unaligned memory access support for ARMv7

src/arm/regexp-macro-assembler-arm.cc

 // Copyright 2009 the V8 project authors. 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.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1192 matching lines @@
 }
 
 
 void RegExpMacroAssemblerARM::LoadCurrentCharacterUnchecked(int cp_offset,
                                                             int characters) {
   Register offset = current_input_offset();
   if (cp_offset != 0) {
     __ add(r0, current_input_offset(), Operand(cp_offset * char_size()));
     offset = r0;
   }
-  // We assume that we cannot do unaligned loads on ARM, so this function
-  // must only be used to load a single character at a time.
+  // LDR, STR, LDRH, STRH instructions in ARMv7 can do unaligned accesses,
+  // if the Operating system running on the target allows so.
+  // Unaligned load/stores are not supported for pre-ARMv7 ISAs. Then
+  // this function must only be used to load a single character at a time.
+#if !V8_TARGET_CAN_READ_UNALIGNED
   ASSERT(characters == 1);
+#endif
+
   if (mode_ == ASCII) {
-    __ ldrb(current_character(), MemOperand(end_of_input_address(), offset));
+    if (characters == 4) {
+      __ ldr(current_character(), MemOperand(end_of_input_address(), offset));
+    } else if (characters == 2) {
+      __ ldrh(current_character(), MemOperand(end_of_input_address(), offset));
+    } else {
+      ASSERT(characters == 1);
+      __ ldrb(current_character(), MemOperand(end_of_input_address(), offset));
+    }
   } else {
     ASSERT(mode_ == UC16);
-    __ ldrh(current_character(), MemOperand(end_of_input_address(), offset));
+    if (characters == 2) {
+      __ ldr(current_character(), MemOperand(end_of_input_address(), offset));
+    } else {
+      ASSERT(characters == 1);
+      __ ldrh(current_character(), MemOperand(end_of_input_address(), offset));
+    }
   }
 }
 
 
 void RegExpCEntryStub::Generate(MacroAssembler* masm_) {
   int stack_alignment = OS::ActivationFrameAlignment();
   if (stack_alignment < kPointerSize) stack_alignment = kPointerSize;
   // Stack is already aligned for call, so decrement by alignment
   // to make room for storing the link register.
   __ str(lr, MemOperand(sp, stack_alignment, NegPreIndex));
   __ mov(r0, sp);
   __ Call(r5);
   __ ldr(pc, MemOperand(sp, stack_alignment, PostIndex));
 }
 
 #undef __
 
 #endif  // V8_INTERPRETED_REGEXP
 
 }}  // namespace v8::internal