Hi Richard, > This is incorrect. Implicit function declarations declare unprototyped > functions, which are *not* variadic, and are in fact supported by Clang's > OpenCL language mode.
We have removed the support for the unprototyped functions from the OpenCL as well. See commit: https://reviews.llvm.org/D33681. This is the reason why in the OpenCL mode we now generated empty parameter list instead of unprototyped function like for C in the examples I provided before (that is not governed now by any standard or any compiler extension). > I would have sympathy for your position if we did not produce an extension > warning on this construct by default. But we do, and it says the construct is > invalid in OpenCL; moreover, in our strict conformance mode > (-pedantic-errors), we reject the code. I understand the motivation for C to maintain the compatibility with the previous standards and other compilers (like gcc) to be able to support the legacy code. However, for OpenCL we don't have this requirement wrt older C standards. And therefore it is desirable to take advantage of this and remove problematic features that are generally confusing for developers or that can't be efficiently supported by the targets (especially if there is a little cost to that). ________________________________ From: Richard Smith <rich...@metafoo.co.uk> Sent: 21 August 2018 22:09:35 To: Anastasia Stulova Cc: cfe-commits; nd Subject: Re: r314872 - We allow implicit function declarations as an extension in all C dialects. Remove OpenCL special case. On Tue, 21 Aug 2018 at 07:41, Anastasia Stulova via cfe-commits <cfe-commits@lists.llvm.org<mailto:cfe-commits@lists.llvm.org>> wrote: If there are no objections I would like to revert this old commit that coverts error about implicit function declaration into a warning. We have decided to generate an error for this https://reviews.llvm.org/D31745 because for OpenCL variadic prototypes are disallowed (section 6.9.e, https://www.khronos.org/registry/OpenCL/specs/opencl-2.0-openclc.pdf) and the implicit prototype requires variadic support. This is incorrect. Implicit function declarations declare unprototyped functions, which are *not* variadic, and are in fact supported by Clang's OpenCL language mode. See C90 6.5.4.3 Semantics, last paragraph, and 6.3.2.2 Semantics, second paragraph. So that argument does not appear to apply. The reason we accept implicitly-declared functions outside of our C89 mode is because this is an explicit, supported Clang extension. Generally, Clang intends to support using all of its extensions together, unless there is some fundamental reason why they cannot be combined. So, just as it doesn't make sense for our OpenCL language mode to conflict with, say, AltiVec vector extensions, it doesn't make sense for the OpenCL language mode to conflict with our implicitly-declared functions extension. I would have sympathy for your position if we did not produce an extension warning on this construct by default. But we do, and it says the construct is invalid in OpenCL; moreover, in our strict conformance mode (-pedantic-errors), we reject the code. As most vendors that support OpenCL don't support variadic functions it was decided to restrict this explicitly in the spec (section s6.9.u). There is a little bit of more history in https://reviews.llvm.org/D17438. Currently the code that can't run correctly on most OpenCL targets compiles successfully. The problem can't be easily seen by the OpenCL developers since it's not very common to retrieve the compilation warning log during online compilation. Also generated IR doesn't seem to be correct if I compare with the similar code in C. Example: 1 typedef long long16 __attribute__((ext_vector_type(16))); 2 void test_somefunc( __global int *d, __global void *s ) 3 { 4 int i = get_global_id(0); 5 d[i] = somefunc((( __global long16 *)s)[i]); 6 } Is generated to: %call1 = call i32 (<16 x i64>*, ...) bitcast (i32 ()* @somefunc to i32 (<16 x i64>*, ...)*)(<16 x i64>* byval nonnull align 128 %indirect-arg-temp) #2 ... declare i32 @somefunc() local_unnamed_addr #1 Equivalent C code at least generates variadic function prototype correctly: %call1 = call i32 (<16 x i64>*, ...) bitcast (i32 (...)* @somefunc to i32 (<16 x i64>*, ...)*)(<16 x i64>* byval align 128 %indirect-arg-temp) ... declare i32 @somefunc(...) Anastasia ________________________________ From: cfe-commits <cfe-commits-boun...@lists.llvm.org<mailto:cfe-commits-boun...@lists.llvm.org>> on behalf of Richard Smith via cfe-commits <cfe-commits@lists.llvm.org<mailto:cfe-commits@lists.llvm.org>> Sent: 04 October 2017 02:58 To: cfe-commits@lists.llvm.org<mailto:cfe-commits@lists.llvm.org> Subject: r314872 - We allow implicit function declarations as an extension in all C dialects. Remove OpenCL special case. Author: rsmith Date: Tue Oct 3 18:58:22 2017 New Revision: 314872 URL: http://llvm.org/viewvc/llvm-project?rev=314872&view=rev Log: We allow implicit function declarations as an extension in all C dialects. Remove OpenCL special case. Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td cfe/trunk/lib/Sema/SemaDecl.cpp cfe/trunk/test/SemaOpenCL/clang-builtin-version.cl<http://clang-builtin-version.cl> cfe/trunk/test/SemaOpenCL/to_addr_builtin.cl<http://to_addr_builtin.cl> Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=314872&r1=314871&r2=314872&view=diff ============================================================================== --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original) +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Tue Oct 3 18:58:22 2017 @@ -355,7 +355,7 @@ def warn_implicit_function_decl : Warnin "implicit declaration of function %0">, InGroup<ImplicitFunctionDeclare>, DefaultIgnore; def ext_implicit_function_decl : ExtWarn< - "implicit declaration of function %0 is invalid in C99">, + "implicit declaration of function %0 is invalid in %select{C99|OpenCL}1">, InGroup<ImplicitFunctionDeclare>; def note_function_suggestion : Note<"did you mean %0?">; @@ -8449,8 +8449,6 @@ def err_opencl_scalar_type_rank_greater_ "element. (%0 and %1)">; def err_bad_kernel_param_type : Error< "%0 cannot be used as the type of a kernel parameter">; -def err_opencl_implicit_function_decl : Error< - "implicit declaration of function %0 is invalid in OpenCL">; def err_record_with_pointers_kernel_param : Error< "%select{struct|union}0 kernel parameters may not contain pointers">; def note_within_field_of_type : Note< Modified: cfe/trunk/lib/Sema/SemaDecl.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDecl.cpp?rev=314872&r1=314871&r2=314872&view=diff ============================================================================== --- cfe/trunk/lib/Sema/SemaDecl.cpp (original) +++ cfe/trunk/lib/Sema/SemaDecl.cpp Tue Oct 3 18:58:22 2017 @@ -12642,17 +12642,15 @@ NamedDecl *Sema::ImplicitlyDefineFunctio } // Extension in C99. Legal in C90, but warn about it. + // OpenCL v2.0 s6.9.u - Implicit function declaration is not supported. unsigned diag_id; if (II.getName().startswith("__builtin_")) diag_id = diag::warn_builtin_unknown; - // OpenCL v2.0 s6.9.u - Implicit function declaration is not supported. - else if (getLangOpts().OpenCL) - diag_id = diag::err_opencl_implicit_function_decl; - else if (getLangOpts().C99) + else if (getLangOpts().C99 || getLangOpts().OpenCL) diag_id = diag::ext_implicit_function_decl; else diag_id = diag::warn_implicit_function_decl; - Diag(Loc, diag_id) << &II; + Diag(Loc, diag_id) << &II << getLangOpts().OpenCL; // If we found a prior declaration of this function, don't bother building // another one. We've already pushed that one into scope, so there's nothing Modified: cfe/trunk/test/SemaOpenCL/clang-builtin-version.cl<http://clang-builtin-version.cl> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaOpenCL/clang-builtin-version.cl?rev=314872&r1=314871&r2=314872&view=diff ============================================================================== --- cfe/trunk/test/SemaOpenCL/clang-builtin-version.cl<http://clang-builtin-version.cl> (original) +++ cfe/trunk/test/SemaOpenCL/clang-builtin-version.cl<http://clang-builtin-version.cl> Tue Oct 3 18:58:22 2017 @@ -1,4 +1,4 @@ -// RUN: %clang_cc1 %s -fblocks -verify -pedantic -fsyntax-only -ferror-limit 100 +// RUN: %clang_cc1 %s -fblocks -verify -pedantic-errors -fsyntax-only -ferror-limit 100 // Confirm CL2.0 Clang builtins are not available in earlier versions Modified: cfe/trunk/test/SemaOpenCL/to_addr_builtin.cl<http://to_addr_builtin.cl> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaOpenCL/to_addr_builtin.cl?rev=314872&r1=314871&r2=314872&view=diff ============================================================================== --- cfe/trunk/test/SemaOpenCL/to_addr_builtin.cl<http://to_addr_builtin.cl> (original) +++ cfe/trunk/test/SemaOpenCL/to_addr_builtin.cl<http://to_addr_builtin.cl> Tue Oct 3 18:58:22 2017 @@ -10,7 +10,7 @@ void test(void) { glob = to_global(glob, loc); #if __OPENCL_C_VERSION__ < CL_VERSION_2_0 - // expected-error@-2{{implicit declaration of function 'to_global' is invalid in OpenCL}} + // expected-warning@-2{{implicit declaration of function 'to_global' is invalid in OpenCL}} // expected-warning@-3{{incompatible integer to pointer conversion assigning to '__global int *' from 'int'}} #else // expected-error@-5{{invalid number of arguments to function: 'to_global'}} _______________________________________________ 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 _______________________________________________ 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 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
