VM: Support phis with pair representations.

runtime/vm/intermediate_language_arm.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_ARM.
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/cpu.h"
@@ skipping 6203 matching lines @@
         reinterpret_cast<int32_t>(locs()->in(1).constant().raw()) >> 1;
     switch (op_kind()) {
       case Token::kSHR: {
         if (shift < 32) {
           __ Lsl(out_lo, left_hi, Operand(32 - shift));
           __ orr(out_lo, out_lo, Operand(left_lo, LSR, shift));
           __ Asr(out_hi, left_hi, Operand(shift));
         } else {
           if (shift == 32) {
             __ mov(out_lo, Operand(left_hi));
+          } else if (shift < 64) {
+            __ Asr(out_lo, left_hi, Operand(shift - 32));
           } else {
-            __ Asr(out_lo, left_hi, Operand(shift - 32));
+            __ Asr(out_lo, left_hi, Operand(31));

[regis, 2015/10/06 17:37:24]

The fix looks good if the constant right shift amount can really be >= 64.

[Florian Schneider, 2015/10/07 09:44:11]

Yes, the regression test shows that this can be the case. The result of such an
operation is either 0 or -1, so no need to deoptimize.

           }
           __ Asr(out_hi, left_hi, Operand(31));
         }
         break;
       }
       case Token::kSHL: {
         if (shift < 32) {
           __ Lsr(out_hi, left_lo, Operand(32 - shift));
           __ orr(out_hi, out_hi, Operand(left_hi, LSL, shift));
           __ Lsl(out_lo, left_lo, Operand(shift));
         } else {
           if (shift == 32) {
             __ mov(out_hi, Operand(left_lo));
           } else {
             __ Lsl(out_hi, left_lo, Operand(shift - 32));

[regis, 2015/10/06 17:37:24]

If the constant left shift amount can be >= 64, this needs fixing too.

[Florian Schneider, 2015/10/07 09:44:11]

For left shift the result woud be a bigint in this case.  So we insert a
deoptimize-instructions in the optimizer and won't inline the mint-code next
time. (instead call the operator from IntegerImplementation)

           }
           __ mov(out_lo, Operand(0));
         }
         // Check for overflow.
         if (can_overflow()) {
           // Compare high word from input with shifted high word from output.
           // If shift > 32, also compare low word from input with high word from
           // output shifted back shift - 32.
           if (shift > 32) {
             __ cmp(left_lo, Operand(out_hi, ASR, shift - 32));

[regis, 2015/10/06 17:37:24]

ditto

             __ cmp(left_hi, Operand(out_hi, ASR, 31), EQ);
           } else if (shift == 32) {
             __ cmp(left_hi, Operand(out_hi, ASR, 31));
           } else {
             __ cmp(left_hi, Operand(out_hi, ASR, shift));
           }
           // Overflow if they aren't equal.
           __ b(deopt, NE);
         }
         break;
@@ skipping 596 matching lines @@
                                 1,
                                 locs());
   __ Drop(1);
   __ Pop(result);
 }
 
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM