在 2023/11/14 上午7:18, Xi Ruoyao 写道:
/* snip */
(define_insn "mem_thread_fence_1"
[(set (match_operand:BLK 0 "" "")
(unspec:BLK [(match_dup 0)] UNSPEC_MEMORY_BARRIER))
(match_operand:SI 1 "const_int_operand" "")] ;; model
""
- "dbar\t0")
+ {
+ enum memmodel model = memmodel_base (INTVAL (operands[1]));
+
+ switch (model)
+ {
+ case MEMMODEL_ACQUIRE:
+ case MEMMODEL_CONSUME:
Hi,
* Before calling this template, the function get_memmodel is called to
process memmodel, which has a piece of code:
*
/* Workaround for Bugzilla 59448. GCC doesn't track consume
properly, so be conservative and promote consume to acquire. */ if
(val == MEMMODEL_CONSUME) val = MEMMODEL_ACQUIRE;
*
* So I think MEMMODEL_CONSUME don't need to be processed here either.
Otherwise is OK.
* Thanks.
+ /* Consume is implemented using the stronger acquire memory order
+ because of a deficiency in C++11's semantics. */
+ return "dbar\t0b10100";
+ case MEMMODEL_RELEASE:
+ return "dbar\t0b10010";
+ case MEMMODEL_ACQ_REL:
+ case MEMMODEL_SEQ_CST:
+ return "dbar\t0b10000";
+ default:
+ /* GCC internal: "For the '__ATOMIC_RELAXED' model no instructions
+ need to be issued and this expansion is not invoked."
+ Other values should not be returned by memmodel_base. */
+ gcc_unreachable ();
+ }
+ })
;; Atomic memory operations.
