Hash all strings as unsigned values

A previous CL (https://crrev.com/c/1926769) changed hashing to always
treat the input as signed values. This causes problems, since the hash
of a one-byte string differs the hash of the identical two-byte string.
Hence this CL switches to treating all values as unsigned in hashing.

The bug cannot easily be reproduced in v8 alone, since we would need to
create an internalized two-byte string, which contains one-byte data.
Blink manages to create such a string via external strings.

R=jkummerow@chromium.org

Bug: chromium:1025184, chromium:1027131
Change-Id: Id41aa0e463691c02099a08c6e9d837a079c872df
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1930615Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65113}

src/strings/string-hasher-inl.h

@@ -54,8 +54,8 @@ uint32_t StringHasher::HashSequentialString(const char_t* chars_raw, int length,
                                             uint64_t seed) {
   STATIC_ASSERT(std::is_integral<char_t>::value);
   STATIC_ASSERT(sizeof(char_t) <= 2);
-  using schar = typename std::make_signed<char_t>::type;
-  const schar* chars = reinterpret_cast<const schar*>(chars_raw);
+  using uchar = typename std::make_unsigned<char_t>::type;
+  const uchar* chars = reinterpret_cast<const uchar*>(chars_raw);
   DCHECK_LE(0, length);
   DCHECK_IMPLIES(0 < length, chars != nullptr);
   if (length >= 1) {
@@ -86,7 +86,7 @@ uint32_t StringHasher::HashSequentialString(const char_t* chars_raw, int length,
         uint32_t is_integer_index = 0;
         uint32_t running_hash = static_cast<uint32_t>(seed);
         uint64_t index_big = index;
-        const schar* end = &chars[length];
+        const uchar* end = &chars[length];
         while (chars != end) {
           if (is_integer_index == 0 && !TryAddIndexChar(&index_big, *chars)) {
             is_integer_index = String::kIsNotIntegerIndexMask;
@@ -107,7 +107,7 @@ uint32_t StringHasher::HashSequentialString(const char_t* chars_raw, int length,
 
   // Non-index hash.
   uint32_t running_hash = static_cast<uint32_t>(seed);
-  const schar* end = &chars[length];
+  const uchar* end = &chars[length];
   while (chars != end) {
     running_hash = AddCharacterCore(running_hash, *chars++);
   }

test/inspector/debugger/wasm-stepping-byte-offsets-expected.txt

 Tests stepping through wasm scripts by byte offsets
 Setting up global instance variable.
-Got wasm script: wasm://wasm/41f464ee
-Requesting source for wasm://wasm/41f464ee...
+Got wasm script: wasm://wasm/7dfc8356
+Requesting source for wasm://wasm/7dfc8356...
 Source retrieved without error: true
-Setting breakpoint on offset 59 (should be propagated to 60, the offset of the call), url wasm://wasm/41f464ee
+Setting breakpoint on offset 59 (should be propagated to 60, the offset of the call), url wasm://wasm/7dfc8356
 {
     columnNumber : 60
     lineNumber : 0
     scriptId : <scriptId>
 }
-Paused at wasm://wasm/41f464ee/41f464ee-1:9:6
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:9:6
 at wasm_B (9:6):
  - scope (global):
    -- skipped
@@ -20,7 +20,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-0:1:2
+Paused at wasm://wasm/7dfc8356/7dfc8356-0:1:2
 at wasm_A (1:2):
  - scope (global):
    -- skipped
@@ -37,7 +37,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepOver called
-Paused at wasm://wasm/41f464ee/41f464ee-0:2:2
+Paused at wasm://wasm/7dfc8356/7dfc8356-0:2:2
 at wasm_A (2:2):
  - scope (global):
    -- skipped
@@ -54,7 +54,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepOut called
-Paused at wasm://wasm/41f464ee/41f464ee-1:10:6
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:10:6
 at wasm_B (10:6):
  - scope (global):
    -- skipped
@@ -65,7 +65,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepOut called
-Paused at wasm://wasm/41f464ee/41f464ee-1:9:6
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:9:6
 at wasm_B (9:6):
  - scope (global):
    -- skipped
@@ -76,7 +76,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepOver called
-Paused at wasm://wasm/41f464ee/41f464ee-1:10:6
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:10:6
 at wasm_B (10:6):
  - scope (global):
    -- skipped
@@ -87,7 +87,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-1:1:2
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:1:2
 at wasm_B (1:2):
  - scope (global):
    -- skipped
@@ -98,7 +98,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.resume called
-Paused at wasm://wasm/41f464ee/41f464ee-1:9:6
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:9:6
 at wasm_B (9:6):
  - scope (global):
    -- skipped
@@ -109,7 +109,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-0:1:2
+Paused at wasm://wasm/7dfc8356/7dfc8356-0:1:2
 at wasm_A (1:2):
  - scope (global):
    -- skipped
@@ -126,7 +126,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepOut called
-Paused at wasm://wasm/41f464ee/41f464ee-1:10:6
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:10:6
 at wasm_B (10:6):
  - scope (global):
    -- skipped
@@ -137,7 +137,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-1:1:2
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:1:2
 at wasm_B (1:2):
  - scope (global):
    -- skipped
@@ -148,7 +148,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-1:2:4
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:2:4
 at wasm_B (2:4):
  - scope (global):
    -- skipped
@@ -159,7 +159,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-1:3:4
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:3:4
 at wasm_B (3:4):
  - scope (global):
    -- skipped
@@ -170,7 +170,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-1:4:6
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:4:6
 at wasm_B (4:6):
  - scope (global):
    -- skipped
@@ -181,7 +181,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-1:5:6
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:5:6
 at wasm_B (5:6):
  - scope (global):
    -- skipped
@@ -192,7 +192,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-1:6:6
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:6:6
 at wasm_B (6:6):
  - scope (global):
    -- skipped
@@ -203,7 +203,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-1:7:6
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:7:6
 at wasm_B (7:6):
  - scope (global):
    -- skipped
@@ -214,7 +214,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-1:8:6
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:8:6
 at wasm_B (8:6):
  - scope (global):
    -- skipped
@@ -225,7 +225,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-1:9:6
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:9:6
 at wasm_B (9:6):
  - scope (global):
    -- skipped
@@ -236,7 +236,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-0:1:2
+Paused at wasm://wasm/7dfc8356/7dfc8356-0:1:2
 at wasm_A (1:2):
  - scope (global):
    -- skipped
@@ -253,7 +253,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-0:2:2
+Paused at wasm://wasm/7dfc8356/7dfc8356-0:2:2
 at wasm_A (2:2):
  - scope (global):
    -- skipped
@@ -270,7 +270,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-0:3:0
+Paused at wasm://wasm/7dfc8356/7dfc8356-0:3:0
 at wasm_A (3:0):
  - scope (global):
    -- skipped
@@ -287,7 +287,7 @@ at (anonymous) (0:17):
  - scope (global):
    -- skipped
 Debugger.stepInto called
-Paused at wasm://wasm/41f464ee/41f464ee-1:10:6
+Paused at wasm://wasm/7dfc8356/7dfc8356-1:10:6
 at wasm_B (10:6):
  - scope (global):
    -- skipped