Add some support for iterative coalescers to calculate a joined live

range's weight properly.  This is turned off right now in the sense that
you'll get an assert if you get into a situation that can only be caused
by an iterative coalescer.  All other code paths operate exactly as
before so there is no functional change with this patch.  The asserts
should be disabled if/when an iterative coalescer gets added to trunk.

llvm-svn: 76680

1 files changed, 17 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/LiveInterval.cpp b/llvm/lib/CodeGen/LiveInterval.cpp
index b786b1d85b0..0d2f6ba76a7 100644
--- a/llvm/lib/CodeGen/LiveInterval.cpp
+++ b/llvm/lib/CodeGen/LiveInterval.cpp
@@ -503,7 +503,23 @@ void LiveInterval::join(LiveInterval &Other, const int *LHSValNoAssignments,
     InsertPos = addRangeFrom(*I, InsertPos);
   }
 
-  weight += Other.weight;
+  // If either of these intervals was spilled, the weight is the
+  // weight of the non-spilled interval.  This can only happen with
+  // iterative coalescers.
+
+  if (weight == HUGE_VALF && !TargetRegisterInfo::isPhysicalRegister(reg)) {
+    // Remove this assert if you have an iterative coalescer
+    assert(0 && "Joining to spilled interval");
+    weight = Other.weight;
+  }
+  else if (Other.weight != HUGE_VALF) {
+    weight += Other.weight;
+  }
+  else {
+    // Remove this assert if you have an iterative coalescer
+    assert(0 && "Joining from spilled interval");
+  }
+  // Otherwise the weight stays the same
 
   // Update regalloc hint if currently there isn't one.
   if (TargetRegisterInfo::isVirtualRegister(reg) &&