Fix overflow check when shifting unboxed mints on 32-bit platforms, except on

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 6050 matching lines @@
         }
         break;
       }
       case Token::kSHL: {
         if (can_overflow()) {
           Register temp1 = locs()->temp(0).reg();
           Register temp2 = locs()->temp(1).reg();
           __ movl(temp1, left_hi);  // Preserve high 32 bits.
           if (shift > 31) {
             __ movl(left_hi, left_lo);  // Shift by 32.
-            __ xorl(left_lo, left_lo);  // Zero left_lo.
             if (shift > 32) {
               __ shll(left_hi, Immediate(shift - 32));
             }
             // Check for overflow by sign extending the high 32 bits
             // and comparing with the input.
             __ movl(temp2, left_hi);
             __ sarl(temp2, Immediate(31));
             __ cmpl(temp1, temp2);
             __ j(NOT_EQUAL, deopt);
+            if (shift > 32) {
+              // Also compare low word from input with high word from
+              // output shifted back shift - 32.
+              __ movl(temp2, left_hi);
+              __ sarl(temp2, Immediate(shift - 32));
+              __ cmpl(left_lo, temp2);
+              __ j(NOT_EQUAL, deopt);
+            }
+            __ xorl(left_lo, left_lo);  // Zero left_lo.
           } else {
             __ shldl(left_hi, left_lo, Immediate(shift));
             __ shll(left_lo, Immediate(shift));
             // Check for overflow by shifting back the high 32 bits
             // and comparing with the input.
             __ movl(temp2, left_hi);
             __ sarl(temp2, Immediate(shift));
             __ cmpl(temp1, temp2);
             __ j(NOT_EQUAL, deopt);
           }
@@ skipping 55 matching lines @@
           // and comparing with the input.
           __ movl(temp2, left_hi);
           __ sarl(temp2, ECX);
           __ cmpl(temp1, temp2);
           __ j(NOT_EQUAL, deopt);
           __ jmp(&done, Assembler::kNearJump);
 
           __ Bind(&large_shift);
           // No need to subtract 32 from CL, only 5 bits used by shll.
           __ movl(left_hi, left_lo);  // Shift by 32.
-          __ xorl(left_lo, left_lo);  // Zero left_lo.
           __ shll(left_hi, ECX);  // Shift count: CL % 32.
           // Check for overflow by sign extending the high 32 bits
           // and comparing with the input.
           __ movl(temp2, left_hi);
           __ sarl(temp2, Immediate(31));
           __ cmpl(temp1, temp2);
           __ j(NOT_EQUAL, deopt);
+          // Also compare low word from input with high word from
+          // output shifted back shift - 32.
+          __ movl(temp2, left_hi);
+          __ sarl(temp2, ECX);  // Shift count: CL % 32.
+          __ cmpl(left_lo, temp2);
+          __ j(NOT_EQUAL, deopt);
+          __ xorl(left_lo, left_lo);  // Zero left_lo.
         } else {
           __ cmpl(ECX, Immediate(31));
           __ j(ABOVE, &large_shift);
 
           __ shldl(left_hi, left_lo);  // Shift count in CL.
           __ shll(left_lo, ECX);  // Shift count in CL.
           __ jmp(&done, Assembler::kNearJump);
 
           __ Bind(&large_shift);
           // No need to subtract 32 from CL, only 5 bits used by shll.
@@ skipping 612 matching lines @@
 #if defined(DEBUG)
   __ movl(EDX, Immediate(kInvalidObjectPointer));
 #endif
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_IA32