[Bug target/54385] New: [4.8 regression] ICE in pre_and_rev_post_order_compute, at cfganal.c:873

[Bug target/54385] New: [4.8 regression] ICE in pre_and_rev_post_order_compute, at cfganal.c:873

[schwab@linux-m68k.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54385

             Bug #: 54385
           Summary: [4.8 regression] ICE in
                    pre_and_rev_post_order_compute, at cfganal.c:873
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Keywords: build, ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: schwab@linux-m68k.org
                CC: steven@gcc.gnu.org
            Target: m68k-*-*


Created attachment 28089
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28089
Reduced from libjava/java/lang/natClassLoader.cc

$ gcc/xgcc -B gcc/ -O2 -fnon-call-exceptions natClassLoader.ii -S
natClassLoader.ii: In function ‘void _Jv_PushClass(jclass)’:
natClassLoader.ii:51:1: internal compiler error: in
pre_and_rev_post_order_compute, at cfganal.c:873

Started with r190602.

[Bug target/54385] [4.8 regression] ICE in pre_and_rev_post_order_compute, at cfganal.c:873

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54385

Steven Bosscher <steven at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2012-08-27
         AssignedTo|unassigned at gcc dot       |steven at gcc dot gnu.org
                   |gnu.org                     |
     Ever Confirmed|0                           |1

[Bug target/54385] [4.8 regression] ICE in pre_and_rev_post_order_compute, at cfganal.c:873

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54385

Steven Bosscher <steven at gcc dot gnu.org> changed:

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

--- Comment #1 from Steven Bosscher <steven at gcc dot gnu.org> 2012-08-27 17:18:27 UTC ---
Starting program: /home/stevenb/devel/build-debug/gcc/cc1plus -quiet PR54385.cc
-O2 -fnon-call-exceptions

Breakpoint 1, fancy_abort (file=0x1147c0a0 "../../trunk/gcc/cfganal.c",
line=873, function=0x1147c1c0 "pre_and_rev_post_order_compute")
    at ../../trunk/gcc/diagnostic.c:1011
1011      internal_error ("in %s, at %s:%d", function, trim_filename (file),
line);
(gdb) up
#1  0x00000000105d7d4c in pre_and_rev_post_order_compute (pre_order=0x0,
rev_post_order=0x116d5580, include_entry_exit=false) at
../../trunk/gcc/cfganal.c:873
873         gcc_assert (pre_order_num == n_basic_blocks - NUM_FIXED_BLOCKS);
(gdb) p brief_dump_cfg(stderr,-1)
;; basic block 2, loop depth 0, count 0, freq 10000, maybe hot
;;  prev block 0, next block 3, flags: (REACHABLE, RTL, MODIFIED)
;;  pred:       ENTRY [100.0%]  (FALLTHRU)
;;  succ:       3 [100.0%]  (FALLTHRU)
;; basic block 3, loop depth 0, count 0, freq 10000, maybe hot
;;  prev block 2, next block 4, flags: (REACHABLE, RTL, MODIFIED)
;;  pred:       2 [100.0%]  (FALLTHRU)
;;  succ:       EXIT [100.0%]  (ABNORMAL,SIBCALL)
;; basic block 4, loop depth 0, count 0, freq 0
;;  prev block 3, next block 1, flags: (REACHABLE, RTL, MODIFIED)
;;  pred:      
;;  succ:      
$5 = void
(gdb) p current_pass->name
$6 = 0x114a27d8 "postreload"

So there's an unreachable block and it confuses pre_and_rev_post_order_compute.
Someone has removed a critical edge between the ICE point and the start of
postreload. This is the CFG on entry to rest_of_handle_postreload:

;; basic block 2, loop depth 0, count 0, freq 10000, maybe hot
;;  prev block 0, next block 3, flags: (REACHABLE, RTL, MODIFIED)
;;  pred:       ENTRY [100.0%]  (FALLTHRU)
;;  succ:       4 (ABNORMAL,EH)
;;              3 [100.0%]  (FALLTHRU)
;; basic block 3, loop depth 0, count 0, freq 10000, maybe hot
;;  prev block 2, next block 4, flags: (REACHABLE, RTL, MODIFIED)
;;  pred:       2 [100.0%]  (FALLTHRU)
;;  succ:       EXIT [100.0%]  (ABNORMAL,SIBCALL)
;; basic block 4, loop depth 0, count 0, freq 0
;;  prev block 3, next block 1, flags: (REACHABLE, RTL, MODIFIED)
;;  pred:       2 (ABNORMAL,EH)
;;  succ:  

The edge disappears in reload_cse_regs_1, which is not CFG aware (like most of
postreload, it seems).

This is a pre-existing problem that happens to be exposed by my patch.

[Bug target/54385] [4.8 regression] ICE in pre_and_rev_post_order_compute, at cfganal.c:873

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54385

--- Comment #2 from Steven Bosscher <steven at gcc dot gnu.org> 2012-08-27 17:54:51 UTC ---
Created attachment 28090
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28090
Try to delete unreachable blocks if any edges were removed

[Bug middle-end/54385] [4.8 regression] ICE in pre_and_rev_post_order_compute, at cfganal.c:873

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54385

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.8.0

[Bug middle-end/54385] [4.8 regression] ICE in pre_and_rev_post_order_compute, at cfganal.c:873

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54385

Mikael Pettersson <mikpe at it dot uu.se> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mikpe at it dot uu.se

--- Comment #3 from Mikael Pettersson <mikpe at it dot uu.se> 2012-10-26 10:15:26 UTC ---
I just hit this ICE trying to built trunk @ r192837 as a cross to m68k-linux
with java enabled.  Steven's patch fixed the ICE.

(The java build also needed my proposed PR49847 patch.)

[Bug middle-end/54385] [4.8 regression] ICE in pre_and_rev_post_order_compute, at cfganal.c:873

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54385

--- Comment #4 from Steven Bosscher <steven at gcc dot gnu.org> 2012-11-09 12:31:40 UTC ---
Author: steven
Date: Fri Nov  9 12:31:32 2012
New Revision: 193359

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=193359
Log:
    PR middle-end/54385
    * postreload.c (reload_cse_simplify): Return a bool indicating
    whether the CFG was changed.
    (reload_cse_regs_1): Traverse the CFG instead of the insns chain.
    Cleanup the CFG if edges may have been removed.
    (reload_cse_regs): Update.


Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/postreload.c

[Bug middle-end/54385] [4.8 regression] ICE in pre_and_rev_post_order_compute, at cfganal.c:873

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54385

Steven Bosscher <steven at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #5 from Steven Bosscher <steven at gcc dot gnu.org> 2012-11-09 12:33:08 UTC ---
.