Message ID | 20220329133931.GA5489@delia.home |
---|---|
State | New |
Headers | show |
Series | [nvptx,doc] Update misa and mptx, add march and march-map | expand |
Hi Tom, On 29.03.22 15:39, Tom de Vries wrote: > Any comments? > +(e.g.@: @samp{sm_35}). Valid architecture strings are @samp{sm_30}, > +@samp{sm_35}, @samp{sm_53} @samp{sm_70}, @samp{sm_75} and > +@samp{sm_80}. The default target architecture is sm_30. Missing comma (",") between sm_53 and sm_70. I want to note that the default is now back at sm_30; for GCC 11 it was changed to sm_35, cf. https://gcc.gnu.org/gcc-11/changes.html (We also need to update the wwwdocs release notes before the release, but it can also be done after branching). > +@item -march-map=@var{architecture-string} > +@opindex march > +Select the closest available @option{-march=} value that is not more > +capable. For instance, for @option{-march-map=sm_50} select > +@option{-march=sm_35}, and for @option{-march-map=sm_53} select > +@option{-march=sm_53}. (Somehow, I am not completely happy with the wording, but, admittedly, I don't have a better suggestion.) Tobias ----------------- Siemens Electronic Design Automation GmbH; Anschrift: Arnulfstraße 201, 80634 München; Gesellschaft mit beschränkter Haftung; Geschäftsführer: Thomas Heurung, Frank Thürauf; Sitz der Gesellschaft: München; Registergericht München, HRB 106955
On 29.03.22 16:28, Tobias Burnus wrote: > On 29.03.22 15:39, Tom de Vries wrote: >> Any comments? I think it would be useful to have additionally some wording for the (new in GCC 12/new since today) macros, i.e. something like: --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -27546,6 +27546,10 @@ strings must be lower-case. Valid ISA strings include @samp{sm_30} and @samp{sm_35}. The default ISA is sm_35. +This option causes the preprocessor macro @code{__PTX_SM__} to be defined +to the architecture number multiplied by ten; for instance, for +@samp{sm_35}, it has the value @samp{350}. + @item -mptx=@var{version-string} @opindex mptx Generate code for given the specified PTX version (e.g.@: @samp{7.0}). @@ -27553,6 +27557,10 @@ @samp{7.0}. The default PTX version is 6.0, unless a higher minimal version is required for specified PTX ISA via option @option{-misa=}. +This option causes the preprocessor macros @code{__PTX_ISA_VERSION_MAJOR__} +and @code{__PTX_ISA_VERSION_MINOR__} to be defined; for instance, +for @samp{3.1} the macros have the values @samp{3} and @samp{1}, respectively. + @item -mmainkernel @opindex mmainkernel Link in code for a __main kernel. This is for stand-alone instead of Tobias ----------------- Siemens Electronic Design Automation GmbH; Anschrift: Arnulfstraße 201, 80634 München; Gesellschaft mit beschränkter Haftung; Geschäftsführer: Thomas Heurung, Frank Thürauf; Sitz der Gesellschaft: München; Registergericht München, HRB 106955
On 3/29/22 16:28, Tobias Burnus wrote: > Hi Tom, > > On 29.03.22 15:39, Tom de Vries wrote: >> Any comments? >> +(e.g.@: @samp{sm_35}). Valid architecture strings are @samp{sm_30}, >> +@samp{sm_35}, @samp{sm_53} @samp{sm_70}, @samp{sm_75} and >> +@samp{sm_80}. The default target architecture is sm_30. > > Missing comma (",") between sm_53 and sm_70. > Ack, fixed. > I want to note that the default is now back at sm_30; > for GCC 11 it was changed to sm_35, cf. > https://gcc.gnu.org/gcc-11/changes.html I think changes are better described in release notes. > (We also need to update the wwwdocs release notes before the release, > but it > can also be done after branching). > Right, I'll follow up on your proposal from beginning of this month. >> +@item -march-map=@var{architecture-string} >> +@opindex march >> +Select the closest available @option{-march=} value that is not more >> +capable. For instance, for @option{-march-map=sm_50} select >> +@option{-march=sm_35}, and for @option{-march-map=sm_53} select >> +@option{-march=sm_53}. > > (Somehow, I am not completely happy with the wording, but, admittedly, I > don't have a better suggestion.) I feel the same, so committed as is. Thanks, - Tom
