From 0219a272ec3c1a3784bd85bd0dc2fa457743ffd6 Mon Sep 17 00:00:00 2001
From: Matthias Braun <matze@braunis.de>
Date: Thu, 16 Jul 2015 18:55:35 +0000
Subject: [PATCH] LiveInterval: Document and enforce rules about empty
subranges.
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
---
include/llvm/CodeGen/LiveIntervalAnalysis.h | 2 ++
lib/CodeGen/LiveInterval.cpp | 2 ++
lib/CodeGen/LiveIntervalAnalysis.cpp | 5 +++++
lib/CodeGen/MachineVerifier.cpp | 2 ++
4 files changed, 11 insertions(+)
diff --git a/include/llvm/CodeGen/LiveIntervalAnalysis.h b/include/llvm/CodeGen/LiveIntervalAnalysis.h
index 70c3b8d5772..47ba1ff0454 100644
--- a/include/llvm/CodeGen/LiveIntervalAnalysis.h
+++ b/include/llvm/CodeGen/LiveIntervalAnalysis.h
@@ -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
diff --git a/lib/CodeGen/LiveInterval.cpp b/lib/CodeGen/LiveInterval.cpp
index d75e4417cb0..3dc4113c639 100644
--- a/lib/CodeGen/LiveInterval.cpp
+++ b/lib/CodeGen/LiveInterval.cpp
@@ -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.
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index ee7c1d30315..9738dac65ad 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -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;
diff --git a/lib/CodeGen/MachineVerifier.cpp b/lib/CodeGen/MachineVerifier.cpp
index ca35ec5fdcf..a5e5bc992ef 100644
--- a/lib/CodeGen/MachineVerifier.cpp
+++ b/lib/CodeGen/MachineVerifier.cpp
@@ -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))
--
2.34.1