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15  <!--*********************************************************************-->
16  <h1>"compiler-rt" Runtime Library</h1>
17  <!--*********************************************************************-->
18  
19  <p>The compiler-rt project is a simple library that provides an implementation
20     of the low-level target-specific hooks required by code generation and
21     other runtime components.  For example, when compiling for a 32-bit target,
22    converting a double to a 64-bit unsigned integer is compiling into a runtime
23    call to the "__fixunsdfdi" function.  The compiler-rt library provides
24    optimized implementations of this and other low-level routines.</p>
25
26  <p>All of the code in the compiler-rt project is available under the standard
27     <a href="http://llvm.org/docs/DeveloperPolicy.html#license">LLVM
28     License</a>, a "BSD-style" license.</p>
29  
30  <!--=====================================================================-->
31  <h2 id="goals">Goals</h2>
32  <!--=====================================================================-->
33  
34  <p>Different targets require different routines.  The compiler-rt project aims
35     to implement these routines in both target-independent C form as well as
36     providing heavily optimized assembly versions of the routines in some
37     cases.  It should be very easy to bring compiler-rt to support a new
38     target by adding the new routines needed by that target.</p>
39     
40  <p>Where it make sense, the compiler-rt project aims to implement interfaces
41     that are drop-in compatible with the libgcc interfaces.</p>
42
43  <!--=====================================================================-->
44  <h2 id="features">Features</h2>
45  <!--=====================================================================-->
46
47   <p>The current feature set of compiler-rt is:</p>
48
49   <ul>
50    <li>Full support for the libgcc interfaces required by these targets:
51      <ul>
52      <li>Darwin i386</li>
53      <li>Darwin X86-64</li>
54      <li>Darwin PowerPC</li>
55      <li>Darwin PowerPC 64</li>
56      </ul></li>
57      
58    <li>High performance hand tuned implementations of commonly used functions
59        like __floatundidf in assembly that are dramatically faster than the
60        libgcc implementations.</li>
61    <li>A target-independent implementation of the Apple "Blocks" runtime
62        interfaces.</li>
63   </ul>
64
65  <!--=====================================================================-->
66  <h2 id="dir-structure">Source Structure</h2>
67  <!--=====================================================================-->
68
69   <p>A short explanation of the directory structure of compiler-rt:</p>
70
71   <p>For testing it is possible to build a generic library and an optimized library.
72       The optimized library is formed by overlaying the optimized versions onto the generic library.
73       Of course, some architectures have additional functions,
74       so the optimized library may have functions not found in the generic version.</p>
75
76   <ul>   
77    <li> lib/ Is a generic portable implementations.</li>
78    <li> lib/<arch> has optimized version for the following supported architectures:
79      <ul>
80      <li>i386</li>
81      <li>X86-64</li>
82      <li>PowerPC</li>
83      <li>PowerPC 64</li>
84      </ul></li>
85   </ul>
86    
87  <!--=====================================================================-->
88  <h2>Get it and get involved!</h2>
89  <!--=====================================================================-->
90  
91  <p>To check out the code, use:</p>
92  
93  <ul>
94  <li>svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk compiler-rt</li>
95  <li>cd compiler-rt</li>
96  <li>make</li>
97  </ul>
98  
99  <p>Note that the library will probably only build out of the box on Darwin,
100     but patches to improve portability are definitely welcome.</p>
101  
102  <p>compiler-rt doesn't have its own mailing list, if you have questions please
103     email the <a
104    href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a> mailing
105    list.  Commits to the compiler-rt SVN module are automatically sent to the
106    <a 
107  href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>
108    mailing list.</p>
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