Bug 193058

Summary: clang-tidy: Save 8 padding bytes on WebCore::BorderEdge
Product: WebKit Reporter: David Kilzer (:ddkilzer) <ddkilzer>
Component: Layout and RenderingAssignee: David Kilzer (:ddkilzer) <ddkilzer>
Status: RESOLVED FIXED    
Severity: Normal CC: bfulgham, commit-queue, simon.fraser, webkit-bug-importer, ysuzuki, zalan
Priority: P2 Keywords: InRadar
Version: WebKit Local Build   
Hardware: Unspecified   
OS: Unspecified   
Attachments:
Description Flags
Patch v1 none

David Kilzer (:ddkilzer)
Reported 2018-12-29 16:53:44 PST
Running `clang-tidy -header-filter=.* -checks='-*,clang-analyzer-optin.performance.*' ...` on WebCore source files found unneeded padding bytes in the WebCore::BorderEdge class. Source/WebCore/rendering/BorderEdge.h:39:7: warning: Excessive padding in 'class WebCore::BorderEdge' (9 padding bytes, where 1 is optimal). Optimal fields order: m_color, m_width, m_flooredToDevicePixelWidth, m_devicePixelRatio, m_style, m_isTransparent, m_isPresent, consider reordering the fields or adding explicit padding members [clang-analyzer-optin.performance.Padding] class BorderEdge { ^
Attachments
Patch v1 (2.65 KB, patch)
2018-12-29 16:58 PST, David Kilzer (:ddkilzer) 		no flags
DetailsFormatted DiffDiff
View All Add attachment proposed patch, testcase, etc.
David Kilzer (:ddkilzer)
Comment 1 2018-12-29 16:55:32 PST
$ ./Tools/Scripts/dump-class-layout -c Release -a x86_64 -b $BUILD_DIR WebCore WebCore::BorderEdge +0 < 32> BorderEdge +0 < 4> WebCore::LayoutUnit m_width +0 < 4> int m_value +4 < 4> <PADDING: 4 bytes> +8 < 8> WebCore::Color m_color +8 < 8> WebCore::Color::(anonymous union) m_colorData +16 < 1> WebCore::BorderStyle m_style +17 < 1> bool m_isTransparent +18 < 1> bool m_isPresent +19 < 1> <PADDING: 1 byte> +20 < 4> float m_flooredToDevicePixelWidth +24 < 4> float m_devicePixelRatio +28 < 4> <PADDING: 4 bytes> Total byte size: 32 Total pad bytes: 9 Padding percentage: 28.12 % Removing 8 padding bytes would make the class 24 bytes.
Radar WebKit Bug Importer
Comment 2 2018-12-29 16:56:20 PST
<rdar://problem/46979275>
David Kilzer (:ddkilzer)
Comment 3 2018-12-29 16:58:54 PST
Created attachment 358141 [details] Patch v1
David Kilzer (:ddkilzer)
Comment 4 2018-12-29 19:24:05 PST
(In reply to David Kilzer (:ddkilzer) from comment #1) > $ ./Tools/Scripts/dump-class-layout -c Release -a x86_64 -b $BUILD_DIR > WebCore WebCore::BorderEdge > +0 < 32> BorderEdge > +0 < 4> WebCore::LayoutUnit m_width > +0 < 4> int m_value > +4 < 4> <PADDING: 4 bytes> > +8 < 8> WebCore::Color m_color > +8 < 8> WebCore::Color::(anonymous union) m_colorData > +16 < 1> WebCore::BorderStyle m_style > +17 < 1> bool m_isTransparent > +18 < 1> bool m_isPresent > +19 < 1> <PADDING: 1 byte> > +20 < 4> float m_flooredToDevicePixelWidth > +24 < 4> float m_devicePixelRatio > +28 < 4> <PADDING: 4 bytes> > Total byte size: 32 > Total pad bytes: 9 > Padding percentage: 28.12 % > > Removing 8 padding bytes would make the class 24 bytes. After the patch is applied: $ ./Tools/Scripts/dump-class-layout -c Release -a x86_64 -b $BUILD_DIR WebCore WebCore::BorderEdge +0 < 24> BorderEdge +0 < 8> WebCore::Color m_color +0 < 8> WebCore::Color::(anonymous union) m_colorData +8 < 4> WebCore::LayoutUnit m_width +8 < 4> int m_value +12 < 4> float m_flooredToDevicePixelWidth +16 < 4> float m_devicePixelRatio +20 < 1> WebCore::BorderStyle m_style +21 < 1> bool m_isTransparent +22 < 1> bool m_isPresent +23 < 1> <PADDING: 1 byte> Total byte size: 24 Total pad bytes: 1 Padding percentage: 4.17 %
Yusuke Suzuki
Comment 5 2018-12-30 13:30:17 PST
Comment on attachment 358141 [details] Patch v1 r=me, nice.
WebKit Commit Bot
Comment 6 2018-12-30 13:56:58 PST
Comment on attachment 358141 [details] Patch v1 Clearing flags on attachment: 358141 Committed r239563: <https://trac.webkit.org/changeset/239563>
WebKit Commit Bot
Comment 7 2018-12-30 13:56:59 PST
All reviewed patches have been landed. Closing bug.
Note You need to log in before you can comment on or make changes to this bug.