On Tue, Jun 02, 2015 at 11:38:29AM +0100, Kyrill Tkachov wrote: > Hi James, Jim, > > On 02/06/15 10:42, James Greenhalgh wrote: > > On Sat, May 23, 2015 at 12:24:00AM +0100, Jim Wilson wrote: > >> The compiler currently ICEs when compiling a stdarg function with > >> +nofp, as reported in PR 66258. > >> > >> The aarch64.md file disables FP instructions using TARGET_FLOAT, which > >> supports both -mgeneral-regs-only and +nofp. But there is code in > >> aarch64.c that checks TARGET_GENERAL_REGS_ONLY. This results in FP > >> instructions when using +nofp, The aarch64.c code needs to use > >> TARGET_FLOAT instead like the md file already does. > >> > >> I can't meaningfully test this with a bootstrap, since the patch has > >> no effect unless I bootstrap with +nofp, and that will fail as gcc > >> contains floating point code. > >> > >> The testsuite already has multiple stdarg tests, so there is no need > >> for another one. > >> > >> I tested this by verifying I get the same results for some simple > >> testcasess with and without the patch, with and without using > >> -mgeneral-regs-only and -mcpu=cortex-a53+nofp. > > This patch doesn't quite look right to me. The cases you change seem > > like they should be (TARGET_FLOAT || TARGET_SIMD), rather than just > > TARGET_FLOAT. In an armv8-a+nofp environment, you still have access to the > > SIMD registers and instructions (reading between the lines on the bug > > report, this is almost certainly not what is intended in Grub!). > > I don't think that's quite right. TARGET_SIMD *always* implies TARGET_FP as > it is a superset of that functionality. > > For the precise relations of them look in aarch64-option-extensions.def. > Turning off fp with +nofp (or -mgeneral-regs-only) always turns off simd > while turning off simd with +nosimd doesn't turn off fp.
Right, understood. I had incorrectly thought we had kept them as fully distinct options to disable parts of the ARMv8-A instruction set. In which case, Jim, your patch is OK. Sorry for my initial confusion. I think I saw a patch kicking around internally to improve the documentation in this area, Alan - was that yours? Thanks, James
