llvm-project/clang
Chris Lattner 055097f024 If coercing something from int or pointer type to int or pointer type
(potentially after unwrapping it from a struct) do it without going through
memory.  We now compile:

struct DeclGroup {
  unsigned NumDecls;
};

int foo(DeclGroup D) {
  return D.NumDecls;
}

into:

%struct.DeclGroup = type { i32 }

define i32 @_Z3foo9DeclGroup(i64) nounwind ssp noredzone {
entry:
  %D = alloca %struct.DeclGroup, align 4          ; <%struct.DeclGroup*> [#uses=2]
  %coerce.dive = getelementptr %struct.DeclGroup* %D, i32 0, i32 0 ; <i32*> [#uses=1]
  %coerce.val.ii = trunc i64 %0 to i32            ; <i32> [#uses=1]
  store i32 %coerce.val.ii, i32* %coerce.dive
  %tmp = getelementptr inbounds %struct.DeclGroup* %D, i32 0, i32 0 ; <i32*> [#uses=1]
  %tmp1 = load i32* %tmp                          ; <i32> [#uses=1]
  ret i32 %tmp1
}

instead of:

%struct.DeclGroup = type { i32 }

define i32 @_Z3foo9DeclGroup(i64) nounwind ssp noredzone {
entry:
  %D = alloca %struct.DeclGroup, align 4          ; <%struct.DeclGroup*> [#uses=2]
  %tmp = alloca i64                               ; <i64*> [#uses=2]
  %coerce.dive = getelementptr %struct.DeclGroup* %D, i32 0, i32 0 ; <i32*> [#uses=1]
  store i64 %0, i64* %tmp
  %1 = bitcast i64* %tmp to i32*                  ; <i32*> [#uses=1]
  %2 = load i32* %1, align 1                      ; <i32> [#uses=1]
  store i32 %2, i32* %coerce.dive
  %tmp1 = getelementptr inbounds %struct.DeclGroup* %D, i32 0, i32 0 ; <i32*> [#uses=1]
  %tmp2 = load i32* %tmp1                         ; <i32> [#uses=1]
  ret i32 %tmp2
}

... which is quite a bit less terrifying.

llvm-svn: 106975
2010-06-27 06:26:04 +00:00
..
INPUTS Add an input file that includes all standard C++ headers 2009-09-29 03:26:11 +00:00
bindings/python Rename 'CIndex' to 'libclang', since it has basically become our stable public 2010-04-30 21:51:10 +00:00
clang.xcodeproj Update Xcode project. 2010-06-08 20:02:04 +00:00
docs build: Get CLANG_VERSION from Version.inc instead of depending on VER file directly. 2010-06-25 17:33:49 +00:00
examples Frontend: Allow passing -cc1 level arguments to plugins. Patch by Troy Straszheim! 2010-06-16 16:59:23 +00:00
include Implement support for -fwrapv, rdar://7221421 2010-06-26 21:25:03 +00:00
lib If coercing something from int or pointer type to int or pointer type 2010-06-27 06:26:04 +00:00
test If coercing something from int or pointer type to int or pointer type 2010-06-27 06:26:04 +00:00
tools Silence warning about C++-style comments. 2010-06-22 09:29:44 +00:00
utils FuzzTest: Add support for reading list of replacements from a file. 2010-05-30 22:27:55 +00:00
www Update checker build. 2010-06-21 22:25:24 +00:00
CMakeLists.txt clang: Derive version name from LLVM unless specified explicitly. This means 2010-06-25 23:34:47 +00:00
INSTALL.txt Add minimal INSTALL.txt 2009-09-13 02:21:31 +00:00
LICENSE.TXT 2010 is here. 2010-01-09 18:40:42 +00:00
Makefile Remove cruft that I didn't intend to commit. 2010-06-26 00:31:14 +00:00
ModuleInfo.txt
NOTES.txt Remove clang-cc tool, it has joined in unholy union with clang. 2009-12-12 00:56:47 +00:00
README.txt Fix typo (test commit) 2010-06-17 12:39:05 +00:00
TODO.txt switch -Werror/-Wfatal-errors error conditions to use diagnostics instead 2009-12-23 18:53:37 +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/