Compile libcilkrts with -funwind-tables (PR target/60290)

[Rainer Orth]

I've finally gotten around to analyzing this testsuite failure on 32-bit
Solaris/x86:

FAIL: g++.dg/cilk-plus/CK/catch_exc.cc  -O1 -fcilkplus execution test
FAIL: g++.dg/cilk-plus/CK/catch_exc.cc  -O3 -fcilkplus execution test
FAIL: g++.dg/cilk-plus/CK/catch_exc.cc  -g -O2 -fcilkplus execution test
FAIL: g++.dg/cilk-plus/CK/catch_exc.cc  -g -fcilkplus execution test

The testcase aborts like this:

Thread 2 received signal SIGABRT, Aborted.
[Switching to Thread 1 (LWP 1)]
0xfe3ba3c5 in __lwp_sigqueue () from /lib/libc.so.1
(gdb) where
#0  0xfe3ba3c5 in __lwp_sigqueue () from /lib/libc.so.1
#1  0xfe3b2d4f in thr_kill () from /lib/libc.so.1
#2  0xfe2f64da in raise () from /lib/libc.so.1
#3  0xfe2c93ee in abort () from /lib/libc.so.1
#4  0xfe525b37 in _Unwind_Resume (exc=0x80a75a0)
    at /vol/gcc/src/hg/trunk/local/libgcc/unwind.inc:234
#5  0xfe783b85 in __cilkrts_gcc_rethrow (sf=0xfeffdb00)
    at /vol/gcc/src/hg/trunk/local/libcilkrts/runtime/except-gcc.cpp:589
#6  0xfe77f0ea in __cilkrts_rethrow (sf=0xfeffdb00)
    at /vol/gcc/src/hg/trunk/local/libcilkrts/runtime/cilk-abi.c:548
#7  0x080513a3 in my_test ()
    at /vol/gcc/src/hg/trunk/local/gcc/testsuite/g++.dg/cilk-plus/CK/catch_exc.cc:38
#8  0x080515bd in main ()
    at /vol/gcc/src/hg/trunk/local/gcc/testsuite/g++.dg/cilk-plus/CK/catch_exc.cc:62

The gcc_assert in _Unwind_Resume triggers since
_Unwind_RaiseException_Phase2 returned _URC_FATAL_PHASE2_ERROR.  I found
that x86_fallback_frame_state had been invoked for this pc:

   0xfe77218e <__cilkrts_rethrow+30>:	add    $0x10,%esp

and returned _URC_END_OF_STACK, which is totally unexpected since
_Unwind_Find_FDE should have found it.  __cilkrts_rethrow is defined in
libcilkrts/cilk-abi.o, but in the 32-bit case EH info is missing:

32-bit:

ro@fuego 339 > elfdump -u .libs/libcilkrts.so|grep rethrow
       0x18def  0x3558c  __cilkrts_gcc_rethrow
  [0x11fc]      initloc:   0x18def [ sdata4 pcrel ]  __cilkrts_gcc_rethrow

64-bit:

ro@fuego 341 > elfdump -u amd64/libcilkrts/.libs/libcilkrts.so|grep rethrow
       0x1c639  0x2010  __cilkrts_rethrow
       0x2388b  0x5510  __cilkrts_gcc_rethrow
   [0x488]      initloc:   0x1c639 [ sdata4 pcrel ]  __cilkrts_rethrow
  [0x3988]      initloc:   0x2388b [ sdata4 pcrel ]  __cilkrts_gcc_rethrow

I traced this to -funwind-tables bein set on 32-bit Linux/x86, while it
is unset on 32-bit Solaris/x86  due to

i386/i386.c (ix86_option_override_internal):

      if (opts->x_flag_asynchronous_unwind_tables == 2)
	opts->x_flag_asynchronous_unwind_tables = !USE_IX86_FRAME_POINTER;

where i386/sol2.h has

#define USE_IX86_FRAME_POINTER 1

while the default is 0.

As expected, compiling libcilkrts with -funwind-tables (which is a no-op
on Linux/x86, Linux/x86_64, and Solaris/amd64) makes the failure go
away.

I'm uncertain if this is ok for mainline at this stage or has to wait
for gcc-7.  Once it goes into mainline, it's probably worth a backport
to all active release branches.

Thoughts?

	Rainer


2016-04-04  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	PR target/60290
	* Makefile.am (GENERAL_FLAGS): Add -funwind-tables.
	* Makefile.in: Regenerate.

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Rainer Orth, Center for Biotechnology, Bielefeld University