Clobber non-live temporaries on some paths involving a possible slow-path allocation.

runtime/vm/intermediate_language_arm.cc

Index: runtime/vm/intermediate_language_arm.cc
diff --git a/runtime/vm/intermediate_language_arm.cc b/runtime/vm/intermediate_language_arm.cc
index 4a53bf031356c89dac1e4b0afa7544867a6e49e6..5f7c5838f5c82230d5d47116f9c8a9a9556b75da 100644
--- a/runtime/vm/intermediate_language_arm.cc
+++ b/runtime/vm/intermediate_language_arm.cc
@@ -1953,6 +1953,9 @@ void LoadCodeUnitsInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
       // If the value cannot fit in a smi then allocate a mint box for it.
       Register value = locs()->temp(0).reg();
       Register temp = locs()->temp(1).reg();
+      // Value register needs to be manually preserved on allocation slow-path.
+      locs()->live_registers()->Add(locs()->temp(0), kUnboxedInt32);
+
       ASSERT(result != value);
       __ MoveRegister(value, result);
       __ SmiTag(result);
@@ -2133,6 +2136,9 @@ void StoreInstanceFieldInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
         locs()->live_registers()->Add(locs()->in(1));
     }
 
+    // Manually preserve temp which could be clobbered on the slow path.
+    locs()->live_registers()->Add(locs()->temp(0));
+
     {
       __ Bind(&store_double);
       EnsureMutableBox(compiler,