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LiveInterval: Document and enforce rules about empty subranges.

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Empty subranges are not allowed in a LiveInterval and must be removed
instead: Check this in the verifiers, put a reminder for this in the
comment of the shrinkToUses variant for a single lane and make it
automatic for the shrinkToUses variant for a LiveInterval.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242431 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Matthias Braun 2015-07-16 18:55:35 +00:00
parent ac40c926aa
commit 0219a272ec
4 changed files with 11 additions and 0 deletions
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2
include/llvm/CodeGen/LiveIntervalAnalysis.h
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@ -160,6 +160,8 @@ extern cl::opt<bool> UseSegmentSetForPhysRegs;
/// shrinkToUses(LiveInterval *li, SmallVectorImpl<MachineInstr*> *dead)
/// that works on a subregister live range and only looks at uses matching
/// the lane mask of the subregister range.
/// This may leave the subrange empty which needs to be cleaned up with
/// LiveInterval::removeEmptySubranges() afterwards.
void shrinkToUses(LiveInterval::SubRange &SR, unsigned Reg);
/// extendToIndices - Extend the live range of LI to reach all points in

2
lib/CodeGen/LiveInterval.cpp
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@ -1110,6 +1110,8 @@ void LiveInterval::verify(const MachineRegisterInfo *MRI) const {
// subrange mask should not contained in maximum lane mask for the vreg.
assert((Mask & ~MaxMask) == 0);
// empty subranges must be removed.
assert(!SR.empty());
SR.verify();
// Main liverange should cover subrange.

5
lib/CodeGen/LiveIntervalAnalysis.cpp
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@ -403,9 +403,14 @@ bool LiveIntervals::shrinkToUses(LiveInterval *li,
&& "Can only shrink virtual registers");
// Shrink subregister live ranges.
bool NeedsCleanup = false;
for (LiveInterval::SubRange &S : li->subranges()) {
shrinkToUses(S, li->reg);
if (S.empty())
NeedsCleanup = true;
}
if (NeedsCleanup)
li->removeEmptySubRanges();
// Find all the values used, including PHI kills.
ShrinkToUsesWorkList WorkList;

2
lib/CodeGen/MachineVerifier.cpp
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@ -1671,6 +1671,8 @@ void MachineVerifier::verifyLiveInterval(const LiveInterval &LI) {
report("Lane masks of sub ranges overlap in live interval", MF, LI);
if ((SR.LaneMask & ~MaxMask) != 0)
report("Subrange lanemask is invalid", MF, LI);
if (SR.empty())
report("Subrange must not be empty", MF, SR, LI.reg, SR.LaneMask);
Mask |= SR.LaneMask;
verifyLiveRange(SR, LI.reg, SR.LaneMask);
if (!LI.covers(SR))