Make arm assembler explicitly take both registers for load/store-pair.

runtime/vm/assembler_arm.h

Index: runtime/vm/assembler_arm.h
diff --git a/runtime/vm/assembler_arm.h b/runtime/vm/assembler_arm.h
index 9ba279c5f571b57fc2a9cf5b28587524ea05d3fa..9c602a62d5c2791e5a26f7801d1dec3c19adf81a 100644
--- a/runtime/vm/assembler_arm.h
+++ b/runtime/vm/assembler_arm.h
@@ -513,8 +513,10 @@ class Assembler : public ValueObject {
   // ldrd and strd actually support the full range of addressing modes, but
   // we don't use them, and we need to split them up into two instructions for
   // ARMv5TE, so we only support the base + offset mode.

[zra, 2015/10/23 03:48:44]

Maybe add a comment about the restrictions on rd and rd2.

[rmacnak, 2015/10/23 16:29:03]

Added

-  void ldrd(Register rd, Register rn, int32_t offset, Condition cond = AL);
-  void strd(Register rd, Register rn, int32_t offset, Condition cond = AL);
+  void ldrd(Register rd, Register rd2, Register rn, int32_t offset,
+            Condition cond = AL);
+  void strd(Register rd, Register rd2, Register rn, int32_t offset,
+            Condition cond = AL);
 
   void ldm(BlockAddressMode am, Register base,
            RegList regs, Condition cond = AL);