Continues Latin-1 support. All tests pass with ENABLE_LATIN_1 flag.

src/x64/regexp-macro-assembler-x64.cc

Index: src/x64/regexp-macro-assembler-x64.cc
diff --git a/src/x64/regexp-macro-assembler-x64.cc b/src/x64/regexp-macro-assembler-x64.cc
index 152aebb9106db1947ebff4b5de0b14c01b96de1c..f5b5e954ad3bb9f3ba97641df73859473504a4b3 100644
--- a/src/x64/regexp-macro-assembler-x64.cc
+++ b/src/x64/regexp-macro-assembler-x64.cc
@@ -393,8 +393,17 @@ void RegExpMacroAssemblerX64::CheckNotBackReferenceIgnoreCase(
     __ j(not_equal, on_no_match);  // Definitely not equal.
     __ subb(rax, Immediate('a'));
     __ cmpb(rax, Immediate('z' - 'a'));
+#ifndef ENABLE_LATIN_1
     __ j(above, on_no_match);  // Weren't letters anyway.
-
+#else
+    __ j(below_equal, &loop_increment);  // In range 'a'-'z'.
+    // Latin-1: Check for values in range [224,254] but not 247.
+    __ subb(rax, Immediate(224 - 'a'));
+    __ cmpb(rax, Immediate(254 - 224));
+    __ j(above, on_no_match);  // Weren't Latin-1 letters.
+    __ cmpb(rax, Immediate(247 - 224));  // Check for 247.
+    __ j(equal, on_no_match);
+#endif
     __ bind(&loop_increment);
     // Increment pointers into match and capture strings.
     __ addq(r11, Immediate(1));