On 28 May 2015, at 23:15, Mike Stump <mikest...@comcast.net> wrote:
> So, the arm memcpy code of aligned data isn’t as good as it can be.
>
> void *memcpy(void *dest, const void *src, unsigned int n);
>
> void foo(char *dst, int i) {
> memcpy (dst, &i, sizeof (i));
> }
>
> generates horrible code, but, it we are willing to notice the src or the
> destination are aligned, we can do much better:
>
This looks like PR 50417, doesn't it?
Cheers,
Oleg
> $ ./cc1 -fschedule-fusion -fdump-tree-all-all -da -march=armv7ve
> -mcpu=cortex-m4 -fomit-frame-pointer -quiet -O2 /tmp/t.c -o t.s
> $ cat t.s
> [ … ]
> foo:
> @ args = 0, pretend = 0, frame = 4
> @ frame_needed = 0, uses_anonymous_args = 0
> @ link register save eliminated.
> sub sp, sp, #4
> str r1, [r0] @ unaligned
> add sp, sp, #4
>
> Index: gcc/config/arm/arm.c
> ===================================================================
> --- gcc/config/arm/arm.c (revision 223842)
> +++ gcc/config/arm/arm.c (working copy)
> @@ -14376,7 +14376,10 @@ arm_block_move_unaligned_straight (rtx d
> srcoffset + j * UNITS_PER_WORD - src_autoinc);
> mem = adjust_automodify_address (srcbase, SImode, addr,
> srcoffset + j * UNITS_PER_WORD);
> - emit_insn (gen_unaligned_loadsi (regs[j], mem));
> + if (src_aligned)
> + emit_move_insn (regs[j], mem);
> + else
> + emit_insn (gen_unaligned_loadsi (regs[j], mem));
> }
> srcoffset += words * UNITS_PER_WORD;
> }
> @@ -14395,7 +14398,10 @@ arm_block_move_unaligned_straight (rtx d
> dstoffset + j * UNITS_PER_WORD - dst_autoinc);
> mem = adjust_automodify_address (dstbase, SImode, addr,
> dstoffset + j * UNITS_PER_WORD);
> - emit_insn (gen_unaligned_storesi (mem, regs[j]));
> + if (dst_aligned)
> + emit_move_insn (mem, regs[j]);
> + else
> + emit_insn (gen_unaligned_storesi (mem, regs[j]));
> }
> dstoffset += words * UNITS_PER_WORD;
> }
>
>
> Ok?
>
> Can someone spin this through an arm test suite run for me, I was doing this
> by inspection and cross compile on a system with no arm bits. Bonus points
> if you can check it in with the test case above marked up as appropriate.
>
> <arm.diffs.txt>
