[Bug target/41156] New: [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[Bug target/41156] New: [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[hjl dot tools at gmail dot com]

+++ This bug was initially created as a clone of Bug #32893 +++

Gcc 4.4/4.5 can align stack properly. But it needs to assume 4 byte
incoming stack alignment instead of 16byte.


-- 
           Summary: [4.4/4.5 Regression] zlib segfault in inflate_table()
                    compiled w/ -O -msse2 ftree-vectorize
           Product: gcc
           Version: 4.4.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hjl dot tools at gmail dot com
 GCC build triplet: i686-linux-gnu
  GCC host triplet: i686-linux-gnu
GCC target triplet: i686-linux-gnu
 BugsThisDependsOn: 32893,40838


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #1 from mahatma at eu dot by  2009-08-25 10:20 -------
Fix: I got bug with -msse only, not -msse2.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[jsm28 at gcc dot gnu dot org]

-- 

jsm28 at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.4.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[jakub at gcc dot gnu dot org]

------- Comment #2 from jakub at gcc dot gnu dot org  2009-08-31 08:10 -------
Why is this considered a regression?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[hjl dot tools at gmail dot com]

------- Comment #3 from hjl dot tools at gmail dot com  2009-08-31 13:51 -------
(In reply to comment #2)
> Why is this considered a regression?
> 

It is a regression for PR 32893, which was fixed by disabling
vectorizer on local variables requiring > 4byte alignment since
we couldn't realign the stack at the time to support 4byte
incoming stack. With automatic stack alignment, this restricting
was removed. But since we assume incoming stack is 16byte, we
don't realign the stack. When incoming stack is 4 byte aligned,
we get segfault.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mmitchel at gcc dot gnu dot org]

------- Comment #4 from mmitchel at gcc dot gnu dot org  2009-08-31 21:47 -------
HJ, this doesn't make sense.  

Either we can assume 16-byte stack alignment, or we can't.  Which is it?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[hjl dot tools at gmail dot com]

------- Comment #5 from hjl dot tools at gmail dot com  2009-08-31 22:25 -------
(In reply to comment #4)
> HJ, this doesn't make sense.  
> 
> Either we can assume 16-byte stack alignment, or we can't.  Which is it?
> 

On ia32, except for MacOS, we don't enforce 16-byte stack alignment.
We get 4-byte incoming stack alignment via object files:

1. Compiled with older gcc.
2. Compiled with gcc 3.x and earlier 4.x using -Os.
3. Compiled with gcc using -mpreferred-stack-boundary=2
4. From assembly code with 4 byte stack alignment.
5. Compiled with other compilers, which generate 4 byte stack
alignment.

It usually won't cause segfault until vectorizer is enabled.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[jakub at gcc dot gnu dot org]

------- Comment #6 from jakub at gcc dot gnu dot org  2009-09-01 09:28 -------
IMHO either standard options compiled code shouldn't be called from
-mpreferred-stack-boundary=2 code, or it needs to be compiled with
-mincoming-stack-boundary=2.  But it should be user's responsibility.  Ensuring
by default outgoing calls are 16 byte aligned, but not assuming it is just a
very stupid thing to do and unnecessarily penalizes normal users.  It is
certainly not true that most code is compiled with
-mpreferred-stack-boundary=2, only kernel and a handful of packages is by
default, and kernel has its own ABI (and doesn't use FPU nor SSE*).


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[hjl dot tools at gmail dot com]

------- Comment #7 from hjl dot tools at gmail dot com  2009-09-01 13:20 -------
Realign the incoming stack for vectorizer has very limited impact
on performance. Here are the differences of -m32 -O3 -msse2
-mfpmath=sse -ffast-math -funroll-loops before and after my patch:

400.perlbench                    -0.384615%
401.bzip2                        0%
403.gcc                          -0.362319%
429.mcf                          -0.813008%
445.gobmk                        0.921659%
456.hmmer                        0.549451%
458.sjeng                        -0.438596%
462.libquantum                   0%
464.h264ref                      0%
471.omnetpp                      -0.478469%
473.astar                        -0.645161%
483.xalancbmk                    -0.727273%
SPECint(R)_base2006              -0.411523%
410.bwaves                       -0.406504%
416.gamess                       0%
433.milc                         -1.36986%
434.zeusmp                       -0.44843%
435.gromacs                      0%
436.cactusADM                    0%
437.leslie3d                     -0.888889%
444.namd                         1.20482%
447.dealII                       -0.350877%
450.soplex                       -0.31746%
453.povray                       0.458716%
454.calculix                     0%
459.GemsFDTD                     0%
465.tonto                        0%
470.lbm                          0%
481.wrf                          0.480769%
482.sphinx3                      0.940439%
SPECfp(R)_base2006               0%

It won't change generated code if vectorizer isn't
enabled. Its benifits outweigh its drawbacks.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #8 from mahatma at eu dot by  2009-09-08 12:08 -------
I don't trying to rebuild all with 4-byte incoming stack alignment while, but
think to unify this step with full ABI change. For me it may solve migration to
-mregparm=3 ("ix86_regparm = REGPARM_MAX;" for x86_32) and others in
crosscompile way (for example, to "i686-eabi-linux-gnu" target). For people it
may solve "ABI standard" orthodox problem too.

Most undiscovered place FOR ME (while I busy in other place): adding support to
"eabi*" (1+*) keyword, eabi/eabi1 may be REGPARM_MAX + 4-byte incoming stack
alignment (or even more safe solution) + any others safe (if exists) changes.
eabi2 - hardcoded -msseregparm (I unsure in softfloat/no-sse compatibility,
then there are must be optional), etc.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #9 from mahatma at eu dot by  2009-09-19 16:12 -------
Created an attachment (id=18608)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18608&action=view)
sse & 32bit -> -mstackrealign (example only!)

Previous my ideas too heavy. :)
IMHO native solution for this problem is "-mstackrealign". It solving problems
with known to me packages (including zlib). I trying to make
STACK_REALIGN_DEFAULT related from TARGET_SSE && !TARGET_64BIT (see patch). But
got "internal compiler error" on gcc self-compiling with "-march=pentium4".
Without sse (=without -mstackrealign) self-compiling works.

Why -mstackrealign may be bad and why gcc dont' self-compiling so?

Error:
===
/var/tmp/portage/sys-devel/gcc-4.4.1/work/build/./gcc/xgcc
-B/var/tmp/portage/sys-devel/gcc-4.4.1/work/build/./gcc/
-B/usr/i686-pc-linux-gnu/bin/ -B/usr/i686-pc-linux-gnu/lib/ -isystem
/usr/i686-pc-linux-gnu/include -isystem /usr/i686-pc-linux-gnu/sys-include -g
-mtune=pentium4 -march=pentium4 -pipe -w -O2 -O2  -g -mtune=pentium4
-march=pentium4 -pipe -w -O2 -DIN_GCC   -W -Wall -Wwrite-strings
-Wstrict-prototypes -Wmissing-prototypes -Wcast-qual -Wold-style-definition 
-isystem ./include  -fPIC -g -DHAVE_GTHR_DEFAULT -DIN_LIBGCC2
-D__GCC_FLOAT_NOT_NEEDED   -I. -I. -I../.././gcc
-I/var/tmp/portage/sys-devel/gcc-4.4.1/work/gcc-4.4.1/libgcc
-I/var/tmp/portage/sys-devel/gcc-4.4.1/work/gcc-4.4.1/libgcc/.
-I/var/tmp/portage/sys-devel/gcc-4.4.1/work/gcc-4.4.1/libgcc/../gcc
-I/var/tmp/portage/sys-devel/gcc-4.4.1/work/gcc-4.4.1/libgcc/../include
-I/var/tmp/portage/sys-devel/gcc-4.4.1/work/gcc-4.4.1/libgcc/config/libbid
-DENABLE_DECIMAL_BID_FORMAT -DHAVE_CC_TLS -DUSE_TLS -o unwind-c.o -MT
unwind-c.o -MD -MP -MF unwind-c.dep -fexceptions -c
/var/tmp/portage/sys-devel/gcc-4.4.1/work/gcc-4.4.1/libgcc/../gcc/unwind-c.c
-fvisibility=hidden -DHIDE_EXPORTS
In file included from
/var/tmp/portage/sys-devel/gcc-4.4.1/work/gcc-4.4.1/libgcc/../gcc/unwind-dw2.c:1555:
/var/tmp/portage/sys-devel/gcc-4.4.1/work/gcc-4.4.1/libgcc/../gcc/unwind.inc:
In function '_Unwind_ForcedUnwind':
/var/tmp/portage/sys-devel/gcc-4.4.1/work/gcc-4.4.1/libgcc/../gcc/unwind.inc:212:
internal compiler error: in ix86_expand_epilogue, at config/i386/i386.c:8570
===


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[hjl dot tools at gmail dot com]

------- Comment #10 from hjl dot tools at gmail dot com  2009-09-19 21:42 -------
(In reply to comment #9)
> Created an attachment (id=18608)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18608&action=view) [edit]
> sse & 32bit -> -mstackrealign (example only!)
> 
> Previous my ideas too heavy. :)
> IMHO native solution for this problem is "-mstackrealign". It solving problems
> with known to me packages (including zlib). I trying to make
> STACK_REALIGN_DEFAULT related from TARGET_SSE && !TARGET_64BIT (see patch). But
> got "internal compiler error" on gcc self-compiling with "-march=pentium4".
> Without sse (=without -mstackrealign) self-compiling works.
> 
> Why -mstackrealign may be bad and why gcc dont' self-compiling so?
> 

Stack alignment in unwind library is unsupported.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #11 from mahatma at eu dot by  2009-09-25 11:03 -------
Created an attachment (id=18650)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18650&action=view)
sse & 32bit -> -mstackrealign (example 2)

Second attempt (while against 4.4.1, sorry). Working with any -march.

For gcc libc -mstackrealign disabled. Tell me:

1) how to isolate cflags for unwind-dw2.c or unwind library or stage1 (exclude
preset STAGE1_LIBCFLAGS, etc before make)?

2) are misaligning may be happened in internal libs and when? (to "-mno-sse" or
question 1)

3) are 3DNOW! must be realigned too? and what other sse-independent
sets/targets must be realigned?


-- 

mahatma at eu dot by changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #18608|0                           |1
        is obsolete|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #12 from mahatma at eu dot by  2009-10-09 14:07 -------
I found new AMD CPUs not required to stack aligning for SSE. IMHO there are
"misalignsse" cpu feature, found near SSE4a (fixme). Then, requirement for
stack realigning may be checked from "misalignsse" (precise) or "sse4a"
(simple).

I don't want (while) to exeperiments with make scripts for isolating
"-mno-stackrealign" CFLAGS for unwinding library and only suggest two variants
of common solution:
1) Checking "misalignsse" for -march=native, -mno-stackrealign (if given) may
produce broken code with SSE, gcc libs not verifyed against it.
2) Use TARGET_SSE4A as "cname" to misalignsse to detect realigning requirement.
Also trying to disable SSE if realigning forced to disable (-mno-stackrealign
given). SSE for gcc libs will be disabled.

This solutions may be mixed, but I see no sense. Or SSE4A is used or no. If no
- I not found way to move "misalignsse" flag to configuration section. Just may
be sense to remove SSE disabling in (2) - just remove i386.c changes.

IMHO last todo in this case: unwinding library (CFLAGS or -mstackrealign
support).

PS Both are untested. But sse-stackrealign-1.patch have not problems for me.

Both are


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #14 from mahatma at eu dot by  2009-10-09 14:09 -------
Created an attachment (id=18762)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18762&action=view)
2) sse-stackrealign-sse4a-4.4.patch


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #13 from mahatma at eu dot by  2009-10-09 14:08 -------
Created an attachment (id=18761)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18761&action=view)
1) sse-stackrealign-misalignsse-4.4.patch


-- 

mahatma at eu dot by changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #18650|0                           |1
        is obsolete|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #15 from mahatma at eu dot by  2009-10-09 14:10 -------
Created an attachment (id=18763)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18763&action=view)
1) sse-stackrealign-misalignsse-4.5.patch


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #16 from mahatma at eu dot by  2009-10-09 14:10 -------
Created an attachment (id=18764)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18764&action=view)
2) sse-stackrealign-sse4a-4.5.patch


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #17 from mahatma at eu dot by  2009-10-09 14:39 -------
Created an attachment (id=18765)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18765&action=view)
(2) for 4.4, fixed


-- 

mahatma at eu dot by changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #18762|0                           |1
        is obsolete|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #18 from mahatma at eu dot by  2009-10-09 14:41 -------
Created an attachment (id=18766)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18766&action=view)
(2) for 4.5, fixed

Originals may produce illegal warnings without SSE.


