ getInterval(*AS).MergeInClobberRanges(SrcInt);
} else {
// Merge use info if the destination is a virtual register.
LiveVariables::VarInfo& dVI = lv_->getVarInfo(repDstReg);
@@ -1279,6 +1296,27 @@
SmallVector<int, 16> LHSValNoAssignments;
SmallVector<int, 16> RHSValNoAssignments;
SmallVector<std::pair<unsigned,unsigned>, 16> ValueNumberInfo;
+
+ // If a live interval is a physical register, conservatively check if any
+ // of its sub-registers is overlapping the live interval of the virtual
+ // register. If so, do not coalesce.
+ if (MRegisterInfo::isPhysicalRegister(LHS.reg) &&
+ *mri_->getSubRegisters(LHS.reg)) {
+ for (const unsigned* SR = mri_->getSubRegisters(LHS.reg); *SR; ++SR)
+ if (hasInterval(*SR) && RHS.overlaps(getInterval(*SR))) {
+ DOUT << "Interfere with sub-register ";
+ DEBUG(getInterval(*SR).print(DOUT, mri_));
+ return false;
+ }
+ } else if (MRegisterInfo::isPhysicalRegister(RHS.reg) &&
+ *mri_->getSubRegisters(RHS.reg)) {
+ for (const unsigned* SR = mri_->getSubRegisters(RHS.reg); *SR; ++SR)
+ if (hasInterval(*SR) && LHS.overlaps(getInterval(*SR))) {
+ DOUT << "Interfere with sub-register ";
+ DEBUG(getInterval(*SR).print(DOUT, mri_));
+ return false;
+ }
+ }
// Compute ultimate value numbers for the LHS and RHS values.
if (RHS.containsOneValue()) {