On 3 December 2014 at 10:30, Alan Lawrence <alan.lawre...@arm.com> wrote: > On Wed, Nov 26, 2014 at 04:35:50PM +0000, James Greenhalgh wrote: >> Why do we want to turn off folding for the V4SF/V2SF/V2DF modes of these >> intrinsics? There should be no difference between the mid-end definition >> and the intrinsic definition of their behaviour. > > Good point. Done. > >> I also note that the integer forms of these now end up as an "abs" RTL >> expression - can we guarantee that preserves the intrinsics behaviour and >> no RTL-folder will come along and mis-optimize? Documentation is vague >> on this point. > > I don't think we can guarantee that indefinitely, but it doesn't seem anyone > has implemented such a rule *at present*. And we'd lose e.g. constant > folding, if we switched to using an AArch64-specific UNSPEC. If anyone does > add such a rule, I'd have some hope that the testcase will catch it... > >> I'm also not convinced by the SIMD_ARG_SCRATCH foo you add. Looking at >> the aarch64.md:absdi2 pattern I can't see why we need that scratch at >> all. It seems we could get away with marking operand 0 early-clobber and >> using it as our scratch register. Then we could drop all the extra >> infrastructure from this patch. > > Hah, good point. Ok, I attach a revised patch, updating the pattern as you > suggest and omitting the infrastructure changes. (I'm leaving the now-unused > qualifier_internal as it stands, as there are arguments both for removing it > and "fixing" it as per previous patch, but I don't think we should hold this > up in the case that we want to have that discussion!) > > Cross-tested check-gcc on aarch64-none-elf, including previously-posted test > of vabs_s8. > > Ok for trunk (with previously-posted testcase) ? > --Alan > > gcc/ChangeLog: > > * config/aarch64/aarch64.md (absdi2): Remove scratch operand by > earlyclobbering result operand. > > * config/aarch64/aarch64-builtins.c (aarch64_types_unop_qualifiers): > Remove final qualifier_internal. > (aarch64_fold_builtin): Stop folding abs builtins, except on floats.
OK, and the test case too /Marcus
