Initial support for copy elimination by commuting its definition MI.

PR1877.
A3 = op A2 B0<kill>                                                                                                                                                                            
...                                                                                                                                                                                     
B1 = A3      <- this copy                                                                                                                                                                      
...                                                                                                                                                                                          
   = op A3   <- more uses                                                                                                                                                                      
                                                                                                                                                                                                 
==>                                                                                                                                                                                             
                                                                                                                                                                                            
B2 = op B0 A2<kill>                                                                                                                                                                            
...                                                                                                                                                                                          
B1 = B2      <- now an identify copy                                                                                                                                                           
...                                                                                                                                                                                          
   = op B2   <- more uses

This speeds up FreeBench/neural by 29%, Olden/bh by 12%, oopack_v1p8 by 53%.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47046 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 0 deletions

diff --git a/include/llvm/CodeGen/LiveIntervalAnalysis.h b/include/llvm/CodeGen/LiveIntervalAnalysis.h
index 34a05ffc7a..6bc02526a3 100644
--- a/include/llvm/CodeGen/LiveIntervalAnalysis.h
+++ b/include/llvm/CodeGen/LiveIntervalAnalysis.h
@@ -213,6 +213,20 @@ namespace llvm {
       }
     }
 
+    /// ReplaceMachineInstrInMaps - Replacing a machine instr with a new one in
+    /// maps used by register allocator.
+    void ReplaceMachineInstrInMaps(MachineInstr *MI, MachineInstr *NewMI) {
+      Mi2IndexMap::iterator mi2i = mi2iMap_.find(MI);
+      if (mi2i != mi2iMap_.end()) {
+        i2miMap_[mi2i->second/InstrSlots::NUM] = NewMI;
+        Mi2IndexMap::const_iterator it = mi2iMap_.find(MI);
+        assert(it != mi2iMap_.end() && "Invalid instruction!");
+        unsigned Index = it->second;
+        mi2iMap_.erase(MI);
+        mi2iMap_[NewMI] = Index;
+      }
+    }
+
     BumpPtrAllocator& getVNInfoAllocator() { return VNInfoAllocator; }
 
     virtual void getAnalysisUsage(AnalysisUsage &AU) const;