[Bug fortran/62142] internal compiler error: Segmentation fault (X = X - L*floor(X/L))

["ondrej.certik at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62142

--- Comment #1 from Ondřej Čertík <ondrej.certik at gmail dot com> ---
One can actually isolate it even further (the same stacktrace):

program test_segfault
implicit none
real, allocatable :: X(:)
X = floor(X)
end program
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Subject: [Bug fortran/62142] internal compiler error: Segmentation fault (X = X - L*floor(X/L))
Date: Thu, 14 Aug 2014 19:03:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62142

kargl at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kargl at gcc dot gnu.org

--- Comment #2 from kargl at gcc dot gnu.org ---
(In reply to Ondřej Čertík from comment #0)
> Created attachment 33327 [details]
> Source file to reproduce the segfault
> 
> $ cat test_segfault.f90 
> program test_segfault
> implicit none
> integer, parameter :: dp=kind(0.d0)
> real(dp) :: L
> real(dp), allocatable :: X(:)
> X = X - L*floor(X/L)
> end program
> 

(snip)

> When I execute "gfortran -v -save-temps  test_segfault.f90", it doesn't
> produce preprocessed sources, I assume the segfault happens in the parser. I
> have isolated the segfault, it happens in a large codebase and prevents its
> compilation (the array is allocated in our code, the above is the simplest
> code to reproduce the problem).
> 
> This is my first bug report, please let me know if you need further
> information.

For such a short program, we don't necessarily need -save-temps.
Note, your reduce test case is nonconforming code because it 
uses L and X in a RHS expression without being defined.  With the
small change

program test_segfault
implicit none
integer, parameter :: dp=kind(0.d0)
real(dp) :: L
real(dp), allocatable :: X(:)
L = 42
X = [1, 2]
X = X - L*floor(X/L)
end program

the code is now conforming and it still exhibits the bug.

I suspect that the bug is due to a combination of -frealloc-lhs
and that floor is generated as inline code.  With -frealloc-lhs,
I get the same ICE that you find.  With -fno-realloc-lhs, I get
a compiled executable but it segfaults at runtime because x = [1,2]
obviously won't work.  If I add an allocate(x(2)) prior to 
x = [1,2], then -fno-realloc-lhs produced executable runs as
expected.  So, as a workaround explicitly allocate memory and
use -fno-realloc-lhs.
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Subject: [Bug tree-optimization/62091] [5 Regression] ice in before_dom_children
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idb091

--- Comment #5 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
Created attachment 33329
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id3329&actioníit
Path I am testing

The disagreemeng actually turned out to be subtle bug in tree-ssa-alias.c where
function_entry_reached was incorrectly incorrectly initialized to false during
recursive walk :(

I am testing the following patch that makes us to not devirtualize in this
case. We still ought to solve the visibility issues