| Daniel Dunbar | 9d284e5 | 2009-06-26 18:14:41 +0000 | [diff] [blame] | 1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" |
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| 6 | <title>Clang - Performance</title> |
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| 16 | <div id="content"> |
| 17 | |
| 18 | <!--*************************************************************************--> |
| 19 | <h1>Clang - Performance</h1> |
| 20 | <!--*************************************************************************--> |
| 21 | |
| 22 | <p>This page shows the compile time performance of Clang on two |
| 23 | interesting benchmarks: |
| 24 | <ul> |
| 25 | <li><i>Sketch</i>: The Objective-C example application shipped on |
| 26 | Mac OS X as part of Xcode. <i>Sketch</i> is indicative of a |
| 27 | "typical" Objective-C app. The source itself has a relatively |
| 28 | small amount of code (~7,500 lines of source code), but it relies |
| 29 | on the extensive Cocoa APIs to build its functionality. Like many |
| 30 | Objective-C applications, it includes <tt>Cocoa/Cocoa.h</tt> in |
| 31 | all of its source files, which represents a significant stress |
| 32 | test of the front-end's performance on lexing, preprocessing, |
| 33 | parsing, and syntax analysis.</li> |
| 34 | <li><i>176.gcc</i>: This is the gcc-2.7.2.2 code base as present in |
| 35 | SPECINT 2000. In contrast to Sketch, <i>176.gcc</i> consists of a |
| 36 | large amount of C source code (~200,000 lines) with few system |
| 37 | dependencies. This stresses the back-end's performance on generating |
| 38 | assembly code and debug information.</li> |
| 39 | </ul> |
| 40 | </p> |
| 41 | |
| 42 | <p> |
| 43 | For previous performance numbers, please |
| 44 | go <a href="performance-2008-10-31.html">here</a>. |
| 45 | </p> |
| 46 | |
| 47 | <!--*************************************************************************--> |
| 48 | <h2><a name="experiments">Experiments</a></h2> |
| 49 | <!--*************************************************************************--> |
| 50 | |
| 51 | <p>Measurements are done by running a full build (using xcodebuild or |
| 52 | make for Sketch and 176.gcc respectively) using Clang and gcc 4.2 as |
| 53 | compilers; gcc is run both with and without the new clang driver (ccc) |
| 54 | in order to evaluate the overhead of the driver itself.</p> |
| 55 | |
| 56 | <p>In order to track the performance of various subsystems the timings |
| 57 | have been broken down into separate stages where possible. This is |
| 58 | done by over-riding the CC environment variable used during the build |
| 59 | to point to one of a few simple shell scripts which may skip part of |
| 60 | the build. |
| 61 | |
| 62 | <ul> |
| 63 | <li><tt>non-compiler</tt>: The overhead of the build system itself; |
| 64 | for Sketch this also includes the time to build/copy various |
| 65 | non-source code resource files.</li> |
| 66 | <li><tt>+ driver</tt>: Add execution of the driver, but do not execute any |
| 67 | commands (by using the -### driver option).</li> |
| 68 | <li><tt>+ pch gen</tt>: Add generation of PCH files.</li> |
| 69 | <li><tt>+ cpp</tt>: Add preprocessing of source files (this time is |
| 70 | include in syntax for gcc).</li> |
| 71 | <li><tt>+ parse</tt>: Add parsing of source files (this time is |
| 72 | include in syntax for gcc).</li> |
| 73 | <li><tt>+ syntax</tt>: Add semantic checking of source files (for |
| 74 | gcc, this includes preprocessing and parsing as well).</li> |
| 75 | <li><tt>+ IRgen</tt>: Add generation of LLVM IR (gcc has no |
| 76 | corresponding phase).</li> |
| 77 | <li><tt>+ codegen</tt>: Add generation of assembler files.</li> |
| 78 | <li><tt>+ assembler</tt>: Add assembler time to generate .o files.</li> |
| 79 | <li><tt>+ linker</tt>: Add linker time.</li> |
| 80 | </ul> |
| 81 | </p> |
| 82 | |
| 83 | <p>This set of stages is chosen to be approximately additive, that is |
| 84 | each subsequent stage simply adds some additional processing. The |
| 85 | timings measure the delta of the given stage from the previous |
| 86 | one. For example, the timings for <tt>+ syntax</tt> below show the |
| 87 | difference of running with <tt>+ syntax</tt> versus running with <tt>+ |
| 88 | parse</tt> (for clang) or <tt>+ driver</tt> with gcc. This amounts to |
| 89 | a fairly accurate measure of only the time to perform semantic |
| 90 | analysis (and preprocessing/parsing, in the case of gcc).</p> |
| 91 | |
| 92 | <!--*************************************************************************--> |
| 93 | <h2><a name="timings">Timing Results</a></h2> |
| 94 | <!--*************************************************************************--> |
| 95 | |
| 96 | <!--=======================================================================--> |
| 97 | <h3><a name="2009-03-02">2009-03-02</a></h3> |
| 98 | <!--=======================================================================--> |
| 99 | |
| 100 | <a href="timing-data/2009-03-02/sketch.pdf"> |
| 101 | <img class="img_slide" |
| 102 | src="timing-data/2009-03-02/sketch.png" alt="Sketch Timings"/> |
| 103 | </a> |
| 104 | |
| 105 | <a href="timing-data/2009-03-02/176.gcc.pdf"> |
| 106 | <img class="img_slide" |
| 107 | src="timing-data/2009-03-02/176.gcc.png" alt="176.gcc Timings"/> |
| 108 | </a> |
| 109 | |
| 110 | </div> |
| 111 | </body> |
| 112 | </html> |