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[Bug debug/44971] [4.6 Regression] -fcompare-debug failure with uninitialized read in walk_gimple_stmt
- From: "rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 18 Jul 2010 20:46:53 -0000
- Subject: [Bug debug/44971] [4.6 Regression] -fcompare-debug failure with uninitialized read in walk_gimple_stmt
- References: <bug-44971-14164@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #4 from rguenth at gcc dot gnu dot org 2010-07-18 20:46 -------
@@ -29,7 +29,7 @@
(note# 0 0 NOTE_INSN_DELETED)
(note# 0 0 [bb 2] NOTE_INSN_BASIC_BLOCK)
(note# 0 0 NOTE_INSN_FUNCTION_BEG)
-(insn:TI# 0 0 pr44971.c:22 (set (reg/f:SI 0 ax [orig:58 D.xxxx ] [58])
+(insn:TI# 0 0 pr44971.c:22 (set (reg/v/f:SI 0 ax [orig:58 info ] [58])
(mem/f/c:SI (symbol_ref:SI ("_XftintInfo") <var_decl # _XftintInfo>)
[ MEM[(struct XftintInfo * *)&_XftintInfo]+0 S4 A32]))# {*movsi_internal}
(nil))
(insn/f:TI# 0 0 pr44971.c:20 (set (mem:SI (pre_dec:SI (reg/f:SI 7 sp)) [ S4
A8])
(reg/f:SI 6 bp))# {*pushsi2} (nil))
@@ -37,7 +37,7 @@
(reg/f:SI 7 sp))# {*movsi_internal} (nil))
(note# 0 0 NOTE_INSN_PROLOGUE_END)
(insn:TI# 0 0 pr44971.c:22 (set (reg:CCZ 17 flags)
- (compare:CCZ (reg/f:SI 0 ax [orig:58 D.xxxx ] [58])
+ (compare:CCZ (reg/v/f:SI 0 ax [orig:58 info ] [58])
(const_int 0 [0])))# {*cmpsi_ccno_1} (nil))
(jump_insn:TI# 0 0 pr44971.c:22 (set (pc)
(if_then_else (eq (reg:CCZ 17 flags)
...
caused by phiprop. It chooses one dereference result to choose the
result. But debug stmts change order of immediate uses.
With debug stmts (uses of prev_1):
# VUSE <.MEM_8(D)>
info_5 = *prev_1;
# DEBUG prev => prev_1
# VUSE <.MEM_8(D)>
D.1973_6 = *prev_1;
without:
# VUSE <.MEM_8(D)>
D.1973_6 = *prev_1;
# VUSE <.MEM_8(D)>
info_5 = *prev_1;
so relying on stable order of immediate uses is now wrong? The compare-debug
failure is spurious, there is no difference in the assembly output.
I can fix it by always degrading debug info and creating a new variable.
Alex, why should the immediate use lists show this behavior?
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |aoliva at gcc dot gnu dot
| |org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44971