[U-Boot] Relocation size penalty calculation

Graeme Russ
2009-10-08T20:58:05Z

On Fri, Oct 9, 2009 at 2:58 AM, J. William Campbell
<jwilliamcampbell@comcast.net> wrote:
> Graeme Russ wrote:
>>
>> Out of curiosity, I wanted to see just how much of a size penalty I am
>> incurring by using gcc -fpic / ld -pic on my x86 u-boot build. Here are
>> the results (fixed width font will help - its space, not tab, formatted):
>>
>> Section non-reloc reloc
>> ---------------------------------------
>> .text 000118c4 000137fc <- 0x1f38 bytes (~8kB) bigger
>> .rodata 00005bad 000059d0
>> .interp n/a 00000013
>> .dynstr n/a 00000648
>> .hash n/a 00000428
>> .eh_frame 00003268 000034fc
>> .data 00000a6c 000001dc
>> .data.rel n/a 00000098
>> .data.rel.ro.local n/a 00000178
>> .data.rel.local n/a 000007e4
>> .got 00000000 000001f0
>> .got.plt n/a 0000000c
>> .rel.got n/a 000003e0
>> .rel.dyn n/a 00001228
>> .dynsym n/a 00000850
>> .dynamic n/a 00000080
>> .u_boot_cmd 000003c0 000003c0
>> .bss 00001a34 00001a34
>> .realmode 00000166 00000166
>> .bios 0000053e 0000053e
>> =======================================
>> Total 0001d5dd 00022287 <- 0x4caa bytes (~19kB) bigger
>>
>> Its more than a 16% increase in size!!!
>>
>> .text accounts for a little under half of the total bloat, and of that,
>> the crude dynamic loader accounts for only 341 bytes
>>
>
> Hi Graeme,
> I would be interested in a third option (column), the x86 build with
> just -mrelocateable but NOT -fpic. It will not be definitive because there
> will be extra code that references the GOT and missing code to do some of
> the relocation, but it would still be interesting.

x86 does not have -mrelocatable. This is a PPC only option :(

>
> Best Regards,
> Bill Campbell
>>
>> Have any metrics been done for PPC?
>>
>> Regards,
>>
>> Graeme

Once the reloc branch has been merged, how many arches are left which do
not support relocation?

Regards,

Graeme