similar to: [LLVMdev] announcing C-Reduce, a test-case reducer for C/C++ programs

The LLVM Foundation is pleased to announce its new Board of Directors: Chandler Carruth Hal Finkel Arnaud de Grandmaison David Kipping Anton Korobeynikov Tanya Lattner Chris Lattner John Regehr Three new members and five continuing members were elected to the eight person board. The new board consists of individuals from corporations and from the academic and scientific communities. They also

LLVM doesn't know about any of this C/C++ specific stuff. If g++ do something (such as the load), so will llvm-g++. I'd suggest you send this to the clang mailing list. BTW, this issue is very interesting. I've never used C++ for embedded systems so never realised this difference. On Sat, Mar 6, 2010 at 1:47 AM, John Regehr <regehr at cs.utah.edu> wrote: > The question is,

The question is, what should C and C++ compilers do with this code? volatile int x; void foo (void) { x; } This question is not totally stupid: embedded systems use code like this when reading a hardware register has a useful side effect (usually clearing the register). It is reasonably clear that a C compiler should load from x and throw away the value. clang and llvm-gcc do

On 07/22/2015 01:28 PM, Sean Silva wrote: > > > On Wed, Jul 22, 2015 at 12:54 PM, Hal Finkel <hfinkel at anl.gov > <mailto:hfinkel at anl.gov>> wrote: > > One thing that is important to consider is where in the pipeline > these kinds of optimizations fit. We normally try to put the IR > into a canonical simplified form in the mid-level optimizer.

One thing that is important to consider is where in the pipeline these kinds of optimizations fit. We normally try to put the IR into a canonical simplified form in the mid-level optimizer. This form is supposed to be whatever is most useful for exposing other optimizations, and for lowering, but only in a generic sense. We do have some optimizations near the end of our pipeline (vectorization,

Cool! Looks like we do lots of provably unnecessary alignment checks. :) On Tue, Nov 25, 2014 at 9:03 AM, John Regehr <regehr at cs.utah.edu> wrote: > Actually, let me save you some time by pointing out the thing that is > perhaps immediately useful about our recent work, which is the fact that > Souper now supports "optimization profiling". > > If you build an

I strongly suspect pointer union and pointer int pair style classes are the source of these... But perhaps I'm wrong On Nov 26, 2014 9:29 AM, "Michael Zolotukhin" <mzolotukhin at apple.com> wrote: > John, > > That’s a great post and really interesting data, thank you! > > On Nov 25, 2014, at 9:58 AM, Reid Kleckner <rnk at google.com> wrote: > >

I'm getting the error below on Ubuntu Hardy on ia32 on r55688. John make[3]: Entering directory `/home/regehr/llvm-gcc/build/gcc' gcc -c -g -DIN_GCC -W -Wall -Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes -pedantic -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -Wold-style-definition -Wmissing-format-attribute -DHAVE_CONFIG_H -I. -I. -I../../gcc

We (the folks working on Souper) would appreciate any feedback on these IR-level superoptimizer results: http://blog.regehr.org/extra_files/souper-jul-15.html My impression is that while there's clearly plenty of material in here that doesn't want to get implemented in an opt pass, there are a number of gems hiding in there that are worth implementing. Blog post containing

My InlineCost refactoring has been noticed in this aspect; that may or may notbe the culprit here. A quick thing you can do is to compile with -ftime-report and compare the top few passes between versions. Dan On Oct 19, 2009, at 8:47 PM, John Regehr <regehr at cs.utah.edu> wrote: > As part of routine testing, I run clang and llvm-gcc a lot of times. > Something happened

I've been playing with quest, a random test generator for C compilers. Just for the heck of it I pasted a test into the LLVM web page and got an interval compiler error on the first try. So you folks may want to take a look. http://www.st.cs.uni-sb.de/~lindig/src/quest/ John Regehr -- John Regehr, regehr at cs.utah.edu Assistant Professor, School of Computing, University of Utah

On Tue, Jan 26, 2010 at 12:36 PM, John Regehr <regehr at cs.utah.edu> wrote: > 2. > Sometimes not: > > http://embed.cs.utah.edu/embarrassing/jan_10/harvest/source/EC/ECC74C0C.shtml The primary issue here is that scalar evolution doesn't know how to deal with loops using "sle" for the exit condition. Shouldn't be too hard to fix now that we have overflow flags

Hi, I'd like to see what parts of LLVM/Clang are being executed. I know that "make ENABLE_COVERAGE=1" used to just work, but so far (on 64-bit Ubuntu 14.04) I've had no luck building either 3.4.x or SVN head using any of Clang 3.4, Clang head, or a recent GCC. The first error that I get when building with GCC is this:

On Tue, Jan 26, 2010 at 5:55 PM, John Regehr <regehr at cs.utah.edu> wrote: >>> Repetitive code with lots of bitwise operations is compiled by LLVM into >>> much larger code than the other compilers: >>> >>> >>> http://embed.cs.utah.edu/embarrassing/jan_10/harvest/source/ED/ED37DAF5.shtml >>> >>>

>> http://www.st.cs.uni-sb.de/~lindig/src/quest/ > > I don't know about Tanu, but we can certainly use this in finding bugs > in LLVM! This has been listed as an "open project" for a long time [1], > but someone already implemented it, saving us the time and effort. > Thanks for the link! > > [1] http://llvm.cs.uiuc.edu/OpenProjects.html#misc_new > >

Sanjoy, in your blog post https://www.playingwithpointers.com/problem-with-undef.html <https://www.playingwithpointers.com/problem-with-undef.html> you describe a problem with LLVM “undef”, yet in your paper http://www.cs.utah.edu/~regehr/papers/undef-pldi17.pdf <http://www.cs.utah.edu/~regehr/papers/undef-pldi17.pdf> you do not suggest fixing this problem, even though in

I'm away from my Linux machines, if this hasn't been resolved by tonight I'll send more details. THe problem in cplus-dem.c is that CPP is conditionally including code that comes when HAVE_STDLIB is not defined, including an alternate protptype for malloc() that conflicts with the existing one. This is just what causes the error I sent-- no idea what the root cause is. Thanks,

Regarding the patches, there are two concerns AFAICT: 1. It’s a new instruction and as usual when introducing a new instruction it will require work for some time until most optimizations know about it, and to get rid of any potential perf regression. No big deal; we just need to do the work (and we have already done some of it). 2. The patch was written by a student, which may not have time to

We have a bitwidth analysis that can be downloaded. It is not in LLVM. There should be a link in the paper: http://www.cs.utah.edu/~regehr/papers/pldi075-cooprider.pdf John Regehr

http://www.cs.utah.edu/~regehr/compiler_correctness/llvm_gcc_x86/ I think these graphs speak for themselves. Feedback is welcome. John Regehr