Revert "[regexp] fix Latin1 ignore-case bug."

This reverts commit 8e9eba36.

Reason for revert:
https://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20noi18n%20-%20debug/builds/18887

Original change's description:
> [regexp] fix Latin1 ignore-case bug.
> 
> R=​jgruber@chromium.org
> 
> Bug: v8:6703
> Change-Id: I6b251191cc00d9ac8db41b91b528c130d1b23fc6
> Reviewed-on: https://chromium-review.googlesource.com/897523
> Commit-Queue: Yang Guo <yangguo@chromium.org>
> Reviewed-by: Jakob Gruber <jgruber@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#51088}

TBR=yangguo@chromium.org,jgruber@chromium.org

Change-Id: I09138cedb2631640709ec717045247362f653cb2
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:6703
Reviewed-on: https://chromium-review.googlesource.com/901184Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51090}

src/regexp/jsregexp.cc

@@ -2768,13 +2768,16 @@ RegExpNode* TextNode::FilterOneByte(int depth) {
       Vector<const uc16> quarks = elm.atom()->data();
       for (int j = 0; j < quarks.length(); j++) {
         uint16_t c = quarks[j];
-        if (elm.atom()->ignore_case()) {
-          c = unibrow::Latin1::TryConvertToLatin1(c);
-        }
-        if (c > unibrow::Latin1::kMaxChar) return set_replacement(nullptr);
-        // Replace quark in case we converted to Latin-1.
-        uint16_t* writable_quarks = const_cast<uint16_t*>(quarks.start());
-        writable_quarks[j] = c;
+        if (c <= String::kMaxOneByteCharCode) continue;
+        if (!IgnoreCase(elm.atom()->flags())) return set_replacement(nullptr);
+        // Here, we need to check for characters whose upper and lower cases
+        // are outside the Latin-1 range.
+        uint16_t converted = unibrow::Latin1::ConvertNonLatin1ToLatin1(c);
+        // Character is outside Latin-1 completely
+        if (converted == 0) return set_replacement(nullptr);
+        // Convert quark to Latin-1 in place.
+        uint16_t* copy = const_cast<uint16_t*>(quarks.start());
+        copy[j] = converted;
       }
     } else {
       DCHECK(elm.text_type() == TextElement::CHAR_CLASS);
@@ -3206,17 +3209,10 @@ void TextNode::TextEmitPass(RegExpCompiler* compiler,
         if (first_element_checked && i == 0 && j == 0) continue;
         if (DeterminedAlready(quick_check, elm.cp_offset() + j)) continue;
         EmitCharacterFunction* emit_function = nullptr;
-        uc16 quark = quarks[j];
-        if (elm.atom()->ignore_case()) {
-          // Everywhere else we assume that a non-Latin-1 character cannot match
-          // a Latin-1 character. Avoid the cases where this is assumption is
-          // invalid by using the Latin1 equivalent instead.
-          quark = unibrow::Latin1::TryConvertToLatin1(quark);
-        }
         switch (pass) {
           case NON_LATIN1_MATCH:
             DCHECK(one_byte);
-            if (quark > String::kMaxOneByteCharCode) {
+            if (quarks[j] > String::kMaxOneByteCharCode) {
               assembler->GoTo(backtrack);
               return;
             }
@@ -3236,8 +3232,8 @@ void TextNode::TextEmitPass(RegExpCompiler* compiler,
         if (emit_function != nullptr) {
           bool bounds_check = *checked_up_to < cp_offset + j || read_backward();
           bool bound_checked =
-              emit_function(isolate, compiler, quark, backtrack, cp_offset + j,
-                            bounds_check, preloaded);
+              emit_function(isolate, compiler, quarks[j], backtrack,
+                            cp_offset + j, bounds_check, preloaded);
           if (bound_checked) UpdateBoundsCheck(cp_offset + j, checked_up_to);
         }
       }

src/unicode-decoder.h

@@ -93,11 +93,15 @@ size_t Utf8Decoder<kBufferSize>::WriteUtf16(uint16_t* data,
 class Latin1 {
  public:
   static const unsigned kMaxChar = 0xff;
-  // Convert the character to Latin-1 case equivalent if possible.
-  static inline uint16_t TryConvertToLatin1(uint16_t);
+  // Returns 0 if character does not convert to single latin-1 character
+  // or if the character doesn't not convert back to latin-1 via inverse
+  // operation (upper to lower, etc).
+  static inline uint16_t ConvertNonLatin1ToLatin1(uint16_t);
 };
 
-uint16_t Latin1::TryConvertToLatin1(uint16_t c) {
+
+uint16_t Latin1::ConvertNonLatin1ToLatin1(uint16_t c) {
+  DCHECK_GT(c, Latin1::kMaxChar);
   switch (c) {
     // This are equivalent characters in unicode.
     case 0x39c:
@@ -108,7 +112,7 @@ uint16_t Latin1::TryConvertToLatin1(uint16_t c) {
     case 0x178:
       return 0xff;
   }
-  return c;
+  return 0;
 }
 
 

test/mjsunit/regress/regress-6703.js

-// Copyright 2018 the V8 project authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-assertTrue(/(\u039C)/i.test("\xB5"));
-assertTrue(/(\u039C)+/i.test("\xB5"));
-assertTrue(/(\u039C)/ui.test("\xB5"));
-assertTrue(/(\u039C)+/ui.test("\xB5"));
-
-assertTrue(/(\u03BC)/i.test("\xB5"));
-assertTrue(/(\u03BC)+/i.test("\xB5"));
-assertTrue(/(\u03BC)/ui.test("\xB5"));
-assertTrue(/(\u03BC)+/ui.test("\xB5"));
-
-assertTrue(/(\u03BC)/i.test("\u039C"));
-assertTrue(/(\u03BC)+/i.test("\u039C"));
-assertTrue(/(\u03BC)/ui.test("\u039C"));
-assertTrue(/(\u03BC)+/ui.test("\u039C"));
-
-assertTrue(/(\u0178)/i.test("\xFF"));
-assertTrue(/(\u0178)+/i.test("\xFF"));
-assertTrue(/(\u0178)/ui.test("\xFF"));
-assertTrue(/(\u0178)+/ui.test("\xFF"));