On Tue, Aug 3, 2021 at 4:47 AM Richard Biener wrote: > > On Sun, Jul 18, 2021 at 3:46 AM H.J. Lu wrote: > > > > On Thu, Apr 22, 2021 at 7:30 AM Richard Biener via Gcc-patches > > wrote: > > > > > > On Thu, Apr 22, 2021 at 2:52 PM Richard Biener > > > wrote: > > > > > > > > On Thu, Apr 22, 2021 at 2:22 PM Jakub Jelinek wrote: > > > > > > > > > > On Thu, Apr 22, 2021 at 01:23:20PM +0200, Richard Biener via Gcc-patches wrote: > > > > > > > The question is if the pragma GCC target right now behaves incrementally > > > > > > > or not, whether > > > > > > > #pragma GCC target("avx2") > > > > > > > adds -mavx2 to options if it was missing before and nothing otherwise, or if > > > > > > > it switches other options off. If it is incremental, we could e.g. try to > > > > > > > use the second least significant bit of global_options_set.x_* to mean > > > > > > > this option has been set explicitly by some surrounding #pragma GCC target. > > > > > > > The normal tests - global_options_set.x_flag_whatever could still work > > > > > > > fine because they wouldn't care if the option was explicit from anywhere > > > > > > > (command line or GCC target or target attribute) and just & 2 would mean > > > > > > > it was explicit from pragma GCC target; though there is the case of > > > > > > > bitfields... And then the inlining decision could check the & 2 flags to > > > > > > > see what is required and what is just from command line. > > > > > > > Or we can have some other pragma GCC that would be like target but would > > > > > > > have flags that are explicit (and could e.g. be more restricted, to ISA > > > > > > > options only, and let those use in addition to #pragma GCC target. > > > > > > > > > > > > I'm still curious as to what you think will break if always-inline does what > > > > > > it is documented to do. > > > > > > > > > > We will silently accept calling intrinsics that must be used only in certain > > > > > ISA contexts, which will lead to people writing non-portable code. > > > > > > > > > > So -O2 -mno-avx > > > > > #include > > > > > > > > > > void > > > > > foo (__m256 *x) > > > > > { > > > > > x[0] = _mm256_sub_ps (x[1], x[2]); > > > > > } > > > > > etc. will now be accepted when it shouldn't be. > > > > > clang rejects it like gcc with: > > > > > 1.c:6:10: error: always_inline function '_mm256_sub_ps' requires target feature 'avx', but would be inlined into function 'foo' that is compiled without support for 'avx' > > > > > x[0] = _mm256_sub_ps (x[1], x[2]); > > > > > ^ > > > > > > > > > > Note, if I do: > > > > > #include > > > > > > > > > > __attribute__((target ("no-sse3"))) void > > > > > foo (__m256 *x) > > > > > { > > > > > x[0] = _mm256_sub_ps (x[1], x[2]); > > > > > } > > > > > and compile > > > > > clang -S -O2 -mavx2 1.c > > > > > 1.c:6:10: error: always_inline function '_mm256_sub_ps' requires target feature 'avx', but would be inlined into function 'foo' that is compiled without support for 'avx' > > > > > x[0] = _mm256_sub_ps (x[1], x[2]); > > > > > ^ > > > > > then from the error message it seems that unlike GCC, clang remembers > > > > > the exact target features that are needed for the intrinsics and checks just > > > > > those. > > > > > Though, looking at the preprocessed source, seems it uses > > > > > static __inline __m256 __attribute__((__always_inline__, __nodebug__, __target__("avx"), __min_vector_width__(256))) > > > > > _mm256_sub_ps(__m256 __a, __m256 __b) > > > > > { > > > > > return (__m256)((__v8sf)__a-(__v8sf)__b); > > > > > } > > > > > and not target pragmas. > > > > > > > > > > Anyway, if we tweak our intrinsic headers so that > > > > > -#ifndef __AVX__ > > > > > #pragma GCC push_options > > > > > #pragma GCC target("avx") > > > > > -#define __DISABLE_AVX__ > > > > > -#endif /* __AVX__ */ > > > > > > > > > > ... > > > > > -#ifdef __DISABLE_AVX__ > > > > > -#undef __DISABLE_AVX__ > > > > > #pragma GCC pop_options > > > > > -#endif /* __DISABLE_AVX__ */ > > > > > and do the opts_set->x_* & 2 stuff on explicit options coming out of > > > > > target/optimize pragmas and attributes, perhaps we don't even need > > > > > to introduce a new attribute and can handle everything magically: > > > > > > Oh, and any such changes will likely interact with Martins ideas to rework > > > how optimize and target attributes work (aka adding ontop of the > > > commandline options). That is, attribute target will then not be enough > > > to remember the exact set of needed ISA features (as opposed to what > > > likely clang implements?) > > > > > > > > 1) if it is gnu_inline extern inline, allow indirect calls, otherwise > > > > > disallow them for always_inline functions > > > > > > > > There are a lot of intrinsics using extern inline __gnu_inline though... > > > > > > > > > 2) for the isa flags and option mismatches, only disallow opts_set->x_* & 2 > > > > > stuff > > > > > This will keep both intrinsics and glibc fortify macros working fine > > > > > in all the needed use cases. > > > > > > > > Yes, see my example in the other mail. > > > > > > > > I think before we add any new attributes we should sort out the > > > > current mess, eventually adding some testcases for desired > > > > diagnostic. > > > > > > > > Richard. > > > > > > > > > Jakub > > > > Here is the v5 patch: > > > > 1. Intrinsics in only require GPR ISAs. Add > > > > #if defined __MMX__ || defined __SSE__ > > #pragma GCC push_options > > #pragma GCC target("general-regs-only") > > #define __DISABLE_GENERAL_REGS_ONLY__ > > #endif > > > > and > > > > #ifdef __DISABLE_GENERAL_REGS_ONLY__ > > #undef __DISABLE_GENERAL_REGS_ONLY__ > > #pragma GCC pop_options > > #endif /* __DISABLE_GENERAL_REGS_ONLY__ */ > > > > to to disable non-GPR ISAs so that they can be used in > > functions with __attribute__ ((target("general-regs-only"))). > > 2. When checking always_inline attribute, if callee only uses GPRs, > > ignore MASK_80387 since enable MASK_80387 in caller has no impact on > > callee inline. > > > > OK for master? > > + > +#include > + > +#include > + > > there are some cases like the above - intentional? Fixed in the v6 patch. > Otherwise I guess I can live with this, hopefully things won't break. > > In the end it's a quite narrow solution to a subpart of the overall > issue of course. > > Thus OK unless any other stakeholder has comments. Thanks. I will wait for a few days before commiting. > Thanks, > Richard. > > > Thanks. > > > > -- > > H.J. -- H.J.