Let shrinkToUses optionally return a list of now dead machine instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127192 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 9 insertions, 2 deletions

diff --git a/include/llvm/CodeGen/LiveIntervalAnalysis.h b/include/llvm/CodeGen/LiveIntervalAnalysis.h
index b09f8d1110..1391f0f95b 100644
--- a/include/llvm/CodeGen/LiveIntervalAnalysis.h
+++ b/include/llvm/CodeGen/LiveIntervalAnalysis.h
@@ -159,7 +159,9 @@ namespace llvm {
     /// range to just the remaining uses. This method does not compute reaching
     /// defs for new uses, and it doesn't remove dead defs.
     /// Dead PHIDef values are marked as unused.
-    void shrinkToUses(LiveInterval *li);
+    /// New dead machine instructions are added to the dead vector.
+    void shrinkToUses(LiveInterval *li,
+                      SmallVectorImpl<MachineInstr*> *dead = 0);
 
     // Interval removal
 
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 4dda548548..8a2db3e1a3 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -746,7 +746,8 @@ LiveInterval* LiveIntervals::dupInterval(LiveInterval *li) {
 /// shrinkToUses - After removing some uses of a register, shrink its live
 /// range to just the remaining uses. This method does not compute reaching
 /// defs for new uses, and it doesn't remove dead defs.
-void LiveIntervals::shrinkToUses(LiveInterval *li) {
+void LiveIntervals::shrinkToUses(LiveInterval *li,
+                                 SmallVectorImpl<MachineInstr*> *dead) {
   DEBUG(dbgs() << "Shrink: " << *li << '\n');
   assert(TargetRegisterInfo::isVirtualRegister(li->reg)
          && "Can't only shrink physical registers");
@@ -852,6 +853,10 @@ void LiveIntervals::shrinkToUses(LiveInterval *li) {
       MachineInstr *MI = getInstructionFromIndex(VNI->def);
       assert(MI && "No instruction defining live value");
       MI->addRegisterDead(li->reg, tri_);
+      if (dead && MI->allDefsAreDead()) {
+        DEBUG(dbgs() << "All defs dead: " << *MI);
+        dead->push_back(MI);
+      }
     }
   }