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Hello all, clang-related PGO documentation recommends using PGO with -O2 (for example: https://clang.llvm.org/docs/UsersManual.html#profile-guided-optimization). The question is: is there any reason why exactly -O2 is used in examples? Are there any factors which can cause problems when using PGO with -O3? Thanks in advance for your advice! -- Best Regards, Victor Leschuk | Software Engineer | Access Softek

...28, 2018 at 6:48 PM, Victor Leschuk via llvm-dev > <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote: > > Hello all, > > clang-related PGO documentation recommends using PGO with -O2 (for > example: > https://clang.llvm.org/docs/UsersManual.html#profile-guided-optimization > <https://clang.llvm.org/docs/UsersManual.html#profile-guided-optimization>). > The question is: is there any reason why exactly -O2 is used in > examples? Are there any factors which can cause problems when > using PGO > wi...

On Oct 29, 2010, at 11:35 AM, Xinliang David Li wrote: > Thanks for the -m tip to pass llvm options. Why is it not documented anywhere. See http://clang.llvm.org/docs/UsersManual.html#commandline -mllvm flags are somewhat equivalent to gcc -param options. -mllvm flags are for compiler hackers to play with, and are not stable or documented. Once TBAA is stable and reliable it will be controlled with -fstrict-aliasing as you'd expect. -Chris > > David > &g...

...using PGO with -O2 and above (including -O3). David On Sun, Jan 28, 2018 at 6:48 PM, Victor Leschuk via llvm-dev < llvm-dev at lists.llvm.org> wrote: > Hello all, > > clang-related PGO documentation recommends using PGO with -O2 (for > example: > https://clang.llvm.org/docs/UsersManual.html#profile-guided-optimization). > The question is: is there any reason why exactly -O2 is used in > examples? Are there any factors which can cause problems when using PGO > with -O3? > > Thanks in advance for your advice! > > -- > Best Regards, > > Victor Leschuk |...

...tem and foreign language interfaces, Tidying and profiling R code, Top @@ -8295,8 +8295,8 @@ to be installed separately, and for checking C++ you may also need @pkg{libubsan}.} of @command{gcc} and @command{clang} on common Linux and macOS platforms. See - at uref{http://clang.llvm.org/@/docs/@/UsersManual.html#controlling-code-generation}, - at uref{http://clang.llvm.org/@/docs/@/AddressSanitizer.html} and + at uref{https://clang.llvm.org/@/docs/@/UsersManual.html#controlling-code-generation}, + at uref{https://clang.llvm.org/@/docs/@/AddressSanitizer.html} and @uref{https://code.google.com/@/p/@/a...

Thanks for the -m tip to pass llvm options. Why is it not documented anywhere. See http://clang.llvm.org/docs/UsersManual.html#commandline <http://clang.llvm.org/docs/UsersManual.html#commandline>David On Fri, Oct 29, 2010 at 2:17 AM, Benjamin Kramer <benny.kra at googlemail.com>wrote: > > On 29.10.2010, at 09:26, Nick Lewycky wrote: > > > * If clang -O2 worked by running 'opt' a...

On Fri, Oct 29, 2010 at 3:54 PM, Chris Lattner <clattner at apple.com> wrote: > On Oct 29, 2010, at 11:35 AM, Xinliang David Li wrote: > > Thanks for the -m tip to pass llvm options. Why is it not documented > anywhere. See http://clang.llvm.org/docs/UsersManual.html#commandline > > > -mllvm flags are somewhat equivalent to gcc -param options. -mllvm flags > are for compiler hackers to play with, and are not stable or documented. > Once TBAA is stable and reliable it will be controlled with > -fstrict-aliasing as you'd expect. >...

On 29.10.2010, at 09:26, Nick Lewycky wrote: > * If clang -O2 worked by running 'opt' and 'llc' under the hood, we > could tell it to pass a flag along to them, but it doesn't. As it > stands, you can't turn -enable-tbaa on when running clang. > > So, putting that together, one way to do it is: > > clang -O2 -fstrict-aliasing foo.c -flto -c -o

The PGO was my first guess but I can get a lot of information. At first, I follow the explanation at http://clang.llvm.org/docs/UsersManual.html#profiling-with-instrumentation but instead of llvm-profdata merge, I used llvm-profdata show *.profraw. Sadly, the information I get is the total number of function, the maximum function count and the maximum internal block count. Do you know if you can tune the -fprofile-instr-generate para...

