Title: [203911] trunk/Source/WTF
- Revision
- 203911
- Author
- [email protected]
- Date
- 2016-07-29 11:52:53 -0700 (Fri, 29 Jul 2016)
Log Message
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=):
Modified Paths
Diff
Modified: trunk/Source/WTF/ChangeLog (203910 => 203911)
--- 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)
@@ -1,3 +1,39 @@
+2016-07-29 Mark Lam <[email protected]>
+
+ 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=):
+
2016-07-29 Csaba Osztrogonác <[email protected]>
Remove PassRef.h after r177259
Modified: trunk/Source/WTF/wtf/text/StringView.h (203910 => 203911)
--- 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)
@@ -48,17 +48,17 @@
using CharacterMatchFunction = bool (*)(UChar);
// StringView is a non-owning reference to a string, similar to the proposed std::string_view.
-// 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.
class StringView {
public:
StringView();
+#if CHECK_STRINGVIEW_LIFETIME
~StringView();
StringView(StringView&&);
StringView(const StringView&);
StringView& operator=(StringView&&);
StringView& operator=(const StringView&);
+#endif
StringView(const String&);
StringView(const StringImpl&);
@@ -202,6 +202,7 @@
// FIXME: It's peculiar that null strings are 16-bit and empty strings return 8-bit (according to the is8Bit function).
}
+#if CHECK_STRINGVIEW_LIFETIME
inline StringView::~StringView()
{
setUnderlyingString(nullptr);
@@ -258,6 +259,7 @@
return *this;
}
+#endif // CHECK_STRINGVIEW_LIFETIME
inline void StringView::initialize(const LChar* characters, unsigned length)
{
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