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* [Bug tree-optimization/66013] New: Missed optimization after inlining va_list parameter, -m32 case
@ 2015-05-05 7:24 vries at gcc dot gnu.org
2015-05-05 7:33 ` [Bug tree-optimization/66013] " vries at gcc dot gnu.org
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: vries at gcc dot gnu.org @ 2015-05-05 7:24 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66013
Bug ID: 66013
Summary: Missed optimization after inlining va_list parameter,
-m32 case
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: trivial
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: vries at gcc dot gnu.org
Target Milestone: ---
[ -m32 twin PR of PR66010 ]
Consider this test-case (based on gcc.dg/tree-ssa/stdarg-2.c, f15):
...
#include <stdarg.h>
int
f1 (int i, ...)
{
int res;
va_list ap;
va_start (ap, i);
res = va_arg (ap, int);
va_end (ap);
return res;
}
inline int __attribute__((always_inline))
f2_1 (va_list ap)
{
return va_arg (ap, int);
}
int
f2 (int i, ...)
{
int res;
va_list ap;
va_start (ap, i);
res = f2_1 (ap);
va_end (ap);
return res;
}
...
When compiling at -O2 with -m32, the optimized dump for f1 and f2 are very
similar:
...
# .MEM_9 = VDEF <.MEM_1(D)>
# USE = anything
# CLB = anything
- ap_8 = __builtin_next_argD.993 (0);
- ap_6 = ap_8;
+ ap_11 = __builtin_next_argD.993 (0);
+ ap_6 = ap_11;
# PT = nonlocal
- ap_7 = ap_6;
+ ap_3 = ap_6;
# VUSE <.MEM_9>
- res_4 = MEM[(intD.1 *)ap_7];
+ _7 = MEM[(intD.1 *)ap_3];
GIMPLE_NOP
# VUSE <.MEM_9>
- return res_4;
+ return _7;
;; succ: EXIT [100.0%]
...
However, at pass_stdarg, we see on one hand:
...
f1: va_list escapes 0, needs to save 4 GPR units and all FPR units.
...
but OTOH:
...
f2: va_list escapes 1, needs to save all GPR units and all FPR units.
...
Still the .s code is identical for f1 and f2:
...
.cfi_startproc
movl 8(%esp), %eax
ret
.cfi_endproc
...
This is because ix86_setup_incoming_varargs doesn't do anything for -m32:
...
static void
ix86_setup_incoming_varargs (cumulative_args_t cum_v, machine_mode mode,
tree type, int *, int no_rtl)
{
CUMULATIVE_ARGS *cum = get_cumulative_args (cum_v);
CUMULATIVE_ARGS next_cum;
tree fntype;
/* This argument doesn't appear to be used anymore. Which is good,
because the old code here didn't suppress rtl generation. */
gcc_assert (!no_rtl);
if (!TARGET_64BIT)
return;
...
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/66013] Missed optimization after inlining va_list parameter, -m32 case
2015-05-05 7:24 [Bug tree-optimization/66013] New: Missed optimization after inlining va_list parameter, -m32 case vries at gcc dot gnu.org
@ 2015-05-05 7:33 ` vries at gcc dot gnu.org
2015-05-05 7:34 ` vries at gcc dot gnu.org
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: vries at gcc dot gnu.org @ 2015-05-05 7:33 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66013
--- Comment #1 from vries at gcc dot gnu.org ---
Before pass_stdarg, we observe in f1 that va_start and va_arg use the same
argument:
...
# .MEM_2 = VDEF <.MEM_1(D)>
# USE = nonlocal escaped
# CLB = nonlocal escaped { D.1806 } (escaped)
__builtin_va_startD.1021 (&apD.1806, 0);
# .MEM_3 = VDEF <.MEM_2>
# USE = nonlocal null { D.1806 } (escaped)
# CLB = nonlocal null { D.1806 } (escaped)
res_4 = VA_ARG (&apD.1806, 0B);
...
Before pass_stdarg, we observe in f2 that va_start and va_arg do not use the
same argument:
...
# .MEM_2 = VDEF <.MEM_1(D)>
# USE = nonlocal escaped
# CLB = nonlocal escaped { D.1814 }
__builtin_va_startD.1021 (&apD.1814, 0);
# VUSE <.MEM_2>
# PT = nonlocal
ap.0_3 = apD.1814;
# .MEM_4 = VDEF <.MEM_2>
apD.1830 = ap.0_3;
# .MEM_8 = VDEF <.MEM_4>
# USE = nonlocal null { D.1830 } (escaped)
# CLB = nonlocal null { D.1830 } (escaped)
_7 = VA_ARG (&apD.1830, 0B);
...
