unaligned memory access support for ARMv7

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

Index: src/arm/regexp-macro-assembler-arm.cc
===================================================================
--- src/arm/regexp-macro-assembler-arm.cc	(revision 4519)
+++ src/arm/regexp-macro-assembler-arm.cc	(working copy)
@@ -1210,14 +1210,31 @@
     __ 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));
+    }
   }
 }