Re: [patch] use .gnu.attributes to detect e500 machine type

[Aleksandar Ristovski <aristovski@qnx.com>]

any thoughts?


Aleksandar Ristovski wrote:
> Hello,
> 
> 
> The patch introduces determining e500 cpu from .gnu.attributes; if gnu 
> attributes section is not present, fall-back to the old way of checking 
> the presence of .PPC.EMB.apuinfo section.
> 
> It also introduces a function for "show powerpc vector-abi" to print 
> both ABI being used and if different, global setting (output can be seen 
> below). This could be a separate patch - let me know if you want it 
> separately.
> 
> Background of the patch:
> 
> Currently, gdb relies on presence .PPC.EMB.apuinfo section. This is not 
> completely correct since apuinfo section can contain information about 
> any APU instructions present, and not only SPE. So we could have a 
> binary with .PPC.EMB.apuinfo section and without SPE APU. Further, 
> .PPC.EMB.apuinfo may not be present at all even if -me500 is specified. 
> This is due to gas emitting this section only if it encounters SPE APU 
> instructions in the assembly.
> 
> .gnu.attributes section records user setting, whether there were SPE 
> instructions generated or not. We use gnu object attributes in rs6000 
> already (for determining vector-abi and float-point abi).
> 
> The only problem with .gnu.attribute is that if binary is compiled with 
> pre-4.3 gcc, .gnu.attributes section does not get generated at all. 
> (.gnu_attribute was added in 4.3). This is why we fall-back to 
> .PPC.EMB.apuinfo presence.
> 
> Results of the patch:
> 
> After starting gdb, no executable:
> (gdb) show powerpc vector-abi
> The vector ABI in use is "generic". Default setting is "auto".
> (gdb) file /mnt/win/ppcspetest_g
> Reading symbols from /mnt/win/ppcspetest_g...done.
> (gdb) show powerpc vector-abi
> The vector ABI in use is "spe". Default setting is "auto".
> 
> ** If user overrides selected vector-abi, this is the display:
> (gdb) set powerpc vector-abi generic
> (gdb) show powerpc vector-abi
> The vector ABI is "generic"
> 
> 
> "show powerpc vector-abi" will now display both selected vector-abi and 
> user setting ("Default setting is ..."). Only if the two concide, it 
> will only say "Target vector ABI is ...").
> 
> 
> Thanks,
> 
> Aleksandar Ristovski
> QNX Software Systems
> 
> 
> ChangeLog
> * rs6000-tdep.c (rs6000_gdbarch_init): Use .gnu.attributes to see
> if this is a e500 binary (with SPE APU).
> (powerpc_show_vector_abi): New function.
> (_initialize_rs6000_tdep): Use powerpc_show_vector_abi.
> 
>