class raw_ostream;
class LiveRegMatrix;
-/// A bitmask representing the parts of a register are alive.
+/// A bitmask representing the covering of a register with sub-registers.
///
+/// This is typically used to track liveness at sub-register granularity.
/// Lane masks for sub-register indices are similar to register units for
/// physical registers. The individual bits in a lane mask can't be assigned
/// any specific meaning. They can be used to check if two sub-register
/// indices overlap.
///
-/// If the target has a register such that:
+/// Iff the target has a register such that:
///
/// getSubReg(Reg, A) overlaps getSubReg(Reg, B)
///
/// then:
///
/// (getSubRegIndexLaneMask(A) & getSubRegIndexLaneMask(B)) != 0
-///
-/// The converse is not necessarily true. If two lane masks have a common
-/// bit, the corresponding sub-registers may not overlap, but it can be
-/// assumed that they usually will.
typedef unsigned LaneBitmask;
class TargetRegisterClass {
return SubRegIndexLaneMasks[SubIdx];
}
- /// Returns true if the given lane mask is imprecise.
- ///
- /// LaneMasks as given by getSubRegIndexLaneMask() have a limited number of
- /// bits, so for targets with more than 31 disjunct subregister indices there
- /// may be cases where:
- /// getSubReg(Reg,A) does not overlap getSubReg(Reg,B)
- /// but we still have
- /// (getSubRegIndexLaneMask(A) & getSubRegIndexLaneMask(B)) != 0.
- /// This function returns true in those cases.
- static bool isImpreciseLaneMask(LaneBitmask LaneMask) {
- return LaneMask & 0x80000000u;
- }
-
/// The lane masks returned by getSubRegIndexLaneMask() above can only be
/// used to determine if sub-registers overlap - they can't be used to
/// determine if a set of sub-registers completely cover another
/// LaneMask are split as necessary. @p LaneMask are the lanes that
/// @p ToMerge will occupy in the coalescer register. @p LI has its subrange
/// lanemasks already adjusted to the coalesced register.
- /// @returns false if live range conflicts couldn't get resolved.
- bool mergeSubRangeInto(LiveInterval &LI, const LiveRange &ToMerge,
+ void mergeSubRangeInto(LiveInterval &LI, const LiveRange &ToMerge,
LaneBitmask LaneMask, CoalescerPair &CP);
/// Join the liveranges of two subregisters. Joins @p RRange into
/// @p LRange, @p RRange may be invalid afterwards.
- /// @returns false if live range conflicts couldn't get resolved.
- bool joinSubRegRanges(LiveRange &LRange, LiveRange &RRange,
+ void joinSubRegRanges(LiveRange &LRange, LiveRange &RRange,
LaneBitmask LaneMask, const CoalescerPair &CP);
/// We found a non-trivially-coalescable copy. If the source value number is
}
}
-bool RegisterCoalescer::joinSubRegRanges(LiveRange &LRange, LiveRange &RRange,
+void RegisterCoalescer::joinSubRegRanges(LiveRange &LRange, LiveRange &RRange,
LaneBitmask LaneMask,
const CoalescerPair &CP) {
SmallVector<VNInfo*, 16> NewVNInfo;
// ranges get mapped to the "overflow" lane mask bit which creates unexpected
// interferences.
if (!LHSVals.mapValues(RHSVals) || !RHSVals.mapValues(LHSVals)) {
- DEBUG(dbgs() << "*** Couldn't join subrange!\n");
- return false;
+ // We already determined that it is legal to merge the intervals, so this
+ // should never fail.
+ llvm_unreachable("*** Couldn't join subrange!\n");
}
if (!LHSVals.resolveConflicts(RHSVals) ||
!RHSVals.resolveConflicts(LHSVals)) {
- DEBUG(dbgs() << "*** Couldn't join subrange!\n");
- return false;
+ // We already determined that it is legal to merge the intervals, so this
+ // should never fail.
+ llvm_unreachable("*** Couldn't join subrange!\n");
}
// The merging algorithm in LiveInterval::join() can't handle conflicting
DEBUG(dbgs() << "\t\tjoined lanes: " << LRange << "\n");
if (EndPoints.empty())
- return true;
+ return;
// Recompute the parts of the live range we had to remove because of
// CR_Replace conflicts.
DEBUG(dbgs() << "\t\trestoring liveness to " << EndPoints.size()
<< " points: " << LRange << '\n');
LIS->extendToIndices(LRange, EndPoints);
- return true;
}
-bool RegisterCoalescer::mergeSubRangeInto(LiveInterval &LI,
+void RegisterCoalescer::mergeSubRangeInto(LiveInterval &LI,
const LiveRange &ToMerge,
LaneBitmask LaneMask,
CoalescerPair &CP) {
CommonRange = &R;
}
LiveRange RangeCopy(ToMerge, Allocator);
- if (!joinSubRegRanges(*CommonRange, RangeCopy, Common, CP))
- return false;
+ joinSubRegRanges(*CommonRange, RangeCopy, Common, CP);
LaneMask &= ~RMask;
}
DEBUG(dbgs() << "\t\tNew Lane " << PrintLaneMask(LaneMask) << '\n');
LI.createSubRangeFrom(Allocator, LaneMask, ToMerge);
}
- return true;
}
bool RegisterCoalescer::joinVirtRegs(CoalescerPair &CP) {
// Determine lanemasks of RHS in the coalesced register and merge subranges.
unsigned SrcIdx = CP.getSrcIdx();
- bool Abort = false;
if (!RHS.hasSubRanges()) {
LaneBitmask Mask = SrcIdx == 0 ? CP.getNewRC()->getLaneMask()
: TRI->getSubRegIndexLaneMask(SrcIdx);
- if (!mergeSubRangeInto(LHS, RHS, Mask, CP))
- Abort = true;
+ mergeSubRangeInto(LHS, RHS, Mask, CP);
} else {
// Pair up subranges and merge.
for (LiveInterval::SubRange &R : RHS.subranges()) {
LaneBitmask Mask = TRI->composeSubRegIndexLaneMask(SrcIdx, R.LaneMask);
- if (!mergeSubRangeInto(LHS, R, Mask, CP)) {
- Abort = true;
- break;
- }
+ mergeSubRangeInto(LHS, R, Mask, CP);
}
}
- if (Abort) {
- // This shouldn't have happened :-(
- // However we are aware of at least one existing problem where we
- // can't merge subranges when multiple ranges end up in the
- // "overflow bit" 32. As a workaround we drop all subregister ranges
- // which means we loose some precision but are back to a well defined
- // state.
- assert(TargetRegisterInfo::isImpreciseLaneMask(
- CP.getNewRC()->getLaneMask())
- && "SubRange merge should only fail when merging into bit 32.");
- DEBUG(dbgs() << "\tSubrange join aborted!\n");
- LHS.clearSubRanges();
- RHS.clearSubRanges();
- } else {
- DEBUG(dbgs() << "\tJoined SubRanges " << LHS << "\n");
+ DEBUG(dbgs() << "\tJoined SubRanges " << LHS << "\n");
- LHSVals.pruneSubRegValues(LHS, ShrinkMask);
- RHSVals.pruneSubRegValues(LHS, ShrinkMask);
- }
+ LHSVals.pruneSubRegValues(LHS, ShrinkMask);
+ RHSVals.pruneSubRegValues(LHS, ShrinkMask);
}
// The merging algorithm in LiveInterval::join() can't handle conflicting
projects / oota-llvm.git / commitdiff