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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Hi Samuel,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Thanks for your work, I would really much like to see OpenMP offloading implemented in clang!<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I can’t judge the necessary changes to the driver infrastructure but will rather focus on an end-user view…<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><div style='border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt'><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> samuelfantao@gmail.com [mailto:samuelfantao@gmail.com] <b>On Behalf Of </b>Samuel F Antao<br><b>Sent:</b> Thursday, February 25, 2016 1:02 AM<br><b>To:</b> cfe-dev@lists.llvm.org<br><b>Cc:</b> Alexey Bataev; Hal Finkel; John McCall; echristo@gmail.com; tra@google.com; Hahnfeld, Jonas<br><b>Subject:</b> [RFC][OpenMP][CUDA] Unified Offloading Support in Clang Driver<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'>[…]</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>g) Reflect the offloading programming model in the naming of the save-temps files.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Given that the same action is interpreted by different toolchains, if using save-temps the resulting file could be append with the programming model name by the target triple so that files don’t get overwritten.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><o:p> </o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>E.g. for OpenMP one would get a.bc and a-openmp-<triple>.bc if the driver is invoked with 'clang -c -save-temps a.c’.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>So these temporary files would all be unbundled so that they can be worked with as before? Or do you intend to save the bundled file as well?<br>a-openmp-<triple>.bc might get you into troubles if you are using the same triple for host and device…<br><br><o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>h) Use special options -target-offload=<triple> to specify offloading targets and delimit options meant for a toolchain.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>To avoid the proliferation of driver (and possibly frontend) options that are specific for a programming model I propose a new option that would specify an offloading device and have all the options following it processed for its toolchain. This would allow using the already existing options like -mcpu or -L/-l to tune the implementation for a given machine or provide linking commands that only make sense for the device.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><o:p> </o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>As an hypothetical example, lets assume we wanted to compile code that uses both CUDA for a nvptx64 device, OpenMP for an x86_64 device, and a powerpc64le host, one could invoke the driver as:<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><o:p> </o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>clang -target powerpc64le-ibm-linux-gnu <more host options><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>-target-offload=nvptx64-nvidia-cuda -fcuda -mcpu sm_35 <more options for the nvptx toolchain><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>-target-offload=x86_64-pc-linux-gnu -fopenmp <more options for the x86_64 toolchain><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>-target-offload=host <more options for the host><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>-target-offload=all <options for all toolchains><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><o:p> </o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>-fcuda or -fopenmp (or any other flag specifying a programming model) associated with an offload target would specify the programming model to be used for that target, and an error would be emitted if no programming model flag is found. I am also proposing having as special target-offload devices “host” and “all” to provide a convenient way for the user to pass options for all toolchains or to the host.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Would you have to specify ‘-fopenmp’ twice if you want to use OpenMP on the host as well? I’m asking because I’m interpreting your proposal that ‘-target-offload’ consumes all following options only for this specific target…<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'>[…]</span><o:p></o:p></p></div></div></div></body></html>