llvm-project/clang
Hal Finkel 64567a80d2 Emit @llvm.assume for non-parameter lvalue align_value-attribute loads
We already add the align parameter attribute for function parameters that have
the align_value attribute (or those with a typedef type having that attribute),
which is an important special case, but does not handle pointers with value
alignment assumptions that come into scope in any other way. To handle the
general case, emit an @llvm.assume-based alignment assumption whenever we load
the pointer-typed lvalue of an align_value-attributed variable (except for
function parameters, which we already deal with at entry).

I'll also note that this is more general than Intel's described support in:
  https://software.intel.com/en-us/articles/data-alignment-to-assist-vectorization
which states that the compiler inserts __assume_aligned directives in response
to align_value-attributed variables only for function parameters and for the
initializers of local variables. I think that we can make the optimizer deal
with this more-general scheme (which could lead to a lot of calls to
@llvm.assume inside of loop bodies, for example), but if not, I'll rework this
to be less aggressive.

llvm-svn: 219052
2014-10-04 15:26:49 +00:00
..
INPUTS
bindings Expose the CUDA shared attribute to the C API. 2014-08-08 14:59:00 +00:00
docs [sphinx clean up] Fix warning introduced by r218957 2014-10-03 12:36:20 +00:00
examples Driver: Update clang-interpreter example for r218938 2014-10-03 01:08:27 +00:00
include -ms-extensions: Allow __super in return stements. 2014-10-04 10:17:57 +00:00
lib Emit @llvm.assume for non-parameter lvalue align_value-attribute loads 2014-10-04 15:26:49 +00:00
runtime Unify the name of compiler-rt builtins library on Linux. 2014-05-22 21:13:30 +00:00
test Emit @llvm.assume for non-parameter lvalue align_value-attribute loads 2014-10-04 15:26:49 +00:00
tools -ms-extensions: Implement __super scope specifier (PR13236). 2014-09-26 00:28:20 +00:00
unittests Adds 'override' to overriding methods. NFC. 2014-10-01 16:56:40 +00:00
utils Adding some FIXMEs to the attribute emitter code regarding whether pretty printing enumerators should use quoted string literals, or identifiers. NFC. 2014-09-15 16:16:14 +00:00
www Tests for DR600-640. 2014-09-29 06:03:56 +00:00
.arcconfig Updated phabricator server. 2014-04-07 03:39:55 +00:00
.clang-format
.clang-tidy Add .clang-tidy configuration file to provide LLVM-optimized defaults for clang-tidy. 2014-09-08 13:33:32 +00:00
.gitignore
CMakeLists.txt Make clang's rewrite engine a core feature 2014-07-16 16:48:33 +00:00
CODE_OWNERS.TXT Every code owner should be reachable via email, so add one for 2014-09-12 08:05:51 +00:00
INSTALL.txt
LICENSE.TXT
Makefile
ModuleInfo.txt
NOTES.txt Remove trailing spaces 2014-07-13 17:11:45 +00:00
README.txt Remove whitespace from test commit. 2014-07-16 19:10:36 +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/