search for: mcpu

Motivation At the moment, when targeting armv7a, clang defaults to generate code as if -mcpu=cortex-a8 was specified. When targeting armv8a, it defaults to generate code as if -mcpu=cortex-a53 was specified. This leads to surprising code generation, by the compiler optimizing for a specific micro-architecture, whereas the intent from the user was probably to generate code that is "bl...

Thanks for everyone giving their feedback! I saw pretty unanimous support for making -mcpu=generic the default and making -mcpu=generic schedule for an in-order CPU (Cortex-A8 in this case). I'll be making those changes shortly. I think the comments also make clear that it's less obvious whether we'd want -mcpu=native to become a default. It's probably good for some use...

.... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... ....... downloaded 437Kb * Installing *source* package 'fields' ... ** libs g77 -mieee-fp -fPIC -O2 -g -pipe -march=i386 -mcpu=i686 -c css.f -o css.o g77 -mieee-fp -fPIC -O2 -g -pipe -march=i386 -mcpu=i686 -c csstr.f -o csstr.o g77 -mieee-fp -fPIC -O2 -g -pipe -march=i386 -mcpu=i686 -c cvrf.f -o cvrf.o g77 -mieee-fp -fPIC -O2 -g -pipe -march=i386 -mcpu=i686 -c dchold.f -o dchold.o g77 -mieee-fp -fPIC -O2 -g -pipe -...

I'm confused about the clang --target, -mcpu, -march Can someone give a clear explanation on what is the difference between them? Originally I thought need to specify -mcpu (which I assume means CPU) and -march but then I can't figure out how --target fits into the picture. Sometimes it tells me that -march or -mcpu options is not used....

Hello everyone, this is most likely Arm specific, but could affect other targets where there is a somewhat complex relationship between the triple and mcpu option. At present when clang is used as a linker driver for the gold-plugin and when using and an explicit -mcpu is not given to clang, then clang will always generate a -Wl,-plugin-opt=mcpu=<default CPU> where the default CPU is based on the triple. I think that this is causing more probl...

...nk with Fortran 77 libraries... unknown configure: error: linking to Fortran libraries from C fails ERROR: configuration failed for package 'Matrix' # R CMD INSTALL akima_0.3-4.tar.gz * Installing *source* package 'akima' ... ** libs g77 -mieee-fp -O3 -fomit-frame-pointer -pipe -mcpu=pentiumpro -march=i586 -fno-fast-math -fno-strength-reduce -O3 -fomit-frame-pointer -pipe -mcpu=pentiumpro -march=i586 -fno-fast-math -fno-strength-reduce -c akima.new.f -o akima.new.o g77 -mieee-fp -O3 -fomit-frame-pointer -pipe -mcpu=pentiumpro -march=i586 -fno-fast-math -fno-strength-reduc...

Thanks Eric, After the original reply to my query I had a good look at the GCC documentation for these options, and what I discovered is that “there is no consensus” in GCC. Basically, saying do what GCC does was a non-answer as it clarified nothing. X86 has deprecated ‘-mcpu’ in favour of ‘-mtune’, and it uses ‘-mtune’ to mean that the scheduling, etc. should be biased in favour of more performant code for the processor identified by ‘-mtune’, but that the code is still 100% functional on all other processors in the family identified by ‘-march’. MIPS and ARM seem...

On Fri, Mar 18, 2016 at 12:49 PM, Eric Christopher <echristo at gmail.com> wrote: > > > On Wed, Mar 16, 2016 at 2:53 PM Rail Shafigulin via llvm-dev < > llvm-dev at lists.llvm.org> wrote: > >> I'm confused about the clang --target, -mcpu, -march >> >> Can someone give a clear explanation on what is the difference between >> them? >> >> > I can try :) > > >> Originally I thought need to specify -mcpu (which I assume means CPU) and >> -march but then I can't figure out how --targ...

...tions, and what I discovered is that “there is no > consensus” in GCC. Basically, saying do what GCC does was a non-answer as > it clarified nothing. > > > That's why I made the comments I did on a generic new target which is the suggested consensus. > X86 has deprecated ‘-mcpu’ in favour of ‘-mtune’, and it uses ‘-mtune’ to > mean that the scheduling, etc. should be biased in favour of more > performant code for the processor identified by ‘-mtune’, but that the > code is still 100% functional on all other processors in the family > identified by ‘-march’. &g...

