Jiufu Guo via Gcc-patches <gcc-patches@gcc.gnu.org> writes: > Hi, > > Segher Boessenkool <seg...@kernel.crashing.org> writes: > >> On Tue, Apr 11, 2023 at 05:40:09PM +0800, Kewen.Lin wrote: >>> on 2023/4/11 17:14, guojiufu wrote: >>> > Thanks for raising this concern. >>> > The behavior to check about bif on FLOAT128_HW and emit an error message >>> > for >>> > requirements on quad-precision is added in gcc12. This is why gcc12 fails >>> > to >>> > compile the case on -m32. >>> > >>> > Before gcc12, altivec_resolve_overloaded_builtin will return the >>> > overloaded >>> > result directly, and does not check more about the result function. >>> >>> Thanks for checking, I wonder which commit caused this behavior change and >>> what's >>> the underlying justification? I know there is one new bif handling >>> framework >>> introduced in gcc12, not sure the checking condition was changed together >>> or by >>> a standalone commit. Anyway, apparently the conditions for the support of >>> these >>> bifs are different on gcc-11 and gcc-12, I wonder why it changed. As >>> mentioned >>> above, PR108758's c#1 said this case (bifs) work well on gcc-11, I >>> suspected the >>> condition change was an overkill, that's why I asked. >> >> It almost certainly was an oversight. The new builtin framework changed >> so many things, there was bound to be some breakage to go with all the >> good things it brought. > > Yes, the condition checking on gcc-12 is different from gcc-11. In > gcc-11, the condition on overloaded bif is not checked. > And, there are a few commits related to the bifs change. e.g. > r12-4977-ga28cfe49203705 introduces a new bif expand function which has > the ability to check more bif's target requirements like ieee128_hw. > And another commit changes the error message (r12-6684). > >> >> So what is the actual thing going wrong? QP insns work fine and are >> valid on all systems and environments, BE or LE, 32-bit or 64-bit. >> Of
I understand that QP insns (e.g. xscmpexpqp) is valid if the system meets ISA3.0, no matter BE/LE, 32-bit/64-bit. I think option -mfloat128-hardware is designed for QP insns. While there is one issue, on BE machine, when compiling with options "-mfloat128-hardware -m32", an error message is generated: "error: '%<-mfloat128-hardware%>' requires '-m64'" (I'm wondering if we need to relax this limitation.) BR, Jeff (Jiufu) >> course you cannot use the "long double" type for those everywhere, but >> that is a very different thing. > > Currently, when compiling bif __builtin_vsx_scalar_cmp_exp_qp_eq, > gcc generates error message: > error: '__builtin_vsx_scalar_cmp_exp_qp_eq' requires quad-precision > floating-point arithmetic > > IMHO, this error would be ok. Because it makes sense that this bif > needs ieee128_hw. > > BR, > Jeff (Jiufu) > >> >> >> Segher
