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%.

llvm-svn: 47046

1 files changed, 8 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SimpleRegisterCoalescing.h b/llvm/lib/CodeGen/SimpleRegisterCoalescing.h
index 1120fb3d05c..32a44da3d89 100644
--- a/llvm/lib/CodeGen/SimpleRegisterCoalescing.h
+++ b/llvm/lib/CodeGen/SimpleRegisterCoalescing.h
@@ -80,6 +80,7 @@ namespace llvm {
   class SimpleRegisterCoalescing : public MachineFunctionPass,
                                    public RegisterCoalescer {
     MachineFunction* mf_;
+    const MachineRegisterInfo* mri_;
     const TargetMachine* tm_;
     const TargetRegisterInfo* tri_;
     const TargetInstrInfo* tii_;
@@ -114,6 +115,9 @@ namespace llvm {
     ///
     SmallPtrSet<MachineInstr*, 32> JoinedCopies;
 
+    /// ChangedCopies - Keep track of copies modified due to commuting.
+    SmallPtrSet<MachineInstr*, 32> ChangedCopies;
+
   public:
     static char ID; // Pass identifcation, replacement for typeid
     SimpleRegisterCoalescing() : MachineFunctionPass((intptr_t)&ID) {}
@@ -168,7 +172,7 @@ namespace llvm {
     /// if the copy was successfully coalesced away. If it is not currently
     /// possible to coalesce this interval, but it may be possible if other
     /// things get coalesced, then it returns true by reference in 'Again'.
-    bool JoinCopy(CopyRec TheCopy, bool &Again);
+    bool JoinCopy(CopyRec &TheCopy, bool &Again);
     
     /// JoinIntervals - Attempt to join these two intervals.  On failure, this
     /// returns false.  Otherwise, if one of the intervals being joined is a
@@ -192,6 +196,9 @@ namespace llvm {
     bool AdjustCopiesBackFrom(LiveInterval &IntA, LiveInterval &IntB,
                               MachineInstr *CopyMI);
 
+    bool RemoveCopyByCommutingDef(LiveInterval &IntA, LiveInterval &IntB,
+                                  MachineInstr *CopyMI);
+
     /// AddSubRegIdxPairs - Recursively mark all the registers represented by the
     /// specified register as sub-registers. The recursion level is expected to be
     /// shallow.