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

runtime/vm/assembler_arm.cc

Index: runtime/vm/assembler_arm.cc
diff --git a/runtime/vm/assembler_arm.cc b/runtime/vm/assembler_arm.cc
index 815b7961c78196994ed2e23ab7eb39719fe789d1..31a188e58b9fbbc25fa45fc9b6fc6fb93ef3cfbe 100644
--- a/runtime/vm/assembler_arm.cc
+++ b/runtime/vm/assembler_arm.cc
@@ -493,10 +493,11 @@ void Assembler::ldrsh(Register rd, Address ad, Condition cond) {
 }
 
 
-void Assembler::ldrd(Register rd, Register rn, int32_t offset, Condition cond) {
+void Assembler::ldrd(Register rd, Register rd2, Register rn, int32_t offset,
+                     Condition cond) {
   ASSERT((rd % 2) == 0);
+  ASSERT(rd2 == rd + 1);
   if (TargetCPUFeatures::arm_version() == ARMv5TE) {
-    const Register rd2 = static_cast<Register>(static_cast<int32_t>(rd) + 1);
     ldr(rd, Address(rn, offset), cond);
     ldr(rd2, Address(rn, offset + kWordSize), cond);
   } else {
@@ -505,10 +506,11 @@ void Assembler::ldrd(Register rd, Register rn, int32_t offset, Condition cond) {
 }
 
 
-void Assembler::strd(Register rd, Register rn, int32_t offset, Condition cond) {
+void Assembler::strd(Register rd, Register rd2, Register rn, int32_t offset,
+                     Condition cond) {
   ASSERT((rd % 2) == 0);
+  ASSERT(rd2 == rd + 1);
   if (TargetCPUFeatures::arm_version() == ARMv5TE) {
-    const Register rd2 = static_cast<Register>(static_cast<int32_t>(rd) + 1);
     str(rd, Address(rn, offset), cond);
     str(rd2, Address(rn, offset + kWordSize), cond);
   } else {
@@ -1712,10 +1714,10 @@ void Assembler::WriteShadowedFieldPair(Register base,
     ASSERT(base != value_odd);
     Operand shadow(GetVerifiedMemoryShadow());
     add(base, base, shadow, cond);
-    strd(value_even, base, offset, cond);
+    strd(value_even, value_odd, base, offset, cond);
     sub(base, base, shadow, cond);
   }
-  strd(value_even, base, offset, cond);
+  strd(value_even, value_odd, base, offset, cond);
 }
 
 
@@ -2854,9 +2856,11 @@ void Assembler::LoadFromOffset(OperandSize size,
     case kWord:
       ldr(reg, Address(base, offset), cond);
       break;
-    case kWordPair:
-      ldrd(reg, base, offset, cond);
+    case kWordPair: {

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

To retain the benefits of passing both registers to ldrd, it might make sense to
split this case off into its own function, like LoadPairFromOffset(r1, r2, base,
offset, condition).

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

Deleted this case as it is unused.

+      Register reg2 = static_cast<Register>(static_cast<int32_t>(reg) + 1);
+      ldrd(reg, reg2, base, offset, cond);
       break;
+    }
     default:
       UNREACHABLE();
   }
@@ -2886,9 +2890,11 @@ void Assembler::StoreToOffset(OperandSize size,
     case kWord:
       str(reg, Address(base, offset), cond);
       break;
-    case kWordPair:
-      strd(reg, base, offset, cond);
+    case kWordPair: {

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

ditto

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

Deleted

+      Register reg2 = static_cast<Register>(static_cast<int32_t>(reg) + 1);
+      strd(reg, reg2, base, offset, cond);
       break;
+    }
     default:
       UNREACHABLE();
   }