| Message ID | DBBPR83MB0613A71DB5403BE3D50B1007F8462@DBBPR83MB0613.EURPRD83.prod.outlook.com |
|---|---|
| State | New |
| Headers | show |
| Series | None | expand |
Evgeny Karpov <Evgeny.Karpov@microsoft.com> writes: > Thursday, September 19, 2024 > Richard Sandiford <richard.sandiford@arm.com> wrote: > >>> For instance: >>> float __attribute__((aligned (32))) large_aligned_array[3]; >>> >>> BIGGEST_ALIGNMENT could be up to 512 bits on x64. >>> This patch has been added to cover this case without needing to >>> change the FFmpeg code. >> >> What goes wrong if we don't do this? I'm not sure from the description >> whether it's a correctness fix, a performance fix, or whether it's about >> avoiding wasted space. > > It is a correctness fix. But you could you explain what goes wrong if you don't do this? (I realise it might be very obvious when you've seen it happen :) But I'm genuinely unsure.) Why do we ignore the alignment if it is less than BIGGEST_ALIGNMENT? >>> +#define ASM_OUTPUT_ALIGNED_LOCAL(FILE, NAME, SIZE, ALIGNMENT) \ >>> + { \ >>> + unsigned HOST_WIDE_INT rounded = MAX ((SIZE), 1); \ >>> + unsigned HOST_WIDE_INT alignment = MAX ((ALIGNMENT), BIGGEST_ALIGNMENT); \ >>> + rounded += (alignment / BITS_PER_UNIT) - 1; \ >>> + rounded = (rounded / (alignment / BITS_PER_UNIT) \ >>> + * (alignment / BITS_PER_UNIT)); \ >> >> There's a ROUND_UP macro that could be used here. > > Here is the patch after applying ROUND_UP. > > Regards, > Evgeny > > diff --git a/gcc/config/aarch64/aarch64-coff.h b/gcc/config/aarch64/aarch64-coff.h > index 3c8aed806c9..1a45256ebfe 100644 > --- a/gcc/config/aarch64/aarch64-coff.h > +++ b/gcc/config/aarch64/aarch64-coff.h > @@ -58,6 +58,13 @@ > assemble_name ((FILE), (NAME)), \ > fprintf ((FILE), "," HOST_WIDE_INT_PRINT_DEC "\n", (ROUNDED))) > > +#define ASM_OUTPUT_ALIGNED_LOCAL(FILE, NAME, SIZE, ALIGNMENT) \ > + { \ > + unsigned rounded = ROUND_UP (MAX ((SIZE), 1), \ > + MAX ((ALIGNMENT), BIGGEST_ALIGNMENT) / BITS_PER_UNIT); \ Better to use "auto" rather than "unsigned". Otherwise it looks good modulo the questions above. Thanks, Richard > + ASM_OUTPUT_LOCAL (FILE, NAME, SIZE, rounded); \ > + } > + > #define ASM_OUTPUT_SKIP(STREAM, NBYTES) \ > fprintf (STREAM, "\t.space\t%d // skip\n", (int) (NBYTES))
diff --git a/gcc/config/aarch64/aarch64-coff.h b/gcc/config/aarch64/aarch64-coff.h index 3c8aed806c9..1a45256ebfe 100644 --- a/gcc/config/aarch64/aarch64-coff.h +++ b/gcc/config/aarch64/aarch64-coff.h @@ -58,6 +58,13 @@ assemble_name ((FILE), (NAME)), \ fprintf ((FILE), "," HOST_WIDE_INT_PRINT_DEC "\n", (ROUNDED))) +#define ASM_OUTPUT_ALIGNED_LOCAL(FILE, NAME, SIZE, ALIGNMENT) \ + { \ + unsigned rounded = ROUND_UP (MAX ((SIZE), 1), \ + MAX ((ALIGNMENT), BIGGEST_ALIGNMENT) / BITS_PER_UNIT); \ + ASM_OUTPUT_LOCAL (FILE, NAME, SIZE, rounded); \ + } + #define ASM_OUTPUT_SKIP(STREAM, NBYTES) \ fprintf (STREAM, "\t.space\t%d // skip\n", (int) (NBYTES))