PPC: protect against malformed branch and memory access instructions.

src/ppc/assembler-ppc-inl.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions
 // are met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 579 matching lines @@
   }
   return offset;
 }
 
 
 void Assembler::PatchConstantPoolAccessInstruction(
     int pc_offset, int offset, ConstantPoolEntry::Access access,
     ConstantPoolEntry::Type type) {
   Address pc = buffer_ + pc_offset;
   bool overflowed = (access == ConstantPoolEntry::OVERFLOWED);
+  CHECK(overflowed != is_int16(offset));
 #ifdef DEBUG
   ConstantPoolEntry::Access access_check =
       static_cast<ConstantPoolEntry::Access>(-1);
   DCHECK(IsConstantPoolLoadStart(pc, &access_check));
   DCHECK(access_check == access);
-  DCHECK(overflowed != is_int16(offset));
 #endif
   if (overflowed) {
     int hi_word = static_cast<int>(offset >> 16);
     int lo_word = static_cast<int>(offset & 0xffff);
     if (lo_word & 0x8000) hi_word++;
 
     Instr instr1 = instr_at(pc);
     Instr instr2 = instr_at(pc + kInstrSize);
     instr1 &= ~kImm16Mask;
     instr1 |= (hi_word & kImm16Mask);
@@ skipping 105 matching lines @@
     }
 #endif
     return;
   }
   UNREACHABLE();
 }
 }
 }  // namespace v8::internal
 
 #endif  // V8_PPC_ASSEMBLER_PPC_INL_H_