Hi! This is a continuation of the PR127336 problem, just in a different file. If TER results in val being expanded as a MEM, we need to force it into a register before the atomic operation (and as a bonus for expand_builtin_atomic_fetch_op even better reuse it also for the atomic call itself).
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? 2026-09-22 Jakub Jelinek <[email protected]> PR middle-end/127492 * builtins.cc (expand_builtin_atomic_fetch_op): Force val into a pseudo if updates to mem could change its value. (expand_ifn_atomic_bit_test_and): Likewise. * gcc.dg/pr127492.c: New test. --- a/gcc/builtins.cc 2026-09-16 22:17:08.702383790 +0200 +++ b/gcc/builtins.cc 2026-09-21 12:48:35.777166119 +0200 @@ -6949,8 +6949,7 @@ expand_builtin_atomic_fetch_op (machine_ { rtx val, mem, ret; enum memmodel model; - tree fndecl; - tree addr; + tree fndecl, addr, oldval; model = get_memmodel (CALL_EXPR_ARG (exp, 2)); @@ -6977,6 +6976,13 @@ expand_builtin_atomic_fetch_op (machine_ gcc_assert (TREE_OPERAND (addr, 0) == fndecl); TREE_OPERAND (addr, 0) = builtin_decl_explicit (ext_call); + oldval = CALL_EXPR_ARG (exp, 1); + + if (!ignore && reg_overlap_mentioned_p (mem, val)) + { + val = force_reg (mode, val); + CALL_EXPR_ARG (exp, 1) = make_tree (TREE_TYPE (oldval), val); + } /* If we will emit code after the call, the call cannot be a tail call. If it is emitted as a tail call, a barrier is emitted after it, and @@ -6993,6 +6999,7 @@ expand_builtin_atomic_fetch_op (machine_ /* Then issue the arithmetic correction to return the right result. */ if (!ignore) { + CALL_EXPR_ARG (exp, 1) = oldval; if (code == NOT) { ret = expand_simple_binop (mode, AND, ret, val, NULL_RTX, true, @@ -7072,6 +7079,9 @@ expand_ifn_atomic_bit_test_and (gcall *c if (maybe_expand_insn (icode, 5, ops)) return; + if (reg_overlap_mentioned_p (mem, val)) + val = force_reg (mode, val); + rtx bitval = val; val = expand_simple_binop (mode, ASHIFT, const1_rtx, val, NULL_RTX, true, OPTAB_DIRECT); --- a/gcc/testsuite/gcc.dg/pr127492.c 2026-09-21 13:41:47.160775175 +0200 +++ b/gcc/testsuite/gcc.dg/pr127492.c 2026-09-21 13:48:58.216043364 +0200 @@ -0,0 +1,19 @@ +/* PR middle-end/127492 */ +/* { dg-do run } */ +/* { dg-options "-O2" } */ +/* { dg-additional-options "-latomic" { target libatomic_available } } */ + +#ifdef __SIZEOF_INT128__ +#define T __int128 +#else +#define T long long +#endif +T v = 1; + +int +main () +{ + T r = __atomic_add_fetch (&v, v, __ATOMIC_RELAXED); + if (r != 2 || v != 2) + __builtin_abort (); +} Jakub
