[Bug target/58139] PowerPC volatile VSX register live across call

["bergner at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58139

--- Comment #2 from Peter Bergner <bergner at gcc dot gnu.org> ---
This looks like a scheduling bug.  Just before sched2, we have:

(call_insn 29 28 31 2 (parallel [
            (set (reg:DF 33 1)
                (call (mem:SI (symbol_ref:DI ("log") [flags 0x41] 
<function_decl 0xfff92c41200 log>) [0 __builtin_log S4 A8])
                    (const_int 64 [0x40])))
            (use (const_int 0 [0]))
            (clobber (reg:SI 65 lr))
        ]) bug.c:17 509 {*call_value_nonlocal_aix64}
     (expr_list:REG_EH_REGION (const_int 0 [0])
        (nil))
    (expr_list:REG_NON_LOCAL_GOTO (use (reg:DF 33 1))
        (nil)))
(insn 31 29 34 2 (set (reg:V2DF 62 30 [orig:140 vb0 ] [140])
        (unspec:V2DF [
                (reg/v:DF 62 30 [orig:123 b0 ] [123])
                (reg/v:DF 61 29 [orig:125 b1 ] [125])
            ] UNSPEC_VSX_CONCAT)) bug.c:18 920 {vsx_concat_v2df}
     (expr_list:REG_DEAD (reg/v:DF 61 29 [orig:125 b1 ] [125])
        (expr_list:REG_EQUIV (mem:V2DF (reg/v/f:DI 30 30 [orig:133 B ] [133])
[2 MEM[(__vector double *)B_2(D)]+0 S16 A128])
            (nil))))

Here, insn 31 sets VSX reg 62 (ie, fpr30,vsr30).  In DFmode, reg 62 is a
non-volatile register, but in V2DFmode, it is volatile.  After sched2, we have:

insn:TI 31 28 29 2 (set (reg:V2DF 62 30 [orig:140 vb0 ] [140])
        (unspec:V2DF [
                (reg/v:DF 62 30 [orig:123 b0 ] [123])
                (reg/v:DF 61 29 [orig:125 b1 ] [125])
            ] UNSPEC_VSX_CONCAT)) bug.c:18 920 {vsx_concat_v2df}
     (expr_list:REG_DEAD (reg/v:DF 61 29 [orig:125 b1 ] [125])
        (expr_list:REG_EQUIV (mem:V2DF (reg/v/f:DI 30 30 [orig:133 B ] [133])
[2 MEM[(__vector double *)B_2(D)]+0 S16 A128])
            (nil))))
(call_insn 29 31 72 2 (parallel [
            (set (reg:DF 33 1)
                (call (mem:SI (symbol_ref:DI ("log") [flags 0x41] 
<function_decl 0xfff92c41200 log>) [0 __builtin_log S4 A8])
                    (const_int 64 [0x40])))
            (use (const_int 0 [0]))
            (clobber (reg:SI 65 lr))
        ]) bug.c:17 509 {*call_value_nonlocal_aix64}
     (expr_list:REG_EH_REGION (const_int 0 [0])
        (nil))
    (expr_list:REG_NON_LOCAL_GOTO (use (reg:DF 33 1))
        (nil)))

So it looks like the scheduler is somehow thinking that reg 62 is non-volatile
when it's really volatile in V2DFmode and moving it before the call which ends
up clobbering it.

Still digging.