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From: Patrick O'Neill <poneill@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-7668] RISC-V: Strengthen atomic stores Date: Mon, 31 Jul 2023 16:18:57 +0000 (GMT) [thread overview] Message-ID: <20230731161857.4B1583858426@sourceware.org> (raw) https://gcc.gnu.org/g:74abe200bc9b06e10f0f3cad74f11da4fae90cd3 commit r13-7668-g74abe200bc9b06e10f0f3cad74f11da4fae90cd3 Author: Patrick O'Neill <patrick@rivosinc.com> Date: Wed Apr 5 09:56:33 2023 -0700 RISC-V: Strengthen atomic stores This change makes atomic stores strictly stronger than table A.6 of the ISA manual. This mapping makes the overall patchset compatible with table A.7 as well. 2023-04-27 Patrick O'Neill <patrick@rivosinc.com> PR target/89835 gcc/ChangeLog: * config/riscv/sync.md (atomic_store<mode>): Use simple store instruction in combination with fence(s). gcc/testsuite/ChangeLog: * gcc.target/riscv/pr89835.c: New test. Signed-off-by: Patrick O'Neill <patrick@rivosinc.com> Diff: --- gcc/config/riscv/sync.md | 21 ++++++++++++++++++--- gcc/testsuite/gcc.target/riscv/pr89835.c | 9 +++++++++ 2 files changed, 27 insertions(+), 3 deletions(-) diff --git a/gcc/config/riscv/sync.md b/gcc/config/riscv/sync.md index 5620d6ffa58..1acb78a9ae4 100644 --- a/gcc/config/riscv/sync.md +++ b/gcc/config/riscv/sync.md @@ -56,7 +56,9 @@ ;; Atomic memory operations. -;; Implement atomic stores with amoswap. Fall back to fences for atomic loads. +;; Implement atomic stores with conservative fences. Fall back to fences for +;; atomic loads. +;; This allows us to be compatible with the ISA manual Table A.6 and Table A.7. (define_insn "atomic_store<mode>" [(set (match_operand:GPR 0 "memory_operand" "=A") (unspec_volatile:GPR @@ -64,9 +66,22 @@ (match_operand:SI 2 "const_int_operand")] ;; model UNSPEC_ATOMIC_STORE))] "TARGET_ATOMIC" - "%F2amoswap.<amo>%A2 zero,%z1,%0" + { + enum memmodel model = (enum memmodel) INTVAL (operands[2]); + model = memmodel_base (model); + + if (model == MEMMODEL_SEQ_CST) + return "fence\trw,w\;" + "s<amo>\t%z1,%0\;" + "fence\trw,rw"; + if (model == MEMMODEL_RELEASE) + return "fence\trw,w\;" + "s<amo>\t%z1,%0"; + else + return "s<amo>\t%z1,%0"; + } [(set_attr "type" "atomic") - (set (attr "length") (const_int 8))]) + (set (attr "length") (const_int 12))]) (define_insn "atomic_<atomic_optab><mode>" [(set (match_operand:GPR 0 "memory_operand" "+A") diff --git a/gcc/testsuite/gcc.target/riscv/pr89835.c b/gcc/testsuite/gcc.target/riscv/pr89835.c new file mode 100644 index 00000000000..ab190e11b60 --- /dev/null +++ b/gcc/testsuite/gcc.target/riscv/pr89835.c @@ -0,0 +1,9 @@ +/* { dg-do compile } */ +/* Verify that relaxed atomic stores use simple store instuctions. */ +/* { dg-final { scan-assembler-not "amoswap" } } */ + +void +foo(int bar, int baz) +{ + __atomic_store_n(&bar, baz, __ATOMIC_RELAXED); +}
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