Ping^2 [Patch, rs6000] Enable overlap memory store for block memory clear

[HAO CHEN GUI <guihaoc@linux.ibm.com>]

Hi,
  Gently ping it.
https://gcc.gnu.org/pipermail/gcc-patches/2024-February/646478.html

Thanks
Gui Haochen

在 2024/5/8 9:55, HAO CHEN GUI 写道:
> Hi,
>   As now it's stage 1, gently ping this:
> https://gcc.gnu.org/pipermail/gcc-patches/2024-February/646478.html
> 
> Thanks
> Gui Haochen
> 
> 在 2024/2/26 10:25, HAO CHEN GUI 写道:
>> Hi,
>>   This patch enables overlap memory store for block memory clear which
>> saves the number of store instructions. The expander calls
>> widest_fixed_size_mode_for_block_clear to get the mode for looped block
>> clear and calls widest_fixed_size_mode_for_block_clear to get the mode
>> for last overlapped clear.
>>
>>     Bootstrapped and tested on x86 and powerpc64-linux BE and LE with no
>> regressions. Is it OK for the trunk or next stage 1?
>>
>> Thanks
>> Gui Haochen
>>
>>
>> ChangeLog
>> rs6000: Enable overlap memory store for block memory clear
>>
>> gcc/
>> 	* config/rs6000/rs6000-string.cc
>> 	(widest_fixed_size_mode_for_block_clear): New.
>> 	(smallest_fixed_size_mode_for_block_clear): New.
>> 	(expand_block_clear): Call widest_fixed_size_mode_for_block_clear to
>> 	get the mode for looped memory stores and call
>> 	smallest_fixed_size_mode_for_block_clear to get the mode for the last
>> 	overlapped memory store.
>>
>> gcc/testsuite
>> 	* gcc.target/powerpc/block-clear-1.c: New.
>>
>>
>> patch.diff
>> diff --git a/gcc/config/rs6000/rs6000-string.cc b/gcc/config/rs6000/rs6000-string.cc
>> index 133e5382af2..c2a6095a586 100644
>> --- a/gcc/config/rs6000/rs6000-string.cc
>> +++ b/gcc/config/rs6000/rs6000-string.cc
>> @@ -38,6 +38,49 @@
>>  #include "profile-count.h"
>>  #include "predict.h"
>>
>> +/* Return the widest mode which mode size is less than or equal to the
>> +   size.  */
>> +static fixed_size_mode
>> +widest_fixed_size_mode_for_block_clear (unsigned int size, unsigned int align,
>> +					bool unaligned_vsx_ok)
>> +{
>> +  machine_mode mode;
>> +
>> +  if (TARGET_ALTIVEC
>> +      && size >= 16
>> +      && (align >= 128
>> +	  || unaligned_vsx_ok))
>> +    mode = V4SImode;
>> +  else if (size >= 8
>> +	   && TARGET_POWERPC64
>> +	   && (align >= 64
>> +	       || !STRICT_ALIGNMENT))
>> +    mode = DImode;
>> +  else if (size >= 4
>> +	   && (align >= 32
>> +	       || !STRICT_ALIGNMENT))
>> +    mode = SImode;
>> +  else if (size >= 2
>> +	   && (align >= 16
>> +	       || !STRICT_ALIGNMENT))
>> +    mode = HImode;
>> +  else
>> +    mode = QImode;
>> +
>> +  return as_a <fixed_size_mode> (mode);
>> +}
>> +
>> +/* Return the smallest mode which mode size is smaller than or eqaul to
>> +   the size.  */
>> +static fixed_size_mode
>> +smallest_fixed_size_mode_for_block_clear (unsigned int size)
>> +{
>> +  if (size > UNITS_PER_WORD)
>> +    return as_a <fixed_size_mode> (V4SImode);
>> +
>> +  return smallest_int_mode_for_size (size * BITS_PER_UNIT);
>> +}
>> +
>>  /* Expand a block clear operation, and return 1 if successful.  Return 0
>>     if we should let the compiler generate normal code.
>>
>> @@ -55,7 +98,6 @@ expand_block_clear (rtx operands[])
>>    HOST_WIDE_INT align;
