[llvm] r242431 - LiveInterval: Document and enforce rules about empty subranges.

[Matthias Braun]

Author: matze
Date: Thu Jul 16 13:55:35 2015
New Revision: 242431

URL: http://llvm.org/viewvc/llvm-project?rev=242431&view=rev
Log:
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.

Modified:
    llvm/trunk/include/llvm/CodeGen/LiveIntervalAnalysis.h
    llvm/trunk/lib/CodeGen/LiveInterval.cpp
    llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp
    llvm/trunk/lib/CodeGen/MachineVerifier.cpp

Modified: llvm/trunk/include/llvm/CodeGen/LiveIntervalAnalysis.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/LiveIntervalAnalysis.h?rev=242431&r1=242430&r2=242431&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/LiveIntervalAnalysis.h (original)
+++ llvm/trunk/include/llvm/CodeGen/LiveIntervalAnalysis.h Thu Jul 16 13:55:35 2015
@@ -160,6 +160,8 @@ extern cl::opt<bool> UseSegmentSetForPhy
     /// 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

Modified: llvm/trunk/lib/CodeGen/LiveInterval.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveInterval.cpp?rev=242431&r1=242430&r2=242431&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LiveInterval.cpp (original)
+++ llvm/trunk/lib/CodeGen/LiveInterval.cpp Thu Jul 16 13:55:35 2015
@@ -1110,6 +1110,8 @@ void LiveInterval::verify(const MachineR
 
     // 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.

Modified: llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp?rev=242431&r1=242430&r2=242431&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp (original)
+++ llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp Thu Jul 16 13:55:35 2015
@@ -403,9 +403,14 @@ bool LiveIntervals::shrinkToUses(LiveInt
          && "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;

Modified: llvm/trunk/lib/CodeGen/MachineVerifier.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineVerifier.cpp?rev=242431&r1=242430&r2=242431&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineVerifier.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineVerifier.cpp Thu Jul 16 13:55:35 2015
@@ -1671,6 +1671,8 @@ void MachineVerifier::verifyLiveInterval
       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))