Use the iOS ABI when running SIMARM on Mac or targeting iOS.

runtime/vm/simulator_arm.cc

Index: runtime/vm/simulator_arm.cc
diff --git a/runtime/vm/simulator_arm.cc b/runtime/vm/simulator_arm.cc
index c7e7b20db6e41711671c0e810168a2780b64946b..f3664d7e74fd29ee69e4d81e3bb91f00f297ebf4 100644
--- a/runtime/vm/simulator_arm.cc
+++ b/runtime/vm/simulator_arm.cc
@@ -145,7 +145,7 @@ static Register LookupCpuRegisterByName(const char* name) {
       R8,  R9,  R10, R11,
       R12, R13, R14, R15,
       PC,  LR,  SP,  IP,
-      FP,  R10, R9
+      FP,  PP,  CTX
   };
   ASSERT(ARRAY_SIZE(kNames) == ARRAY_SIZE(kRegisters));
   for (unsigned i = 0; i < ARRAY_SIZE(kNames); i++) {
@@ -3735,7 +3735,9 @@ int64_t Simulator::Call(int32_t entry,
   int32_t r6_val = get_register(R6);
   int32_t r7_val = get_register(R7);
   int32_t r8_val = get_register(R8);
+#if !defined(TARGET_OS_MACOS)
   int32_t r9_val = get_register(R9);
+#endif
   int32_t r10_val = get_register(R10);
   int32_t r11_val = get_register(R11);
 
@@ -3767,7 +3769,9 @@ int64_t Simulator::Call(int32_t entry,
   set_register(R6, callee_saved_value);
   set_register(R7, callee_saved_value);
   set_register(R8, callee_saved_value);
+#if !defined(TARGET_OS_MACOS)
   set_register(R9, callee_saved_value);
+#endif
   set_register(R10, callee_saved_value);
   set_register(R11, callee_saved_value);
 
@@ -3793,7 +3797,9 @@ int64_t Simulator::Call(int32_t entry,
   ASSERT(callee_saved_value == get_register(R6));
   ASSERT(callee_saved_value == get_register(R7));
   ASSERT(callee_saved_value == get_register(R8));
+#if !defined(TARGET_OS_MACOS)
   ASSERT(callee_saved_value == get_register(R9));
+#endif
   ASSERT(callee_saved_value == get_register(R10));
   ASSERT(callee_saved_value == get_register(R11));
 
@@ -3814,7 +3820,9 @@ int64_t Simulator::Call(int32_t entry,
   set_register(R6, r6_val);
   set_register(R7, r7_val);
   set_register(R8, r8_val);
+#if !defined(TARGET_OS_MACOS)
   set_register(R9, r9_val);
+#endif
   set_register(R10, r10_val);
   set_register(R11, r11_val);