[asmjs] Fix parsing hex numeric literals ending with 'e'.

When parsing a numeric literal in a line like "a=0x0e+b|0;",
currently the scanner consumes the "e+" part (as it thinks
it's the start of an exponent).
In the ECMAScript lexical grammar HexIntegerLiteral cannot
contain exponents, which means the '+' character should be
parsed as a binary operator.

R=bradnelson@chromium.org
BUG=v8:7893

Change-Id: I97a0d4ea2ee1d38a3462efbfaef5eb87b8ea704b
Reviewed-on: https://chromium-review.googlesource.com/1116551Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54132}

AUTHORS

@@ -73,6 +73,7 @@ Felix Geisendörfer <haimuiba@gmail.com>
 Filipe David Manana <fdmanana@gmail.com>
 Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
 Geoffrey Garside <ggarside@gmail.com>
+Gergely Nagy <ngg@ngg.hu>
 Gus Caplan <me@gus.host>
 Gwang Yoon Hwang <ryumiel@company100.net>
 Henrique Ferreiro <henrique.ferreiro@gmail.com>

src/asmjs/asm-scanner.cc

@@ -274,17 +274,22 @@ void AsmJsScanner::ConsumeNumber(uc32 ch) {
   std::string number;
   number = ch;
   bool has_dot = ch == '.';
+  bool has_prefix = false;
   for (;;) {
     ch = stream_->Advance();
     if ((ch >= '0' && ch <= '9') || (ch >= 'a' && ch <= 'f') ||
         (ch >= 'A' && ch <= 'F') || ch == '.' || ch == 'b' || ch == 'o' ||
         ch == 'x' ||
-        ((ch == '-' || ch == '+') && (number[number.size() - 1] == 'e' ||
-                                      number[number.size() - 1] == 'E'))) {
+        ((ch == '-' || ch == '+') && !has_prefix &&
+         (number[number.size() - 1] == 'e' ||
+          number[number.size() - 1] == 'E'))) {
       // TODO(bradnelson): Test weird cases ending in -.
       if (ch == '.') {
         has_dot = true;
       }
+      if (ch == 'b' || ch == 'o' || ch == 'x') {
+        has_prefix = true;
+      }
       number.push_back(ch);
     } else {
       break;

test/mjsunit/regress/regress-7893.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.
+
+// Flags: --validate-asm --allow-natives-syntax
+
+function Module(stdlib, imports, buffer) {
+  "use asm";
+  function f() {
+    var bar = 0;
+    return 0x1e+bar|0;
+  }
+  return f;
+}
+var f = Module(this);
+assertTrue(%IsWasmCode(f));
+assertTrue(%IsAsmWasmCode(Module));
+assertEquals(0x1e, f());