-- 

mahatma at eu dot by changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #18764|0                           |1
        is obsolete|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[hjl dot tools at gmail dot com]

------- Comment #19 from hjl dot tools at gmail dot com  2009-10-09 14:43 -------
Without a testcase, people may not review the patch.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #20 from mahatma at eu dot by  2009-10-10 13:48 -------
(In reply to comment #19)
> Without a testcase, people may not review the patch.
> 

May be just include your tests from Bug 40838? (even without testing)
>From http://gcc.gnu.org/bugzilla/attachment.cgi?id=18656
Your suggestions?

I understand so there are same results with your gcc-4.4-pr40838-*.patch, but
realigning whole code and exclude "misaligned" AMD CPUs. And warrantied to
realign in any place.

Your gcc-4.4-pr40838-3.patch lost realigning in unknown place - runtime
segfaults in Seamonkey. *-4.patch I don't test becouse alredy use simple
"-mstackrealign" solution - first there are dummy testing - surfing with
Seamonkey until sometimes segfault, second - I got new desktop with Athlon (but
was alredy satisfyed by "-mstackrealign" on old Celeron). Now I prefer to use
safe "-mstackrealign" solution for Intel CPUs on 32bit servers and to be sure
in safe SSE code. And see no visual defferences in perfomance whith global
"-mstackrealign".


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #21 from mahatma at eu dot by  2009-10-10 13:51 -------
Created an attachment (id=18773)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18773&action=view)
tests proposal from PR 40838 (from H.J. Lu)

Are there are good?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[hjl dot tools at gmail dot com]

------- Comment #22 from hjl dot tools at gmail dot com  2009-10-10 14:46 -------
(In reply to comment #20)
> (In reply to comment #19)
> > Without a testcase, people may not review the patch.
> > 
> 
> May be just include your tests from Bug 40838? (even without testing)
> From http://gcc.gnu.org/bugzilla/attachment.cgi?id=18656
> Your suggestions?
> 
> I understand so there are same results with your gcc-4.4-pr40838-*.patch, but
> realigning whole code and exclude "misaligned" AMD CPUs. And warrantied to
> realign in any place.
> 
> Your gcc-4.4-pr40838-3.patch lost realigning in unknown place - runtime
> segfaults in Seamonkey. *-4.patch I don't test becouse alredy use simple

We can't check Seamonkey into gcc/testsuite. We need something
much smaller. 

> "-mstackrealign" solution - first there are dummy testing - surfing with
> Seamonkey until sometimes segfault, second - I got new desktop with Athlon (but
> was alredy satisfyed by "-mstackrealign" on old Celeron). Now I prefer to use
> safe "-mstackrealign" solution for Intel CPUs on 32bit servers and to be sure
> in safe SSE code. And see no visual defferences in perfomance whith global
> "-mstackrealign".
> 

If you think adding -mstackrealign to your build is an acceptable solution,
we can close this bug. Otherwise, please test my latest gcc 4.4 patch for
PR 40838.  Thanks.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #23 from mahatma at eu dot by  2009-10-12 11:40 -------
(In reply to comment #22)

> We can't check Seamonkey into gcc/testsuite. We need something
> much smaller. 

I understand this. But even if I will use your testsuite addons (I unsure in
it, Gentoo "USE=test emerge sys-deve/gcc" on unpatched gcc & Celeron don't
breaks), unknown bug from at least old *-3.patch will be present. This is like
communicative problem, but problem...

> If you think adding -mstackrealign to your build is an acceptable solution,
> we can close this bug. Otherwise, please test my latest gcc 4.4 patch for
> PR 40838.  Thanks.

