Ensure that BoxInt32 input is correctly preserved on the slow-path.

runtime/vm/intermediate_language_arm64.cc

Index: runtime/vm/intermediate_language_arm64.cc
diff --git a/runtime/vm/intermediate_language_arm64.cc b/runtime/vm/intermediate_language_arm64.cc
index 5fe4a782b71bf2db54d95b7d11ec73a2c67a1493..fa8908149b4958c32bc8926e0b502b4f9712a62a 100644
--- a/runtime/vm/intermediate_language_arm64.cc
+++ b/runtime/vm/intermediate_language_arm64.cc
@@ -1744,6 +1744,12 @@ void StoreInstanceFieldInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
     const Register temp = locs()->temp(0).reg();
     const Register temp2 = locs()->temp(1).reg();
 
+    if (ShouldEmitStoreBarrier()) {
+      // Value input is a writable register and should be manually preserved
+      // across allocation slow-path.
+      locs()->live_registers()->Add(locs()->in(1), kTagged);
+    }
+
     Label store_pointer;
     Label store_double;
     Label store_float32x4;