https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85859
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2018-05-22
Target Milestone|--- |6.5
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed. foo is discovered as 'const', it is nothrow anyways
(-fno-exceptions)
and thus overall it is considered not having side-effects (in particular not
trap). Quoting tree-ssa-ifcombine.c:
/* Verify if the basic block BB does not have side-effects. Return
true in this case, else false. */
static bool
bb_no_side_effects_p (basic_block bb)
{
gimple_stmt_iterator gsi;
for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
{
gimple *stmt = gsi_stmt (gsi);
if (is_gimple_debug (stmt))
continue;
if (gimple_has_side_effects (stmt)
|| gimple_uses_undefined_value_p (stmt)
|| gimple_could_trap_p (stmt)
|| gimple_vuse (stmt)
/* const calls don't match any of the above, yet they could
still have some side-effects - they could contain
gimple_could_trap_p statements, like floating point
exceptions or integer division by zero. See PR70586.
FIXME: perhaps gimple_has_side_effects or gimple_could_trap_p
should handle this. */
|| is_gimple_call (stmt))
and it is ifcombine pulling the call out of conditional context.
