Use the i12 variant of load / store opcodes if offset is zero. Now we pass all of multisource as well.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77939 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/Thumb2InstrInfo.cpp b/lib/Target/ARM/Thumb2InstrInfo.cpp
index f56fc2b..cf2d099 100644
--- a/lib/Target/ARM/Thumb2InstrInfo.cpp
+++ b/lib/Target/ARM/Thumb2InstrInfo.cpp
@@ -421,8 +421,12 @@
       if (AddrMode == ARMII::AddrMode5)
         // FIXME: Not consistent.
         ImmedOffset |= 1 << NumBits;
-      else
+      else {
         ImmedOffset = -ImmedOffset;
+        if (ImmedOffset == 0)
+          // Change the opcode back if the encoded offset is zero.
+          MI.setDesc(TII.get(positiveOffsetOpcode(NewOpc)));
+      }
     }
     ImmOp.ChangeToImmediate(ImmedOffset);
     Offset &= ~(Mask*Scale);