@@ -43,6 +43,7 @@ along with GCC; see the file COPYING3. If not see
#include "common/common-target.h"
#include "ipa-utils.h"
#include "tree-ssa-live.h"
+#include "diagnostic-core.h"
/* The file implements the tail recursion elimination. It is also used to
analyze the tail calls in general, passing the results to the rtl level
@@ -402,6 +403,36 @@ propagate_through_phis (tree var, edge e)
return var;
}
+/* Report an error for failing to tail convert must call CALL
+ with error message ERR. */
+
+static void
+maybe_error_musttail (gcall *call, const char *err)
+{
+ if (gimple_call_must_tail_p (call))
+ {
+ error_at (call->location, "cannot tail-call: %s", err);
+ gimple_call_set_must_tail (call, false); /* Avoid another error. */
+ gimple_call_set_tail (call, false);
+ }
+}
+
+/* Count succ edges for BB and return in NUM_OTHER and NUM_EH. */
+
+static void
+bb_get_succ_edge_count (basic_block bb, int &num_other, int &num_eh)
+{
+ edge e;
+ edge_iterator ei;
+ num_eh = 0;
+ num_other = 0;
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if (e->flags & EDGE_EH)
+ num_eh++;
+ else
+ num_other++;
+}
+
/* Argument for compute_live_vars/live_vars_at_stmt and what compute_live_vars
returns. Computed lazily, but just once for the function. */
static live_vars_map *live_vars;
@@ -426,7 +457,14 @@ find_tail_calls (basic_block bb, struct tailcall **ret, bool only_musttail)
tree var;
if (!single_succ_p (bb))
- return;
+ {
+ int num_eh, num_other;
+ bb_get_succ_edge_count (bb, num_eh, num_other);
+ /* Allow a single EH edge so that we can give a better
+ error message later. */
+ if (!(num_eh == 1 && num_other == 1))
+ return;
+ }
for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi))
{
@@ -489,13 +527,20 @@ find_tail_calls (basic_block bb, struct tailcall **ret, bool only_musttail)
if (ass_var
&& !is_gimple_reg (ass_var)
&& !auto_var_in_fn_p (ass_var, cfun->decl))
- return;
+ {
+ maybe_error_musttail (call, "complex return value");
+ return;
+ }
/* If the call might throw an exception that wouldn't propagate out of
cfun, we can't transform to a tail or sibling call (82081). */
if (stmt_could_throw_p (cfun, stmt)
&& !stmt_can_throw_external (cfun, stmt))
+ {
+ maybe_error_musttail (call,
+ "call may throw exception that does not propagate");
return;
+ }
/* If the function returns a value, then at present, the tail call
must return the same type of value. There is conceptually a copy
@@ -524,7 +569,10 @@ find_tail_calls (basic_block bb, struct tailcall **ret, bool only_musttail)
if (result_decl
&& may_be_aliased (result_decl)
&& ref_maybe_used_by_stmt_p (call, result_decl, false))
- return;
+ {
+ maybe_error_musttail (call, "tail call must be same type");
+ return;
+ }
/* We found the call, check whether it is suitable. */
tail_recursion = false;
@@ -605,6 +653,7 @@ find_tail_calls (basic_block bb, struct tailcall **ret, bool only_musttail)
{
if (local_live_vars)
BITMAP_FREE (local_live_vars);
+ maybe_error_musttail (call, "call invocation refers to locals");
return;
}
else
@@ -613,6 +662,7 @@ find_tail_calls (basic_block bb, struct tailcall **ret, bool only_musttail)
if (bitmap_bit_p (local_live_vars, *v))
{
BITMAP_FREE (local_live_vars);
+ maybe_error_musttail (call, "call invocation refers to locals");
return;
}
}
@@ -663,12 +713,13 @@ find_tail_calls (basic_block bb, struct tailcall **ret, bool only_musttail)
/* This is a gimple assign. */
par ret = process_assignment (as_a <gassign *> (stmt), gsi,
&tmp_m, &tmp_a, &ass_var, to_move_defs);
- if (ret == FAIL)
- return;
+ if (ret == FAIL || (ret == TRY_MOVE && !tail_recursion))
+ {
+ maybe_error_musttail (call, "return value changed after call");
+ return;
+ }
else if (ret == TRY_MOVE)
{
- if (! tail_recursion)
- return;
/* Do not deal with checking dominance, the real fix is to
do path isolation for the transform phase anyway, removing
the need to compute the accumulators with new stmts. */
@@ -716,7 +767,10 @@ find_tail_calls (basic_block bb, struct tailcall **ret, bool only_musttail)
if (ret_var
&& (ret_var != ass_var
&& !(is_empty_type (TREE_TYPE (ret_var)) && !ass_var)))
- return;
+ {
+ maybe_error_musttail (call, "call must be the same type");
+ return;
+ }
/* If this is not a tail recursive call, we cannot handle addends or
multiplicands. */
When musttail is set, make tree-tailcall to give error messages when it cannot handle a call. This avoids vague "other reasons" error messages later at expand time. This doesn't always work, for example when find_tail_call walking gives up because the control flow is too complicated then it won't find the tail call and can't give a suitable error message. gcc/ChangeLog: * tree-tailcall.cc (maybe_error_musttail): Add. (bb_get_succ_edge_count): Add. (find_tail_calls): Add error messages. Keep searching for basic blocks with multiple BBs if all but one is EH only. --- gcc/tree-tailcall.cc | 70 +++++++++++++++++++++++++++++++++++++++----- 1 file changed, 62 insertions(+), 8 deletions(-)