Re: [PATCH] i386: Emit 16b atomics inline with -m64 -mcx16 -mavx [PR104688]

[Uros Bizjak <ubizjak@gmail.com>]

On Mon, Nov 14, 2022 at 8:52 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> Hi!
>
> Working virtually out of Baker Island.
>
> Given
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104688#c10
> the following patch implements atomic load/store (and therefore also
> enabling compare and exchange) for -m64 -mcx16 -mavx.
>
> Ok for trunk if it passes bootstrap/regtest?

We only have guarantee from Intel and AMD, there can be other vendors.

Uros.

>
> 2022-11-13  Jakub Jelinek  <jakub@redhat.com>
>
>         PR target/104688
>         * config/i386/sync.md (atomic_loadti, atomic_storeti): New
>         define_expand patterns.
>         (atomic_loadti_1, atomic_storeti_1): New define_insn patterns.
>
>         * gcc.target/i386/pr104688-1.c: New test.
>         * gcc.target/i386/pr104688-2.c: New test.
>         * gcc.target/i386/pr104688-3.c: New test.
>
> --- gcc/config/i386/sync.md.jj  2022-11-07 20:54:37.259400942 -1200
> +++ gcc/config/i386/sync.md     2022-11-13 19:27:22.977987355 -1200
> @@ -225,6 +225,31 @@ (define_insn_and_split "atomic_loaddi_fp
>    DONE;
>  })
>
> +;; Intel SDM guarantees that 16-byte VMOVDQA on 16-byte aligned address
> +;; is atomic.  AMD will give a similar guarantee.
> +(define_expand "atomic_loadti"
> +  [(set (match_operand:TI 0 "register_operand" "=x,Yv")
> +       (unspec:TI [(match_operand:TI 1 "memory_operand" "m,m")
> +                   (match_operand:SI 2 "const_int_operand")]
> +                  UNSPEC_LDA))]
> +  "TARGET_64BIT && TARGET_CMPXCHG16B && TARGET_AVX"
> +{
> +  emit_insn (gen_atomic_loadti_1 (operands[0], operands[1]));
> +  DONE;
> +})
> +
> +(define_insn "atomic_loadti_1"
> +  [(set (match_operand:TI 0 "register_operand" "=x,Yv")
> +       (unspec:TI [(match_operand:TI 1 "memory_operand" "m,m")]
> +                  UNSPEC_LDA))]
> +  "TARGET_64BIT && TARGET_CMPXCHG16B && TARGET_AVX"
> +  "@
> +   vmovdqa\t{%1, %0|%0, %1}
> +   vmovdqa64\t{%1, %0|%0, %1}"
> +  [(set_attr "type" "ssemov")
> +   (set_attr "prefix" "vex,evex")
> +   (set_attr "mode" "TI")])
> +
>  (define_expand "atomic_store<mode>"
>    [(set (match_operand:ATOMIC 0 "memory_operand")
>         (unspec:ATOMIC [(match_operand:ATOMIC 1 "nonimmediate_operand")
> @@ -276,6 +301,36 @@ (define_insn "atomic_store<mode>_1"
>    ""
>    "%K2mov{<imodesuffix>}\t{%1, %0|%0, %1}")
>
> +(define_expand "atomic_storeti"
> +  [(set (match_operand:TI 0 "memory_operand")
> +       (unspec:TI [(match_operand:TI 1 "register_operand")
> +                   (match_operand:SI 2 "const_int_operand")]
> +                  UNSPEC_STA))]
> +  "TARGET_64BIT && TARGET_CMPXCHG16B && TARGET_AVX"
> +{
> +  enum memmodel model = memmodel_from_int (INTVAL (operands[2]));
> +
> +  emit_insn (gen_atomic_storeti_1 (operands[0], operands[1], operands[2]));
> +
> +  /* ... followed by an MFENCE, if required.  */
> +  if (is_mm_seq_cst (model))
> +    emit_insn (gen_mem_thread_fence (operands[2]));
> +  DONE;
> +})
> +
> +(define_insn "atomic_storeti_1"
> +  [(set (match_operand:TI 0 "memory_operand" "=m,m")
> +       (unspec:TI [(match_operand:TI 1 "register_operand" "x,Yv")
> +                    (match_operand:SI 2 "const_int_operand")]
> +                   UNSPEC_STA))]
> +  ""
> +  "@
> +   %K2vmovdqa\t{%1, %0|%0, %1}
> +   %K2vmovdqa64\t{%1, %0|%0, %1}"
> +  [(set_attr "type" "ssemov")
> +   (set_attr "prefix" "vex,evex")
> +   (set_attr "mode" "TI")])
> +
>  (define_insn_and_split "atomic_storedi_fpu"
>    [(set (match_operand:DI 0 "memory_operand" "=m,m,m")
>         (unspec:DI [(match_operand:DI 1 "nonimmediate_operand" "x,m,?r")]
> --- gcc/testsuite/gcc.target/i386/pr104688-1.c.jj       2022-11-13 19:36:43.251332612 -1200
> +++ gcc/testsuite/gcc.target/i386/pr104688-1.c  2022-11-13 19:40:22.649334650 -1200
> @@ -0,0 +1,34 @@
> +/* PR target/104688 */
> +/* { dg-do compile { target int128 } } */
> +/* { dg-options "-O2 -mno-cx16" } */
> +/* { dg-final { scan-assembler "\t__sync_val_compare_and_swap_16" } } */
> +/* { dg-final { scan-assembler "\t__atomic_load_16" } } */
> +/* { dg-final { scan-assembler "\t__atomic_store_16" } } */
> +/* { dg-final { scan-assembler "\t__atomic_compare_exchange_16" } } */
> +
> +__int128 v;
> +
> +__int128
> +f1 (void)
> +{
> +  return __sync_val_compare_and_swap (&v, 42, 0);
> +}
> +
> +__int128
> +f2 (void)
> +{
> +  return __atomic_load_n (&v, __ATOMIC_SEQ_CST);
> +}
> +
> +void
> +f3 (__int128 x)
> +{
> +  __atomic_store_n (&v, 42, __ATOMIC_SEQ_CST);
> +}
> +
> +__int128
> +f4 (void)
> +{
> +  __int128 y = 42;
> +  __atomic_compare_exchange_n (&v, &y, 0, 0, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
> +}
> --- gcc/testsuite/gcc.target/i386/pr104688-2.c.jj       2022-11-13 19:36:46.513288025 -1200
> +++ gcc/testsuite/gcc.target/i386/pr104688-2.c  2022-11-13 19:40:34.676170305 -1200
> @@ -0,0 +1,34 @@
> +/* PR target/104688 */
> +/* { dg-do compile { target int128 } } */
> +/* { dg-options "-O2 -mno-avx" } */
> +/* { dg-final { scan-assembler "\t__sync_val_compare_and_swap_16" } } */
> +/* { dg-final { scan-assembler "\t__atomic_load_16" } } */
> +/* { dg-final { scan-assembler "\t__atomic_store_16" } } */
> +/* { dg-final { scan-assembler "\t__atomic_compare_exchange_16" } } */
> +
> +__int128 v;
> +
> +__int128
> +f1 (void)
> +{
> +  return __sync_val_compare_and_swap (&v, 42, 0);
> +}
> +
> +__int128
> +f2 (void)
> +{
> +  return __atomic_load_n (&v, __ATOMIC_SEQ_CST);
> +}
> +
> +void
> +f3 (__int128 x)
> +{
> +  __atomic_store_n (&v, 42, __ATOMIC_SEQ_CST);
> +}
> +
> +__int128
> +f4 (void)
> +{
> +  __int128 y = 42;
> +  __atomic_compare_exchange_n (&v, &y, 0, 0, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
> +}
> --- gcc/testsuite/gcc.target/i386/pr104688-3.c.jj       2022-11-13 19:37:00.899091450 -1200
> +++ gcc/testsuite/gcc.target/i386/pr104688-3.c  2022-11-13 19:40:41.984070460 -1200
> @@ -0,0 +1,34 @@
> +/* PR target/104688 */
> +/* { dg-do compile { target int128 } } */
> +/* { dg-options "-O2 -mcx16 -mavx" } */
> +/* { dg-final { scan-assembler-not "\t__sync_val_compare_and_swap_16" } } */
> +/* { dg-final { scan-assembler-not "\t__atomic_load_16" } } */
> +/* { dg-final { scan-assembler-not "\t__atomic_store_16" } } */
> +/* { dg-final { scan-assembler-not "\t__atomic_compare_exchange_16" } } */
> +
> +__int128 v;
> +
> +__int128
> +f1 (void)
> +{
> +  return __sync_val_compare_and_swap (&v, 42, 0);
> +}
> +
> +__int128
> +f2 (void)
> +{
> +  return __atomic_load_n (&v, __ATOMIC_SEQ_CST);
> +}
> +
> +void
> +f3 (__int128 x)
> +{
> +  __atomic_store_n (&v, 42, __ATOMIC_SEQ_CST);
> +}
> +
> +__int128
> +f4 (void)
> +{
> +  __int128 y = 42;
> +  __atomic_compare_exchange_n (&v, &y, 0, 0, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
> +}
>
>
>         Jakub
>