Re: [PATCH] Use TImode for piecewise move in 64-bit mode

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Wed, Aug 10, 2016 at 8:55 AM, Uros Bizjak <ubizjak@gmail.com> wrote:
> On Wed, Aug 10, 2016 at 5:32 PM, H.J. Lu <hongjiu.lu@intel.com> wrote:
>> Use TImode for piecewise move in 64-bit mode.  When vector register
>> is used for piecewise move, we don't increase stack_alignment_needed
>> since vector register spill isn't required for piecewise move.  Since
>> stack_realign_needed is set to true by checking stack_alignment_estimated
>> set by pseudo vector register usage, we also need to check
>> stack_realign_needed to eliminate frame pointer.
>
> Why only in 64-bit mode? We can use SSE moves also in 32-bit mode.

I will extend it to 32-bit mode.

> I don't think we can handle crtl->stack_realign_needed in this way. If
> there are other insns with 32byte vector registers in use in the same
> (large) function as converted __builtin_memcpy, we will *still* need
> realigned stack.

We don't align stack in leaf functions using SSE/AVX/AVX512 vector
registers if there is no spill when __builtin_memcpy isn't optimized with
SSE load/store.  My change just extends it to __builtin_memcpy optimized
with SSE load/store with or without 32byte vector registers in use.