> > -Most- targets use -march. > > -eric > Do you meat that in most cases -target is used along with -march instead of -target and -mcpu? -- Rail Shafigulin Software Engineer Esencia Technologies -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20160318/9efe3d1b/attachment.html>

On 3/15/2018 9:43 AM, Peter Smith via llvm-dev wrote: > Hello everyone, this is most likely Arm specific, but could affect > other targets where there is a somewhat complex relationship between > the triple and mcpu option. > > At present when clang is used as a linker driver for the gold-plugin > and when using and an explicit -mcpu is not given to clang, then clang > will always generate a -Wl,-plugin-opt=mcpu=<default CPU> where the > default CPU is based on the triple. > > I thin...

Thanks very much Eric for taking the time to carefully explain this to me. So if I am the author of the backend for a new processor technology, or willing to modernise my existing implementation, you would recommend that the ‘-mcpu’ option is deprecated and probably best not used at all, or perhaps just as a synonym for ‘-march + -mtune’? The first part of the target triple guides the overall high level processor architecture - essentially the CPU - and that I would be better using ‘-march’ to specify the variants of this...

Dear All, when I try to: install.packages("Design"); install.packages("Hmisc") I get the following error messages: * Installing *source* package 'Design' ... ** libs g77 -mieee-fp -O2 -fomit-frame-pointer -pipe -march=i586 -mcpu=pentiumpro -O2 -fomit-frame-pointer -pipe -march=i586 -mcpu=pentiumpro -c lrmfit.f -o lrmfit.o make: g77: Command not found make: *** [lrmfit.o] Error 127 ERROR: compilation failed for package 'Design' * Installing *source* package 'Hmisc' ... ** libs g77 -mieee-fp -O2 -fomit-fra...

llc -mcpu=help doesn't print any output, just tries to silently read from standard input. Am I doing something wrong?

...more info please let me know. ---- install log --------- /u/geware/programs/analysis/R-packages (root) ->R CMD INSTALL izbi * Installing *source* package 'izbi' ... ** libs gcc -I/usr/lib/R/include -I/usr/local/include -D__NO_MATH_INLINES -mieee-fp -fPIC -O2 -g -pipe -march=i386 -mcpu=i686 -c aggreg.c -o aggreg.o gcc -I/usr/lib/R/include -I/usr/local/include -D__NO_MATH_INLINES -mieee-fp -fPIC -O2 -g -pipe -march=i386 -mcpu=i686 -c grptest.c -o grptest.o gcc -I/usr/lib/R/include -I/usr/local/include -D__NO_MATH_INLINES -mieee-fp -fPIC -O2 -g -pipe -march=i386 -mcpu=i68...

That's right. In your example, if the target isn't specified anywhere, an llc invocation would be equivalent to "llc -mtriple=x86_64-unknown-linux-gnu -mcpu=generic". TTI queries (in e.g., CodeGenPrepare) would be based on this. From opt, if the target triple is left unspecified, we will use the "base" TTI implementation (not x86). -- Matt On Wed, Nov 30, 2016 at 2:07 PM, Michael Kuperstein via llvm-dev < llvm-dev at lists.llvm.org&...

Hi everyone, I'm working in a company to port LLVM on their own processors. I'm try to support several set of instructions and several architectures. I'm using the "--target" options to choose my set of instructions, and I would like to use the "-mcpu" to choose the architecture of which I want to compile the code. Does it seem right? But at the moment I cannot manage to have the CPU information in my "LLVMTargetMachine" constructor. I have it when I go through llc: clang -emit-llvm ... llc -mcpu=mycpu ... But not when I go...

Hi, Recently, I committed a patch adding default features for '-mcpu'. And after that, Eric replied me here's a proposal toward using '-march' instead of '-mcpu'. As it's half a year later from original proposal, some background may changes. One thing worth to mention is, during this time, Apple Contributed its backend and introduced anot...

I knew I'd regret leaving that option in for the MIPS port back in 99. Basically this is the only acceptable way for mcpu to exist, but should never have been added to the GCC aarch64 port at all since there's no compatibility with existing build systems to worry about. I would still like you to show this mythical piece of software that needs this compatibility. -eric On Jan 8, 2014 3:06 AM, "Bernie Ogden&q...

Hi Anitha, Thanks for your answer but -mcpu=cortex-a9 -mattr=+vfp4 doesn' t enable fused mac generation for me. I would like just to understand why -mtriple=armv7-eabi enables it while -mcpu=cortex-a9 seems to disable it ? Seb > -----Original Message----- > From: Anitha Boyapati [mailto:anitha.boyapati at gmail.com] > Sent: Th...