Add CoalescerPair helper class.

Given a copy instruction, CoalescerPair can determine which registers to
coalesce in order to eliminate the copy. It deals with all the subreg fun to
determine a tuple (DstReg, SrcReg, SubIdx) such that:

- SrcReg is a virtual register that will disappear after coalescing.
- DstReg is a virtual or physical register whose live range will be extended.
- SubIdx is 0 when DstReg is a physical register.
- SrcReg can be joined with DstReg:SubIdx.

CoalescerPair::isCoalescable() determines if another copy instruction is
compatible with the same tuple. This fixes some NEON miscompilations where
shuffles are getting coalesced as if they were copies.

The CoalescerPair class will replace a lot of the spaghetti logic in JoinCopy
later.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@105997 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 7 deletions

diff --git a/lib/CodeGen/SimpleRegisterCoalescing.h b/lib/CodeGen/SimpleRegisterCoalescing.h
index 1be04f3..2f9c69c 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.h
+++ b/lib/CodeGen/SimpleRegisterCoalescing.h
@@ -111,14 +111,15 @@ namespace llvm {
     /// physreg, this method always canonicalizes DestInt to be it.  The output
     /// "SrcInt" will not have been modified, so we can use this information
     /// below to update aliases.
-    bool JoinIntervals(LiveInterval &LHS, LiveInterval &RHS, bool &Swapped);
+    bool JoinIntervals(LiveInterval &LHS, LiveInterval &RHS, bool &Swapped,
+                       CoalescerPair &CP);
     
     /// SimpleJoin - Attempt to join the specified interval into this one. The
     /// caller of this method must guarantee that the RHS only contains a single
     /// value number and that the RHS is not defined by a copy from this
     /// interval.  This returns false if the intervals are not joinable, or it
     /// joins them and returns true.
-    bool SimpleJoin(LiveInterval &LHS, LiveInterval &RHS);
+    bool SimpleJoin(LiveInterval &LHS, LiveInterval &RHS, CoalescerPair &CP);
     
     /// Return true if the two specified registers belong to different register
     /// classes.  The registers may be either phys or virt regs.
@@ -210,11 +211,10 @@ namespace llvm {
     bool ValueLiveAt(LiveInterval::iterator LRItr, LiveInterval::iterator LREnd, 
                      SlotIndex defPoint) const;                                  
 
-    /// RangeIsDefinedByCopyFromReg - Return true if the specified live range of
-    /// the specified live interval is defined by a copy from the specified
-    /// register.
-    bool RangeIsDefinedByCopyFromReg(LiveInterval &li, LiveRange *LR,
-                                     unsigned Reg);
+    /// RangeIsDefinedByCopy - Return true if the specified live range of the
+    /// specified live interval is defined by a coalescable copy.
+    bool RangeIsDefinedByCopy(LiveInterval &li, LiveRange *LR,
+                              CoalescerPair &CP);
 
     /// UpdateRegDefsUses - Replace all defs and uses of SrcReg to DstReg and
     /// update the subregister number if it is not zero. If DstReg is a