tree-ssa-dse: Fix up handling of lhs of internal calls [PR108657]

The r13-1778 PR106378 tree-ssa-dse change didn't just add special support
for IFN_LEN_STORE and IFN_MASK_STORE internal function calls as I believe
was intended, but given that the function was
if (is builtin) { ... }
else if (lhs present and non-SSA_NAME) { ... }
return false;
and it added a new
else if (is internal builtin) { ... }
in between the two, the last if used to be done before on all stmts
with non-SSA_NAME lhs except for calls to builtin functions, but newly
isn't done also for calls to internal functions.  In the testcase
the important internal function is .DEFERRED_INIT, which often has
non-SSA_NAME lhs, and the change resulted in them no longer being DSEd,
so a block with nothing in it left but var = .DEFERRED_INIT () and
var = {CLOBBER} was unrolled several times.

The following patch does the lhs handling for all stmts with non-SSA_NAME lhs
unless initialize_ao_ref_for_dse handled those specially already and
returned (which is the case for various mem* builtins which don't have
such lhs, for some cases of calloc which again is fine,and since r13-1778
also for IFN_LEN_STORE call and some IFN_MASK_STORE calls.
As IFN_MASK_STORE doesn't have a lhs, the break for the !may_def_ok case
doesn't seem to change anything, and because we've handled internal fns
that way in the past, I think it is the right thing to do that again.
That said, if it is inappropriate for some new ifn, I guess it could
be added to the switch and just return false; for it instead of break;.

2023-02-16  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/108657
	* tree-ssa-dse.cc (initialize_ao_ref_for_dse): If lhs of stmt
	exists and is not a SSA_NAME, call ao_ref_init even if the stmt
	is a call to internal or builtin function.

	* gcc.dg/pr108657.c: New test.

0 files changed, 0 insertions, 0 deletions