> Indeed, but can't an analysis find at least one value for each variable > where the behavior is not undefined? > Such a value must exist, or the entire function is useless if it always > has undefined behavior. Good point :). > Sure, testing on 1 such value (or a random) value won't prove that the > result is correct, but may help finding trivial > miscompilations

...w if there is better (i.e. more complete) documentation for UBSan somewhere? This one is pretty good, but it doesn't talk about many things. E.g. it doesn't describe the runtime options that are possible to pass to UBSan (like the one that I talked about earlier). http://clang.llvm.org/docs/UsersManual.html This page below doesn't seems to mention UBSan at all (unlike the others most commonly used sanitizers). Is it done on purpose? Or it's a work in progress? http://clang.llvm.org/docs/ Thanks, Katya. -------------- next part -------------- An HTML attachment was scrubbed... URL: &lt...

Dear Duncan, I am generating branch-weights annotated IR files as described in the documentation of LLVM, using profiling with instrumentation. http://clang.llvm.org/docs/UsersManual.html#profiling-with-instrumentation e.g. llvm-profdata merge -output=$(BENCH).profdata default.profraw > clang -S -emit-llvm -O3 -fprofile-instr-use=$(BENCH).profdata -o > bench.prof.ll bench.c The issue is that in some benchmarks I get crazy numbers in the annotated metadata inside the g...

...for a part of it I need to use some profiling information generated by > existing LLVM tools from the latest version of LLVM. In more detail, I am > trying to map profiling information generated from LLVM (Profiling with > instrumentation) to IR. > > ( > http://clang.llvm.org/docs/UsersManual.html#profiling-with-instrumentation > ) > > > > Specifically, I want to annotate each Basic Block with its respective > execution frequency. In order to accomplish that I am using the branch > weight metadata annotated to conditional branches in the terminator > instructions...

...h64 as the example target, but this is not target-dependent (as long as the target has FMA). 2. This is *not* -ffast-math...or is it? The C standard only shows on/off settings for the associated FP_CONTRACT pragma. 3. AFAIK, clang has no documentation for -ffp-contract: http://clang.llvm.org/docs/UsersManual.html 4. GCC says: https://gcc.gnu.org/onlinedocs/gcc-6.2.0/gcc/Optimize-Options.html#Optimize-Options "-ffp-contract=fast enables floating-point expression contraction such as forming of fused multiply-add operations if the target has native support for them." 5. The LLVM backend (where...

...on myself. Makes sense. > > There has been talk (I don't remember where) about a Clang option for > detecting undefined behavior. Is there any progress on this? This > could be used to enable automated random testing. *Yes, -fcatch-undefined-behavior. http://clang.llvm.org/docs/UsersManual.html#codegen * Best regards, --Edwin

...ly, this hypothetical option would suppress the folding of unsafe integer expressions altogether. Would an option such as this benefit the community at large? Clang's -fsanitize=integer-divide-by-zero option seems to provide what you want. See the Clang User Manual: http://clang.llvm.org/docs/UsersManual.html#controlling-code-generation --Owen -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130405/b37d9dd7/attachment.html>

Hello all, I'm wondering as to the status of control flow profiling in llvm. From what I can gather there was an old system (using opt -insert-edge-profiling and the like) which was removed in this commit llvm.org/viewvc/llvm-project?view=revision&revision=191835 . The commit message mentions "modern PGO efforts", but I can't find anything in the source tree or

Hi, Here is a small C++ program: vec.cc: #include <cmath> using v4f32 = float __attribute__((__vector_size__(16))); v4f32 fct1(v4f32 x) { return 1.0 / x; } v4f32 fct2(v4f32 x) { return __builtin_ia32_rcpps(x); } Which is compiled to: vec.o: file format elf64-x86-64 Disassembly of section .text: 0000000000000000 <_Z4fct1Dv4_f>: 0: c4 e2 79 18 0d 00 00 vbroadcastss

...2016, which is around half an year later then 3.8.0. > > Can you please try using newer clang. > Thanks. Travis does not allow an upgrade of the compiler in this instance. I already tried. Do you know where Clang keeps its documentation? I found https://releases.llvm.org/3.8.1/tools/docs/UsersManual.html#powerpc, but it lacks detail. Thanks for your help. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20191024/895403f5/attachment.html> -------------- next part -------------- A non-text attachment was...

Yeah I have already see pintool but I need this to work with ARM and Intel. If I remember correctly, pintool does not work on ARM (or quite bad). My goal with the instrumentation is, once I have the information (time + call), to choose (during a second compilation) if some of my passes are applicable or not. Greetings, Johan On 17 Jul 2015, at 16:09, Kenneth Adam Miller <kennethadammiller