Process two 32-bit digits as one 64-bit digit in all bigint intrinsics on ARM64.

runtime/vm/disassembler_arm64.cc

 // Copyright (c) 2014, 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/disassembler.h"
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_ARM64.
 #if defined(TARGET_ARCH_ARM64)
 #include "platform/assert.h"
 
@@ skipping 1043 matching lines @@
       Unknown(instr);
       break;
   }
 }
 
 
 void ARM64Decoder::DecodeMiscDP3Source(Instr* instr) {
   if ((instr->Bits(29, 2) == 0) && (instr->Bits(21, 3) == 0) &&
       (instr->Bit(15) == 0)) {
     if (instr->RaField() == R31) {
-      Format(instr, "mul'sf, 'rd, 'rn, 'rm");
+      Format(instr, "mul'sf 'rd, 'rn, 'rm");
     } else {
       Format(instr, "madd'sf 'rd, 'rn, 'rm, 'ra");
     }
   } else if ((instr->Bits(29, 2) == 0) && (instr->Bits(21, 3) == 0) &&
              (instr->Bit(15) == 1)) {
     Format(instr, "msub'sf 'rd, 'rn, 'rm, 'ra");
   } else if ((instr->Bits(29, 2) == 0) && (instr->Bits(21, 3) == 2) &&
              (instr->Bit(15) == 0)) {
     Format(instr, "smulh 'rd, 'rn, 'rm");
+  } else if ((instr->Bits(29, 2) == 0) && (instr->Bits(21, 3) == 6) &&
+             (instr->Bit(15) == 0)) {
+    Format(instr, "umulh 'rd, 'rn, 'rm");
   } else if ((instr->Bits(29, 3) == 4) && (instr->Bits(21, 3) == 5) &&
              (instr->Bit(15) == 0)) {
     Format(instr, "umaddl 'rd, 'rn, 'rm, 'ra");
   } else {
     Unknown(instr);
   }
 }
 
 
 void ARM64Decoder::DecodeConditionalSelect(Instr* instr) {
@@ skipping 347 matching lines @@
   int32_t instruction_bits = Instr::At(pc)->InstructionBits();
   OS::SNPrint(hex_buffer, hex_size, "%08x", instruction_bits);
   if (out_instr_size) {
     *out_instr_size = Instr::kInstrSize;
   }
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM