Wilco Dijkstra <wilco.dijks...@arm.com> writes:
> OK to backport to GCC13 (it applies cleanly and regress/bootstrap passes)?
Yes, thanks.
Richard
>
> Cheers,
> Wilco
>
> On 29/11/2023 18:09, Richard Sandiford wrote:
>> Wilco Dijkstra <wilco.dijks...@arm.com> writes:
>>> v2: Use UINTVAL, rename max_mops_size.
>>>
>>> The cpymemdi/setmemdi implementation doesn't fully support strict alignment.
>>> Block the expansion if the alignment is less than 16 with STRICT_ALIGNMENT.
>>> Clean up the condition when to use MOPS.
>>>
>>> Passes regress/bootstrap, OK for commit?
>>>
>>> gcc/ChangeLog/
>>> PR target/103100
>>> * config/aarch64/aarch64.md (cpymemdi): Remove pattern condition.
>>> (setmemdi): Likewise.
>>> * config/aarch64/aarch64.cc (aarch64_expand_cpymem): Support
>>> strict-align. Cleanup condition for using MOPS.
>>> (aarch64_expand_setmem): Likewise.
>>>
>>> ---
>>>
>>> diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
>>> index
>>> dd6874d13a75f20d10a244578afc355b25c73da2..8a12894d6b80de1031d6e7d02dca680c57bce136
>>> 100644
>>> --- a/gcc/config/aarch64/aarch64.cc
>>> +++ b/gcc/config/aarch64/aarch64.cc
>>> @@ -25261,27 +25261,23 @@ aarch64_expand_cpymem (rtx *operands)
>>> int mode_bits;
>>> rtx dst = operands[0];
>>> rtx src = operands[1];
>>> + unsigned align = UINTVAL (operands[3]);
>>> rtx base;
>>> machine_mode cur_mode = BLKmode;
>>> + bool size_p = optimize_function_for_size_p (cfun);
>>>
>>> - /* Variable-sized memcpy can go through the MOPS expansion if available.
>>> */
>>> - if (!CONST_INT_P (operands[2]))
>>> + /* Variable-sized or strict-align copies may use the MOPS expansion. */
>>> + if (!CONST_INT_P (operands[2]) || (STRICT_ALIGNMENT && align < 16))
>>> return aarch64_expand_cpymem_mops (operands);
>>>
>>> - unsigned HOST_WIDE_INT size = INTVAL (operands[2]);
>>> -
>>> - /* Try to inline up to 256 bytes or use the MOPS threshold if available.
>>> */
>>> - unsigned HOST_WIDE_INT max_copy_size
>>> - = TARGET_MOPS ? aarch64_mops_memcpy_size_threshold : 256;
>>> + unsigned HOST_WIDE_INT size = UINTVAL (operands[2]);
>>>
>>> - bool size_p = optimize_function_for_size_p (cfun);
>>> + /* Try to inline up to 256 bytes. */
>>> + unsigned max_copy_size = 256;
>>> + unsigned mops_threshold = aarch64_mops_memcpy_size_threshold;
>>>
>>> - /* Large constant-sized cpymem should go through MOPS when possible.
>>> - It should be a win even for size optimization in the general case.
>>> - For speed optimization the choice between MOPS and the SIMD sequence
>>> - depends on the size of the copy, rather than number of instructions,
>>> - alignment etc. */
>>> - if (size > max_copy_size)
>>> + /* Large copies use MOPS when available or a library call. */
>>> + if (size > max_copy_size || (TARGET_MOPS && size > mops_threshold))
>>> return aarch64_expand_cpymem_mops (operands);
>>
>> It feels a little unintuitive to be calling aarch64_expand_cpymem_mops
>> for !TARGET_MOPS, but that's pre-existing, and I can see there are
>> arguments both ways.
>>
>> Although !TARGET_SIMD is a niche interest on current trunk, it becomes
>> important for streaming-compatible mode. So we might want to look
>> again at the different handling of !TARGET_SIMD in this function (where
>> we lower the copy size but not the threshold) and aarch64_expand_setmem
>> (where we bail out early). That's not something for this patch though,
>> just mentioning it.
>>
>> The patch is OK with me, but please give Richard E a day to object.
>
> This is fine by me.
>
> R.
>
>>
>> Thanks,
>> Richard
>>
>>>
>>> int copy_bits = 256;
>>> @@ -25445,12 +25441,13 @@ aarch64_expand_setmem (rtx *operands)
>>> unsigned HOST_WIDE_INT len;
>>> rtx dst = operands[0];
>>> rtx val = operands[2], src;
>>> + unsigned align = UINTVAL (operands[3]);
>>> rtx base;
>>> machine_mode cur_mode = BLKmode, next_mode;
>>>
>>> - /* If we don't have SIMD registers or the size is variable use the MOPS
>>> - inlined sequence if possible. */
>>> - if (!CONST_INT_P (operands[1]) || !TARGET_SIMD)
>>> + /* Variable-sized or strict-align memset may use the MOPS expansion. */
>>> + if (!CONST_INT_P (operands[1]) || !TARGET_SIMD
>>> + || (STRICT_ALIGNMENT && align < 16))
>>> return aarch64_expand_setmem_mops (operands);
>>>
>>> bool size_p = optimize_function_for_size_p (cfun);
>>> @@ -25458,10 +25455,13 @@ aarch64_expand_setmem (rtx *operands)
>>> /* Default the maximum to 256-bytes when considering only libcall vs
>>> SIMD broadcast sequence. */
>>> unsigned max_set_size = 256;
>>> + unsigned mops_threshold = aarch64_mops_memset_size_threshold;
>>>
>>> - len = INTVAL (operands[1]);
>>> - if (len > max_set_size && !TARGET_MOPS)
>>> - return false;
>>> + len = UINTVAL (operands[1]);
>>> +
>>> + /* Large memset uses MOPS when available or a library call. */
>>> + if (len > max_set_size || (TARGET_MOPS && len > mops_threshold))
>>> + return aarch64_expand_setmem_mops (operands);
>>>
>>> int cst_val = !!(CONST_INT_P (val) && (INTVAL (val) != 0));
>>> /* The MOPS sequence takes:
>>> @@ -25474,12 +25474,6 @@ aarch64_expand_setmem (rtx *operands)
>>> the arguments + 1 for the call. */
>>> unsigned libcall_cost = 4;
>>>
>>> - /* Upper bound check. For large constant-sized setmem use the MOPS
>>> sequence
>>> - when available. */
>>> - if (TARGET_MOPS
>>> - && len >= (unsigned HOST_WIDE_INT)
>>> aarch64_mops_memset_size_threshold)
>>> - return aarch64_expand_setmem_mops (operands);
>>> -
>>> /* Attempt a sequence with a vector broadcast followed by stores.
>>> Count the number of operations involved to see if it's worth it
>>> against the alternatives. A simple counter simd_ops on the
>>> @@ -25521,10 +25515,8 @@ aarch64_expand_setmem (rtx *operands)
>>> simd_ops++;
>>> n -= mode_bits;
>>>
>>> - /* Do certain trailing copies as overlapping if it's going to be
>>> - cheaper. i.e. less instructions to do so. For instance doing a 15
>>> - byte copy it's more efficient to do two overlapping 8 byte copies
>>> than
>>> - 8 + 4 + 2 + 1. Only do this when -mstrict-align is not supplied.
>>> */
>>> + /* Emit trailing writes using overlapping unaligned accesses
>>> + (when !STRICT_ALIGNMENT) - this is smaller and faster. */
>>> if (n > 0 && n < copy_limit / 2 && !STRICT_ALIGNMENT)
>>> {
>>> next_mode = smallest_mode_for_size (n, MODE_INT);
>>> diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
>>> index
>>> 6d0f072a9dd6d094e8764a513222a9129d8296fa..96508a2580876d1fdbdfa6c67d1a3d02608c1d24
>>> 100644
>>> --- a/gcc/config/aarch64/aarch64.md
>>> +++ b/gcc/config/aarch64/aarch64.md
>>> @@ -1627,7 +1627,7 @@ (define_expand "cpymemdi"
>>> (match_operand:BLK 1 "memory_operand")
>>> (match_operand:DI 2 "general_operand")
>>> (match_operand:DI 3 "immediate_operand")]
>>> - "!STRICT_ALIGNMENT || TARGET_MOPS"
>>> + ""
>>> {
>>> if (aarch64_expand_cpymem (operands))
>>> DONE;
>>> @@ -1724,7 +1724,7 @@ (define_expand "setmemdi"
>>> (match_operand:QI 2 "nonmemory_operand")) ;; Value
>>> (use (match_operand:DI 1 "general_operand")) ;; Length
>>> (match_operand 3 "immediate_operand")] ;; Align
>>> - "TARGET_SIMD || TARGET_MOPS"
>>> + ""
>>> {
>>> if (aarch64_expand_setmem (operands))
>>> DONE;