> Uros.
>
>
>> Tested on x86-64.  OK for trunk?
>>
>> H.J.
>> ---
>> gcc/
>>
>>         * config/i386/i386.c (ix86_finalize_stack_realign_flags): Also
>>         check stack_realign_needed for stack realignment.
>>         * config/i386/i386.h (MOVE_MAX_PIECES): Set to 16 in 64-bit mode
>>         if unaligned SSE load and store are optimal.
>>
>> gcc/testsuite/
>>
>>         * gcc.target/i386/pieces-memcpy-1.c: New test.
>>         * gcc.target/i386/pieces-memcpy-2.c: Likewise.
>>         * gcc.target/i386/pieces-memcpy-3.c: Likewise.
>>         * gcc.target/i386/pieces-memcpy-4.c: Likewise.
>>         * gcc.target/i386/pieces-memcpy-5.c: Likewise.
>>         * gcc.target/i386/pieces-memcpy-6.c: Likewise.
>> ---
>>  gcc/config/i386/i386.c                          | 11 +++++++++--
>>  gcc/config/i386/i386.h                          |  6 +++++-
>>  gcc/testsuite/gcc.target/i386/pieces-memcpy-1.c | 17 +++++++++++++++++
>>  gcc/testsuite/gcc.target/i386/pieces-memcpy-2.c | 17 +++++++++++++++++
>>  gcc/testsuite/gcc.target/i386/pieces-memcpy-3.c | 17 +++++++++++++++++
>>  gcc/testsuite/gcc.target/i386/pieces-memcpy-4.c | 17 +++++++++++++++++
>>  gcc/testsuite/gcc.target/i386/pieces-memcpy-5.c | 17 +++++++++++++++++
>>  gcc/testsuite/gcc.target/i386/pieces-memcpy-6.c | 17 +++++++++++++++++
>>  8 files changed, 116 insertions(+), 3 deletions(-)
>>  create mode 100644 gcc/testsuite/gcc.target/i386/pieces-memcpy-1.c
>>  create mode 100644 gcc/testsuite/gcc.target/i386/pieces-memcpy-2.c
>>  create mode 100644 gcc/testsuite/gcc.target/i386/pieces-memcpy-3.c
>>  create mode 100644 gcc/testsuite/gcc.target/i386/pieces-memcpy-4.c
>>  create mode 100644 gcc/testsuite/gcc.target/i386/pieces-memcpy-5.c
>>  create mode 100644 gcc/testsuite/gcc.target/i386/pieces-memcpy-6.c
>>
>> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
>> index 93eaab1..60dc160 100644
>> --- a/gcc/config/i386/i386.c
>> +++ b/gcc/config/i386/i386.c
>> @@ -13286,8 +13286,15 @@ ix86_finalize_stack_realign_flags (void)
>>    /* If the only reason for frame_pointer_needed is that we conservatively
>>       assumed stack realignment might be needed, but in the end nothing that
>>       needed the stack alignment had been spilled, clear frame_pointer_needed
>> -     and say we don't need stack realignment.  */
>> -  if (stack_realign
>> +     and say we don't need stack realignment.
>> +
>> +     When vector register is used for piecewise move and store, we don't
>> +     increase stack_alignment_needed as there is no register spill for
>> +     piecewise move and store.  Since stack_realign_needed is set to true
>> +     by checking stack_alignment_estimated which is updated by pseudo
>> +     vector register usage, we also need to check stack_realign_needed to
>> +     eliminate frame pointer.  */
>> +  if ((stack_realign || crtl->stack_realign_needed)
>>        && frame_pointer_needed
>>        && crtl->is_leaf
>>        && flag_omit_frame_pointer
>> diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
>> index 9b66264..24db855 100644
>> --- a/gcc/config/i386/i386.h
>> +++ b/gcc/config/i386/i386.h
>> @@ -1951,7 +1951,11 @@ typedef struct ix86_args {
>>  /* MOVE_MAX_PIECES is the number of bytes at a time which we can
>>     move efficiently, as opposed to  MOVE_MAX which is the maximum
>>     number of bytes we can move with a single instruction.  */
>> -#define MOVE_MAX_PIECES UNITS_PER_WORD
>> +#define MOVE_MAX_PIECES \
>> +  ((TARGET_64BIT \
>> +    && TARGET_SSE2 \
>> +    && TARGET_SSE_UNALIGNED_LOAD_OPTIMAL \
>> +    && TARGET_SSE_UNALIGNED_STORE_OPTIMAL) ? 16 : UNITS_PER_WORD)
>>
>>  /* If a memory-to-memory move would take MOVE_RATIO or more simple
>>     move-instruction pairs, we will do a movmem or libcall instead.
>> diff --git a/gcc/testsuite/gcc.target/i386/pieces-memcpy-1.c b/gcc/testsuite/gcc.target/i386/pieces-memcpy-1.c
>> new file mode 100644
>> index 0000000..adc0aa8
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/i386/pieces-memcpy-1.c
>> @@ -0,0 +1,17 @@
>> +/* { dg-do compile { target { ! ia32 } } } */
>> +/* { dg-options "-O2 -mno-avx -msse2 -mtune=generic" } */
>> +
>> +extern char *dst, *src;
>> +
>> +void
>> +foo (void)
>> +{
>> +  __builtin_memcpy (dst, src, 64);
>> +}
>> +
>> +/* { dg-final { scan-assembler-times "movdqu\[ \\t\]+\[^\n\]*%xmm" 4 } } */
>> +/* { dg-final { scan-assembler-times "movups\[ \\t\]+\[^\n\]*%xmm" 4 } } */
>> +/* No need to dynamically realign the stack here.  */
>> +/* { dg-final { scan-assembler-not "and\[^\n\r]*%\[re\]sp" } } */
