static void
eliminate_tail_call (struct tailcall *t)
{
tree param, rslt;
gimple stmt, call;
tree arg;
size_t idx;
basic_block bb, first;
edge e;
gimple phi;
gimple_stmt_iterator gsi;
gimple orig_stmt;
stmt = orig_stmt = gsi_stmt (t->call_gsi);
bb = gsi_bb (t->call_gsi);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Eliminated tail recursion in bb %d : ",
bb->index);
print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
fprintf (dump_file, "\n");
}
gcc_assert (is_gimple_call (stmt));
first = single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun));
/* Remove the code after call_gsi that will become unreachable. The
possibly unreachable code in other blocks is removed later in
cfg cleanup. */
gsi = t->call_gsi;
gsi_next (&gsi);
while (!gsi_end_p (gsi))
{
gimple t = gsi_stmt (gsi);
/* Do not remove the return statement, so that redirect_edge_and_branch
sees how the block ends. */
if (gimple_code (t) == GIMPLE_RETURN)
break;
gsi_remove (&gsi, true);
release_defs (t);
}
/* Number of executions of function has reduced by the tailcall. */
e = single_succ_edge (gsi_bb (t->call_gsi));
decrease_profile (EXIT_BLOCK_PTR_FOR_FN (cfun), e->count, EDGE_FREQUENCY (e));
decrease_profile (ENTRY_BLOCK_PTR_FOR_FN (cfun), e->count,
EDGE_FREQUENCY (e));
if (e->dest != EXIT_BLOCK_PTR_FOR_FN (cfun))
decrease_profile (e->dest, e->count, EDGE_FREQUENCY (e));
/* Replace the call by a jump to the start of function. */
e = redirect_edge_and_branch (single_succ_edge (gsi_bb (t->call_gsi)),
first);
gcc_assert (e);
PENDING_STMT (e) = NULL;
/* Add phi node entries for arguments. The ordering of the phi nodes should
be the same as the ordering of the arguments. */
for (param = DECL_ARGUMENTS (current_function_decl),
idx = 0, gsi = gsi_start_phis (first);
param;
param = DECL_CHAIN (param), idx++)
{
if (!arg_needs_copy_p (param))
continue;
arg = gimple_call_arg (stmt, idx);
phi = gsi_stmt (gsi);
gcc_assert (param == SSA_NAME_VAR (PHI_RESULT (phi)));
add_phi_arg (phi, arg, e, gimple_location (stmt));
gsi_next (&gsi);
}
/* Update the values of accumulators. */
adjust_accumulator_values (t->call_gsi, t->mult, t->add, e);
call = gsi_stmt (t->call_gsi);
rslt = gimple_call_lhs (call);
if (rslt != NULL_TREE)
{
/* Result of the call will no longer be defined. So adjust the
SSA_NAME_DEF_STMT accordingly. */
SSA_NAME_DEF_STMT (rslt) = gimple_build_nop ();
}
gsi_remove (&t->call_gsi, true);
release_defs (call);
}
basic_block
isolate_path (basic_block bb, basic_block duplicate,
edge e, gimple stmt, tree op)
{
gimple_stmt_iterator si, si2;
edge_iterator ei;
edge e2;
/* First duplicate BB if we have not done so already and remove all
the duplicate's outgoing edges as duplicate is going to unconditionally
trap. Removing the outgoing edges is both an optimization and ensures
we don't need to do any PHI node updates. */
if (!duplicate)
{
duplicate = duplicate_block (bb, NULL, NULL);
for (ei = ei_start (duplicate->succs); (e2 = ei_safe_edge (ei)); )
remove_edge (e2);
}
/* Complete the isolation step by redirecting E to reach DUPLICATE. */
e2 = redirect_edge_and_branch (e, duplicate);
if (e2)
flush_pending_stmts (e2);
/* There may be more than one statement in DUPLICATE which exhibits
undefined behaviour. Ultimately we want the first such statement in
DUPLCIATE so that we're able to delete as much code as possible.
So each time we discover undefined behaviour in DUPLICATE, search for
the statement which triggers undefined behaviour. If found, then
transform the statement into a trap and delete everything after the
statement. If not found, then this particular instance was subsumed by
an earlier instance of undefined behaviour and there's nothing to do.
This is made more complicated by the fact that we have STMT, which is in
BB rather than in DUPLICATE. So we set up two iterators, one for each
block and walk forward looking for STMT in BB, advancing each iterator at
each step.
When we find STMT the second iterator should point to STMT's equivalent in
duplicate. If DUPLICATE ends before STMT is found in BB, then there's
nothing to do.
Ignore labels and debug statements. */
si = gsi_start_nondebug_after_labels_bb (bb);
si2 = gsi_start_nondebug_after_labels_bb (duplicate);
while (!gsi_end_p (si) && !gsi_end_p (si2) && gsi_stmt (si) != stmt)
{
gsi_next_nondebug (&si);
gsi_next_nondebug (&si2);
}
/* This would be an indicator that we never found STMT in BB, which should
never happen. */
gcc_assert (!gsi_end_p (si));
/* If we did not run to the end of DUPLICATE, then SI points to STMT and
SI2 points to the duplicate of STMT in DUPLICATE. Insert a trap
before SI2 and remove SI2 and all trailing statements. */
if (!gsi_end_p (si2))
insert_trap_and_remove_trailing_statements (&si2, op);
return duplicate;
}
