S390: Enable unaligned accesses and character preloading in regexp.

src/regexp/s390/regexp-macro-assembler-s390.cc

Index: src/regexp/s390/regexp-macro-assembler-s390.cc
diff --git a/src/regexp/s390/regexp-macro-assembler-s390.cc b/src/regexp/s390/regexp-macro-assembler-s390.cc
index d9ca1df3124c8c660f2ac8a41524c02d6d23f228..3b68c7b9a289e9184eb35d96fd2e8e51497bb085 100644
--- a/src/regexp/s390/regexp-macro-assembler-s390.cc
+++ b/src/regexp/s390/regexp-macro-assembler-s390.cc
@@ -1232,17 +1232,52 @@ bool RegExpMacroAssemblerS390::CanReadUnaligned() {
 
 void RegExpMacroAssemblerS390::LoadCurrentCharacterUnchecked(int cp_offset,
                                                              int characters) {
-  DCHECK(characters == 1);
+  DCHECK(characters == 1 || CanReadUnaligned());
   if (mode_ == LATIN1) {
-    __ LoadlB(current_character(),
-              MemOperand(current_input_offset(), end_of_input_address(),
-                         cp_offset * char_size()));
+    // using load reverse for endian issue

[john.yan, 2016/08/02 03:06:15]

There is no 'issue' here when using reversed load. An appropriate comment would
be "using load reverse for big-endian platform"

+    if (characters == 4) {
+#if V8_TARGET_LITTLE_ENDIAN
+      __ LoadlW(current_character(),
+                MemOperand(current_input_offset(), end_of_input_address(),
+                           cp_offset * char_size()));
+#else
+      __ LoadLogicalReversedWordP(current_character(),
+                MemOperand(current_input_offset(), end_of_input_address(),
+                           cp_offset * char_size()));
+#endif
+    } else if (characters == 2) {
+#if V8_TARGET_LITTLE_ENDIAN
+      __ LoadLogicalHalfWordP(current_character(),
+                MemOperand(current_input_offset(), end_of_input_address(),
+                           cp_offset * char_size()));
+#else
+      __ LoadLogicalReversedHalfWordP(current_character(),
+                MemOperand(current_input_offset(), end_of_input_address(),
+                           cp_offset * char_size()));
+#endif
+    } else {
+      DCHECK(characters == 1);
+      __ LoadlB(current_character(),
+                MemOperand(current_input_offset(), end_of_input_address(),
+                           cp_offset * char_size()));
+    }
   } else {
     DCHECK(mode_ == UC16);
-    __ LoadLogicalHalfWordP(
-        current_character(),
-        MemOperand(current_input_offset(), end_of_input_address(),
-                   cp_offset * char_size()));
+    if (characters == 2) {
+      __ LoadlW(current_character(),
+                MemOperand(current_input_offset(), end_of_input_address(),
+                           cp_offset * char_size()));
+#if !V8_TARGET_LITTLE_ENDIAN
+      // need to swap the order of the characters for endian issue

[john.yan, 2016/08/02 03:06:15]

same here.

+      __ rll(current_character(), current_character(), Operand(16));
+#endif
+    } else {
+      DCHECK(characters == 1);
+      __ LoadLogicalHalfWordP(
+          current_character(),
+                MemOperand(current_input_offset(), end_of_input_address(),
+                           cp_offset * char_size()));
+    }
   }
 }