Hi Haochen,
on 2023/12/20 16:51, HAO CHEN GUI wrote:
> Hi,
> The patch corrects the definition of
> TARGET_EFFICIENT_OVERLAPPING_UNALIGNED and replace it with the call of
> slow_unaligned_access.
>
> Compared with last version,
> https://gcc.gnu.org/pipermail/gcc-patches/2023-December/640832.html
> the main change is to pass alignment measured by bits to
> slow_unaligned_access.
For a record in case someone would be confused here, Haochen and I had
a discussion offlist, the target hook slow_unaligned_access requires
alignment in bits, the previous version mainly adopts alignment in bytes
excepting for the "UINTVAL (align_rtx)" aforementioned.
>
> Bootstrapped and tested on x86 and powerpc64-linux BE and LE with no
> regressions. Is this OK for trunk?
>
> Thanks
> Gui Haochen
>
> ChangeLog
> rs6000: Correct definition of macro of fixed point efficient unaligned
>
> Marco TARGET_EFFICIENT_OVERLAPPING_UNALIGNED is used in rs6000-string.cc to
> guard the platform which is efficient on fixed point unaligned load/store.
> It's originally defined by TARGET_EFFICIENT_UNALIGNED_VSX which is enabled
> from P8 and can be disabled by mno-vsx option. So the definition is wrong.
> This patch corrects the problem and call slow_unaligned_access to judge if
> fixed point unaligned load/store is efficient or not.
>
> gcc/
> * config/rs6000/rs6000.h (TARGET_EFFICIENT_OVERLAPPING_UNALIGNED):
> Remove.
> * config/rs6000/rs6000-string.cc (select_block_compare_mode):
> Replace TARGET_EFFICIENT_OVERLAPPING_UNALIGNED with
> targetm.slow_unaligned_access.
> (expand_block_compare_gpr): Likewise.
> (expand_block_compare): Likewise.
> (expand_strncmp_gpr_sequence): Likewise.
>
> gcc/testsuite/
> * gcc.target/powerpc/block-cmp-1.c: New.
> * gcc.target/powerpc/block-cmp-2.c: New.
>
> patch.diff
> diff --git a/gcc/config/rs6000/rs6000-string.cc
> b/gcc/config/rs6000/rs6000-string.cc
> index 44a946cd453..05dc41622f4 100644
> --- a/gcc/config/rs6000/rs6000-string.cc
> +++ b/gcc/config/rs6000/rs6000-string.cc
> @@ -305,7 +305,7 @@ select_block_compare_mode (unsigned HOST_WIDE_INT offset,
> else if (bytes == GET_MODE_SIZE (QImode))
> return QImode;
> else if (bytes < GET_MODE_SIZE (SImode)
> - && TARGET_EFFICIENT_OVERLAPPING_UNALIGNED
> + && !targetm.slow_unaligned_access (SImode, align * BITS_PER_UNIT)
> && offset >= GET_MODE_SIZE (SImode) - bytes)
> /* This matches the case were we have SImode and 3 bytes
> and offset >= 1 and permits us to move back one and overlap
> @@ -313,7 +313,7 @@ select_block_compare_mode (unsigned HOST_WIDE_INT offset,
> unwanted bytes off of the input. */
> return SImode;
> else if (word_mode_ok && bytes < UNITS_PER_WORD
> - && TARGET_EFFICIENT_OVERLAPPING_UNALIGNED
> + && !targetm.slow_unaligned_access (word_mode, align * BITS_PER_UNIT)
> && offset >= UNITS_PER_WORD-bytes)
> /* Similarly, if we can use DImode it will get matched here and
> can do an overlapping read that ends at the end of the block. */
> @@ -1749,7 +1749,8 @@ expand_block_compare_gpr(unsigned HOST_WIDE_INT bytes,
> unsigned int base_align,
> load_mode_size = GET_MODE_SIZE (load_mode);
> if (bytes >= load_mode_size)
> cmp_bytes = load_mode_size;
> - else if (TARGET_EFFICIENT_OVERLAPPING_UNALIGNED)
> + else if (!targetm.slow_unaligned_access (load_mode,
> + align * BITS_PER_UNIT))
> {
> /* Move this load back so it doesn't go past the end.
