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Chris Lattner 0725a8b653 First tiny step to implementing PR9322: build infrastructure for only emitting the 
live case of a switch statement when switching on a constant.  This is terribly
limited, but enough to handle the trivial example included.  Before we would 
emit:

define void @test1(i32 %i) nounwind {
entry:
  %i.addr = alloca i32, align 4
  store i32 %i, i32* %i.addr, align 4
  switch i32 1, label %sw.epilog [
    i32 1, label %sw.bb
  ]

sw.bb:                                            ; preds = %entry
  %tmp = load i32* %i.addr, align 4
  %inc = add nsw i32 %tmp, 1
  store i32 %inc, i32* %i.addr, align 4
  br label %sw.epilog

sw.epilog:                                        ; preds = %sw.bb, %entry
  switch i32 0, label %sw.epilog3 [
    i32 1, label %sw.bb1
  ]

sw.bb1:                                           ; preds = %sw.epilog
  %tmp2 = load i32* %i.addr, align 4
  %add = add nsw i32 %tmp2, 2
  store i32 %add, i32* %i.addr, align 4
  br label %sw.epilog3

sw.epilog3:                                       ; preds = %sw.bb1, %sw.epilog
  ret void
}

now we emit:

define void @test1(i32 %i) nounwind {
entry:
  %i.addr = alloca i32, align 4
  store i32 %i, i32* %i.addr, align 4
  %tmp = load i32* %i.addr, align 4
  %inc = add nsw i32 %tmp, 1
  store i32 %inc, i32* %i.addr, align 4
  ret void
}

This improves -O0 compile time (less IR to generate and shove through the code 
generator) and the clever linux kernel people found a way to fail to build if we 
don't do this optimization.  This step isn't enough to handle the kernel case
though.

llvm-svn: 126597
 		2011-02-28 00:22:07 +00:00
..
INPUTS
…
bindings/python python bindings: Add support for different kind of completion chunks 2011-02-05 17:54:10 +00:00
clang.xcodeproj In the clang.xcodeproj modify the 'clang' target to do nothing, not try to build anything. 2011-02-23 00:15:56 +00:00
docs Update the www to indicate that auto is now implemented. 2011-02-23 00:41:16 +00:00
examples [analyzer] Add LangOptions in CheckerManager. 2011-02-23 07:19:14 +00:00
include add a const version of this accessor. 2011-02-28 00:17:41 +00:00
lib First tiny step to implementing PR9322: build infrastructure for only emitting the 2011-02-28 00:22:07 +00:00
runtime build/compiler-rt: Fake Clang into using the right assembler to build the ARM 2011-02-11 01:29:49 +00:00
test First tiny step to implementing PR9322: build infrastructure for only emitting the 2011-02-28 00:22:07 +00:00
tools Fix an obvious typo. 2011-02-27 18:07:41 +00:00
unittests Put targets on folders, if the IDE supports the feature. 2011-02-20 22:06:44 +00:00
utils Minor fix for clang-completion-mode, from Dve Abrahams 2010-12-14 16:52:29 +00:00
www Update the www to indicate that auto is now implemented. 2011-02-23 00:41:16 +00:00
CMakeLists.txt CMake: add version information into the clang executable and libclang 2011-02-25 19:24:02 +00:00
INSTALL.txt
…
LICENSE.TXT
…
Makefile Add gTest unittests to clang, and write the first one. 2011-02-03 04:51:52 +00:00
ModuleInfo.txt
…
NOTES.txt A Release-Asserts build is now called a Release build. 2010-07-07 07:49:17 +00:00
README.txt Fix typo (test commit) 2010-06-17 12:39:05 +00:00
TODO.txt Test commit; added blank line to TODO.txt 2011-01-04 19:19:20 +00:00

README.txt 

//===----------------------------------------------------------------------===//
// C Language Family Front-end
//===----------------------------------------------------------------------===//

Welcome to Clang.  This is a compiler front-end for the C family of languages
(C, C++, Objective-C, and Objective-C++) which is built as part of the LLVM
compiler infrastructure project.

Unlike many other compiler frontends, Clang is useful for a number of things
beyond just compiling code: we intend for Clang to be host to a number of
different source level tools.  One example of this is the Clang Static Analyzer.

If you're interested in more (including how to build Clang) it is best to read
the relevant web sites.  Here are some pointers:

Information on Clang:              http://clang.llvm.org/
Building and using Clang:          http://clang.llvm.org/get_started.html
Clang Static Analyzer:             http://clang-analyzer.llvm.org/
Information on the LLVM project:   http://llvm.org/

If you have questions or comments about Clang, a great place to discuss them is
on the Clang development mailing list:
  http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev

If you find a bug in Clang, please file it in the LLVM bug tracker:
  http://llvm.org/bugs/