This patch restructures how the prologues/epilogues are inserted. Sibcalls
that run without prologue are now handled in shrink-wrap.c; it communicates
what is already handled by setting the EDGE_IGNORE flag. The
try_shrink_wrapping function then doesn't need to be passed the bb_flags
anymore.
Tested like the previous two patches; is this okay for trunk?
Segher
2016-05-16 Segher Boessenkool <seg...@kernel.crashing.org>
* function.c (make_epilogue_seq): Remove epilogue_end parameter.
(thread_prologue_and_epilogue_insns): Remove bb_flags. Restructure
code. Ignore sibcalls on EDGE_IGNORE edges.
* shrink-wrap.c (handle_simple_exit): New function. Set EDGE_IGNORE
on edges for sibcalls that run without prologue. The rest of the
function is combined from...
(fix_fake_fallthrough_edge): ... this, and ...
(try_shrink_wrapping): ... a part of this. Remove the bb_with
function argument, make it a local variable.
---
gcc/function.c | 168 ++++++++++++++++++++++--------------------------------
gcc/shrink-wrap.c | 88 ++++++++++++++--------------
gcc/shrink-wrap.h | 3 +-
3 files changed, 113 insertions(+), 146 deletions(-)
diff --git a/gcc/function.c b/gcc/function.c
index 75d2ad4..278aaf6 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -5819,13 +5819,13 @@ make_prologue_seq (void)
}
static rtx_insn *
-make_epilogue_seq (rtx_insn **epilogue_end)
+make_epilogue_seq (void)
{
if (!targetm.have_epilogue ())
return NULL;
start_sequence ();
- *epilogue_end = emit_note (NOTE_INSN_EPILOGUE_BEG);
+ emit_note (NOTE_INSN_EPILOGUE_BEG);
rtx_insn *seq = targetm.gen_epilogue ();
if (seq)
emit_jump_insn (seq);
@@ -5897,66 +5897,29 @@ make_epilogue_seq (rtx_insn **epilogue_end)
void
thread_prologue_and_epilogue_insns (void)
{
- bool inserted;
- bitmap_head bb_flags;
- rtx_insn *epilogue_end ATTRIBUTE_UNUSED;
- edge e, entry_edge, orig_entry_edge, exit_fallthru_edge;
- edge_iterator ei;
-
df_analyze ();
- rtl_profile_for_bb (ENTRY_BLOCK_PTR_FOR_FN (cfun));
-
- inserted = false;
- epilogue_end = NULL;
-
/* Can't deal with multiple successors of the entry block at the
moment. Function should always have at least one entry
point. */
gcc_assert (single_succ_p (ENTRY_BLOCK_PTR_FOR_FN (cfun)));
- entry_edge = single_succ_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun));
- orig_entry_edge = entry_edge;
+
+ edge entry_edge = single_succ_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun));
+ edge orig_entry_edge = entry_edge;
rtx_insn *split_prologue_seq = make_split_prologue_seq ();
rtx_insn *prologue_seq = make_prologue_seq ();
- rtx_insn *epilogue_seq = make_epilogue_seq (&epilogue_end);
-
- bitmap_initialize (&bb_flags, &bitmap_default_obstack);
+ rtx_insn *epilogue_seq = make_epilogue_seq ();
/* Try to perform a kind of shrink-wrapping, making sure the
prologue/epilogue is emitted only around those parts of the
function that require it. */
- try_shrink_wrapping (&entry_edge, &bb_flags, prologue_seq);
+ try_shrink_wrapping (&entry_edge, prologue_seq);
- if (split_prologue_seq != NULL_RTX)
- {
- insert_insn_on_edge (split_prologue_seq, orig_entry_edge);
- inserted = true;
- }
- if (prologue_seq != NULL_RTX)
- {
- insert_insn_on_edge (prologue_seq, entry_edge);
- inserted = true;
- }
-
- /* If the exit block has no non-fake predecessors, we don't need
- an epilogue. */
- FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR_FOR_FN (cfun)->preds)
- if ((e->flags & EDGE_FAKE) == 0)
- break;
- if (e == NULL)
- goto epilogue_done;
rtl_profile_for_bb (EXIT_BLOCK_PTR_FOR_FN (cfun));
- exit_fallthru_edge = find_fallthru_edge (EXIT_BLOCK_PTR_FOR_FN
(cfun)->preds);
-
- /* If nothing falls through into the exit block, we don't need an
- epilogue. */
- if (exit_fallthru_edge == NULL)
- goto epilogue_done;
-
/* A small fib -- epilogue is not yet completed, but we wish to re-use
this marker for the splits of EH_RETURN patterns, and nothing else
uses the flag in the meantime. */
@@ -5967,6 +5930,8 @@ thread_prologue_and_epilogue_insns (void)
code. In order to be able to properly annotate these with unwind
info, try to split them now. If we get a valid split, drop an
EPILOGUE_BEG note and mark the insns as epilogue insns. */
+ edge e;
+ edge_iterator ei;
FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR_FOR_FN (cfun)->preds)
{
rtx_insn *prev, *last, *trial;
@@ -5986,78 +5951,84 @@ thread_prologue_and_epilogue_insns (void)
emit_note_after (NOTE_INSN_EPILOGUE_BEG, prev);
}
- if (epilogue_seq)
- {
- insert_insn_on_edge (epilogue_seq, exit_fallthru_edge);
- inserted = true;
- }
- else
- {
- basic_block cur_bb;
+ edge exit_fallthru_edge = find_fallthru_edge (EXIT_BLOCK_PTR_FOR_FN
(cfun)->preds);
- if (! next_active_insn (BB_END (exit_fallthru_edge->src)))
- goto epilogue_done;
- /* We have a fall-through edge to the exit block, the source is not
- at the end of the function, and there will be an assembler epilogue
- at the end of the function.
