Hi!
If DCE is not going to remove some insn, as it is needed, but the pseudo
it sets is REG_DEAD before some debug insn which uses the pseudo, DCE +
valtrack still insert a debug temporary before the insn with the value
instead of after it with the pseudo it sets. This is undesirable if
SET_SRC of the insn is something that is never useable in debug info
(e.g. ASM_OPERANDS) or just wastes size of RTL by unnecessarily duplicating
the rhs. This patch fixes it, when insn is needed and is not a control
insn that must be at the end of a bb (we can't insert debug insns after
those (unless it would be put at the beginning of all successor bbs)).
The existing DEBUG_TEMP_AFTER_WITH_REG mode isn't usable for this,
because it omits emitting a debug temporary if there is just a single
trivial debug use (which is desirable for df-*.c uses but not for dce).
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2012-10-26 Jakub Jelinek <ja...@redhat.com>
PR debug/54953
* valtrack.h (DEBUG_TEMP_AFTER_WITH_REG_FORCE): New.
* valtrack.c (dead_debug_insert_temp): Use emit_debug_insn_after
even for where == DEBUG_TEMP_AFTER_WITH_REG_FORCE.
* dce.c (word_dce_process_block, dce_process_block): Pass
DEBUG_TEMP_AFTER_WITH_REG_FORCE if insn is needed and therefore
not going to be eliminated.
--- gcc/valtrack.h.jj 2012-10-03 09:01:35.000000000 +0200
+++ gcc/valtrack.h 2012-10-26 10:21:31.655376061 +0200
@@ -130,7 +130,12 @@ enum debug_temp_where
/* Bind a newly-created debug temporary to a REG for UREGNO, and
insert the debug insn after INSN. REG is expected to be set at
INSN. */
- DEBUG_TEMP_AFTER_WITH_REG = 1
+ DEBUG_TEMP_AFTER_WITH_REG = 1,
+ /* Like DEBUG_TEMP_AFTER_WITH_REG, but force addition of a debug
+ temporary even if there is just a single debug use. This is used
+ on regs that are becoming REG_DEAD on INSN and so uses of the
+ reg later on are invalid. */
+ DEBUG_TEMP_AFTER_WITH_REG_FORCE = 2
};
extern void dead_debug_global_init (struct dead_debug_global *, bitmap);
--- gcc/valtrack.c.jj 2012-10-03 09:01:35.000000000 +0200
+++ gcc/valtrack.c 2012-10-26 10:22:38.646999016 +0200
@@ -648,7 +648,8 @@ dead_debug_insert_temp (struct dead_debu
DEBUG_EXPR_TREE_DECL (dval), breg,
VAR_INIT_STATUS_INITIALIZED);
- if (where == DEBUG_TEMP_AFTER_WITH_REG)
+ if (where == DEBUG_TEMP_AFTER_WITH_REG
+ || where == DEBUG_TEMP_AFTER_WITH_REG_FORCE)
bind = emit_debug_insn_after (bind, insn);
else
bind = emit_debug_insn_before (bind, insn);
--- gcc/dce.c.jj 2012-10-19 11:01:03.000000000 +0200
+++ gcc/dce.c 2012-10-26 10:24:11.956465043 +0200
@@ -1,5 +1,5 @@
/* RTL dead code elimination.
- Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011
+ Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012
Free Software Foundation, Inc.
This file is part of GCC.
@@ -880,7 +880,10 @@ word_dce_process_block (basic_block bb,
for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
dead_debug_insert_temp (&debug, DF_REF_REGNO (*def_rec), insn,
- DEBUG_TEMP_BEFORE_WITH_VALUE);
+ marked_insn_p (insn)
+ && !control_flow_insn_p (insn)
+ ? DEBUG_TEMP_AFTER_WITH_REG_FORCE
+ : DEBUG_TEMP_BEFORE_WITH_VALUE);
}
if (dump_file)
@@ -981,7 +984,9 @@ dce_process_block (basic_block bb, bool
if (debug.used && !bitmap_empty_p (debug.used))
for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
dead_debug_insert_temp (&debug, DF_REF_REGNO (*def_rec), insn,
- DEBUG_TEMP_BEFORE_WITH_VALUE);
+ needed && !control_flow_insn_p (insn)
+ ? DEBUG_TEMP_AFTER_WITH_REG_FORCE
+ : DEBUG_TEMP_BEFORE_WITH_VALUE);
}
dead_debug_local_finish (&debug, NULL);
Jakub
