Re: Re: Miscompilation at -O2

[Camm Maguire <camm@maguirefamily.org>]

Greetings, and thanks for your reply!  I can try to get a simpler
example, but first let me try to simplify the post, to see if that
illumines the issue by itself.  My comments after //


    Breakpoint 4, 0x00000000004c1f72 in LI46 (V457=0x60000000047b1258,
        V458=0x60000000040400e0 <Cnil_body>) at gcl_cmpfun.c:2657
    2657            V459= (*(LnkLI268))((V458),((object)VV[165]));
    1: x/i $pc
    => 0x4c1f72 <LI46+242>:             br.call.sptk.many b0=b6;;
=============================================================================
        // Here is the call to *LnkLI268
=============================================================================
    (gdb) ni
    0x00000000004c1f80      2657            V459= (*(LnkLI268))((V458),((object)VV[165]));
    1: x/i $pc
    => 0x4c1f80 <LI46+256>: [MMI]       mov r14=r8
    (gdb) ni
    0x00000000004c1f81      2657            V459= (*(LnkLI268))((V458),((object)VV[165]));
    1: x/i $pc
    => 0x4c1f81 <LI46+257>:             mov r1=r40
    (gdb)
    2661            {object V460 = (*(LnkLI250))((V459));
    1: x/i $pc
    => 0x4c1f82 <LI46+258>:             mov r41=r8;;
    (gdb)
    2658            if(((V459))==Cnil){
    1: x/i $pc
    => 0x4c1f90 <LI46+272>: [MMI]       cmp.eq p6,p7=r8,r14
    (gdb) i reg r14
    r14            0x6000000004af3450       6917529027719672912
    (gdb) i reg r1
    r1             0x600000000001921c       6917529027641184796
    (gdb) i reg r41
    r41            0x6000000004af3450       6917529027719672912
    (gdb) p V459
    $45 = (object) 0x6000000004af3450

=============================================================================
    // Here is the return of 0x6000000004af3450 to V459.
    // Cnil is 0x60000000040400e0, so the comparison on 2658 should fail
=============================================================================

    (gdb) ni
    2661            {object V460 = (*(LnkLI250))((V459));
    1: x/i $pc
    => 0x4c1f91 <LI46+273>:             nop.m 0x0
    (gdb)
    0x00000000004c1f92      2661            {object V460 = (*(LnkLI250))((V459));
    1: x/i $pc
    => 0x4c1f92 <LI46+274>:             addl r18=71588,r1;;
    (gdb)
    2667            VMR46(V461)}}
    1: x/i $pc
    => 0x4c1fa0 <LI46+288>: [MIB] (p06) st8 [r34]=r37
    (gdb)
    2658            if(((V459))==Cnil){
    1: x/i $pc
    => 0x4c1fa1 <LI46+289>:             nop.i 0x0
    (gdb)
    0x00000000004c1fa2      2658            if(((V459))==Cnil){
    1: x/i $pc
    => 0x4c1fa2 <LI46+290>:       (p06) br.cond.dpnt.few 0x4c2080 <LI46+512>;;
    (gdb)

=============================================================================
    // Here is the comparison that should fail, but jumps over the
    // following code instead returning V459 from the function.  *LnkLI250 is
    // never called.
=============================================================================

    2670    }
    1: x/i $pc
    => 0x4c2080 <LI46+512>: [MII]       nop.m 0x0
    (gdb) ni
    0x00000000004c2081      2670    }
    1: x/i $pc
    => 0x4c2081 <LI46+513>:             mov.i ar.pfs=r39
    (gdb)
    0x00000000004c2082      2670    }
    1: x/i $pc
    => 0x4c2082 <LI46+514>:             nop.i 0x0;;
    (gdb)
    0x00000000004c2090      2670    }
    1: x/i $pc
    => 0x4c2090 <LI46+528>: [MIB]       nop.m 0x0
    (gdb)
    0x00000000004c2091      2670    }
    1: x/i $pc
    => 0x4c2091 <LI46+529>:             mov b0=r38
    (gdb)
    0x00000000004c2092      2670    }
    1: x/i $pc
    => 0x4c2092 <LI46+530>:             br.ret.sptk.many b0;;
    (gdb)


Please let me know if this helps.

Take care,
-- 
Camm Maguire			     		    camm@maguirefamily.org
==========================================================================
"The earth is but one country, and mankind its citizens."  --  Baha'u'llah