- We can't use force_nonfallthru here, because that would try to
- use return. Inserting a jump 'by hand' is extremely messy, so
- we take advantage of cfg_layout_finalize using
- fixup_fallthru_exit_predecessor. */
- cfg_layout_initialize (0);
- FOR_EACH_BB_FN (cur_bb, cfun)
- if (cur_bb->index >= NUM_FIXED_BLOCKS
- && cur_bb->next_bb->index >= NUM_FIXED_BLOCKS)
- cur_bb->aux = cur_bb->next_bb;
- cfg_layout_finalize ();
+ if (exit_fallthru_edge)
+ {
+ if (epilogue_seq)
+ {
+ insert_insn_on_edge (epilogue_seq, exit_fallthru_edge);
+
+ /* The epilogue insns we inserted may cause the exit edge to no longer
+ be fallthru. */
+ FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR_FOR_FN (cfun)->preds)
+ {
+ if (((e->flags & EDGE_FALLTHRU) != 0)
+ && returnjump_p (BB_END (e->src)))
+ e->flags &= ~EDGE_FALLTHRU;
+ }
+ }
+ else if (next_active_insn (BB_END (exit_fallthru_edge->src)))
+ {
+ /* We have a fall-through edge to the exit block, the source is not
+ at the end of the function, and there will be an assembler epilogue
+ at the end of the function.
+ We can't use force_nonfallthru here, because that would try to
+ use return. Inserting a jump 'by hand' is extremely messy, so
+ we take advantage of cfg_layout_finalize using
+ fixup_fallthru_exit_predecessor. */
+ cfg_layout_initialize (0);
+ basic_block cur_bb;
+ FOR_EACH_BB_FN (cur_bb, cfun)
+ if (cur_bb->index >= NUM_FIXED_BLOCKS
+ && cur_bb->next_bb->index >= NUM_FIXED_BLOCKS)
+ cur_bb->aux = cur_bb->next_bb;
+ cfg_layout_finalize ();
+ }
}
-epilogue_done:
+ /* Insert the prologue. */
- default_rtl_profile ();
+ rtl_profile_for_bb (ENTRY_BLOCK_PTR_FOR_FN (cfun));
- if (inserted)
+ if (split_prologue_seq || prologue_seq)
{
- sbitmap blocks;
+ if (split_prologue_seq)
+ insert_insn_on_edge (split_prologue_seq, orig_entry_edge);
+
+ if (prologue_seq)
+ insert_insn_on_edge (prologue_seq, entry_edge);
commit_edge_insertions ();
/* Look for basic blocks within the prologue insns. */
- blocks = sbitmap_alloc (last_basic_block_for_fn (cfun));
+ sbitmap blocks = sbitmap_alloc (last_basic_block_for_fn (cfun));
bitmap_clear (blocks);
bitmap_set_bit (blocks, entry_edge->dest->index);
bitmap_set_bit (blocks, orig_entry_edge->dest->index);
find_many_sub_basic_blocks (blocks);
sbitmap_free (blocks);
-
- /* The epilogue insns we inserted may cause the exit edge to no longer
- be fallthru. */
- FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR_FOR_FN (cfun)->preds)
- {
- if (((e->flags & EDGE_FALLTHRU) != 0)
- && returnjump_p (BB_END (e->src)))
- e->flags &= ~EDGE_FALLTHRU;
- }
}
- /* Emit sibling epilogues before any sibling call sites. */
- for (ei = ei_start (EXIT_BLOCK_PTR_FOR_FN (cfun)->preds); (e =
- ei_safe_edge (ei));
- )
- {
- basic_block bb = e->src;
- rtx_insn *insn = BB_END (bb);
+ default_rtl_profile ();
- if (!CALL_P (insn)
- || ! SIBLING_CALL_P (insn)
- || (targetm.have_simple_return ()
- && entry_edge != orig_entry_edge
- && !bitmap_bit_p (&bb_flags, bb->index)))
+ /* Emit sibling epilogues before any sibling call sites. */
+ for (ei = ei_start (EXIT_BLOCK_PTR_FOR_FN (cfun)->preds);
+ (e = ei_safe_edge (ei));
+ ei_next (&ei))
+ {
+ /* Skip those already handled, the ones that run without prologue. */
+ if (e->flags & EDGE_IGNORE)
{
- ei_next (&ei);
+ e->flags &= ~EDGE_IGNORE;
continue;
}
+ rtx_insn *insn = BB_END (e->src);
+
+ if (!(CALL_P (insn) && SIBLING_CALL_P (insn)))
