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[PATCH][RFC] Merge 'expand' and 'rtl_eh'
- From: Richard Guenther <rguenther at suse dot de>
- To: gcc-patches at gcc dot gnu dot org
- Cc: Jan Hubicka <jh at suse dot de>
- Date: Mon, 19 Mar 2012 16:41:57 +0100 (CET)
- Subject: [PATCH][RFC] Merge 'expand' and 'rtl_eh'
We have the unfortunate situation that expand may leave us with
unreachable blocks that are required by proper rtl_eh functioning
(unreachable landing-pads, that is). This is bad for any verification
pass the pass manager may want to call that requires dominators to
be computed (I'm thinking of verifying loop structures, which I really
want to do after expand as I am trying to preserve loop structures
from tree loop optimization until after RTL loop optimization).
This limitation has been introduced with the introduction of
rtl_eh - and is, IMHO, bad as it exposed a partly broken IL state
to the passmanager.
Thus the following patch makes sure we can leave cfgexpand with
no unreachable blocks around and simply merges the rtl_eh pass
and expand.
Yes, we do have several tests in the testsuite where EH landing
pads get unreachable during expansion, by a disconnect of what
GIMPLE thinks can throw and what the expanded code sequence says
(bogus SSE builtin definitions in the x86_64 backend for example,
see g++.dg/other/i386-1.C for two cases).
Bootstrap and regtest on x86_64-unknown-linux-gnu running.
Comments?
Thanks,
Richard.
2012-03-19 Richard Guenther <rguenther@suse.de>
* tree-pass.h (pass_rtl_eh): Remove.
* except.c (gate_handle_eh): Likewise.
(rest_of_handle_eh): Likewise.
(pass_rtl_eh): Likewise.
(finish_eh_generation): Export.
* except.h (finish_eh_generation): Declare.
* passes.c (init_optimization_passes): Remove pass_rtl_eh.
* cfgexpand.c (gimple_expand_cfg): Call finish_eh_generation
after expanding stack alignment. Instead of compacting blocks
call cleanup_cfg.
Index: gcc/tree-pass.h
===================================================================
--- gcc/tree-pass.h.orig 2012-03-19 16:29:36.000000000 +0100
+++ gcc/tree-pass.h 2012-03-19 16:28:03.000000000 +0100
@@ -488,7 +488,6 @@ extern struct gimple_opt_pass pass_fixup
extern struct rtl_opt_pass pass_expand;
extern struct rtl_opt_pass pass_init_function;
extern struct rtl_opt_pass pass_jump;
-extern struct rtl_opt_pass pass_rtl_eh;
extern struct rtl_opt_pass pass_initial_value_sets;
extern struct rtl_opt_pass pass_unshare_all_rtl;
extern struct rtl_opt_pass pass_instantiate_virtual_regs;
Index: gcc/except.c
===================================================================
--- gcc/except.c.orig 2012-03-19 16:29:36.000000000 +0100
+++ gcc/except.c 2012-03-19 16:29:06.000000000 +0100
@@ -81,7 +81,7 @@ along with GCC; see the file COPYING3.
gimple to eh_region mapping that had been recorded in the
THROW_STMT_TABLE.
- During pass_rtl_eh (except.c), we generate the real landing pads
+ Then, via finish_eh_generation, we generate the real landing pads
to which the runtime will actually transfer control. These new
landing pads perform whatever bookkeeping is needed by the target
backend in order to resume execution within the current function.
@@ -1414,7 +1414,7 @@ sjlj_build_landing_pads (void)
/* After initial rtl generation, call back to finish generating
exception support code. */
-static void
+void
finish_eh_generation (void)
{
basic_block bb;
@@ -1461,41 +1461,6 @@ finish_eh_generation (void)
}
}
}
-
-static bool
-gate_handle_eh (void)
-{
- /* Nothing to do if no regions created. */
- return cfun->eh->region_tree != NULL;
-}
-
-/* Complete generation of exception handling code. */
-static unsigned int
-rest_of_handle_eh (void)
-{
- finish_eh_generation ();
- cleanup_cfg (CLEANUP_NO_INSN_DEL);
- return 0;
-}
-
-struct rtl_opt_pass pass_rtl_eh =
-{
- {
- RTL_PASS,
- "rtl_eh", /* name */
- gate_handle_eh, /* gate */
- rest_of_handle_eh, /* execute */
- NULL, /* sub */
- NULL, /* next */
- 0, /* static_pass_number */
- TV_JUMP, /* tv_id */
- 0, /* properties_required */
- 0, /* properties_provided */
- 0, /* properties_destroyed */
- 0, /* todo_flags_start */
- 0 /* todo_flags_finish */
- }
-};
/* This section handles removing dead code for flow. */
Index: gcc/except.h
===================================================================
--- gcc/except.h.orig 2011-07-25 10:50:26.000000000 +0200
+++ gcc/except.h 2012-03-19 16:24:58.000000000 +0100
@@ -291,6 +291,8 @@ extern void assign_filter_values (void);
extern eh_region get_eh_region_from_rtx (const_rtx);
extern eh_landing_pad get_eh_landing_pad_from_rtx (const_rtx);
+extern void finish_eh_generation (void);
+
struct GTY(()) throw_stmt_node {
gimple stmt;
int lp_nr;
Index: gcc/passes.c
===================================================================
--- gcc/passes.c.orig 2012-03-19 14:52:11.000000000 +0100
+++ gcc/passes.c 2012-03-19 16:27:22.000000000 +0100
@@ -1431,7 +1431,6 @@ init_optimization_passes (void)
struct opt_pass **p = &pass_rest_of_compilation.pass.sub;
NEXT_PASS (pass_init_function);
NEXT_PASS (pass_jump);
- NEXT_PASS (pass_rtl_eh);
NEXT_PASS (pass_initial_value_sets);
NEXT_PASS (pass_unshare_all_rtl);
NEXT_PASS (pass_instantiate_virtual_regs);
Index: gcc/cfgexpand.c
===================================================================
*** gcc/cfgexpand.c (revision 185518)
--- gcc/cfgexpand.c (working copy)
*************** gimple_expand_cfg (void)
*** 4623,4632 ****
sbitmap_free (blocks);
purge_all_dead_edges ();
- compact_blocks ();
-
expand_stack_alignment ();
#ifdef ENABLE_CHECKING
verify_flow_info ();
#endif
--- 4632,4653 ----
sbitmap_free (blocks);
purge_all_dead_edges ();
expand_stack_alignment ();
+ /* After initial rtl generation, call back to finish generating
+ exception support code. We need to do this before cleaning up
+ the CFG as the code does not expect dead landing pads. */
+ if (cfun->eh->region_tree != NULL)
+ finish_eh_generation ();
+
+ /* Remove unreachable blocks, otherwise we cannot compute dominators
+ which are needed for loop state verification. As a side-effect
+ this also compacts blocks.
+ ??? We cannot remove trivially dead insns here as for example
+ the DRAP reg on i?86 is not magically live at this point.
+ gcc.c-torture/execute/ipa-sra-2.c execution, -Os -m32 fails otherwise. */
+ cleanup_cfg (CLEANUP_NO_INSN_DEL);
+
#ifdef ENABLE_CHECKING
verify_flow_info ();
#endif