[llvm-commits] [llvm] r146428 - in /llvm/trunk/lib/CodeGen: InlineSpiller.cpp LiveRangeEdit.cpp LiveRangeEdit.h

[Pete Cooper]

Author: pete
Date: Mon Dec 12 16:16:27 2011
New Revision: 146428

URL: http://llvm.org/viewvc/llvm-project?rev=146428&view=rev
Log:
Fixed register allocator splitting a live range on a spilling variable.

If we create new intervals for a variable that is being spilled, then those new intervals are not guaranteed to also spill.  This means that anything reading from the original spilling value might not get the correct value if spills were missed.

Fixes <rdar://problem/10546864>

Modified:
    llvm/trunk/lib/CodeGen/InlineSpiller.cpp
    llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp
    llvm/trunk/lib/CodeGen/LiveRangeEdit.h

Modified: llvm/trunk/lib/CodeGen/InlineSpiller.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/InlineSpiller.cpp?rev=146428&r1=146427&r2=146428&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/InlineSpiller.cpp (original)
+++ llvm/trunk/lib/CodeGen/InlineSpiller.cpp Mon Dec 12 16:16:27 2011
@@ -957,7 +957,7 @@
   if (DeadDefs.empty())
     return;
   DEBUG(dbgs() << "Remat created " << DeadDefs.size() << " dead defs.\n");
-  Edit->eliminateDeadDefs(DeadDefs, LIS, VRM, TII);
+  Edit->eliminateDeadDefs(DeadDefs, LIS, VRM, TII, RegsToSpill);
 
   // Get rid of deleted and empty intervals.
   for (unsigned i = RegsToSpill.size(); i != 0; --i) {
@@ -1240,7 +1240,7 @@
   // Hoisted spills may cause dead code.
   if (!DeadDefs.empty()) {
     DEBUG(dbgs() << "Eliminating " << DeadDefs.size() << " dead defs\n");
-    Edit->eliminateDeadDefs(DeadDefs, LIS, VRM, TII);
+    Edit->eliminateDeadDefs(DeadDefs, LIS, VRM, TII, RegsToSpill);
   }
 
   // Finally delete the SnippetCopies.

Modified: llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp?rev=146428&r1=146427&r2=146428&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp (original)
+++ llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp Mon Dec 12 16:16:27 2011
@@ -210,7 +210,8 @@
 
 void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
                                       LiveIntervals &LIS, VirtRegMap &VRM,
-                                      const TargetInstrInfo &TII) {
+                                      const TargetInstrInfo &TII,
+                                      ArrayRef<unsigned> RegsBeingSpilled) {
   SetVector<LiveInterval*,
             SmallVector<LiveInterval*, 8>,
             SmallPtrSet<LiveInterval*, 8> > ToShrink;
@@ -290,6 +291,21 @@
       delegate_->LRE_WillShrinkVirtReg(LI->reg);
     if (!LIS.shrinkToUses(LI, &Dead))
       continue;
+    
+    // Don't create new intervals for a register being spilled.
+    // The new intervals would have to be spilled anyway so its not worth it.
+    // Also they currently aren't spilled so creating them and not spilling
+    // them results in incorrect code.
+    bool BeingSpilled = false;
+    for (unsigned i = 0, e = RegsBeingSpilled.size(); i != e; ++i) {
+      if (LI->reg == RegsBeingSpilled[i]) {
+        BeingSpilled = true;
+        break;
+      }
+    }
+    
+    if (BeingSpilled) continue;
+    
 
     // LI may have been separated, create new intervals.
     LI->RenumberValues(LIS);

Modified: llvm/trunk/lib/CodeGen/LiveRangeEdit.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveRangeEdit.h?rev=146428&r1=146427&r2=146428&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LiveRangeEdit.h (original)
+++ llvm/trunk/lib/CodeGen/LiveRangeEdit.h Mon Dec 12 16:16:27 2011
@@ -191,9 +191,14 @@
   /// eliminateDeadDefs - Try to delete machine instructions that are now dead
   /// (allDefsAreDead returns true). This may cause live intervals to be trimmed
   /// and further dead efs to be eliminated.
+  /// RegsBeingSpilled lists registers currently being spilled by the register
+  /// allocator.  These registers should not be split into new intervals
+  /// as currently those new intervals are not guaranteed to spill.
   void eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
                          LiveIntervals&, VirtRegMap&,
-                         const TargetInstrInfo&);
+                         const TargetInstrInfo&,
+                         ArrayRef<unsigned> RegsBeingSpilled 
+                          = ArrayRef<unsigned>());
 
   /// calculateRegClassAndHint - Recompute register class and hint for each new
   /// register.