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/66013] Missed optimization after inlining va_list parameter, -m32 case
2015-05-05 7:24 [Bug tree-optimization/66013] New: Missed optimization after inlining va_list parameter, -m32 case vries at gcc dot gnu.org
2015-05-05 7:33 ` [Bug tree-optimization/66013] " vries at gcc dot gnu.org
@ 2015-05-05 7:34 ` vries at gcc dot gnu.org
2015-05-05 7:41 ` vries at gcc dot gnu.org
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: vries at gcc dot gnu.org @ 2015-05-05 7:34 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66013
--- Comment #2 from vries at gcc dot gnu.org ---
And in the pass_stdarg dump, for f2 we see why the va_list escapes:
...
va_list escapes in # .MEM_4 = VDEF <.MEM_2>
apD.1830 = ap.0_3;
...
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/66013] Missed optimization after inlining va_list parameter, -m32 case
2015-05-05 7:24 [Bug tree-optimization/66013] New: Missed optimization after inlining va_list parameter, -m32 case vries at gcc dot gnu.org
2015-05-05 7:33 ` [Bug tree-optimization/66013] " vries at gcc dot gnu.org
2015-05-05 7:34 ` vries at gcc dot gnu.org
@ 2015-05-05 7:41 ` vries at gcc dot gnu.org
2015-05-07 22:17 ` vries at gcc dot gnu.org
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: vries at gcc dot gnu.org @ 2015-05-05 7:41 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66013
--- Comment #3 from vries at gcc dot gnu.org ---
Before postponing expansion of va_arg to pass_stdarg, we had at pass_stdarg:
...
f2: va_list escapes 0, needs to save 4 GPR units and all FPR units.
...
On one hand, the optimization in pass_stdarg has regressed. OTOH, that hasn't
brought a regression in code generation.
So I'm not sure if this should be marked as a '6 Regression', and/or tagged
with missing optimization.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/66013] Missed optimization after inlining va_list parameter, -m32 case
2015-05-05 7:24 [Bug tree-optimization/66013] New: Missed optimization after inlining va_list parameter, -m32 case vries at gcc dot gnu.org
` (2 preceding siblings ...)
2015-05-05 7:41 ` vries at gcc dot gnu.org
@ 2015-05-07 22:17 ` vries at gcc dot gnu.org
2015-05-08 15:37 ` vries at gcc dot gnu.org
2015-06-08 12:29 ` vries at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: vries at gcc dot gnu.org @ 2015-05-07 22:17 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66013
--- Comment #4 from vries at gcc dot gnu.org ---
Tentative patch:
...
diff --git a/gcc/tree-stdarg.c b/gcc/tree-stdarg.c
index efabda7..b334e79 100644
--- a/gcc/tree-stdarg.c
+++ b/gcc/tree-stdarg.c
@@ -62,6 +62,7 @@ along with GCC; see the file COPYING3. If not see
#include "tree-cfg.h"
#include "tree-pass.h"
#include "tree-stdarg.h"
+#include "tree-ssa.h"
/* A simple pass that attempts to optimize stdarg functions on architectures
that need to save register arguments to stack on entry to stdarg functions.
@@ -1111,6 +1112,7 @@ expand_ifn_va_arg_1 (function *fun)
free_dominance_info (CDI_DOMINATORS);
update_ssa (TODO_update_ssa);
+ execute_update_addresses_taken ();
}
/* Expand IFN_VA_ARGs in FUN, if necessary. */
...
We just update address_taken between ifn_va_arg expansion and the pass_stdarg
optimization.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/66013] Missed optimization after inlining va_list parameter, -m32 case
2015-05-05 7:24 [Bug tree-optimization/66013] New: Missed optimization after inlining va_list parameter, -m32 case vries at gcc dot gnu.org
` (3 preceding siblings ...)
2015-05-07 22:17 ` vries at gcc dot gnu.org
@ 2015-05-08 15:37 ` vries at gcc dot gnu.org
2015-06-08 12:29 ` vries at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: vries at gcc dot gnu.org @ 2015-05-08 15:37 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66013
vries at gcc dot gnu.org changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |patch
--- Comment #5 from vries at gcc dot gnu.org ---
https://gcc.gnu.org/ml/gcc-patches/2015-05/msg00685.html
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/66013] Missed optimization after inlining va_list parameter, -m32 case
2015-05-05 7:24 [Bug tree-optimization/66013] New: Missed optimization after inlining va_list parameter, -m32 case vries at gcc dot gnu.org
` (4 preceding siblings ...)
2015-05-08 15:37 ` vries at gcc dot gnu.org
@ 2015-06-08 12:29 ` vries at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: vries at gcc dot gnu.org @ 2015-06-08 12:29 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66013
vries at gcc dot gnu.org changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords|patch |
--- Comment #6 from vries at gcc dot gnu.org ---
Removing patch keyword. Discussed patch in
https://gcc.gnu.org/ml/gcc-patches/2015-05/msg00886.html .
^ permalink raw reply [flat|nested] 7+ messages in thread
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2015-05-05 7:24 [Bug tree-optimization/66013] New: Missed optimization after inlining va_list parameter, -m32 case vries at gcc dot gnu.org
2015-05-05 7:33 ` [Bug tree-optimization/66013] " vries at gcc dot gnu.org
2015-05-05 7:34 ` vries at gcc dot gnu.org
2015-05-05 7:41 ` vries at gcc dot gnu.org
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