From: Jeff Law <law@redhat.com>
To: Jakub Jelinek <jakub@redhat.com>, Alexandre Oliva <aoliva@redhat.com>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] Var-tracking initialization fix (PR debug/63623)
Date: Thu, 23 Oct 2014 22:40:00 -0000 [thread overview]
Message-ID: <54497494.6070404@redhat.com> (raw)
In-Reply-To: <20141023073015.GZ10376@tucnak.redhat.com>
On 10/23/14 01:30, Jakub Jelinek wrote:
> Hi!
>
> As I wrote in the PR, vt_stack_adjustments can often compute wrong offsets,
> because it never considers pops with autoinc addressing, which can lead
> either to wrong debug info, or turning off -fvar-tracking altogether for
> a function on which that issue resulted in stack depth inconsistencies on
> the edges.
>
> Here are some stats from --enable-checking=yes,rtl cc1plus bootstrapped
> with/without the patch (without the patch got then rebuilt stage3 with the
> patch, i.e. just var-tracking.o and cc1plus-checksum.o got recompiled, so
> I'm comparing identical code, different debug info):
>
> x86_64-linux cc1plus built without the patch:
> cov% samples cumul
> 0.0 506230/38% 506230/38%
> 0..10 10327/0% 516557/39%
> 11..20 12390/0% 528947/39%
> 21..30 31265/2% 560212/42%
> 31..40 18775/1% 578987/43%
> 41..50 20631/1% 599618/45%
> 51..60 24921/1% 624539/47%
> 61..70 40959/3% 665498/50%
> 71..80 23771/1% 689269/52%
> 81..90 41771/3% 731040/55%
> 91..99 81667/6% 812707/61%
> 100 510564/38% 1323271/100%
>
> x86_64-linux cc1plus built with the patch:
> cov% samples cumul
> 0.0 382214/28% 382214/28%
> 0..10 13100/0% 395314/29%
> 11..20 14568/1% 409882/30%
> 21..30 33708/2% 443590/33%
> 31..40 21927/1% 465517/35%
> 41..50 23924/1% 489441/36%
> 51..60 28736/2% 518177/39%
> 61..70 45847/3% 564024/42%
> 71..80 29284/2% 593308/44%
> 81..90 52085/3% 645393/48%
> 91..99 99971/7% 745364/56%
> 100 577907/43% 1323271/100%
>
> i686-linux cc1plus built without the patch:
> cov% samples cumul
> 0.0 631348/48% 631348/48%
> 0..10 7764/0% 639112/48%
> 11..20 9690/0% 648802/49%
> 21..30 25036/1% 673838/51%
> 31..40 16113/1% 689951/52%
> 41..50 19753/1% 709704/54%
> 51..60 14563/1% 724267/55%
> 61..70 34093/2% 758360/58%
> 71..80 17450/1% 775810/59%
> 81..90 31339/2% 807149/61%
> 91..99 60368/4% 867517/66%
> 100 437548/33% 1305065/100%
>
> i686-linux cc1plus built with the patch:
> cov% samples cumul
> 0.0 377352/28% 377352/28%
> 0..10 16077/1% 393429/30%
> 11..20 15390/1% 408819/31%
> 21..30 31790/2% 440609/33%
> 31..40 23889/1% 464498/35%
> 41..50 29267/2% 493765/37%
> 51..60 22902/1% 516667/39%
> 61..70 45629/3% 562296/43%
> 71..80 29511/2% 591807/45%
> 81..90 50536/3% 642343/49%
> 91..99 93584/7% 735927/56%
> 100 569138/43% 1305065/100%
>
> .debug_info/.debug_loc sizes in bytes:
> x86_64-linux cc1plus without patch .debug_info 75411710, .debug_loc 75421077
> x86_64-linux cc1plus with patch .debug_info 78498790, .debug_loc 90530117
> i686-linux cc1plus without patch .debug_info 59921183, .debug_loc 37823166
> i686-linux cc1plus with patch .debug_info 63009554, .debug_loc 59535100
>
> I've also performed instrumented bootstraps/regtests (x86_64-linux and
> i686-linux), where I've logged in how many functions the result of
> vt_stack_adjustments differed between the bad old way and new way.
> In both the bootstraps/regtests, it affected 16892 32-bit and 6646 64-bit
> functions, in all cases it was old way giving up and new way succeeding.
