[Bug target/66703] New: [4.9] gcc.target/i386/readeflags-1.c aborts on -march=i586

[Bug target/66703] New: [4.9] gcc.target/i386/readeflags-1.c aborts on -march=i586

[julia.koval at intel dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66703

            Bug ID: 66703
           Summary: [4.9] gcc.target/i386/readeflags-1.c aborts on
                    -march=i586
           Product: gcc
           Version: 4.9.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: julia.koval at intel dot com
  Target Milestone: ---

Reproduce:
$ gcc ../../gcc/testsuite/gcc.target/i386/readeflags-1.c -O0 -m32 -march=i586
-lm
$ ./a.out
Aborted (core dumped)

Carry flag is reset in andl instruction in readeflags_test function.

[Bug target/66703] [4.9/5/6] gcc.target/i386/readeflags-1.c aborts on -march=i586 or on -miamcu

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66703

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |WONTFIX

--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> ---
We have

unsigned int
readeflags_test (unsigned int a, unsigned int b)
{
  unsigned x = (a == b);
  return __builtin_ia32_readeflags_u32 ();
}

For

unsigned x = (a == b);

-march=i586 generates:



;; _3 = a_1(D) == b_2(D);

(insn 5 4 6 (set (reg:SI 90)
        (mem/c:SI (reg/f:SI 81 virtual-incoming-args) [0 a+0 S4 A32])) y.i:4 -1
     (nil))

(insn 6 5 7 (set (reg:CCZ 17 flags)
        (compare:CCZ (reg:SI 90)
            (mem/c:SI (plus:SI (reg/f:SI 81 virtual-incoming-args)
                    (const_int 4 [0x4])) [0 b+0 S4 A32]))) y.i:4 -1
     (nil))

(insn 7 6 0 (set (reg:QI 87 [ D.1413 ])
        (eq:QI (reg:CCZ 17 flags)
            (const_int 0 [0]))) y.i:4 -1
     (nil))

;; x_4 = (unsigned int) _3;

(insn 8 7 9 (parallel [
            (set (reg:SI 91)
                (zero_extend:SI (reg:QI 87 [ D.1413 ])))
            (clobber (reg:CC 17 flags))
        ]) y.i:4 -1
     (nil))

(insn 9 8 0 (set (mem/c:SI (plus:SI (reg/f:SI 82 virtual-stack-vars)
                (const_int -4 [0xfffffffffffffffc])) [0 x+0 S4 A32])
        (reg:SI 91)) y.i:4 -1
     (nil))

EFLAGS register is clobbered and __builtin_ia32_readeflags_u32
returns clobbered value.  So the testcase is expected to fail
if zero-extend bool to unsigned int clobbers EFLAGS register.  Since
we have

/* X86_TUNE_ZERO_EXTEND_WITH_AND: Use AND instruction instead
   of mozbl/movwl.  */  
DEF_TUNE (X86_TUNE_ZERO_EXTEND_WITH_AND, "zero_extend_with_and",
          m_486 | m_PENT)

This test should fail with -march=i486, -march=i586 or -miamcu.

[Bug target/66703] [4.9/5/6] gcc.target/i386/readeflags-1.c aborts on -march=i586 or on -miamcu

[julia.koval at intel dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66703

--- Comment #2 from Yulia Koval <julia.koval at intel dot com> ---
Why zero-extend with and is better than zero-extend with movz? Why it's ok to
clobber the flags?

[Bug target/66703] [4.9/5/6] gcc.target/i386/readeflags-1.c aborts on -march=i586 or on -miamcu

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66703

--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Yulia Koval from comment #2)
> Why zero-extend with and is better than zero-extend with movz? Why it's ok
> to clobber the flags?

According to Intel Pentium optimization guide, zero-extend with and is
faster than zero-extend with movz.  It is OK to clobber EFLAGS to do

unsigned int x = (unsigned int) b;

where b is a boolean value.

