[llvm-commits] [llvm] r127096 - in /llvm/trunk/lib/CodeGen: SplitKit.cpp SplitKit.h

[Jakob Stoklund Olesen]

Author: stoklund
Date: Sat Mar  5 12:33:49 2011
New Revision: 127096

URL: http://llvm.org/viewvc/llvm-project?rev=127096&view=rev
Log:
Work around a coalescer bug.

The coalescer can in very rare cases leave too large live intervals around after
rematerializing cheap-as-a-move instructions.

Linear scan doesn't really care, but live range splitting gets very confused
when a live range is killed by a ghost instruction.

I will fix this properly in the coalescer after 2.9 branches.

Modified:
    llvm/trunk/lib/CodeGen/SplitKit.cpp
    llvm/trunk/lib/CodeGen/SplitKit.h

Modified: llvm/trunk/lib/CodeGen/SplitKit.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SplitKit.cpp?rev=127096&r1=127095&r2=127096&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SplitKit.cpp (original)
+++ llvm/trunk/lib/CodeGen/SplitKit.cpp Sat Mar  5 12:33:49 2011
@@ -81,7 +81,20 @@
     UsingBlocks[MBB]++;
   }
   array_pod_sort(UseSlots.begin(), UseSlots.end());
-  calcLiveBlockInfo();
+
+  // Compute per-live block info.
+  if (!calcLiveBlockInfo()) {
+    // FIXME: calcLiveBlockInfo found inconsistencies in the live range.
+    // I am looking at you, SimpleRegisterCoalescing!
+    DEBUG(dbgs() << "*** Fixing inconsistent live interval! ***\n");
+    const_cast<LiveIntervals&>(LIS)
+      .shrinkToUses(const_cast<LiveInterval*>(CurLI));
+    LiveBlocks.clear();
+    bool fixed = calcLiveBlockInfo();
+    (void)fixed;
+    assert(fixed && "Couldn't fix broken live interval");
+  }
+
   DEBUG(dbgs() << "  counted "
                << UsingInstrs.size() << " instrs, "
                << UsingBlocks.size() << " blocks.\n");
@@ -89,9 +102,9 @@
 
 /// calcLiveBlockInfo - Fill the LiveBlocks array with information about blocks
 /// where CurLI is live.
-void SplitAnalysis::calcLiveBlockInfo() {
+bool SplitAnalysis::calcLiveBlockInfo() {
   if (CurLI->empty())
-    return;
+    return true;
 
   LiveInterval::const_iterator LVI = CurLI->begin();
   LiveInterval::const_iterator LVE = CurLI->end();
@@ -154,6 +167,11 @@
     BI.LiveThrough = !hasGap && BI.LiveIn && BI.LiveOut;
     LiveBlocks.push_back(BI);
 
+    // FIXME: This should never happen. The live range stops or starts without a
+    // corresponding use. An earlier pass did something wrong.
+    if (!BI.LiveThrough && !BI.Uses)
+      return false;
+
     // LVI is now at LVE or LVI->end >= Stop.
     if (LVI == LVE)
       break;
@@ -168,6 +186,7 @@
     else
       MFI = LIS.getMBBFromIndex(LVI->start);
   }
+  return true;
 }
 
 bool SplitAnalysis::isOriginalEndpoint(SlotIndex Idx) const {

Modified: llvm/trunk/lib/CodeGen/SplitKit.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SplitKit.h?rev=127096&r1=127095&r2=127096&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SplitKit.h (original)
+++ llvm/trunk/lib/CodeGen/SplitKit.h Sat Mar  5 12:33:49 2011
@@ -103,7 +103,7 @@
   void analyzeUses();
 
   /// calcLiveBlockInfo - Compute per-block information about CurLI.
-  void calcLiveBlockInfo();
+  bool calcLiveBlockInfo();
 
   /// canAnalyzeBranch - Return true if MBB ends in a branch that can be
   /// analyzed.