[Bug c/12455] New: Invalid ia64 unwind data when compiling with -pg

["kaos at ocs dot com dot au" <gcc-bugzilla at gcc dot gnu dot org>]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12455

           Summary: Invalid ia64 unwind data when compiling with -pg
           Product: gcc
           Version: 3.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kaos at ocs dot com dot au
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: ia64-unknown-linux
  GCC host triplet: ia64-unknown-linux
GCC target triplet: ia64-unknown-linux

gcc version 3.4 20030929 (experimental).  Compile hello.c without and with -pg.
-pg adds two bundles to the start of main but the unwind data for main is not
changed.

objdump and readelf -u without -pg

<main>:
        00 08 15 08 80 05       [MII]       alloc r33=ar.pfs,5,4,0
        20 02 30 00 42 60                   mov r34=r12
        04 08 00 84                         mov r35=r1
        01 00 00 00 01 00       [MII]       nop.m 0x0
        00 02 00 62 00 80                   mov r32=b0
        84 0c 00 90                         addl r36=72,r1;;
        1c 20 01 48 18 10       [MFB]       ld8 r36=[r36]
        00 00 00 02 00 00                   nop.f 0x0
        08 fe ff 58                         br.call.sptk.many 
b0=4000000000000440 <_init+0x150>
        02 08 00 46 00 21       [MII]       mov r1=r35
        e0 00 00 00 42 00                   mov r14=r0;;
        01 70 00 84                         mov r8=r14
        00 00 00 00 01 00       [MII]       nop.m 0x0
        00 08 01 55 00 00                   mov.i ar.pfs=r33
        00 0a 00 07                         mov b0=r32
        1d 60 00 44 00 21       [MFB]       mov r12=r34
        00 00 00 02 00 80                   nop.f 0x0
        08 00 84 00                         br.ret.sptk.many b0;;

<main>: [0x4000000000000620-0x4000000000000680), info at +0x828
  v1, flags=0x0 ( ), len=16 bytes
    R2:prologue_gr(mask=[rp,ar.pfs,psp],grsave=r32,rlen=5)
        P7:pfs_when(t=0)
        P7:mem_stack_v(t=1)
        P7:rp_when(t=4)
    R1:body(rlen=13)
        B2:epilogue(t=2,ecount=0)
    R1:prologue(rlen=0)
    R1:prologue(rlen=0)
    R1:prologue(rlen=0)
    R1:prologue(rlen=0)

objdump and readelf -u with -pg

        02 40 31 10 80 05       [MII]       alloc r40=ar.pfs,12,8,0
        b0 42 07 00 48 20                   addl r43=104,r1;;
        05 08 00 84                         mov r41=r1
        11 00 00 00 01 00       [MIB]       nop.m 0x0
        a0 02 00 62 00 00                   mov r42=b0
        38 fd ff 58                         br.call.sptk.many 
b0=40000000000005a0 <_init+0x1a0>;;
        00 08 15 08 80 05       [MII]       alloc r33=ar.pfs,5,4,0
        20 02 30 00 42 60                   mov r34=r12
        04 08 00 84                         mov r35=r1
        01 00 00 00 01 00       [MII]       nop.m 0x0
        00 02 00 62 00 80                   mov r32=b0
        04 0f 00 90                         addl r36=112,r1;;
        1c 20 01 48 18 10       [MFB]       ld8 r36=[r36]
        00 00 00 02 00 00                   nop.f 0x0
        e8 fc ff 58                         br.call.sptk.many 
b0=4000000000000580 <_init+0x180>
        02 08 00 46 00 21       [MII]       mov r1=r35
        e0 00 00 00 42 00                   mov r14=r0;;
        01 70 00 84                         mov r8=r14
        00 00 00 00 01 00       [MII]       nop.m 0x0
        00 08 01 55 00 00                   mov.i ar.pfs=r33
        00 0a 00 07                         mov b0=r32
        1d 60 00 44 00 21       [MFB]       mov r12=r34
        00 00 00 02 00 80                   nop.f 0x0
        08 00 84 00                         br.ret.sptk.many b0;;

<main>: [0x4000000000000860-0x40000000000008e0), info at +0xb30
  v1, flags=0x0 ( ), len=16 bytes
    R2:prologue_gr(mask=[rp,ar.pfs,psp],grsave=r32,rlen=5)
        P7:pfs_when(t=0)
        P7:mem_stack_v(t=1)
        P7:rp_when(t=4)
    R1:body(rlen=13)
        B2:epilogue(t=2,ecount=0)
    R1:prologue(rlen=0)
    R1:prologue(rlen=0)
    R1:prologue(rlen=0)
    R1:prologue(rlen=0)

Despite the fact that -pg added two bundles to the start of main which changes
the state or ar.pfs and b0, this is not reflected in the unwind data.  Backtrace
from mcount() or an interrupt while executing the -pg prologue will terminate
early.  -pg cannot be used with profiling tools that rely on interrupts.

The body length in the -pg case does not take account of the two extra bundles.
Any error in the last two bundles of the modified body will appear to be outside
the body of the procedure and will use the default unwind data for leaf
functions.  Any error in the last two bundles will get an incorrect backtrace.

My best guess at what the unwind data should look like for the second case, it
may be possible to shrink this a bit.  Untested.

<main>: [0x4000000000000860-0x40000000000008e0), info at +0xb30
  v1, flags=0x0 ( ), len=?? bytes
    R1:prologue(rlen=6)
        P3:pfs_gr(reg=r40)
        P7:pfs_when(t=0)
        P3:rp_gr(reg=r42)
        P7:rp_when(t=5)
    R1:body(rlen=0)
        B2:epilogue(t=0,ecount=0)
    R2:prologue_gr(mask=[rp,ar.pfs,psp],grsave=r32,rlen=5)
        P7:pfs_when(t=0)
        P7:mem_stack_v(t=1)
        P7:rp_when(t=4)
    R1:body(rlen=13)
        B2:epilogue(t=2,ecount=0)