+ continue;
+
if (rtx_insn *ep_seq = targetm.gen_sibcall_epilogue ())
{
start_sequence ();
@@ -6074,10 +6045,9 @@ epilogue_done:
emit_insn_before (seq, insn);
}
- ei_next (&ei);
}
- if (epilogue_end)
+ if (epilogue_seq)
{
rtx_insn *insn, *next;
@@ -6086,17 +6056,15 @@ epilogue_done:
of such a note. Also possibly move
NOTE_INSN_FUNCTION_BEG notes, as those can be relevant for debug
info generation. */
- for (insn = epilogue_end; insn; insn = next)
+ for (insn = epilogue_seq; insn; insn = next)
{
next = NEXT_INSN (insn);
if (NOTE_P (insn)
&& (NOTE_KIND (insn) == NOTE_INSN_FUNCTION_BEG))
- reorder_insns (insn, insn, PREV_INSN (epilogue_end));
+ reorder_insns (insn, insn, PREV_INSN (epilogue_seq));
}
}
- bitmap_clear (&bb_flags);
-
/* Threading the prologue and epilogue changes the artificial refs
in the entry and exit blocks. */
epilogue_completed = 1;
diff --git a/gcc/shrink-wrap.c b/gcc/shrink-wrap.c
index 0ba1fed..b85b1c3 100644
--- a/gcc/shrink-wrap.c
+++ b/gcc/shrink-wrap.c
@@ -529,30 +529,49 @@ can_dup_for_shrink_wrapping (basic_block bb, basic_block
pro, unsigned max_size)
return true;
}
-/* If the source of edge E has more than one successor, the verifier for
- branch probabilities gets confused by the fake edges we make where
- simple_return statements will be inserted later (because those are not
- marked as fallthrough edges). Fix this by creating an extra block just
- for that fallthrough. */
+/* Do whatever needs to be done for exits that run without prologue.
+ Sibcalls need nothing done. Normal exits get a simple_return inserted. */
-static edge
-fix_fake_fallthrough_edge (edge e)
+static void
+handle_simple_exit (edge e)
{
- if (EDGE_COUNT (e->src->succs) <= 1)
- return e;
- basic_block old_bb = e->src;
- rtx_insn *end = BB_END (old_bb);
- rtx_note *note = emit_note_after (NOTE_INSN_DELETED, end);
- basic_block new_bb = create_basic_block (note, note, old_bb);
- BB_COPY_PARTITION (new_bb, old_bb);
- BB_END (old_bb) = end;
+ if (e->flags & EDGE_SIBCALL)
+ {
+ /* Tell function.c to take no further action on this edge. */
+ e->flags |= EDGE_IGNORE;
- redirect_edge_succ (e, new_bb);
- e->flags |= EDGE_FALLTHRU;
- e->flags &= ~EDGE_FAKE;
+ e->flags &= ~EDGE_FALLTHRU;
+ emit_barrier_after_bb (e->src);
+ return;
+ }
- return make_edge (new_bb, EXIT_BLOCK_PTR_FOR_FN (cfun), EDGE_FAKE);
+ /* If the basic block the edge comes from has multiple successors,
+ split the edge. */
+ if (EDGE_COUNT (e->src->succs) > 1)
+ {
+ basic_block old_bb = e->src;
+ rtx_insn *end = BB_END (old_bb);
+ rtx_note *note = emit_note_after (NOTE_INSN_DELETED, end);
+ basic_block new_bb = create_basic_block (note, note, old_bb);
+ BB_COPY_PARTITION (new_bb, old_bb);
+ BB_END (old_bb) = end;
+
+ redirect_edge_succ (e, new_bb);
+ e->flags |= EDGE_FALLTHRU;
+
+ e = make_edge (new_bb, EXIT_BLOCK_PTR_FOR_FN (cfun), 0);
+ }
+
+ e->flags &= ~EDGE_FALLTHRU;
+ rtx_jump_insn *ret = emit_jump_insn_after (targetm.gen_simple_return (),
+ BB_END (e->src));
+ JUMP_LABEL (ret) = simple_return_rtx;
+ emit_barrier_after_bb (e->src);
+
+ if (dump_file)
+ fprintf (dump_file, "Made simple_return with UID %d in bb %d\n",
+ INSN_UID (ret), e->src->index);
}
/* Try to perform a kind of shrink-wrapping, making sure the
@@ -610,13 +629,10 @@ fix_fake_fallthrough_edge (edge e)
(bb 4 is duplicated to 5; the prologue is inserted on the edge 5->3).
