optimization/10287: [3.2/3.4 regression] Loop/conditional store bug (ARM)

[drow at mvista dot com]

>Number:         10287
>Category:       optimization
>Synopsis:       [3.2/3.4 regression] Loop/conditional store bug (ARM)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Apr 01 18:46:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     drow at mvista dot com
>Release:        3.2.2 (release), 3.4 CVS (2003-03-27)
>Organization:
>Environment:
i686-pc-linux-gnu host, arm-linux target (or arm-elf, xscale-elf, et cetera)
>Description:
The attached test case aborts when compiled with -O2 for
an ARM target.

The diff between failing and succeeding binaries is:
        cmp     ip, #0
-       moveq   r3, r1
-       movne   r3, lr
        str     r1, [r5], #4
+       strne   lr, [r5], #4
        subs    ip, ip, #2
-       str     r3, [r5], #4

Note that the failing binary has an unconditional store
of a conditional value.  My guess is that something is
not respecting post-increment when distinguishing between
the two stores.


This is a 3.2 and 3.4 regression; it worked in 2.95 and
it works in 3.3.  The bug was fixed in 3.3 and HEAD by:

 2002-09-18  Richard Henderson  <rth at redhat dot com>
 
       * ifcvt.c (noce_process_if_block): Correctly detect X modified
       with INSN_B before COND_EARLIEST.  Don't check A and B for 
       modification in condition range.  Reorder INSN_B for A==B properly.
       (if_convert): Iterate until no matches for a block.

It was then broken again in HEAD by:
Wed Jan  8 12:10:57 CET 2003  Jan Hubicka  <jh at suse dot cz>

       * i386.md (adddi3_carry_rex64, subdi3_carry_rex64): Name pattern.
       (addhi3_carry, addqi3_carry, subhi3_carry, subqi3_carry): New patterns.
       (add??cc): New expanders.
       * i386.c (expand_int_addcc): New function.
       * i386-protos.h (expand_int_addcc): Declare.

       * alias.c (memory_modified_1): New static function.
       (memory_modified): New static varaible.
       (memory_modified_in_insn_p): New global function.
       * rtl.h (memory_modified_in_insn_p): Declare.
       * rtlanal.c (modified_between_p, modified_in_p): Be smart about memory
       references.

       * expr.h (emit_conditional_add): Declare.
>How-To-Repeat:

>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
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