[Bug target/66703] [4.9/5/6] gcc.target/i386/readeflags-1.c aborts on -march=i586 or on -miamcu

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66703

--- Comment #4 from Uroš Bizjak <ubizjak at gmail dot com> ---
This patch makes testcase more robust:

--cut here--
Index: readeflags-1.c
===================================================================
--- readeflags-1.c      (revision 225648)
+++ readeflags-1.c      (working copy)
@@ -11,10 +11,11 @@
 #define EFLAGS_TYPE unsigned int
 #endif

-static EFLAGS_TYPE
+__attribute__((noinline, noclone))
+EFLAGS_TYPE
 readeflags_test (unsigned int a, unsigned int b)
 {
-  unsigned x = (a == b);
+  volatile char x = (a == b);
   return __readeflags ();
 }

--cut here--
>From gcc-bugs-return-491948-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Fri Jul 10 08:57:03 2015
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Subject: [Bug other/66827] New: [6 Regression] left shifts of negative value warnings due to C++14 switch
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf827

            Bug ID: 66827
           Summary: [6 Regression] left shifts of negative value warnings
                    due to C++14 switch
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: trippels at gcc dot gnu.org
  Target Milestone: ---

For C++98 -fsanitize=undefined didn't warn in case of left shifts of negative
values.
Now that trunk switched to C++14 a number of new warnings popped up:

gcc/config/rs6000/rs6000.c:5398:36: runtime error: left shift of negative value
-12301
gcc/config/rs6000/rs6000.md:3126:17: runtime error: left shift of negative
value -1
gcc/dce.c:287:16: runtime error: ../../gcc/gcc/haifa-sched.c:1442:26:left shift
of negative value -1
gcc/expmed.c:3002:15: runtime error: left shift of negative value -1
gcc/haifa-sched.c:1164:24: runtime error: left shift of negative value -1
gcc/haifa-sched.c:1442:26: runtime error: left shift of negative value -1
gcc/hwint.h:250:19: runtime error: left shift of negative value -1000013824
gcc/real.c:2861:25: runtime error: left shift of negative value -63
gcc/sched-deps.c:112:20: runtime error: left shift of negative value -1
gcc/sreal.c:231:20: runtime error: left shift of negative value -1092263868
libcpp/files.c:683:30: runtime error: left shift of negative value -1
libiberty/regex.c:6970:11: runtime error: left shift of negative value -1
libiberty/regex.c:7165:4: runtime error: left shift of negative value -1

[Bug target/66703] [4.9/5/6] gcc.target/i386/readeflags-1.c aborts on -march=i586 or on -miamcu

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66703

--- Comment #5 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Uroš Bizjak from comment #4)
> This patch makes testcase more robust:
> 
> --cut here--
> Index: readeflags-1.c
> ===================================================================
> --- readeflags-1.c      (revision 225648)
> +++ readeflags-1.c      (working copy)
> @@ -11,10 +11,11 @@
>  #define EFLAGS_TYPE unsigned int
>  #endif
>  
> -static EFLAGS_TYPE
> +__attribute__((noinline, noclone))
> +EFLAGS_TYPE
>  readeflags_test (unsigned int a, unsigned int b)
>  {
> -  unsigned x = (a == b);
> +  volatile char x = (a == b);
>    return __readeflags ();
>  }
>  
> --cut here--

It looks fine.  Thanks.
>From gcc-bugs-return-491975-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Fri Jul 10 13:05:22 2015
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From: "pleuba at swissonline dot ch" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/66830] New: Problem with C++ unique symbols in plugins
Date: Fri, 10 Jul 2015 13:05:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf830

            Bug ID: 66830
           Summary: Problem with C++ unique symbols in plugins
           Product: gcc
           Version: 4.9.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pleuba at swissonline dot ch
  Target Milestone: ---

I have a problem in an application loading several plugins using the same
library containing a static variable (object of class, not POD) in an inline
function.

The compiler generates STB_GNU_UNIQUE symbols for the the variable and its
guard.

Scenario:
- dlopen plugin1 (dynamic loader detect the unique variables and mark DSO as
not unloadable)
- dlopen plugin2 (dynamic loader will uses the unique variables of plugin1 and
do NOT mark DSO as unloadable, because its unique symbol is not used)
- Invoke some code in plugin2 that call the inline function, so the variable
(of plugin 1) is constructed and its guard marked initialized, but the
destructor of the variable is incorrectly registered with __cxa_atexit to be
called on unload of plugin2.
- dlclose the plugin2, so it is unloaded, __CXA_finalize calls the destructor
of the global variable owned by plugin1 !, keeping the guard marked as
initialised.
- If we reload the plugin2, it will not reconstruct the global variable as it
is still marked as initialised and access it. This results either immediately
or later in crash.

