Changeset 243544 in webkit

Timestamp:

Mar 27, 2019, 9:12:22 AM (7 years ago)

Author:

pvollan@apple.com

Message:

Layout Test js/math-clz32.html is failing
​https://bugs.webkit.org/show_bug.cgi?id=196209

Reviewed by Ross Kirsling.

Source/WTF:

Use the correct number of loop iterations when counting leading zeros. Also, the
count was off by one for the Win64 case.

• wtf/MathExtras.h:

(WTF::clz):

LayoutTests:

• platform/win/TestExpectations:

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/platform/win/TestExpectations (modified) (1 diff)
• Source/WTF/ChangeLog (modified) (1 diff)
• Source/WTF/wtf/MathExtras.h (modified) (3 diffs)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2019-03-27  Per Arne Vollan  <pvollan@apple.com>
+
+        Layout Test js/math-clz32.html is failing
+        https://bugs.webkit.org/show_bug.cgi?id=196209
+
+        Reviewed by Ross Kirsling.
+
+        * platform/win/TestExpectations:
+
 2019-03-26  Simon Fraser  <simon.fraser@apple.com>
 

trunk/LayoutTests/platform/win/TestExpectations

@@ -4304 +4304 @@
 webkit.org/b/195461 http/tests/referrer-policy-iframe/unsafe-url/cross-origin-http.https.html [ Failure ]
 
-webkit.org/b/196209 js/math-clz32.html [ Failure ]

trunk/Source/WTF/ChangeLog

@@ +1 @@
+2019-03-27  Per Arne Vollan  <pvollan@apple.com>
+
+        Layout Test js/math-clz32.html is failing
+        https://bugs.webkit.org/show_bug.cgi?id=196209
+
+        Reviewed by Ross Kirsling.
+
+        Use the correct number of loop iterations when counting leading zeros. Also, the
+        count was off by one for the Win64 case.
+
+        * wtf/MathExtras.h:
+        (WTF::clz):
+
 2019-03-26  Keith Rollin  <krollin@apple.com>
 

trunk/Source/WTF/wtf/MathExtras.h

@@ -620 +620 @@
 {
     constexpr unsigned bitSize = sizeof(T) * CHAR_BIT;
-    constexpr unsigned bitSize64 = sizeof(uint64_t) * CHAR_BIT;
 
     using UT = typename std::make_unsigned<T>::type;
@@ -626 +625 @@
 
 #if COMPILER(GCC_COMPATIBLE)
+    constexpr unsigned bitSize64 = sizeof(uint64_t) * CHAR_BIT;
     if (uValue)
         return __builtin_clzll(uValue) - (bitSize64 - bitSize);
@@ -635 +635 @@
     unsigned long ret = 0;
     if (_BitScanReverse64(&ret, uValue))
-        return bitSize - ret;
+        return bitSize - 1 - ret;
     return bitSize;
 #else
     unsigned zeroCount = 0;
-    for (int i = bitSize64 - 1; i >= 0; i--) {
-        if (!(static_cast<uint64_t>(uValue) >> i))
-            zeroCount++;
-        else
+    for (int i = bitSize - 1; i >= 0; i--) {
+        if (uValue >> i)
             break;
+        zeroCount++;
     }
     return zeroCount;