From 8b64115dfb289777300c4e84e278ab3d8ec4fe86 Mon Sep 17 00:00:00 2001 From: Jinyang He Date: Tue, 15 Nov 2022 21:03:28 +0800 Subject: [PATCH v2] LoongArch: Fix atomic_exchange expanding [PR107713] We used to expand atomic_exchange_n(ptr, new, mem_order) for subword types into something like: { __typeof__(*ptr) t = atomic_load_n(ptr, mem_order); atomic_compare_exchange_n(ptr, &t, new, true, mem_order, mem_order); return t; } It's incorrect because another thread may store a different value into *ptr after atomic_load_n. Then atomic_compare_exchange_n will not store into *ptr, but atomic_exchange_n should always perform the store. gcc/ChangeLog: PR target/107713 * config/loongarch/sync.md (atomic_cas_value_exchange_7_): New define_insn. (atomic_exchange): Use atomic_cas_value_exchange_7_si instead of atomic_cas_value_cmp_and_7_si. gcc/testsuite/ChangeLog: PR target/107713 * gcc.target/loongarch/pr107713-1.c: New test. * gcc.target/loongarch/pr107713-2.c: New test. --- gcc/config/loongarch/sync.md | 27 +++++++++- .../gcc.target/loongarch/pr107713-1.c | 50 +++++++++++++++++++ .../gcc.target/loongarch/pr107713-2.c | 9 ++++ 3 files changed, 84 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/gcc.target/loongarch/pr107713-1.c create mode 100644 gcc/testsuite/gcc.target/loongarch/pr107713-2.c diff --git a/gcc/config/loongarch/sync.md b/gcc/config/loongarch/sync.md index 0c4f1983e88..45be1442439 100644 --- a/gcc/config/loongarch/sync.md +++ b/gcc/config/loongarch/sync.md @@ -448,6 +448,29 @@ } [(set (attr "length") (const_int 32))]) +(define_insn "atomic_cas_value_exchange_7_" + [(set (match_operand:GPR 0 "register_operand" "=&r") + (match_operand:GPR 1 "memory_operand" "+ZC")) + (set (match_dup 1) + (unspec_volatile:GPR [(match_operand:GPR 2 "reg_or_0_operand" "rJ") + (match_operand:GPR 3 "reg_or_0_operand" "rJ") + (match_operand:GPR 4 "reg_or_0_operand" "rJ") + (match_operand:GPR 5 "reg_or_0_operand" "rJ") + (match_operand:SI 6 "const_int_operand")] ;; model + UNSPEC_SYNC_EXCHANGE)) + (clobber (match_scratch:GPR 7 "=&r"))] + "" +{ + return "%G6\\n\\t" + "1:\\n\\t" + "ll.\\t%0,%1\\n\\t" + "and\\t%7,%0,%z3\\n\\t" + "or%i5\\t%7,%7,%5\\n\\t" + "sc.\\t%7,%1\\n\\t" + "beqz\\t%7,1b\\n\\t"; +} + [(set (attr "length") (const_int 20))]) + (define_expand "atomic_exchange" [(set (match_operand:SHORT 0 "register_operand") (unspec_volatile:SHORT @@ -459,9 +482,9 @@ "" { union loongarch_gen_fn_ptrs generator; - generator.fn_7 = gen_atomic_cas_value_cmp_and_7_si; + generator.fn_7 = gen_atomic_cas_value_exchange_7_si; loongarch_expand_atomic_qihi (generator, operands[0], operands[1], - operands[1], operands[2], operands[3]); + const0_rtx, operands[2], operands[3]); DONE; }) diff --git a/gcc/testsuite/gcc.target/loongarch/pr107713-1.c b/gcc/testsuite/gcc.target/loongarch/pr107713-1.c new file mode 100644 index 00000000000..d1536c95b27 --- /dev/null +++ b/gcc/testsuite/gcc.target/loongarch/pr107713-1.c @@ -0,0 +1,50 @@ +/* { dg-do run } */ +/* { dg-require-effective-target pthread } */ +/* { dg-options "-pthread" } */ + +#include + +char x, x1, x2; + +void * +work1 (void *) +{ + for (int i = 0; i < 100; i++) + x1 = __atomic_exchange_n (&x, x1, __ATOMIC_SEQ_CST); + return NULL; +} + +void * +work2 (void *) +{ + for (int i = 0; i < 100; i++) + x2 = __atomic_exchange_n (&x, x2, __ATOMIC_SEQ_CST); + return NULL; +} + +void +test (void) +{ + x = 0; + x1 = 1; + x2 = 2; + pthread_t w1, w2; + if (pthread_create (&w1, NULL, work1, NULL) != 0) + __builtin_abort (); + if (pthread_create (&w2, NULL, work2, NULL) != 0) + __builtin_abort (); + if (pthread_join (w1, NULL) != 0) + __builtin_abort (); + if (pthread_join (w2, NULL) != 0) + __builtin_abort (); + if ((x ^ x1 ^ x2) != 3) + __builtin_abort (); +} + +int +main () +{ + int i; + for (i = 0; i < 10000; i++) + test (); +} diff --git a/gcc/testsuite/gcc.target/loongarch/pr107713-2.c b/gcc/testsuite/gcc.target/loongarch/pr107713-2.c new file mode 100644 index 00000000000..82d44db3d51 --- /dev/null +++ b/gcc/testsuite/gcc.target/loongarch/pr107713-2.c @@ -0,0 +1,9 @@ +/* { dg-do compile } */ +/* { dg-options "-O2" } */ +/* { dg-final { scan-assembler-times "beq|bne" 1 } } */ + +char +t (char *p, char x) +{ + return __atomic_exchange_n (p, x, __ATOMIC_RELAXED); +} -- 2.37.3