Your patch, by idea, more accurate - if now realign stack in ALL requred
places. But also it unmotivated realign with AMDs too. I alredy ask: "Why
-mstackrealign may be bad?". This is dark place. In manpage "-mstackrealign"
described against SSE aligning problem. This is like wellknown solution, but
unused wide. Why? What side-effects of "-mstackrealign"? Perfomance?
Compatibility? Just ABI standard? Related from this "-mstackrealign" may be
hardcoded for SSE in simple way - just "SSE -> -mstackrealign" or overcoded
patch to disable -mstackrealign for AMDs. Or unuse whole. I will not fast
testing your patch on old Celeron (after few days) to close this theme too, but
for final solution IMHO information about -mstackrealign [history] required.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[hjl dot tools at gmail dot com]

------- Comment #24 from hjl dot tools at gmail dot com  2009-10-12 13:59 -------
(In reply to comment #23)
> > If you think adding -mstackrealign to your build is an acceptable solution,
> > we can close this bug. Otherwise, please test my latest gcc 4.4 patch for
> > PR 40838.  Thanks.
> 
> Your patch, by idea, more accurate - if now realign stack in ALL requred
> places. But also it unmotivated realign with AMDs too. I alredy ask: "Why
> -mstackrealign may be bad?". This is dark place. In manpage "-mstackrealign"
> described against SSE aligning problem. This is like wellknown solution, but
> unused wide. Why? What side-effects of "-mstackrealign"? Perfomance?

Please see PR 40838.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[dirtyepic at gentoo dot org]

------- Comment #25 from dirtyepic at gentoo dot org  2009-10-12 22:48 -------
would you please just test the patch on PR 40838 and tell HJ if it works or
not?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #26 from mahatma at eu dot by  2009-10-13 12:16 -------
(In reply to comment #25)
> would you please just test the patch on PR 40838 and tell HJ if it works or
> not?
> 

In progress. There are only one Celeron PC leased without distcc to build and
runtime test big packages.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #27 from mahatma at eu dot by  2009-10-13 13:26 -------
(In reply to comment #24)

> > unused wide. Why? What side-effects of "-mstackrealign"? Perfomance?
> 
> Please see PR 40838.

As seen on... a...
I found only ABI standard reasons. FIXME!
But SSE usage still optional like -mstackrealign option. I see no political
differences: "-msse" or "-march=pentium4" or "-mstackrealign". Default "i686"
builds will be same unaligned.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[jakub at gcc dot gnu dot org]

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jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.4.2                       |4.4.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #28 from mahatma at eu dot by  2009-11-27 12:45 -------
Yes, I read PR 40838. But last (IMHO) in this thread:

Disabling SSE in whole GCC libs may cause various build problems in SSE-related
-march (mostly with -ffast-math, but IMHO more). So, to use this simple
solution, SSE disabling code better to remove. If still paranoid about GCC libs
SSE compatibility - better to build GCC with "-march=i686". Next stripped
patches:


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #29 from mahatma at eu dot by  2009-11-27 12:49 -------
Created an attachment (id=19162)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=19162&action=view)
(2) for 4.4


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mahatma at eu dot by]

------- Comment #30 from mahatma at eu dot by  2009-11-27 12:51 -------
Created an attachment (id=19163)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=19163&action=view)
(2) for 4.5


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[jakub at gcc dot gnu dot org]

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jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.4.3                       |4.4.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[mmitchel at gcc dot gnu dot org]

------- Comment #31 from mmitchel at gcc dot gnu dot org  2010-02-17 16:49 -------
I still have no idea what this PR is about.  Someone needs to make a clear
statement of what they believe the ABI to be.  There are some simple questions:

* Can we expect that the stack is 16-byte aligned, or not?

* If we cannot (because of legacy requirements), then is there any reason to
try to align the stack automatically at entry to every function, or at every
call site?  I can see that this might be useful as an option, but it does not
seem like a sensible default to me.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[hjl dot tools at gmail dot com]

------- Comment #32 from hjl dot tools at gmail dot com  2010-02-17 17:09 -------
(In reply to comment #31)
> I still have no idea what this PR is about.  Someone needs to make a clear
> statement of what they believe the ABI to be.  There are some simple questions:
> 
> * Can we expect that the stack is 16-byte aligned, or not?

Not if we want to be binary compatible with object files compiled by
compilers, including gcc 1.x/2.x/3.x, which generate 4byte stack alignment.