On 3/29/22 16:47, Tobias Burnus wrote: > On 29.03.22 16:28, Tobias Burnus wrote: > >> On 29.03.22 15:39, Tom de Vries wrote: >>> Any comments? > > I think it would be useful to have additionally some wording for the > (new in GCC 12/new since today) macros, Agreed. > i.e. something like: > > --- a/gcc/doc/invoke.texi > +++ b/gcc/doc/invoke.texi > @@ -27546,6 +27546,10 @@ > strings must be lower-case. Valid ISA strings include @samp{sm_30} and > @samp{sm_35}. The default ISA is sm_35. > > +This option causes the preprocessor macro @code{__PTX_SM__} to be defined > +to the architecture number multiplied by ten; for instance, for > +@samp{sm_35}, it has the value @samp{350}. > + The macro is defined also if the option is not specified, so I think this formulation is not 100% clear in that aspect. I've reformulated to fix that. Also, I took out the detail of how the value is determined, since we're just following __CUDA_ARCH__ rather than defining our own policy. > @item -mptx=@var{version-string} > @opindex mptx > Generate code for given the specified PTX version (e.g.@: @samp{7.0}). > @@ -27553,6 +27557,10 @@ > @samp{7.0}. The default PTX version is 6.0, unless a higher minimal > version is required for specified PTX ISA via option @option{-misa=}. > > +This option causes the preprocessor macros > @code{__PTX_ISA_VERSION_MAJOR__} > +and @code{__PTX_ISA_VERSION_MINOR__} to be defined; for instance, > +for @samp{3.1} the macros have the values @samp{3} and @samp{1}, > respectively. > + Reformulated this as well. Any comments? Thanks, - Tom
On 30.03.22 10:03, Tom de Vries wrote: > On 3/29/22 16:47, Tobias Burnus wrote: >> I think it would be useful to have additionally some wording for the >> (new in GCC 12/new since today) macros, [...] > The macro is defined also if the option is not specified, so I think > this formulation is not 100% clear in that aspect. I've reformulated > to fix that. Fine. (It was a copy, paste + modify from elsewhere.) > Also, I took out the detail of how the value is determined, since > we're just following __CUDA_ARCH__ rather than defining our own policy. OK. While I am not sure that it is obvious, also the example makes clear what value to expect. Combining the two, I concur that the details aren't required. > Any comments? LGTM. Tobias PS: Regarding the sm_30 -> sm_35 change (before in this email thread). That was not meant to be in the the .texi file, but just as item to remember when updating the wwwdocs / gcc-12/changes.html document. It was/is also not completely clear to me whether there is still this CUDA 11.x issue of not supporting sm_30 (only sm_35 and higher) or not. I assume it still exists but is mitigated at compiler-usage/libgomp-runtime-usage time as PTX ISA now defaults to 6.0 such that CUDA – but shouldn't it still see sm_30 instead of sm_35 in this case? If so, I think it will still show up when using either explicitly PTX ISA 3.1 or when building GCC itself and all of the following holds: nvptx-tools is installed, CUDA (in a too new version) is installed (ptxas in $PATH) , and the the pending pull request nvptx-tools has not been applied that ignores the non-explicit '--verify' when .target sm_xx or PTX ISA .version is not supported by ptxas. ----------------- Siemens Electronic Design Automation GmbH; Anschrift: Arnulfstraße 201, 80634 München; Gesellschaft mit beschränkter Haftung; Geschäftsführer: Thomas Heurung, Frank Thürauf; Sitz der Gesellschaft: München; Registergericht München, HRB 106955
On 3/30/22 11:02, Tobias Burnus wrote: > On 30.03.22 10:03, Tom de Vries wrote: > >> On 3/29/22 16:47, Tobias Burnus wrote: >>> I think it would be useful to have additionally some wording for the >>> (new in GCC 12/new since today) macros, > [...] >> The macro is defined also if the option is not specified, so I think >> this formulation is not 100% clear in that aspect. I've reformulated >> to fix that. > Fine. (It was a copy, paste + modify from elsewhere.) > >> Also, I took out the detail of how the value is determined, since >> we're just following __CUDA_ARCH__ rather than defining our own policy. > > OK. While I am not sure that it is obvious, also the example makes clear > what value to expect. Combining the two, I concur that the details > aren't required. > >> Any comments? > > LGTM. > > Tobias > > > PS: Regarding the sm_30 -> sm_35 change (before in this