ENTRY_EDGE is the edge where the prologue will be placed, possibly
- changed by this function. BB_WITH is a bitmap that, if we do shrink-
- wrap, will on return contain the interesting blocks that run with
- prologue. PROLOGUE_SEQ is the prologue we will insert. */
+ changed by this function. PROLOGUE_SEQ is the prologue we will insert. */
void
-try_shrink_wrapping (edge *entry_edge, bitmap_head *bb_with,
- rtx_insn *prologue_seq)
+try_shrink_wrapping (edge *entry_edge, rtx_insn *prologue_seq)
{
/* If we cannot shrink-wrap, are told not to shrink-wrap, or it makes
no sense to shrink-wrap: then do not shrink-wrap! */
@@ -739,6 +755,7 @@ try_shrink_wrapping (edge *entry_edge, bitmap_head *bb_with,
reachable from PRO that we already found, and in VEC a stack of
those we still need to consider (to find successors). */
+ bitmap bb_with = BITMAP_ALLOC (NULL);
bitmap_set_bit (bb_with, pro->index);
vec<basic_block> vec;
@@ -851,6 +868,7 @@ try_shrink_wrapping (edge *entry_edge, bitmap_head *bb_with,
if (pro == entry)
{
+ BITMAP_FREE (bb_with);
free_dominance_info (CDI_DOMINATORS);
return;
}
@@ -952,26 +970,7 @@ try_shrink_wrapping (edge *entry_edge, bitmap_head
*bb_with,
if (!bitmap_bit_p (bb_with, bb->index))
FOR_EACH_EDGE (e, ei, bb->succs)
if (e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun))
- {
- e = fix_fake_fallthrough_edge (e);
-
- e->flags &= ~EDGE_FALLTHRU;
- if (!(e->flags & EDGE_SIBCALL))
- {
- rtx_insn *ret = targetm.gen_simple_return ();
- rtx_insn *end = BB_END (e->src);
- rtx_jump_insn *start = emit_jump_insn_after (ret, end);
- JUMP_LABEL (start) = simple_return_rtx;
- e->flags &= ~EDGE_FAKE;
-
- if (dump_file)
- fprintf (dump_file,
- "Made simple_return with UID %d in bb %d\n",
- INSN_UID (start), e->src->index);
- }
-
- emit_barrier_after_bb (e->src);
- }
+ handle_simple_exit (e);
/* Finally, we want a single edge to put the prologue on. Make a new
block before the PRO block; the edge beteen them is the edge we want.
@@ -1004,5 +1003,6 @@ try_shrink_wrapping (edge *entry_edge, bitmap_head
*bb_with,
*entry_edge = make_single_succ_edge (new_bb, pro, EDGE_FALLTHRU);
force_nonfallthru (*entry_edge);
+ BITMAP_FREE (bb_with);
free_dominance_info (CDI_DOMINATORS);
}
diff --git a/gcc/shrink-wrap.h b/gcc/shrink-wrap.h
index 4d821d7..e06ab37 100644
--- a/gcc/shrink-wrap.h
+++ b/gcc/shrink-wrap.h
@@ -24,8 +24,7 @@ along with GCC; see the file COPYING3. If not see
/* In shrink-wrap.c. */
extern bool requires_stack_frame_p (rtx_insn *, HARD_REG_SET, HARD_REG_SET);
-extern void try_shrink_wrapping (edge *entry_edge, bitmap_head *bb_flags,
- rtx_insn *prologue_seq);
+extern void try_shrink_wrapping (edge *entry_edge, rtx_insn *prologue_seq);
#define SHRINK_WRAPPING_ENABLED \
(flag_shrink_wrap && targetm.have_simple_return ())
--
1.9.3
