[Bug ipa/61986] New: ICE on valid code at -O3 on x86_64-linux-gnu indecide_about_value, at ipa-cp.c:3480

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61986

            Bug ID: 61986
           Summary: ICE on valid code at -O3 on x86_64-linux-gnu
                    indecide_about_value, at ipa-cp.c:3480
           Product: gcc
           Version: 4.10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ipa
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu

The following code causes an ICE when compiled with the current gcc trunk at
-O3 on x86_64-linux-gnu (in both 32-bit and 64-bit modes).

It is a regression from 4.9.x.

$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-unknown-linux-gnu/4.10.0/lto-wrapper
Target: x86_64-unknown-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 4.10.0 20140731 (experimental) [trunk revision 213316] (GCC) 
$ 
$ gcc-trunk -O2 -c small.c
$ gcc-4.9 -O3 -c small.c
$ 
$ gcc-trunk -O3 -c small.c
small.c:45:1: internal compiler error: in decide_about_value, at ipa-cp.c:3480
 }
 ^
0xee657c decide_about_value
    ../../gcc-trunk/gcc/ipa-cp.c:3480
0xee8978 decide_whether_version_node
    ../../gcc-trunk/gcc/ipa-cp.c:3539
0xee8978 ipcp_decision_stage
    ../../gcc-trunk/gcc/ipa-cp.c:3668
0xee8978 ipcp_driver
    ../../gcc-trunk/gcc/ipa-cp.c:3714
0xee8978 execute
    ../../gcc-trunk/gcc/ipa-cp.c:3805
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.
$ 

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

int a, b, c;

struct S
{
  int f0;
  int f1;
} d;

static int fn2 (struct S);
void fn3 (struct S);

void
fn1 (struct S p)
{
  struct S h = { 0, 0 };
  fn3 (p);
  fn2 (h);
}

int
fn2 (struct S p)
{
  struct S j = { 0, 0 };
  fn3 (p);
  fn2 (j);
  return 0;
}

void
fn3 (struct S p)
{
  for (; b; a++)
    c = p.f0;
  fn1 (d);
}

void
fn4 ()
{
  for (;;)
    {
      struct S f = { 0, 0 };
      fn1 (f);
    }
}