email thread). > That was not meant to be in the the .texi file, but just as item to > remember when updating the wwwdocs / gcc-12/changes.html document. > I see, I misunderstood then. FWIW, it's already added to the version in my sandbox. > It was/is also not completely clear to me whether there is still this > CUDA 11.x issue of not supporting sm_30 (only sm_35 and higher) or not. Thanks for reminding me of this issue. > I assume it still exists but is mitigated at > compiler-usage/libgomp-runtime-usage time as PTX ISA now defaults to 6.0 > such that CUDA – but shouldn't it still see sm_30 instead of sm_35 in > this case? > > If so, I think it will still show up when using either explicitly PTX > ISA 3.1 or when building GCC itself and all of the following holds: > nvptx-tools is installed, CUDA (in a too new version) is installed > (ptxas in $PATH) , and the the pending pull request nvptx-tools has not > been applied that ignores the non-explicit '--verify' when .target sm_xx > or PTX ISA .version is not supported by ptxas. I don't think the 6.0 default has any influence (and I'll be using -mptx=3.1 below to make sure we run into the worst-case behaviour). Anyway, in absence of an nvptx-tools fix I committed a work-around in the compiler: ... #define ASM_SPEC "%{misa=*:-m %*; :-m sm_35}%{misa=sm_30:--no-verify}" ... Note that this was before reverting back the default to sm_30, and I probably forgot to update this spot when changing the default. So now, there are effectively two workarounds in place. This (implicitly using sm_30) passes: ... $ ( PATH=$PATH:~/cuda/11.6.0/bin; ./gcc.sh ~/hello.c -c -save-temps -Wa,--verify -mptx=3.1 ) ... because as we can see with -v, sm_35 is used to verify: ... ./build-gcc/gcc/as -m sm_35 --verify -o hello.o hello.s ... This (explicitly using sm_30) passes: ... $ ( PATH=$PATH:~/cuda/11.6.0/bin; ./gcc.sh ~/hello.c -c -save-temps -march=sm_30 -mptx=3.1 ) ... because as we can see with -v, the --no-verify workaround is triggered: ... ./build-gcc/gcc/as -m sm_30 --no-verify -o hello.o hello.s ... But that one stops working once we use an explicit -Wa,--verify: ... $ ( PATH=$PATH:~/cuda/11.6.0/bin; ./gcc.sh ~/hello.c -c -save-temps -Wa,--verify -march=sm_30 -mptx=3.1 ) ptxas fatal : Value 'sm_30' is not defined for option 'gpu-name' nvptx-as: ptxas returned 255 exit status ... So, it seems using sm_35 to verify sm_30 is the most robust workaround. I'm currently testing attached patch. Thanks, - Tom
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 554e04ecbf3a..eb2fe959e600 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -27540,18 +27540,31 @@ These options are defined for Nvidia PTX: Ignored, but preserved for backward compatibility. Only 64-bit ABI is supported. -@item -misa=@var{ISA-string} +@item -march=@var{architecture-string} @opindex march -Generate code for given the specified PTX ISA (e.g.@: @samp{sm_35}). ISA -strings must be lower-case. Valid ISA strings include @samp{sm_30} and -@samp{sm_35}. The default ISA is sm_35. +Generate code for the specified PTX ISA target architecture +(e.g.@: @samp{sm_35}). Valid architecture strings are @samp{sm_30}, +@samp{sm_35}, @samp{sm_53} @samp{sm_70}, @samp{sm_75} and +@samp{sm_80}. The default target architecture is sm_30. + +@item -misa=@var{architecture-string} +@opindex misa +Alias of @option{-march=}. + +@item -march-map=@var{architecture-string} +@opindex march +Select the closest available @option{-march=} value that is not more +capable. For instance, for @option{-march-map=sm_50} select +@option{-march=sm_35}, and for @option{-march-map=sm_53} select +@option{-march=sm_53}. @item -mptx=@var{version-string} @opindex mptx -Generate code for given the specified PTX version (e.g.@: @samp{7.0}). +Generate code for the specified PTX ISA version (e.g.@: @samp{7.0}). Valid version strings include @samp{3.1}, @samp{6.0}, @samp{6.3}, and -@samp{7.0}. The default PTX version is 6.0, unless a higher minimal -version is required for specified PTX ISA via option @option{-misa=}. +@samp{7.0}. The default PTX version is 6.0, unless a higher version +is required for specified PTX ISA target architecture via option +@option{-march=}. @item -mmainkernel @opindex mmainkernel