>>    HOST_WIDE_INT bytes;
>>    int offset;
>> -  int clear_bytes;
>>    int clear_step;
>>
>>    /* If this is not a fixed size move, just call memcpy */
>> @@ -89,62 +131,36 @@ expand_block_clear (rtx operands[])
>>
>>    bool unaligned_vsx_ok = (bytes >= 32 && TARGET_EFFICIENT_UNALIGNED_VSX);
>>
>> -  for (offset = 0; bytes > 0; offset += clear_bytes, bytes -= clear_bytes)
>> +  auto mode = widest_fixed_size_mode_for_block_clear (bytes, align,
>> +						      unaligned_vsx_ok);
>> +  offset = 0;
>> +  rtx dest;
>> +
>> +  do
>>      {
>> -      machine_mode mode = BLKmode;
>> -      rtx dest;
>> +      unsigned int size = GET_MODE_SIZE (mode);
>>
>> -      if (TARGET_ALTIVEC
>> -	  && (bytes >= 16 && (align >= 128 || unaligned_vsx_ok)))
>> +      while (bytes >= size)
>>  	{
>> -	  clear_bytes = 16;
>> -	  mode = V4SImode;
>> -	}
>> -      else if (bytes >= 8 && TARGET_POWERPC64
>> -	       && (align >= 64 || !STRICT_ALIGNMENT))
>> -	{
>> -	  clear_bytes = 8;
>> -	  mode = DImode;
>> -	  if (offset == 0 && align < 64)
>> -	    {
>> -	      rtx addr;
>> +	  dest = adjust_address (orig_dest, mode, offset);
>> +	  emit_move_insn (dest, CONST0_RTX (mode));
>>
>> -	      /* If the address form is reg+offset with offset not a
>> -		 multiple of four, reload into reg indirect form here
>> -		 rather than waiting for reload.  This way we get one
>> -		 reload, not one per store.  */
>> -	      addr = XEXP (orig_dest, 0);
>> -	      if ((GET_CODE (addr) == PLUS || GET_CODE (addr) == LO_SUM)
>> -		  && CONST_INT_P (XEXP (addr, 1))
>> -		  && (INTVAL (XEXP (addr, 1)) & 3) != 0)
>> -		{
>> -		  addr = copy_addr_to_reg (addr);
>> -		  orig_dest = replace_equiv_address (orig_dest, addr);
>> -		}
>> -	    }
>> -	}
>> -      else if (bytes >= 4 && (align >= 32 || !STRICT_ALIGNMENT))
>> -	{			/* move 4 bytes */
>> -	  clear_bytes = 4;
>> -	  mode = SImode;
>> -	}
>> -      else if (bytes >= 2 && (align >= 16 || !STRICT_ALIGNMENT))
>> -	{			/* move 2 bytes */
>> -	  clear_bytes = 2;
>> -	  mode = HImode;
>> -	}
>> -      else /* move 1 byte at a time */
>> -	{
>> -	  clear_bytes = 1;
>> -	  mode = QImode;
>> +	  offset += size;
>> +	  bytes -= size;
>>  	}
>>
>> -      dest = adjust_address (orig_dest, mode, offset);
>> +      if (bytes == 0)
>> +	return 1;
>>
>> -      emit_move_insn (dest, CONST0_RTX (mode));
>> +      mode = smallest_fixed_size_mode_for_block_clear (bytes);
>> +      int gap = GET_MODE_SIZE (mode) - bytes;
>> +      if (gap > 0)
>> +	{
>> +	  offset -= gap;
>> +	  bytes += gap;
>> +	}
>>      }
>> -
>> -  return 1;
>> +  while (1);
>>  }
>>
>>  /* Figure out the correct instructions to generate to load data for
>> diff --git a/gcc/testsuite/gcc.target/powerpc/block-clear-1.c b/gcc/testsuite/gcc.target/powerpc/block-clear-1.c
>> new file mode 100644
>> index 00000000000..5e16c44fea3
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/powerpc/block-clear-1.c
>> @@ -0,0 +1,9 @@
>> +/* { dg-do compile } */
>> +/* { dg-options "-O2" } */
>> +/* { dg-final { scan-assembler-not {\mst[hb]\M} } } */
>> +
>> +/* Verify that memclear takes overlap store. */
>> +void* foo (char* s1)
>> +{
>> +  __builtin_memset (s1, 0, 31);
>> +}