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 > 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