> 
> * If we cannot (because of legacy requirements), then is there any reason to
> try to align the stack automatically at entry to every function, or at every
> call site?  I can see that this might be useful as an option, but it does not
> seem like a sensible default to me.
> 

See PR 40838.  "-mstackrealign" now aligns the stack only if SSE vector
instructions are used in the function. The performance impact of
"-mstackrealign" is minimum:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40838#c65


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[joseph at codesourcery dot com]

------- Comment #33 from joseph at codesourcery dot com  2010-02-17 17:24 -------
Subject: Re:  [4.4/4.5 Regression] zlib segfault in
 inflate_table() compiled w/ -O -msse2 ftree-vectorize

I believe the ABI *is* that the stack must be 16-byte aligned at function 
boundaries, although this is not documented other than as a statement of 
what GCC does 
<http://groups.google.com/group/ia32-abi/browse_thread/thread/4f9b3e5069943bf1>. 
This does not of course stop smaller alignment being used for particular 
code by private arrangement as long as 16-byte alignment is used when 
calling back into user code (for example, it's fine for glibc to build 
code not using callbacks with smaller alignment, or for the Linux kernel 
to use smaller alignment internally as long as it ensures the full 
alignment for signal frames in userspace processes).


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[jakub at gcc dot gnu dot org]

------- Comment #34 from jakub at gcc dot gnu dot org  2010-02-17 19:31 -------
Yeah, I completely agree with that.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5/4.6 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[jakub at gcc dot gnu dot org]

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jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.4.4                       |4.4.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5/4.6 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[phmagic at mail dot ru]

------- Comment #35 from phmagic at mail dot ru  2010-06-10 19:08 -------
Hello,

I just upgraded to gcc-4.4.3 (from Gentoo distribution) and recompiled the
whole system (on x86). Then I had to discover the (as it turned to be,
infamous) mozilla-firefox + zlib bug. I reported it to the distribution here:
http://bugs.gentoo.org/show_bug.cgi?id=323431

As I learned later, everybody accounts for incoming misaligned stack to be the
cause of the crashes. But what I see:

inflate_table:
.LFB45:
        .file 1 "inftrees.c"
        .loc 1 39 0
.LVL0:
        pushl   %ebp     ; stack misaligned to -4
.LCFI0:
        .loc 1 108 0
        pxor    %xmm0, %xmm0
        .loc 1 39 0
        movl    %esp, %ebp ; $ebp % 16 = 4
.LCFI1:
        pushl   %edi
.LCFI2:
        pushl   %esi
.LCFI3:
        pushl   %ebx
.LCFI4:
        call    .L101
.L101:
        popl    %ebx
        addl    $_GLOBAL_OFFSET_TABLE_+[.-.L101], %ebx
        subl    $188, %esp
.LCFI5:
        .loc 1 108 0
        movdqa  %xmm0, -56(%ebp) ; -56-4=60, 60%16=4
; <snip>

Even if the stack were 16 bytes aligned on the entry, the instruction in the
last line would attempt an unaligned access and thus would fault. Please
correct me, if I miscounted.

My concern is: even with ABI which guarantees 16-byte aligned incoming stacks,
gcc generates code which would segfault.


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phmagic at mail dot ru changed:

           What    |Removed                     |Added
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                 CC|                            |phmagic at mail dot ru


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5/4.6 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[ed at catmur dot co dot uk]

------- Comment #36 from ed at catmur dot co dot uk  2010-06-10 21:28 -------
Alexander, you're omitting to consider that call pushes EIP + 4 onto the stack.
 Thus on entry the stack is already misaligned by -4, so gcc is correct.


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ed at catmur dot co dot uk changed:

           What    |Removed                     |Added
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                 CC|                            |ed at catmur dot co dot uk


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156

[Bug target/41156] [4.4/4.5/4.6 Regression] zlib segfault in inflate_table() compiled w/ -O -msse2 ftree-vectorize

[phmagic at mail dot ru]

------- Comment #37 from phmagic at mail dot ru  2010-06-11 01:43 -------
Thank you, Ed. I missed that. I wrongly (obviously wrongly, because this would
negatively affect performance) thought that ABI is such that stack is aligned
after the call, not before.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41156