Re: [PATCH][RFC] Consolidate -O3 torture options

[Richard Biener <rguenther@suse.de>]

On Tue, 14 Jul 2015, Jeff Law wrote:

> On 07/14/2015 05:58 AM, Richard Biener wrote:
> > 
> > The following patch tries to consolidate the -O3 torture testing
> > options in the attempt to reduce testing time while not losing
> > coverage.
> > 
> > It drops testing of -funroll-all-loops (which nobody should use)
> > and retains only one non-default -O3 set of options - namely
> > -O3 plus those flags that would be enabled by -fprofile-use.
> > 
> > One should hope for ~20% less time in the C and dg tortures this way.
> > 
> > Didn't look into other tortures to apply the same yet (objc-torture?)
> > 
> > Currently testing on x86_64-unknown-linux-gnu.
> > 
> > For weird flag combinations we do have contributors that test
> > them and regularly report bugzillas.
> > 
> > Ok?
> > 
> > Comments?
> > 
> > Thanks,
> > Richard.
> > 
> > 2015-07-14  Richard Biener  <rguenther@suse.de>
> > 
> > 	* lib/c-torture.exp (C_TORTURE_OPTIONS): Remove
> > 	{ -O3 -fomit-frame-pointer },
> > 	{ -O3 -fomit-frame-pointer -funroll-loops } and
> > 	{ -O3 -fomit-frame-pointer -funroll-all-loops -finline-functions }
> > 	in favor of
> > 	{ -O3 -fomit-frame-pointer -funroll-loops -fpeel-loops -ftracer
> > 	  -finline-functions }
> > 	* lib/gcc-dg.exp (DG_TORTURE_OPTIONS): Likewise.
> I think this is OK -- I've occasionally wondered about the additional coverage
> we get vs the amount of time spent for the various options.
> 
> I can't recall specific cases where one of those 3 options would trigger a
> failure, but the two didn't. I'm sure it's happened, but it's just common
> enough to warrant the amount of time we spend testing it.
> 
> This patch has the additional benefit that I think we can eliminate scanning
> the source for loops and eliminating the -funroll[-all]-loops options.   Hmm,
> that code may have already been dead... Hmmm.

Testing reveals one fallout:

FAIL: gcc.c-torture/execute/builtins/snprintf-chk.c execution,  -O3 
-fomit-frame
-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions 
FAIL: gcc.c-torture/execute/builtins/vsnprintf-chk.c execution,  -O3 
-fomit-fram
e-pointer -funroll-loops -fpeel-loops -ftracer -finline-functions 

this is because -ftracer manages to thread things in a way that we
optimize away a _chk variant at compile-time and hit

  if (chk_calls != 5)
    abort ();

with chk_calls == 4.  I'm going to install the following alongside
(we've had similar issues with -ftree-loop-distribute-patterns enabled
by -O3).

Richard.

Index: gcc/testsuite/gcc.c-torture/execute/builtins/builtins.exp
===================================================================
--- gcc/testsuite/gcc.c-torture/execute/builtins/builtins.exp   (revision 
225768)
+++ gcc/testsuite/gcc.c-torture/execute/builtins/builtins.exp   (working 
copy)
@@ -37,7 +37,7 @@ load_lib c-torture.exp
 torture-init
 set-torture-options $C_TORTURE_OPTIONS {{}} $LTO_TORTURE_OPTIONS
 
-set additional_flags "-fno-tree-loop-distribute-patterns"
+set additional_flags "-fno-tree-loop-distribute-patterns -fno-tracer"
 if [istarget "powerpc-*-darwin*"] {
    lappend additional_flags "-Wl,-multiply_defined,suppress"
 }