Teach ConnectedVNInfoEqClasses::Classify to deal with unused values.

We don't want unused values forming their own equivalence classes, so we lump
them all together in one class, and then merge them with the class of the last
used value.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117670 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/LiveInterval.cpp b/lib/CodeGen/LiveInterval.cpp
index 27a572c0ea75713aa40cf7530ff875a7a22717b9..3c18017f3fc3c442c50f86ba5844dcff94780952 100644 (file)
--- a/lib/CodeGen/LiveInterval.cpp
+++ b/lib/CodeGen/LiveInterval.cpp
@@ -740,11 +740,20 @@ unsigned ConnectedVNInfoEqClasses::Classify(const LiveInterval *LI) {
   for (unsigned i = 0, e = LI->getNumValNums(); i != e; ++i)
     eqClass_.push_back(i);
 
+  const VNInfo *used = 0, *unused = 0;
+
   // Determine connections.
   for (LiveInterval::const_vni_iterator I = LI->vni_begin(), E = LI->vni_end();
        I != E; ++I) {
     const VNInfo *VNI = *I;
-    assert(!VNI->isUnused() && "Cannot handle unused values");
+    // Group all unused values into one class.
+    if (VNI->isUnused()) {
+      if (unused)
+        Connect(unused->id, VNI->id);
+      unused = VNI;
+      continue;
+    }
+    used = VNI;
     if (VNI->isPHIDef()) {
       const MachineBasicBlock *MBB = lis_.getMBBFromIndex(VNI->def);
       assert(MBB && "Phi-def has no defining MBB");
@@ -762,6 +771,11 @@ unsigned ConnectedVNInfoEqClasses::Classify(const LiveInterval *LI) {
         Connect(VNI->id, UVNI->id);
     }
   }
+
+  // Lump all the unused values in with the last used value.
+  if (used && unused)
+    Connect(used->id, unused->id);
+
   return Renumber();
 }