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

diff --git a/include/llvm/CodeGen/LiveIntervalAnalysis.h b/include/llvm/CodeGen/LiveIntervalAnalysis.h
index 70c3b8d57724033e4283c8872fae7cf96e1a8e07..47ba1ff0454289181c1ddfb45bc10bc466715c32 100644 (file)
--- 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 d75e4417cb0366f0bc492881d5e0fff5e2b33e2e..3dc4113c6396854ca37afbac8f79b7c4b468584c 100644 (file)
--- 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 ee7c1d303153ba6dd221e657b2c0d1edf7b27950..9738dac65ad8e6fa351f4809d92930ffb5ae9caa 100644 (file)
--- 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 ca35ec5fdcf8238e243122b1351777f0b55c4cec..a5e5bc992ef95516d98b22b58c0dd7d807cdd322 100644 (file)
--- 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))