When forcing the condition to be split out from COND_EXPRs I see
a runtime failure of libgomp.fortran/atomic-19.f90 which can be
reduced to
!$omp atomic update, compare, capture
if (x == 69_2 - r) x = 6_8
v = x
being miscompiled, the difference being
- _13 = .ATOMIC_COMPARE_EXCHANGE (_9, _10, _11, 4, 0, 0);
- _14 = IMAGPART_EXPR <_13>;
- _15 = REALPART_EXPR <_13>;
- _16 = _14 != 0 ? _11 : _15;
- _2 = (integer(kind=4)) _16;
- v_17 = _2;
+ _14 = .ATOMIC_COMPARE_EXCHANGE (_10, _11, _12, 4, 0, 0);
+ _15 = IMAGPART_EXPR <_14>;
+ _16 = REALPART_EXPR <_14>;
+ _2 = (logical(kind=1)) _15;
+ _3 = (integer(kind=4)) _16;
+ v_17 = _3;
where one can see a missing COND_EXPR. It seems to be a latent
issue to me given the code can be exercised, it just maybe misses
a 'need_new' testcase combined with 'cond_stmt'. Appearantly
the if (cond_stmt) code is just to avoid creating a temporary
(and possibly to preserve the condition compute if used elsewhere
since the original stmt is going to be deleted). The following
makes the failure go away for me in my patched tree and it
also survives libgomp and gomp testing in an unpatched tree.
Full bootstrap & regtest running on x86_64-unknown-linux-gnu.
OK?
Thanks,
Richard.
2022-05-13 Richard Biener <rguent...@suse.de>
* omp-expand.cc (expand_omp_atomic_cas): Do not short-cut
computation of the new value.
---
gcc/omp-expand.cc | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/gcc/omp-expand.cc b/gcc/omp-expand.cc
index ee708314793..9fcc67a3448 100644
--- a/gcc/omp-expand.cc
+++ b/gcc/omp-expand.cc
@@ -9092,16 +9092,17 @@ expand_omp_atomic_cas (basic_block load_bb, tree addr,
if (cond_stmt)
{
- g = gimple_build_assign (gimple_assign_lhs (cond_stmt),
- NOP_EXPR, im);
+ g = gimple_build_assign (cond, NOP_EXPR, im);
gimple_set_location (g, loc);
gsi_insert_before (&gsi, g, GSI_SAME_STMT);
}
- else if (need_new)
+
+ if (need_new)
{
g = gimple_build_assign (create_tmp_reg (itype), COND_EXPR,
- build2 (NE_EXPR, boolean_type_node,
- im, build_zero_cst (itype)),
+ cond_stmt
+ ? cond : build2 (NE_EXPR, boolean_type_node,
+ im, build_zero_cst (itype)),
d, re);
gimple_set_location (g, loc);
gsi_insert_before (&gsi, g, GSI_SAME_STMT);
--
2.35.3
