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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/203911">203911</a></dd>
<dt>Author</dt> <dd>mark.lam@apple.com</dd>
<dt>Date</dt> <dd>2016-07-29 11:52:53 -0700 (Fri, 29 Jul 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>Make StringView capable of being passed or returned in only 2 registers.
https://bugs.webkit.org/show_bug.cgi?id=160344
Reviewed by Geoffrey Garen.
We just need to #if out copy and move constructors and assignment operators.
After this change, the following test code:
JS_EXPORT_PRIVATE StringView returnStringView(StringView sv)
{
return sv;
}
... compiles to the following for x86_64:
__ZN3JSC16returnStringViewEN3WTF10StringViewE:
000000000093fb20 pushq %rbp
000000000093fb21 movq %rsp, %rbp
000000000093fb24 movq %rdi, %rax // Copy from arg word 0 to ret word 0.
000000000093fb27 movq %rsi, %rdx // Copy from arg word 1 to ret word 1.
000000000093fb2a popq %rbp
000000000093fb2b retq
... and this for arm64:
__ZN3JSC16returnStringViewEN3WTF10StringViewE:
0000000000818504 ret // arg word 0 and 1 are in the same regs as ret word 0 and 1.
* wtf/text/StringView.h:
(WTF::StringView::StringView):
(WTF::StringView::~StringView):
(WTF::StringView::operator=):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWTFChangeLog">trunk/Source/WTF/ChangeLog</a></li>
<li><a href="#trunkSourceWTFwtftextStringViewh">trunk/Source/WTF/wtf/text/StringView.h</a></li>
</ul>
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<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWTFChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WTF/ChangeLog (203910 => 203911)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WTF/ChangeLog 2016-07-29 18:47:52 UTC (rev 203910)
+++ trunk/Source/WTF/ChangeLog 2016-07-29 18:52:53 UTC (rev 203911)
</span><span class="lines">@@ -1,3 +1,39 @@
</span><ins>+2016-07-29 Mark Lam <mark.lam@apple.com>
+
+ Make StringView capable of being passed or returned in only 2 registers.
+ https://bugs.webkit.org/show_bug.cgi?id=160344
+
+ Reviewed by Geoffrey Garen.
+
+ We just need to #if out copy and move constructors and assignment operators.
+
+ After this change, the following test code:
+
+ JS_EXPORT_PRIVATE StringView returnStringView(StringView sv)
+ {
+ return sv;
+ }
+
+ ... compiles to the following for x86_64:
+
+ __ZN3JSC16returnStringViewEN3WTF10StringViewE:
+ 000000000093fb20 pushq %rbp
+ 000000000093fb21 movq %rsp, %rbp
+ 000000000093fb24 movq %rdi, %rax // Copy from arg word 0 to ret word 0.
+ 000000000093fb27 movq %rsi, %rdx // Copy from arg word 1 to ret word 1.
+ 000000000093fb2a popq %rbp
+ 000000000093fb2b retq
+
+ ... and this for arm64:
+
+ __ZN3JSC16returnStringViewEN3WTF10StringViewE:
+ 0000000000818504 ret // arg word 0 and 1 are in the same regs as ret word 0 and 1.
+
+ * wtf/text/StringView.h:
+ (WTF::StringView::StringView):
+ (WTF::StringView::~StringView):
+ (WTF::StringView::operator=):
+
</ins><span class="cx"> 2016-07-29 Csaba Osztrogonác <ossy@webkit.org>
</span><span class="cx">
</span><span class="cx"> Remove PassRef.h after r177259
</span></span></pre></div>
<a id="trunkSourceWTFwtftextStringViewh"></a>
<div class="modfile"><h4>Modified: trunk/Source/WTF/wtf/text/StringView.h (203910 => 203911)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WTF/wtf/text/StringView.h 2016-07-29 18:47:52 UTC (rev 203910)
+++ trunk/Source/WTF/wtf/text/StringView.h 2016-07-29 18:52:53 UTC (rev 203911)
</span><span class="lines">@@ -48,17 +48,17 @@
</span><span class="cx"> using CharacterMatchFunction = bool (*)(UChar);
</span><span class="cx">
</span><span class="cx"> // StringView is a non-owning reference to a string, similar to the proposed std::string_view.
</span><del>-// Whether the string is 8-bit or 16-bit is encoded in the upper bit of the length member.
-// This means that strings longer than 2 gigacharacters cannot be represented.
</del><span class="cx">
</span><span class="cx"> class StringView {
</span><span class="cx"> public:
</span><span class="cx"> StringView();
</span><ins>+#if CHECK_STRINGVIEW_LIFETIME
</ins><span class="cx"> ~StringView();
</span><span class="cx"> StringView(StringView&&);
</span><span class="cx"> StringView(const StringView&);
</span><span class="cx"> StringView& operator=(StringView&&);
</span><span class="cx"> StringView& operator=(const StringView&);
</span><ins>+#endif
</ins><span class="cx">
</span><span class="cx"> StringView(const String&);
</span><span class="cx"> StringView(const StringImpl&);
</span><span class="lines">@@ -202,6 +202,7 @@
</span><span class="cx"> // FIXME: It's peculiar that null strings are 16-bit and empty strings return 8-bit (according to the is8Bit function).
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+#if CHECK_STRINGVIEW_LIFETIME
</ins><span class="cx"> inline StringView::~StringView()
</span><span class="cx"> {
</span><span class="cx"> setUnderlyingString(nullptr);
</span><span class="lines">@@ -258,6 +259,7 @@
</span><span class="cx">
</span><span class="cx"> return *this;
</span><span class="cx"> }
</span><ins>+#endif // CHECK_STRINGVIEW_LIFETIME
</ins><span class="cx">
</span><span class="cx"> inline void StringView::initialize(const LChar* characters, unsigned length)
</span><span class="cx"> {
</span></span></pre>
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