>
> Not adding a testcase, as the one in the PR failed to produce proper debug
> info only in 4.8 (then got latent), there already are some guality improvements with the
> patch:
> -FAIL: gcc.dg/guality/pr54693-2.c -O3 -fomit-frame-pointer -funroll-all-loops -finline-functions line 21 i == v + 1
> -FAIL: gcc.dg/guality/pr54693-2.c -O3 -fomit-frame-pointer -funroll-loops line 21 i == v + 1
> on x86_64 and:
> -FAIL: gcc.dg/guality/pr54519-1.c -O2 line 20 y == 25
> -FAIL: gcc.dg/guality/pr54519-1.c -O2 line 20 z == 6
> -FAIL: gcc.dg/guality/pr54519-1.c -O2 line 23 y == 117
> -FAIL: gcc.dg/guality/pr54519-1.c -O2 line 23 z == 8
> -FAIL: gcc.dg/guality/pr54519-1.c -O3 -fomit-frame-pointer line 20 x == 36
> -FAIL: gcc.dg/guality/pr54519-1.c -O3 -fomit-frame-pointer line 20 y == 25
> -FAIL: gcc.dg/guality/pr54519-1.c -O3 -fomit-frame-pointer line 20 z == 6
> -FAIL: gcc.dg/guality/pr54519-1.c -O3 -g line 20 x == 36
> -FAIL: gcc.dg/guality/pr54519-1.c -O3 -g line 20 y == 25
> -FAIL: gcc.dg/guality/pr54519-1.c -O3 -g line 20 z == 6
> -FAIL: gcc.dg/guality/pr54519-3.c -O2 line 20 x == 36
> -FAIL: gcc.dg/guality/pr54519-3.c -O2 line 20 y == 25
> -FAIL: gcc.dg/guality/pr54519-3.c -O2 line 20 z == 6
> -FAIL: gcc.dg/guality/pr54519-3.c -O2 line 23 x == 98
> -FAIL: gcc.dg/guality/pr54519-3.c -O2 line 23 y == 117
> -FAIL: gcc.dg/guality/pr54519-3.c -O2 line 23 z == 8
> -FAIL: gcc.dg/guality/pr54519-3.c -O2 -flto line 20 x == 36
> -FAIL: gcc.dg/guality/pr54519-3.c -O2 -flto line 23 x == 98
> -FAIL: gcc.dg/guality/pr54519-3.c -O2 -flto -flto-partition=none line 20 x == 36
> -FAIL: gcc.dg/guality/pr54519-3.c -O2 -flto -flto-partition=none line 23 x == 98
> -FAIL: gcc.dg/guality/pr54519-3.c -O3 -fomit-frame-pointer line 20 x == 36
> -FAIL: gcc.dg/guality/pr54519-3.c -O3 -fomit-frame-pointer line 20 y == 25
> -FAIL: gcc.dg/guality/pr54519-3.c -O3 -fomit-frame-pointer line 20 z == 6
> -FAIL: gcc.dg/guality/pr54519-3.c -O3 -fomit-frame-pointer line 23 x == 98
> -FAIL: gcc.dg/guality/pr54519-3.c -O3 -fomit-frame-pointer line 23 y == 117
> -FAIL: gcc.dg/guality/pr54519-3.c -O3 -fomit-frame-pointer line 23 z == 8
> -FAIL: gcc.dg/guality/pr54519-3.c -O3 -g line 20 x == 36
> -FAIL: gcc.dg/guality/pr54519-3.c -O3 -g line 20 y == 25
> -FAIL: gcc.dg/guality/pr54519-3.c -O3 -g line 20 z == 6
> -FAIL: gcc.dg/guality/pr54519-3.c -O3 -g line 23 x == 98
> -FAIL: gcc.dg/guality/pr54519-3.c -O3 -g line 23 y == 117
> -FAIL: gcc.dg/guality/pr54519-3.c -O3 -g line 23 z == 8
> -FAIL: gcc.dg/guality/pr54693-2.c -O3 -fomit-frame-pointer -funroll-all-loops -finline-functions line 21 i == v + 1
> -FAIL: gcc.dg/guality/pr54693-2.c -O3 -fomit-frame-pointer -funroll-loops line 21 i == v + 1
> on i686.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> Not sure about branches, to some extent this must be a serious debug info
> quality regression, since the problem got significantly worse with omitting
> frame pointer by default on i686, and/or shrink wrapping and simple_return
> changes where there are more pops in the middle of functions. So with a short
> patch we could significantly improve debug info. The risk is compile time
> regressions, if we gave up on var-tracking, we threw away all the hard tracked
> debug stmts/debug insns, but don't need to costly propagate the values through
> the dataflow.
>
> 2014-10-23 Jakub Jelinek <jakub@redhat.com>
>
> PR debug/63623
> * var-tracking.c (stack_adjust_offset_pre_post_cb): New function.
> (stack_adjust_offset_pre_post): Use it through for_each_inc_dec,
> instead of only handling autoinc in dest if it is a MEM.
> (vt_stack_adjustments): Fix up formatting.
OK.
Jeff
prev parent reply other threads:[~2014-10-23 21:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-23 7:42 Jakub Jelinek
2014-10-23 11:28 ` Richard Biener
2014-10-23 22:40 ` Jeff Law [this message]
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