Using compiler flag -fno-gnu-unique prevents the problem.

Is this problem already known ?

Philippe

[Bug target/66703] [4.9/5/6] gcc.target/i386/readeflags-1.c aborts on -march=i586 or on -miamcu

[uros at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66703

--- Comment #6 from uros at gcc dot gnu.org ---
Author: uros
Date: Fri Jul 10 15:32:48 2015
New Revision: 225680

URL: https://gcc.gnu.org/viewcvs?rev=225680&root=gcc&view=rev
Log:
        PR target/66703
        * gcc.target/i386/readeflags-1.c (readeflags_test): Declare with
        __attribute__((noinline, noclone)).  Change "x" to "volatile char"
        type to prevent possible flag-clobbering zero-extensions.


Modified:
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.target/i386/readeflags-1.c

[Bug target/66703] [4.9/5/6] gcc.target/i386/readeflags-1.c aborts on -march=i586 or on -miamcu

[uros at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66703

--- Comment #7 from uros at gcc dot gnu.org ---
Author: uros
Date: Fri Jul 17 16:30:53 2015
New Revision: 225941

URL: https://gcc.gnu.org/viewcvs?rev=225941&root=gcc&view=rev
Log:
        Backport from mainline:
        2015-07-10  Uros Bizjak  <ubizjak@gmail.com>

        PR target/66703
        * gcc.target/i386/readeflags-1.c (readeflags_test): Declare with
        __attribute__((noinline, noclone)).  Change "x" to "volatile char"
        type to prevent possible flag-clobbering zero-extensions.
        * gcc.target/i386/pr66703.c: New test.


Added:
    branches/gcc-5-branch/gcc/testsuite/gcc.target/i386/pr66703.c
Modified:
    branches/gcc-5-branch/gcc/testsuite/ChangeLog
    branches/gcc-5-branch/gcc/testsuite/gcc.target/i386/readeflags-1.c

[Bug target/66703] [4.9/5/6] gcc.target/i386/readeflags-1.c aborts on -march=i586 or on -miamcu

[uros at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66703

--- Comment #8 from uros at gcc dot gnu.org ---
Author: uros
Date: Fri Jul 17 18:45:50 2015
New Revision: 225962

URL: https://gcc.gnu.org/viewcvs?rev=225962&root=gcc&view=rev
Log:
        Backport from mainline:
        2015-07-10  Uros Bizjak  <ubizjak@gmail.com>

        PR target/66703
        * gcc.target/i386/readeflags-1.c (readeflags_test): Declare with
        __attribute__((noinline, noclone)).  Change "x" to "volatile char"
        type to prevent possible flag-clobbering zero-extensions.
        * gcc.target/i386/pr66703.c: New test.


Added:
    branches/gcc-4_9-branch/gcc/testsuite/gcc.target/i386/pr66703.c
Modified:
    branches/gcc-4_9-branch/gcc/testsuite/ChangeLog
    branches/gcc-4_9-branch/gcc/testsuite/gcc.target/i386/readeflags-1.c

[Bug target/66703] [4.9/5/6] gcc.target/i386/readeflags-1.c aborts on -march=i586 or on -miamcu

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66703

Uroš Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |x86
         Resolution|WONTFIX                     |FIXED
           Assignee|unassigned at gcc dot gnu.org      |ubizjak at gmail dot com
   Target Milestone|---                         |4.9.4

--- Comment #9 from Uroš Bizjak <ubizjak at gmail dot com> ---
Testcase was fixed everywhere.
>From gcc-bugs-return-492674-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Fri Jul 17 19:21:55 2015
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ide850

AK <hiraditya at msn dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hiraditya at msn dot com

--- Comment #4 from AK <hiraditya at msn dot com> ---
This bug appears to be a duplicate of #61929. The fix (r225942) has been pushed
today. Please verify if this fixes your problem.