>> +/* Nor use a frame pointer.  */
>> +/* { dg-final { scan-assembler-not "%\[re\]bp" } } */
>> diff --git a/gcc/testsuite/gcc.target/i386/pieces-memcpy-2.c b/gcc/testsuite/gcc.target/i386/pieces-memcpy-2.c
>> new file mode 100644
>> index 0000000..c52c1d9
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/i386/pieces-memcpy-2.c
>> @@ -0,0 +1,17 @@
>> +/* { dg-do compile { target { ! ia32 } } } */
>> +/* { dg-options "-O2 -mno-avx -msse2 -mtune=generic" } */
>> +
>> +extern char *dst, *src;
>> +
>> +void
>> +foo (void)
>> +{
>> +  __builtin_memcpy (dst, src, 33);
>> +}
>> +
>> +/* { dg-final { scan-assembler-times "movdqu\[ \\t\]+\[^\n\]*%xmm" 2 } } */
>> +/* { dg-final { scan-assembler-times "movups\[ \\t\]+\[^\n\]*%xmm" 2 } } */
>> +/* No need to dynamically realign the stack here.  */
>> +/* { dg-final { scan-assembler-not "and\[^\n\r]*%\[re\]sp" } } */
>> +/* Nor use a frame pointer.  */
>> +/* { dg-final { scan-assembler-not "%\[re\]bp" } } */
>> diff --git a/gcc/testsuite/gcc.target/i386/pieces-memcpy-3.c b/gcc/testsuite/gcc.target/i386/pieces-memcpy-3.c
>> new file mode 100644
>> index 0000000..c532bbd
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/i386/pieces-memcpy-3.c
>> @@ -0,0 +1,17 @@
>> +/* { dg-do compile { target { ! ia32 } } } */
>> +/* { dg-options "-O2 -mno-avx -msse2 -mtune=generic" } */
>> +
>> +extern char *dst, *src;
>> +
>> +void
>> +foo (void)
>> +{
>> +  __builtin_memcpy (dst, src, 17);
>> +}
>> +
>> +/* { dg-final { scan-assembler-times "movdqu\[ \\t\]+\[^\n\]*%xmm" 1 } } */
>> +/* { dg-final { scan-assembler-times "movups\[ \\t\]+\[^\n\]*%xmm" 1 } } */
>> +/* No need to dynamically realign the stack here.  */
>> +/* { dg-final { scan-assembler-not "and\[^\n\r]*%\[re\]sp" } } */
>> +/* Nor use a frame pointer.  */
>> +/* { dg-final { scan-assembler-not "%\[re\]bp" } } */
>> diff --git a/gcc/testsuite/gcc.target/i386/pieces-memcpy-4.c b/gcc/testsuite/gcc.target/i386/pieces-memcpy-4.c
>> new file mode 100644
>> index 0000000..4ef763d
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/i386/pieces-memcpy-4.c
>> @@ -0,0 +1,17 @@
>> +/* { dg-do compile { target { ! ia32 } } } */
>> +/* { dg-options "-O2 -mno-avx2 -mavx -mtune=generic" } */
>> +
>> +extern char *dst, *src;
>> +
>> +void
>> +foo (void)
>> +{
>> +  __builtin_memcpy (dst, src, 18);
>> +}
>> +
>> +/* { dg-final { scan-assembler-times "vmovdqu\[ \\t\]+\[^\n\]*%xmm" 1 } } */
>> +/* { dg-final { scan-assembler-times "vmovups\[ \\t\]+\[^\n\]*%xmm" 1 } } */
>> +/* No need to dynamically realign the stack here.  */
>> +/* { dg-final { scan-assembler-not "and\[^\n\r]*%\[re\]sp" } } */
>> +/* Nor use a frame pointer.  */
>> +/* { dg-final { scan-assembler-not "%\[re\]bp" } } */
>> diff --git a/gcc/testsuite/gcc.target/i386/pieces-memcpy-5.c b/gcc/testsuite/gcc.target/i386/pieces-memcpy-5.c
>> new file mode 100644
>> index 0000000..2687560
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/i386/pieces-memcpy-5.c
>> @@ -0,0 +1,17 @@
>> +/* { dg-do compile { target { ! ia32 } } } */
>> +/* { dg-options "-O2 -mavx512f -mtune=generic" } */
>> +
>> +extern char *dst, *src;
>> +
>> +void
>> +foo (void)
>> +{
>> +  __builtin_memcpy (dst, src, 19);
>> +}
>> +
>> +/* { dg-final { scan-assembler-times "vmovdqu\[ \\t\]+\[^\n\]*%xmm" 1 } } */
>> +/* { dg-final { scan-assembler-times "vmovups\[ \\t\]+\[^\n\]*%xmm" 1 } } */
>> +/* No need to dynamically realign the stack here.  */
>> +/* { dg-final { scan-assembler-not "and\[^\n\r]*%\[re\]sp" } } */
>> +/* Nor use a frame pointer.  */
>> +/* { dg-final { scan-assembler-not "%\[re\]bp" } } */
>> diff --git a/gcc/testsuite/gcc.target/i386/pieces-memcpy-6.c b/gcc/testsuite/gcc.target/i386/pieces-memcpy-6.c
>> new file mode 100644
>> index 0000000..a205f83
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/i386/pieces-memcpy-6.c
>> @@ -0,0 +1,17 @@
>> +/* { dg-do compile { target { ! ia32 } } } */
>> +/* { dg-options "-O2 -mno-avx2 -mavx -mtune=sandybridge" } */
>> +
>> +extern char *dst, *src;
>> +
>> +void
>> +foo (void)
>> +{
>> +  __builtin_memcpy (dst, src, 33);
>> +}
>> +
>> +/* { dg-final { scan-assembler-times "vmovdqu\[ \\t\]+\[^\n\]*%xmm" 2 } } */
>> +/* { dg-final { scan-assembler-times "vmovups\[ \\t\]+\[^\n\]*%xmm" 2 } } */
>> +/* No need to dynamically realign the stack here.  */
>> +/* { dg-final { scan-assembler-not "and\[^\n\r]*%\[re\]sp" } } */
>> +/* Nor use a frame pointer.  */
>> +/* { dg-final { scan-assembler-not "%\[re\]bp" } } */
>> --
>> 2.7.4
>>



-- 
H.J.