[Bug rtl-optimization/68011] New: wrong code at -O1 and above on x86_64-linux-gnu in 64-bit mode

[Bug rtl-optimization/68011] New: wrong code at -O1 and above on x86_64-linux-gnu in 64-bit mode

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68011

            Bug ID: 68011
           Summary: wrong code at -O1 and above on x86_64-linux-gnu in
                    64-bit mode
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu
  Target Milestone: ---

The current gcc trunk mis-compiles the following code on x86_64-linux-gnu at
-O1 and above in the 64-bit mode (but not in the 32-bit mode). 

This is a regression from 5.2.x.


$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 6.0.0 20151018 (experimental) [trunk revision 228953] (GCC) 
$ 
$ gcc-trunk -m64 -O0 small.c; ./a.out
$ gcc-trunk -m32 -O1 small.c; ./a.out
$ gcc-5.2 -m64 -O1 small.c; ./a.out
$ 
$ gcc-trunk -m64 -O1 small.c
$ ./a.out
Aborted (core dumped)
$ 


------------------------------


struct S
{
  int f0;
  int f1;
  int f2;
  short f3;
  int f4:1;
} a, c = {0, 0, 1, 0, 0};

int d;

int
main ()
{
  struct S e = c;
  e.f0++;
  d = e.f3;
  a = e;

  if (a.f2 != 1)
    __builtin_abort ();

  return 0;
}

[Bug rtl-optimization/68011] [6 Regression] wrong code at -O1 and above on x86_64-linux-gnu in 64-bit mode

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68011

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |6.0
            Summary|wrong code at -O1 and above |[6 Regression] wrong code
                   |on x86_64-linux-gnu in      |at -O1 and above on
                   |64-bit mode                 |x86_64-linux-gnu in 64-bit
                   |                            |mode

[Bug rtl-optimization/68011] [6 Regression] wrong code at -O1 and above on x86_64-linux-gnu in 64-bit mode

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68011

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-10-19
                 CC|                            |mpolacek at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Started with r225852.

[Bug rtl-optimization/68011] [6 Regression] wrong code at -O1 and above on x86_64-linux-gnu in 64-bit mode

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68011

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
So likely a target bug.

[Bug rtl-optimization/68011] [6 Regression] wrong code at -O1 and above on x86_64-linux-gnu in 64-bit mode

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68011

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Possibly a dup of that reload/LRA issue

[Bug rtl-optimization/68011] [6 Regression] wrong code at -O1 and above on x86_64-linux-gnu in 64-bit mode

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68011

Uroš Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #4 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Richard Biener from comment #3)
> Possibly a dup of that reload/LRA issue

Exactly.

We start with:

(insn 18 17 19 2 (parallel [
            (set (subreg:DI (reg/v:TI 92 [ e ]) 0)
                (ior:DI (reg:DI 100)
                    (reg:DI 98 [ _3 ])))
            (clobber (reg:CC 17 flags))
        ]) pr68011.c:18 398 {*iordi_1}
     (expr_list:REG_DEAD (reg:DI 100)
        (expr_list:REG_DEAD (reg:DI 98 [ _3 ])
            (expr_list:REG_UNUSED (reg:CC 17 flags)
                (nil)))))
(insn 19 18 21 2 (set (reg:V8HI 103)
        (vec_merge:V8HI (vec_duplicate:V8HI (reg:HI 91 [ e$12 ]))
            (subreg:V8HI (reg/v:TI 92 [ e ]) 0)
            (const_int 64 [0x40]))) pr68011.c:18 3597 {sse2_pinsrw}

and reload generates (insn 41) that clears high word:

(insn 18 39 40 2 (parallel [
            (set (reg:DI 0 ax [100])
                (ior:DI (reg:DI 0 ax [100])
                    (reg:DI 2 cx [orig:98 _3 ] [98])))
            (clobber (reg:CC 17 flags))
        ]) pr68011.c:18 398 {*iordi_1}
     (nil))

...

(insn 41 40 19 2 (set (reg:DI 21 xmm0 [orig:92 e ] [92])
        (mem/c:DI (plus:DI (reg/f:DI 7 sp)
                (const_int 8 [0x8])) [0 %sfp+-8 S8 A64])) pr68011.c:18 85
{*movdi_internal}
     (nil))
(insn 19 41 21 2 (set (reg:V8HI 21 xmm0 [103])
        (vec_merge:V8HI (vec_duplicate:V8HI (reg:HI 1 dx [orig:91 e$12 ] [91]))
            (reg:V8HI 21 xmm0 [orig:92 e ] [92])
            (const_int 64 [0x40]))) pr68011.c:18 3597 {sse2_pinsrw}

*** This bug has been marked as a duplicate of bug 67124 ***
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Subject: [Bug rtl-optimization/67124] [6 Regression] wrong code at -O1, -O2 and -O3 on x86_64-linux-gnu
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67124

--- Comment #14 from Uroš Bizjak <ubizjak at gmail dot com> ---
*** Bug 68011 has been marked as a duplicate of this bug. ***
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Subject: [Bug tree-optimization/68021] [6 Regression] ice in rewrite_use_nonlinear_expr with -O3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idh021

Markus Trippelsdorf <trippels at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
      Known to work|                            |4.9.3, 5.2.0
   Last reconfirmed|                            |2015-10-19
          Component|c++                         |tree-optimization
                 CC|                            |trippels at gcc dot gnu.org
     Ever confirmed|0                           |1
            Summary|ice in                      |[6 Regression] ice in
                   |rewrite_use_nonlinear_expr  |rewrite_use_nonlinear_expr
                   |with -O3                    |with -O3
      Known to fail|                            |6.0

--- Comment #1 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Needs -O3:

char a;
int b;
void fn1(char *p1, int p2, int p3) {
  int x;
  for (; b;) {
    for (x = 0; x < p3; x++) {
      *p1 = a;
      p1--;
    }
    p1 += p2;
  }
}