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

runtime/vm/intermediate_language_ia32.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_IA32.
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/dart_entry.h"
@@ skipping 1833 matching lines @@
     return;
   }
 
   if (IsPotentialUnboxedStore()) {
     __ Comment("PotentialUnboxedStore");
     Register value_reg = locs()->in(1).reg();
     Register temp = locs()->temp(0).reg();
     Register temp2 = locs()->temp(1).reg();
     FpuRegister fpu_temp = locs()->temp(2).fpu_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;
     Label store_float64x2;
 
     __ LoadObject(temp, Field::ZoneHandle(field().raw()));
 
     __ cmpl(FieldAddress(temp, Field::is_nullable_offset()),
             Immediate(kNullCid));
     __ j(EQUAL, &store_pointer);
@@ skipping 4592 matching lines @@
   Register out = locs()->out(0).reg();
 
   if (out != value) {
     __ movl(out, value);
   }
   __ shll(out, Immediate(1));
   if (!ValueFitsSmi()) {
     Label done;
     __ j(NO_OVERFLOW, &done);
     // Allocate a mint.
+    // Value input is writable register and has to be manually preserved
+    // on the slow path.
+    locs()->live_registers()->Add(locs()->in(0), kUnboxedInt32);
     BoxAllocationSlowPath::Allocate(
         compiler, this, compiler->mint_class(), out, kNoRegister);
     __ movl(FieldAddress(out, Mint::value_offset()), value);
     __ sarl(value, Immediate(31));  // Sign extend.
     __ movl(FieldAddress(out, Mint::value_offset() + kWordSize), value);
     __ Bind(&done);
   }
 }
 
 
@@ skipping 552 matching lines @@
   __ movl(EDX, Immediate(kInvalidObjectPointer));
   __ movl(EDX, Immediate(kInvalidObjectPointer));
 #endif
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_IA32