> P8/P9 can do this efficiently. */
> @@ -2026,7 +2027,7 @@ expand_block_compare (rtx operands[])
> /* The code generated for p7 and older is not faster than glibc
> memcmp if alignment is small and length is not short, so bail
> out to avoid those conditions. */
> - if (!TARGET_EFFICIENT_OVERLAPPING_UNALIGNED
> + if (targetm.slow_unaligned_access (word_mode, base_align * BITS_PER_UNIT)
Nit: Maybe add one variable for UINTVAL (align_rtx) before and use it
for base_align and here.
OK for trunk with or without this nit tweaked. Thanks!
BR,
Kewen
> && ((base_align == 1 && bytes > 16)
> || (base_align == 2 && bytes > 32)))
> return false;
> @@ -2168,7 +2169,8 @@ expand_strncmp_gpr_sequence (unsigned HOST_WIDE_INT
> bytes_to_compare,
> load_mode_size = GET_MODE_SIZE (load_mode);
> if (bytes_to_compare >= load_mode_size)
> cmp_bytes = load_mode_size;
> - else if (TARGET_EFFICIENT_OVERLAPPING_UNALIGNED)
> + else if (!targetm.slow_unaligned_access (load_mode,
> + align * BITS_PER_UNIT))
> {
> /* Move this load back so it doesn't go past the end.
> P8/P9 can do this efficiently. */
> diff --git a/gcc/config/rs6000/rs6000.h b/gcc/config/rs6000/rs6000.h
> index 326c45221e9..3971a56c588 100644
> --- a/gcc/config/rs6000/rs6000.h
> +++ b/gcc/config/rs6000/rs6000.h
> @@ -483,10 +483,6 @@ extern int rs6000_vector_align[];
> #define TARGET_NO_SF_SUBREG TARGET_DIRECT_MOVE_64BIT
> #define TARGET_ALLOW_SF_SUBREG (!TARGET_DIRECT_MOVE_64BIT)
>
> -/* This wants to be set for p8 and newer. On p7, overlapping unaligned
> - loads are slow. */
> -#define TARGET_EFFICIENT_OVERLAPPING_UNALIGNED TARGET_EFFICIENT_UNALIGNED_VSX
> -
> /* Byte/char syncs were added as phased in for ISA 2.06B, but are not present
> in power7, so conditionalize them on p8 features. TImode syncs need quad
> memory support. */
> diff --git a/gcc/testsuite/gcc.target/powerpc/block-cmp-1.c
> b/gcc/testsuite/gcc.target/powerpc/block-cmp-1.c
> new file mode 100644
> index 00000000000..bcf0cb2ab4f
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/block-cmp-1.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -mdejagnu-cpu=power8 -mno-vsx" } */
> +/* { dg-final { scan-assembler-not {\mb[l]? memcmp\M} } } */
> +
> +/* Test that it still can do expand for memcmpsi instead of calling library
> + on P8 with vsx disabled. */
> +
> +int foo (const char* s1, const char* s2)
> +{
> + return __builtin_memcmp (s1, s2, 20);
> +}
> diff --git a/gcc/testsuite/gcc.target/powerpc/block-cmp-2.c
> b/gcc/testsuite/gcc.target/powerpc/block-cmp-2.c
> new file mode 100644
> index 00000000000..dfee15b2147
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/block-cmp-2.c
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target opt_mstrict_align } */
> +/* { dg-options "-O2 -mstrict-align" } */
> +/* { dg-final { scan-assembler-times {\mb[l]? memcmp\M} 1 } } */
> +
> +/* Test that it calls library for block memory compare when strict-align
> + is set. The flag causes rs6000_slow_unaligned_access returns true. */
> +
> +int foo (const char* s1, const char* s2)
> +{
> + return __builtin_memcmp (s1, s2, 20);
> +}
