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[RFC 3/3, debug] Add fdebug-nops and fkeep-vars-live to Og only


On Tue, Jul 24, 2018 at 01:30:30PM +0200, Tom de Vries wrote:
> On 07/16/2018 05:10 PM, Tom de Vries wrote:
> > On 07/16/2018 03:50 PM, Richard Biener wrote:
> >> On Mon, 16 Jul 2018, Tom de Vries wrote:
> >>> Any comments?
> >>
> >> Interesting idea.  I wonder if that should be generalized
> >> to other places
> > 
> > I kept the option name general, to allow for that.
> > 
> > And indeed, this is a point-fix patch. I've been playing around with a
> > more generic patch that adds nops such that each is_stmt .loc is
> > associated with a unique insn, but that was embedded in an
> > fkeep-vars-live branch, so this patch is minimally addressing the first
> > problem I managed to reproduce on trunk.
> > 
> >> and how we can avoid compare-debug failures
> >> (var-tracking usually doesn't change code-generation).
> >>
> > 
> 
> I'll post this patch series (the current state of my fkeep-vars-live
> branch) in reply to this email:
> 
>      1  [debug] Add fdebug-nops
>      2  [debug] Add fkeep-vars-live
>      3  [debug] Add fdebug-nops and fkeep-vars-live to Og only
> 
> Bootstrapped and reg-tested on x86_64. ChangeLog entries and function
> header comments missing.
> 
> Comments welcome.
> 

This switches on fdebug-nops and fkeep-vars-live by default for Og only, in
order to excercise the new switches in combination with the optimization
option they're intended to be used with.

Resulting fixes:
...
FAIL: gcc.dg/guality/pr54200.c  -Og -DPREVENT_OPTIMIZATION  line . z == 3
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+4 a[0] == 1
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+3 a[1] == 2
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+2 a[2] == 3
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+1 *p == 3
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line . *q == 2
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+4 a[0] == 1
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+3 a[1] == 2
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+2 a[2] == 13
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+1 *p == 13
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line . *q == 2
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+4 a[0] == 1
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+3 a[1] == 12
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+2 a[2] == 13
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+1 *p == 13
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line . *q == 12
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+3 a[1] == 5
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+2 a[2] == 6
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+1 *p == 6
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line . *q == 5
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+3 a[1] == 5
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+2 a[2] == 26
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+1 *p == 26
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line . *q == 5
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+7 a[1] == 25
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+6 a[2] == 26
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+5 *p == 26
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+4 p[-1] == 25
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line .+1 q[1] == 26
FAIL: gcc.dg/guality/pr54970.c  -Og -DPREVENT_OPTIMIZATION  line . *q == 25
...

The intended nature of Og is: offering a reasonable level of optimization
while maintaining fast compilation and a good debugging experience.
Todo: assess compile time and runtime cost of adding adding fdebug-nops and
fkeep-vars-live to Og, to see if nature of Og has been changed.

PR debug/78685

[debug] Add fdebug-nops and fkeep-vars-live to Og only

---
 gcc/common/common-target.h     | 1 +
 gcc/opts.c                     | 6 ++++++
 gcc/testsuite/gcc.dg/pr84614.c | 2 +-
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/gcc/common/common-target.h b/gcc/common/common-target.h
index 9b796c8f085..17e8950a027 100644
--- a/gcc/common/common-target.h
+++ b/gcc/common/common-target.h
@@ -34,6 +34,7 @@ enum opt_levels
   OPT_LEVELS_1_PLUS, /* -O1 and above, including -Os and -Og.  */
   OPT_LEVELS_1_PLUS_SPEED_ONLY, /* -O1 and above, but not -Os or -Og.  */
   OPT_LEVELS_1_PLUS_NOT_DEBUG, /* -O1 and above, but not -Og.  */
+  OPT_LEVELS_1_DEBUG, /* -Og.  */
   OPT_LEVELS_2_PLUS, /* -O2 and above, including -Os.  */
   OPT_LEVELS_2_PLUS_SPEED_ONLY, /* -O2 and above, but not -Os or -Og.  */
   OPT_LEVELS_3_PLUS, /* -O3 and above.  */
diff --git a/gcc/opts.c b/gcc/opts.c
index 17d91988ada..e8142eb6920 100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -370,6 +370,10 @@ maybe_default_option (struct gcc_options *opts,
       enabled = (level >= 1 && !debug);
       break;
 
+    case OPT_LEVELS_1_DEBUG:
+      enabled = (level == 1 && debug);
+      break;
+
     case OPT_LEVELS_2_PLUS:
       enabled = (level >= 2);
       break;
@@ -477,6 +481,8 @@ static const struct default_options default_options_table[] =
     { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fssa_phiopt, NULL, 1 },
     { OPT_LEVELS_1_PLUS, OPT_ftree_builtin_call_dce, NULL, 1 },
     { OPT_LEVELS_1_PLUS, OPT_fomit_frame_pointer, NULL, 1 },
+    { OPT_LEVELS_1_DEBUG, OPT_fdebug_nops, NULL, 1 },
+    { OPT_LEVELS_1_DEBUG, OPT_fkeep_vars_live, NULL, 1 },
 
     /* -O2 optimizations.  */
     { OPT_LEVELS_2_PLUS, OPT_finline_small_functions, NULL, 1 },
diff --git a/gcc/testsuite/gcc.dg/pr84614.c b/gcc/testsuite/gcc.dg/pr84614.c
index 98af26ba4e5..b7a5b9c1c84 100644
--- a/gcc/testsuite/gcc.dg/pr84614.c
+++ b/gcc/testsuite/gcc.dg/pr84614.c
@@ -1,6 +1,6 @@
 /* PR target/84614 */
 /* { dg-do run { target int128 } } */
-/* { dg-options "-Og -fno-split-wide-types -fno-tree-coalesce-vars -g --param=max-combine-insns=3 -fcompare-debug" } */
+/* { dg-options "-Og -fno-split-wide-types -fno-tree-coalesce-vars -g --param=max-combine-insns=3 -fcompare-debug -fno-debug-nops" } */
 
 unsigned __int128 a;
 


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