[Bug target/63891] New: [5.0 regression] Failure of darwin-weakimport-3.c

[Bug target/63891] New: [5.0 regression] Failure of darwin-weakimport-3.c

[fxcoudert at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63891

            Bug ID: 63891
           Summary: [5.0 regression] Failure of darwin-weakimport-3.c
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fxcoudert at gcc dot gnu.org

Current trunk shows runtime failure for gcc.dg/darwin-weakimport-3.c on
x86_64-apple-darwin14 with -m32. The difference in the assembler between the
4.9.2 compiler (good) and the trunk compiler (bad, revision 217599) is:

$ diff -pu good-49.s bad-trunk.s 
--- good-49.s    2014-11-15 16:33:50.000000000 +0100
+++ bad-trunk.s    2014-11-15 16:33:30.000000000 +0100
@@ -3,6 +3,15 @@
 _foo:
     pushl    %ebp
     movl    %esp, %ebp
+    call    ___x86.get_pc_thunk.ax
+L1$pb:
+    nop
     popl    %ebp
     ret
+    .section __TEXT,__textcoal_nt,coalesced,pure_instructions
+    .weak_definition    ___x86.get_pc_thunk.ax
+    .private_extern    ___x86.get_pc_thunk.ax
+___x86.get_pc_thunk.ax:
+    movl    (%esp), %eax
+    ret
     .subsections_via_symbols


The presence of the line with "coalesced" makes the test fail.

[Bug target/63891] [5.0 regression] Failure of darwin-weakimport-3.c

[fxcoudert at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63891

Francois-Xavier Coudert <fxcoudert at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |x86_64-apple-darwin14
             Status|UNCONFIRMED                 |NEW
           Keywords|                            |wrong-code
   Last reconfirmed|                            |2014-11-15
                 CC|                            |iains at gcc dot gnu.org
               Host|                            |x86_64-apple-darwin14
     Ever confirmed|0                           |1
              Build|                            |x86_64-apple-darwin14

[Bug target/63891] [5.0 regression] Failure of darwin-weakimport-3.c

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63891

Iain Sandoe <iains at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |evstupac at gmail dot com

--- Comment #1 from Iain Sandoe <iains at gcc dot gnu.org> ---
confirmed on x86_64-darwin12.

this is generating an unnecesary picbase (since it is unused in the function),
and thus the thunk - which triggers the failure.

This is probably more fallout from the EBX changes.

[Bug target/63891] [5.0 regression] Failure of darwin-weakimport-3.c

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63891

--- Comment #2 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
> This is probably more fallout from the EBX changes.

Yep! I see the failure with r216154 but not with 216153.

[Bug target/63891] [5.0 regression] Failure of darwin-weakimport-3.c

[fxcoudert at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63891

--- Comment #3 from Francois-Xavier Coudert <fxcoudert at gcc dot gnu.org> ---
This same bug may also be the root for:
 FAIL: gcc.dg/torture/builtin-self.c   -O0   scan-assembler-not \\tcall

which is also a 5.0 regression, due to the extra "call   
___x86.get_pc_thunk.ax". Dominique, could you check whether both appeared at
the same time?

[Bug target/63891] [5.0 regression] Failure of darwin-weakimport-3.c

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63891

--- Comment #4 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
> Dominique, could you check whether both appeared at the same time?

Yes: r216154.

[Bug target/63891] [5.0 regression] Failure of darwin-weakimport-3.c

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63891

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |5.0

[Bug target/63891] [5 regression] Failure of darwin-weakimport-3.c

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63891

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1

[Bug target/63891] [5 regression] Failure of darwin-weakimport-3.c

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63891

--- Comment #5 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
FAIL: gcc.dg/torture/builtin-self.c   -O0   scan-assembler-not \\tcall

is also seen on i686-pc-linux-gnu with -fpic: see

https://gcc.gnu.org/ml/gcc-testresults/2014-12/msg01216.html

[Bug target/63891] [5 regression] Failure of darwin-weakimport-3.c

[law at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63891

Jeffrey A. Law <law at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|wrong-code                  |
           Priority|P1                          |P4
                 CC|                            |law at redhat dot com

--- Comment #6 from Jeffrey A. Law <law at redhat dot com> ---
AFAICT, this is actually a false positive and mostly points to an inefficiency
in our -O0 32-bit PIC code generation on x86.

The test wants to make sure that _foo doesn't end up in textcoal_nt section,
which is marked with the coalesced section attribute.

The test (reasonably so) just blindly looks for the existence of the magic
section declaration without any regard to what's in it.

In this case we emit PIC setup.  It's not strictly necessary as there aren't
any uses of the PIC register, but since the optimizer isn't on, DCE is not run
and thus the PIC setup remains.

Once we have PIC setup, we have the get_pc_thunk routine which gets put into
that magic section.  Which then triggers the false positive.

For darwin-weakimport-3.c, the right fix is probably to turn on -O1.  Not sure
what the best fix for builtin-self.c is (maybe an xfail), but in both cases
this isn't worthy of a P1 regresion.  I'd peg it more at a P4/P5 level since
the inefficiencies only show up at -O0.

[Bug target/63891] [5/6 regression] Failure of darwin-weakimport-3.c

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63891

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|5.0                         |5.2

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 5.1 has been released.

[Bug target/63891] [5/6 regression] Failure of darwin-weakimport-3.c

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63891

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|5.2                         |5.3

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 5.2 is being released, adjusting target milestone to 5.3.