Actually OpenCL specification has the following text in “Built-in Functions” chapter (OpenCL C 2.0 rev. 33):
“ User defined OpenCL C functions, behave per C standard rules for functions (C99, TC2, Section 6.9.1). On entry to the function, the size of each variably modified parameter is evaluated and the value of each argument expression is converted to the type of the corresponding parameter as per usual arithmetic conversion rules described in section 6.2.6. Built-in functions described in this section behave similarly, except that in order to avoid ambiguity between multiple forms of the same built-in function, implicit scalar widening shall not occur. Note that some built-in functions described in this section do have forms that operate on mixed scalar and vector types, however.” If I understand it correctly this text can help to resolve the overloading, since “usual arithmetic conversion rules” from section 6.2.6 rank floating point and integer data types including vector flavors. On the other hand I don’t think it’s good idea to adopt this rule, since it doesn’t follow C++ overloading rules and definitely will deviate OpenCL behavior from C or C++. Thanks, Alexey From: Anastasia Stulova [mailto:anastasia.stul...@arm.com] Sent: Monday, December 5, 2016 9:21 PM To: Richard Smith <rich...@metafoo.co.uk>; Bruno Cardoso Lopes via Phabricator <revi...@reviews.llvm.org>; reviews+d27334+public+f2c5a66032c4c...@reviews.llvm.org Cc: Bader, Alexey <alexey.ba...@intel.com>; egor.chur...@gmail.com; yaxun....@amd.com; cfe-commits@lists.llvm.org; nd <n...@arm.com> Subject: RE: [PATCH] D27334: [OpenCL] Ambiguous function call. > Perhaps that is the problem (that there are two modes that do different > things)? Could we make the double overload be present but unselectable to > diagnose this problem in that mode too? If we could resolve the overload candidate to prefer ‘int -> float’ than ‘int->double’, it would work best. From: meta...@gmail.com<mailto:meta...@gmail.com> [mailto:meta...@gmail.com] On Behalf Of Richard Smith Sent: 05 December 2016 17:53 To: Bruno Cardoso Lopes via Phabricator; reviews+d27334+public+f2c5a66032c4c...@reviews.llvm.org<mailto:reviews+d27334+public+f2c5a66032c4c...@reviews.llvm.org> Cc: alexey.ba...@intel.com<mailto:alexey.ba...@intel.com>; egor.chur...@gmail.com<mailto:egor.chur...@gmail.com>; yaxun....@amd.com<mailto:yaxun....@amd.com>; Anastasia Stulova; cfe-commits@lists.llvm.org<mailto:cfe-commits@lists.llvm.org> Subject: Re: [PATCH] D27334: [OpenCL] Ambiguous function call. On 5 Dec 2016 9:42 am, "Anastasia Stulova via Phabricator via cfe-commits" <cfe-commits@lists.llvm.org<mailto:cfe-commits@lists.llvm.org>> wrote: Anastasia added a comment. In https://reviews.llvm.org/D27334#612858, @bader wrote: > In https://reviews.llvm.org/D27334#611703, @Anastasia wrote: > > > This change seems to modify normal C behavior again. Is there any strong > > motivation for doing this and if yes could it be done generically with C? > > > Motivation: > > // Non-portable OpenCL 1.2 code > __kernel void foo(global float* out) { > out[get_global_id(0)] = sin(get_global_id(0)); > } > > > This program compiles fine on OpenCL platform w/o doubles support Perhaps that is the problem (that there are two modes that do different things)? Could we make the double overload be present but unselectable to diagnose this problem in that mode too? and fails otherwise. > If OpenCL driver supports doubles it provides at least two versions of 'sin' > built-in math function and compiler will not be able to choose the right one > for 'size_t' argument. Do you have a real example? If someone passes an integer to 'sin', I think there's a better warning we can give them :) > The goal of this warning is to let OpenCL developer know about potential > issues with code portability. I would argue this improves the portability much as it can also be misleading in some situations (because it refers to a potentially hypothetical problem). For example there can be builtin functions that only have a float parameter (without a double version of it). This is for example the case with read_image functions that take a float coordinate value between 0 and 1. Unfortunately this warning won't be triggered on read_image functions because there is an overload candidate with an int type of the same parameter too. But we can't exclude this situations to appear in the future or from some vendor extensions or even custom OpenCL code. https://reviews.llvm.org/D27334 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org<mailto:cfe-commits@lists.llvm.org> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits -------------------------------------------------------------------- Joint Stock Company Intel A/O Registered legal address: Krylatsky Hills Business Park, 17 Krylatskaya Str., Bldg 4, Moscow 121614, Russian Federation This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies.
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