[Bug middle-end/52353] New: -ftrapv -fnon-call-exceptions does not work

[Bug middle-end/52353] New: -ftrapv -fnon-call-exceptions does not work

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52353

             Bug #: 52353
           Summary: -ftrapv -fnon-call-exceptions does not work
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: rguenth@gcc.gnu.org


The testcase from PR47086

void
foo ()
{
  int n = 0;
  while (1)
    {
      int i[n % 1];
      n++;
    }
}

reveals that while on the tree level n++ has an outgoing EH edge, RTL
expansion leaves us with

;; n_5 = n_1 + 1;

(insn 12 11 13 (set (reg:DI 67)
        (sign_extend:DI (reg/v:SI 61 [ n ])))
/space/rguenther/src/svn/trunk/gcc/testsuite/gcc.dg/pr47086.c:11 -1
     (nil))

(insn 13 12 14 (set (reg:DI 4 si)
        (const_int 1 [0x1]))
/space/rguenther/src/svn/trunk/gcc/testsuite/gcc.dg/pr47086.c:11 -1
     (nil))

(insn 14 13 15 (set (reg:DI 5 di)
        (reg:DI 67))
/space/rguenther/src/svn/trunk/gcc/testsuite/gcc.dg/pr47086.c:11 -1
     (nil))

(call_insn/u 15 14 16 (set (reg:DI 0 ax)
        (call (mem:QI (symbol_ref:DI ("__addvdi3") [flags 0x41]) [0 S1 A8])
            (const_int 0 [0])))
/space/rguenther/src/svn/trunk/gcc/testsuite/gcc.dg/pr47086.c:11 -1
     (expr_list:REG_EH_REGION (const_int -2147483648 [0xffffffff80000000])
        (nil))
    (expr_list:REG_DEP_TRUE (use (reg:DI 4 si))
        (expr_list:REG_DEP_TRUE (use (reg:DI 5 di))
            (nil))))

(insn 16 15 17 (set (reg:DI 68)
        (reg:DI 0 ax))
/space/rguenther/src/svn/trunk/gcc/testsuite/gcc.dg/pr47086.c:11 -1
     (expr_list:REG_EQUAL (plus:DI (reg:DI 67)
            (const_int 1 [0x1]))
        (nil)))

(insn 17 16 0 (set (reg/v:SI 63 [ n ])
        (subreg:SI (reg:DI 68) 0))
/space/rguenther/src/svn/trunk/gcc/testsuite/gcc.dg/pr47086.c:11 -1
     (nil))

note that the call is marked CONST.  The EH edge is simply thrown away:

;; Basic block 4 , prev 3, next 5, loop_depth 1, count 0, freq 10000, maybe
hot, flags: new reachable rtl modified.
;; Predecessors:  3 [100.0%]  (fallthru) 5 [100.0%]  (dfs_back)
...
(call_insn/u 15 14 16 4 (set (reg:DI 0 ax)
        (call (mem:QI (symbol_ref:DI ("__addvdi3") [flags 0x41]) [0 S1 A8])
            (const_int 0 [0])))
/space/rguenther/src/svn/trunk/gcc/testsuite/gcc.dg/pr47086.c:11 -1
     (expr_list:REG_EH_REGION (const_int -2147483648 [0xffffffff80000000])
        (nil))
    (expr_list:REG_DEP_TRUE (use (reg:DI 4 si))
        (expr_list:REG_DEP_TRUE (use (reg:DI 5 di))
            (nil))))

(insn 16 15 17 4 (set (reg:DI 68)
        (reg:DI 0 ax))
/space/rguenther/src/svn/trunk/gcc/testsuite/gcc.dg/pr47086.c:11 -1
     (expr_list:REG_EQUAL (plus:DI (reg:DI 67)
            (const_int 1 [0x1]))
        (nil)))

(insn 17 16 18 4 (set (reg/v:SI 63 [ n ])
        (subreg:SI (reg:DI 68) 0))
/space/rguenther/src/svn/trunk/gcc/testsuite/gcc.dg/pr47086.c:11 -1
     (nil))

;; Successors:  5 [100.0%]  (fallthru)


So we seem to leave around the libcall because of the EH side-effect
but do not consider that call as possibly throwing (as it is marked
nothrow on RTL) in find_many_sub_basic_blocks
(at least) and DCE it later, too (sounds similar to PR19020).

Currently generated assembly for gcc.dg/pr47086.c on x86_64 is

foo:
.LFB0:
        .cfi_startproc
        .cfi_personality 0x3,__gcc_personality_v0
        pushq   %rbx
        .cfi_def_cfa_offset 16
        .cfi_offset 3, -16
        movl    $0, %ebx
.L2:
        addl    $1, %ebx
        jmp     .L2


I'm running into this issue when removing unreachable blocks during
expansion, then the landing pad unwind info expansion ICEs because the landing
pad was removed.

We mark the call as not throwing via emit_libcall_block because we pass
it (plus (reg) 1) as EQUIV, which may not trap.

[Bug middle-end/52353] -ftrapv -fnon-call-exceptions does not work

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52353

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-02-23 13:05:30 UTC ---
Created attachment 26732
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26732
patch

Patch that fixes my issue and works until rtl_dce, which still removes the
call,
even though it throws internally

(call_insn/u 15 13 36 3 (set (reg:DI 0 ax)
        (call (mem:QI (symbol_ref:DI ("__addvdi3") [flags 0x41]) [0 S1 A8])
            (const_int 0 [0])))
/space/rguenther/src/svn/trunk/gcc/testsuite/gcc.dg/pr47086.c:11 636
{*call_value}
     (expr_list:REG_DEAD (reg:DI 5 di)
        (expr_list:REG_DEAD (reg:DI 4 si)
            (expr_list:REG_UNUSED (reg:DI 0 ax)
                (expr_list:REG_EH_REGION (const_int 1 [0x1])
                    (nil)))))
    (expr_list:REG_DEP_TRUE (use (reg:DI 4 si))
        (expr_list:REG_DEP_TRUE (use (reg:DI 5 di))
            (nil))))

;; Successors:  5 (ab,abcall,eh,loop_exit) 4 [100.0%]  (fallthru)
;; lr  out       3 [bx] 6 [bp] 7 [sp] 16 [argp] 20 [frame] 41 [r12]

[Bug middle-end/52353] -ftrapv -fnon-call-exceptions does not work

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52353

--- Comment #2 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-03-05 13:08:59 UTC ---
Author: rguenth
Date: Mon Mar  5 13:08:55 2012
New Revision: 184932

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=184932
Log:
2012-03-05  Richard Guenther  <rguenther@suse.de>

    PR middle-end/52353
    * optabs.h (trapv_unoptab_p): New function.
    (trapv_binoptab_p): Likewise.
    * optabs.c (expand_binop): Use emit_libcall_block_1 with
    a proper equiv_may_trap argument.
    (expand_unop): Likewise.
    (emit_libcall_block_1): Take extra argument whether the
    instruction may trap.  Renamed from ...
    (emit_libcall_block): ... this.  New wrapper.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/optabs.c
    trunk/gcc/optabs.h

[Bug middle-end/52353] -ftrapv -fnon-call-exceptions does not work

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52353

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
      Known to work|                            |4.8.0
         Resolution|                            |FIXED

--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-03-05 13:10:27 UTC ---
Fixed for trunk.