Attachment 373745 Details for Bug 199636 – Patch

[patch] Patch

bug-199636-20190709214948.patch (text/plain), 3.56 KB, created by Tadeu Zagallo on 2019-07-09 12:49:49 PDT

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Creator: Tadeu Zagallo

Created: 2019-07-09 12:49:49 PDT

Size: 3.56 KB

patch

obsolete

>Subversion Revision: 247166
>diff --git a/Source/JavaScriptCore/ChangeLog b/Source/JavaScriptCore/ChangeLog
>index e903e4fd97709af5acd3934d319f42049f6f6196..020801884e475b7881fd5a9ba60812f0049b85e6 100644
>--- a/Source/JavaScriptCore/ChangeLog
>+++ b/Source/JavaScriptCore/ChangeLog
>@@ -1,3 +1,27 @@
>+2019-07-09  Tadeu Zagallo  <tzagallo@apple.com>
>+
>+        Optimize join of large empty arrays
>+        https://bugs.webkit.org/show_bug.cgi?id=199636
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        Replicate the behavior of `str.repeat(count)` when performing `new Array(count + 1).join(str)`.
>+        I added a new microbenchmark, large-empty-array-join, which runs ~44x faster and uses ~18x less memory.
>+
>+                                         baseline                    diff
>+        large-empty-array-join     2713.9698+-72.7621    ^     61.2335+-10.4836       ^ definitely 44.3217x faster
>+
>+        Memory usage with baseline (dirty):
>+            733012 kB current_mem
>+            756824 kB lifetime_peak
>+
>+        Memory usage with diff (dirty):
>+            41904 kB current_mem
>+            41972 kB lifetime_peak
>+
>+        * runtime/ArrayPrototype.cpp:
>+        (JSC::fastJoin):
>+
> 2019-07-05  Tadeu Zagallo  <tzagallo@apple.com>
> 
>         Unreviewed, change the value used to scribble Heap::m_worldState
>diff --git a/Source/JavaScriptCore/runtime/ArrayPrototype.cpp b/Source/JavaScriptCore/runtime/ArrayPrototype.cpp
>index 7f0fc37dab699bd01f73f32b5822cba4d090e86d..1ba6107b71ab1a431a4cf60a890f1999aad8d368 100644
>--- a/Source/JavaScriptCore/runtime/ArrayPrototype.cpp
>+++ b/Source/JavaScriptCore/runtime/ArrayPrototype.cpp
>@@ -516,6 +516,21 @@ inline JSValue fastJoin(ExecState& state, JSObject* thisObject, StringView separ
>             if (separator.is8Bit())
>                 RELEASE_AND_RETURN(scope, repeatCharacter(state, separator.characters8()[0], length - 1));
>             RELEASE_AND_RETURN(scope, repeatCharacter(state, separator.characters16()[0], length - 1));
>+        default:
>+            JSString* result = jsEmptyString(&state);
>+            JSString* operand = jsString(&vm, separator.toString());
>+            unsigned count = length - 1;
>+            for (;;) {
>+                if (count & 1) {
>+                    result = jsString(&state, result, operand);
>+                    RETURN_IF_EXCEPTION(scope, { });
>+                }
>+                count >>= 1;
>+                if (!count)
>+                    return result;
>+                operand = jsString(&state, operand, operand);
>+                RETURN_IF_EXCEPTION(scope, { });
>+            }
>         }
>         }
>     }
>diff --git a/JSTests/ChangeLog b/JSTests/ChangeLog
>index c6d1889cbef5fd572fdbab9916559e3c80163af4..d1d5cec18ba51ac1dca0457ffd9f6e99209dc7c5 100644
>--- a/JSTests/ChangeLog
>+++ b/JSTests/ChangeLog
>@@ -1,3 +1,12 @@
>+2019-07-09  Tadeu Zagallo  <tzagallo@apple.com>
>+
>+        Optimize join of large empty arrays
>+        https://bugs.webkit.org/show_bug.cgi?id=199636
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        * microbenchmarks/large-empty-array-join.js: Added.
>+
> 2019-07-02  Michael Saboff  <msaboff@apple.com>
> 
>         Exception from For..of loop assignment eliminates TDZ checks in subsequent code
>diff --git a/JSTests/microbenchmarks/large-empty-array-join.js b/JSTests/microbenchmarks/large-empty-array-join.js
>new file mode 100644
>index 0000000000000000000000000000000000000000..1a2ae07c6419f3c4b7f7ec5dafee9a47115f0a94
>--- /dev/null
>+++ b/JSTests/microbenchmarks/large-empty-array-join.js
>@@ -0,0 +1,3 @@
>+const array = [];
>+for (let i = 0; i < 100; ++i)
>+    array.push(new Array(1e6).join('â' + i));

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