> -----Original Message----- > From: Richard Biener [mailto:rguent...@suse.de] > Sent: Wednesday, November 15, 2017 08:24 > To: Tamar Christina <tamar.christ...@arm.com> > Cc: gcc-patches@gcc.gnu.org; nd <n...@arm.com>; l...@redhat.com; > i...@airs.com > Subject: Re: [PATCH][GCC][mid-end] Allow larger copies when target > supports unaligned access [Patch (1/2)] > > On Tue, 14 Nov 2017, Tamar Christina wrote: > > > Hi All, > > > > This patch allows larger bitsizes to be used as copy size when the > > target does not have SLOW_UNALIGNED_ACCESS. > > > > fun3: > > adrp x2, .LANCHOR0 > > add x2, x2, :lo12:.LANCHOR0 > > mov x0, 0 > > sub sp, sp, #16 > > ldrh w1, [x2, 16] > > ldrb w2, [x2, 18] > > add sp, sp, 16 > > bfi x0, x1, 0, 8 > > ubfx x1, x1, 8, 8 > > bfi x0, x1, 8, 8 > > bfi x0, x2, 16, 8 > > ret > > > > is turned into > > > > fun3: > > adrp x0, .LANCHOR0 > > add x0, x0, :lo12:.LANCHOR0 > > sub sp, sp, #16 > > ldrh w1, [x0, 16] > > ldrb w0, [x0, 18] > > strh w1, [sp, 8] > > strb w0, [sp, 10] > > ldr w0, [sp, 8] > > add sp, sp, 16 > > ret > > > > which avoids the bfi's for a simple 3 byte struct copy. > > > > Regression tested on aarch64-none-linux-gnu and x86_64-pc-linux-gnu and > no regressions. > > > > This patch is just splitting off from the previous combined patch with > > AArch64 and adding a testcase. > > > > I assume Jeff's ACK from > > https://gcc.gnu.org/ml/gcc-patches/2017-08/msg01523.html is still valid as > the code did not change. > > Given your no_slow_unalign isn't mode specific can't you use the existing > non_strict_align?
No because non_strict_align checks if the target supports unaligned access at all, This no_slow_unalign corresponds instead to the target slow_unaligned_access which checks that the access you want to make has a greater cost than doing an aligned access. ARM for instance always return 1 (value of STRICT_ALIGNMENT) for slow_unaligned_access while for non_strict_align it may return 0 or 1 based on the options provided to the compiler. The problem is I have no way to test STRICT_ALIGNMENT or slow_unaligned_access So I had to hardcode some targets that I know it does work on. Thanks, Tamar > > Otherwise the expr.c change looks ok. > > Thanks, > Richard. > > > Thanks, > > Tamar > > > > > > gcc/ > > 2017-11-14 Tamar Christina <tamar.christ...@arm.com> > > > > * expr.c (copy_blkmode_to_reg): Fix bitsize for targets > > with fast unaligned access. > > * doc/sourcebuild.texi (no_slow_unalign): New. > > > > gcc/testsuite/ > > 2017-11-14 Tamar Christina <tamar.christ...@arm.com> > > > > * gcc.dg/struct-simple.c: New. > > * lib/target-supports.exp > > (check_effective_target_no_slow_unalign): New. > > > > > > -- > Richard Biener <rguent...@suse.de> > SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, > HRB 21284 (AG Nuernberg)
