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analyzer: handle self-referential phis

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gcc/analyzer/ChangeLog:
	* state-purge.cc (self_referential_phi_p): New.
	(state_purge_per_ssa_name::process_point): Don't purge an SSA name
	at its def-stmt if the def-stmt is self-referential.

gcc/testsuite/ChangeLog:
	* gcc.dg/analyzer/phi-1.c: New test.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>
This commit is contained in:
David Malcolm 2021-07-15 15:01:57 -04:00
parent 797358f42f
commit a9241df96e
2 changed files with 58 additions and 3 deletions
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37
gcc/analyzer/state-purge.cc
View file

@ -288,6 +288,20 @@ state_purge_per_ssa_name::add_to_worklist (const function_point &point,
}
}
/* Does this phi depend on itself?
e.g. in:
added_2 = PHI <added_6(2), added_2(3), added_11(4)>
the middle defn (from edge 3) requires added_2 itself. */
static bool
self_referential_phi_p (const gphi *phi)
{
for (unsigned i = 0; i < gimple_phi_num_args (phi); i++)
if (gimple_phi_arg_def (phi, i) == gimple_phi_result (phi))
return true;
return false;
}
/* Process POINT, popped from WORKLIST.
Iterate over predecessors of POINT, adding to WORKLIST. */
@ -326,11 +340,28 @@ state_purge_per_ssa_name::process_point (const function_point &point,
!gsi_end_p (gpi); gsi_next (&gpi))
{
gphi *phi = gpi.phi ();
/* Are we at the def-stmt for m_name? */
if (phi == def_stmt)
{
if (logger)
logger->log ("def stmt within phis; terminating");
return;
/* Does this phi depend on itself?
e.g. in:
added_2 = PHI <added_6(2), added_2(3), added_11(4)>
the middle defn (from edge 3) requires added_2 itself
so we can't purge it here. */
if (self_referential_phi_p (phi))
{
if (logger)
logger->log ("self-referential def stmt within phis;"
" continuing");
}
else
{
/* Otherwise, we can stop here, so that m_name
can be purged. */
if (logger)
logger->log ("def stmt within phis; terminating");
return;
}
}
}

24
gcc/testsuite/gcc.dg/analyzer/phi-1.c Normal file
View file

@ -0,0 +1,24 @@
/* { dg-do "compile" } */
typedef __SIZE_TYPE__ size_t;
#define NULL ((void *) 0)
extern const char *foo (void);
extern size_t bar (void);
void
_nl_expand_alias (const char *locale_alias_path)
{
size_t added;
do
{
added = 0;
while (added == 0 && locale_alias_path[0] != '\0')
{
const char *start = foo ();
if (start < locale_alias_path)
added = bar ();
}
}
while (added != 0);
}