On 2/20/24 12:37, Jose E. Marchesi wrote:
>
> Hi Faust.
>
>> +bool
>> +bpf_expand_cpymem (rtx *operands, bool is_move)
>> +{
>> + /* Size must be constant for this expansion to work. */
>> + if (!CONST_INT_P (operands[2]))
>> + {
>> + const char *name = is_move ? "memmove" : "memcpy";
>> + if (flag_building_libgcc)
>> + warning (RTL_LOCATION (operands[2]),
>> + "could not expand call to %<__builtin_%s%> inline: "
>> + "size must be constant", name);
>> + else
>> + error ("could not expand call to %<__builtin_%s%> inline: "
>> + "size must be constant", name);
>> + return false;
>> + }
>
> I think you want to use warning_at and error_at above... the first
> argument to `warning' (and second to warning_at) is not a location but
> an OPT_W* value. You should pass 0 to the opt argument in this case as
> there is no -W option to handle this warning.
Oops. Thanks.
After fixing the arguments, `warning' and `error' generally give better
messages than `warning_at' and `error_at' since the
RTL_LOCATION (operands[2]) seems to be NULL for most (all?) cases, which
causes the diagnostic message to refer only to the containing function.
The non-`_at' versions highlight the builtin call being expanded, which
is much nicer.
>
> Also, I would not mention 'expand' in the error/warning message, as it
> is a GCC internal concept. I would use perhaps "could not inline call
> to %<__builtin_%s%>".
OK.
>
>> + /* Alignment is a CONST_INT. */
>> + gcc_assert (CONST_INT_P (operands[3]));
>> +
>> + rtx dst = operands[0];
>> + rtx src = operands[1];
>> + rtx size = operands[2];
>> + unsigned HOST_WIDE_INT size_bytes = UINTVAL (size);
>> + unsigned align = UINTVAL (operands[3]);
>> + enum machine_mode mode;
>> + switch (align)
>> + {
>> + case 1: mode = QImode; break;
>> + case 2: mode = HImode; break;
>> + case 4: mode = SImode; break;
>> + case 8: mode = DImode; break;
>> + default:
>> + gcc_unreachable ();
>> + }
>> +
>> + unsigned iters = size_bytes >> ceil_log2 (align);
>> + unsigned remainder = size_bytes & (align - 1);
>> +
>> + int inc = GET_MODE_SIZE (mode);
>> + rtx_code_label *fwd_label, *done_label;
>> + if (is_move)
>> + {
>> + /* For memmove, be careful of overlap. It is not a concern for
>> memcpy.
>> + To handle overlap, we check (at runtime) if SRC < DST, and if so do
>> + the move "backwards" starting from SRC + SIZE. */
>> + fwd_label = gen_label_rtx ();
>> + done_label = gen_label_rtx ();
>> +
>> + rtx dst_addr = copy_to_mode_reg (Pmode, XEXP (dst, 0));
>> + rtx src_addr = copy_to_mode_reg (Pmode, XEXP (src, 0));
>> + emit_cmp_and_jump_insns (src_addr, dst_addr, GEU, NULL_RTX, Pmode,
>> + true, fwd_label, profile_probability::even ());
>> +
>> + /* Emit the "backwards" unrolled loop. */
>> + emit_move_loop (src, dst, mode, size_bytes, -inc, iters, remainder);
>> + emit_jump_insn (gen_jump (done_label));
>> + emit_barrier ();
>> +
>> + emit_label (fwd_label);
>> + }
>> +
>> + emit_move_loop (src, dst, mode, 0, inc, iters, remainder);
>> +
>> + if (is_move)
>> + emit_label (done_label);
>> +
>> + return true;
>> +}
>> +
>> /* Finally, build the GCC target. */
>>
>> struct gcc_target targetm = TARGET_INITIALIZER;
>> diff --git a/gcc/config/bpf/bpf.md b/gcc/config/bpf/bpf.md
>> index 50df1aaa3e2..ca677bc6b50 100644
>> --- a/gcc/config/bpf/bpf.md
>> +++ b/gcc/config/bpf/bpf.md
>> @@ -627,4 +627,40 @@ (define_insn "ldabs<ldop>"
>> "{ldabs<ldop>\t%0|r0 = *(<pldop> *) skb[%0]}"
>> [(set_attr "type" "ld")])
>>
>> +;;; memmove and memcopy
>> +
>> +;; 0 is dst
>> +;; 1 is src
>> +;; 2 is size of copy in bytes
>> +;; 3 is alignment
>> +
>> +(define_expand "cpymemdi"
>> + [(match_operand:BLK 0 "memory_operand")
>> + (match_operand:BLK 1 "memory_operand")
>> + (match_operand:DI 2 "general_operand")
>> + (match_operand:DI 3 "immediate_operand")]
>> + ""
>> +{
>> + if (bpf_expand_cpymem (operands, false))
>> + DONE;
>> + FAIL;
>> +})
>> +
>> +;; 0 is dst
>> +;; 1 is src
>> +;; 2 is size of copy in bytes
>> +;; 3 is alignment
>> +
>> +(define_expand "movmemdi"
>> + [(match_operand:BLK 0 "memory_operand")
>> + (match_operand:BLK 1 "memory_operand")
>> + (match_operand:DI 2 "general_operand")
>> + (match_operand:DI 3 "immediate_operand")]
>> + ""
>> +{
>> + if (bpf_expand_cpymem (operands, true))
>> + DONE;
>> + FAIL;
>> +})
>> +
>> (include "atomic.md")
>> diff --git a/gcc/testsuite/gcc.target/bpf/memcpy-1.c
>> b/gcc/testsuite/gcc.target/bpf/memcpy-1.c
>> new file mode 100644
>> index 00000000000..6c9707f24e8
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/bpf/memcpy-1.c
>> @@ -0,0 +1,26 @@
>> +/* Ensure memcpy is expanded inline rather than emitting a libcall. */
>> +
>> +/* { dg-do compile } */
>> +/* { dg-options "-O2" } */
>> +
>> +struct context {
>> + unsigned int data;
>> + unsigned int data_end;
>> + unsigned int data_meta;
>> + unsigned int ingress;
>> + unsigned int queue_index;
>> + unsigned int egress;
>> +};
>> +
>> +void
>> +cpy_1(struct context *ctx)
>> +{
>> + void *data = (void *)(long)ctx->data;
>> + char *dest;
>> + dest = data;
>> + dest += 16;
>> +
>> + __builtin_memcpy (dest, data, 8);
>> +}
>> +
>> +/* { dg-final { scan-assembler-times "call" 0 } } */
>> diff --git a/gcc/testsuite/gcc.target/bpf/memmove-1.c
>> b/gcc/testsuite/gcc.target/bpf/memmove-1.c
>> new file mode 100644
>> index 00000000000..3b8ba82639e
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/bpf/memmove-1.c
>> @@ -0,0 +1,46 @@
>> +/* Ensure memmove is expanded inline rather than emitting a libcall. */
>> +
>> +/* { dg-do compile } */
>> +/* { dg-options "-O2" } */
>> +
>> +struct context {
>> + unsigned int data;
>> + unsigned int data_end;
>> + unsigned int data_meta;
>> + unsigned int ingress;
>> + unsigned int queue_index;
>> + unsigned int egress;
>> +};
>> +
>> +void
>> +mov_1_nooverlap (struct context *ctx)
>> +{
>> + void *data = (void *)(long)ctx->data;
>> + char *dest;
>> + dest = data;
>> + dest += 16;
>> +
>> + __builtin_memmove (dest, data, 12);
>> +}
>> +
>> +void
>> +mov_1_overlap (struct context *ctx)
>> +{
>> + void *data = (void *)(long)ctx->data;
>> + char *dest;
>> + dest = data;
>> + dest += 4;
>> +
>> + __builtin_memmove (dest, data, 12);
>> +}
>> +
>> +void
>> +mov_1_arbitrary (struct context *ctx_a, struct context *ctx_b)
>> +{
>> + void *src = (void *)(long)ctx_a->data;
>> + void *dst = (void *)(long)ctx_b->data;
>> +
>> + __builtin_memmove (dst, src, 12);
>> +}
>> +
>> +/* { dg-final { scan-assembler-times "call" 0 } } */
>> diff --git a/gcc/testsuite/gcc.target/bpf/memmove-2.c
>> b/gcc/testsuite/gcc.target/bpf/memmove-2.c
>> new file mode 100644
>> index 00000000000..7fae96095a3
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/bpf/memmove-2.c
>> @@ -0,0 +1,23 @@
>> +/* Test that we error if memmove cannot be expanded inline. */
>> +
>> +/* { dg-do compile } */
>> +/* { dg-options "-O2" } */
>> +
>> +typedef unsigned int __u32;
>> +
>> +struct context {
>> + unsigned int data;
>> + unsigned int data_end;
>> + unsigned int data_meta;
>> +};
>> +
>> +void
>> +mov_2_unsupported (struct context *ctx)
>> +{
>> + void *data = (void *)(long)ctx->data;
>> + char *dest;
>> + dest = data;
>> + dest += 4;
>> +
>> + __builtin_memmove (dest, data, ctx->data_meta); /* { dg-error "could not
>> expand" } */
>> +}
