On Thu, 2009-10-08 at 22:54 +1100, 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
Have any metrics been done for PPC?
Things actually improve a little bit when we use -mrelocatable and get rid of all the manual "+= gd->reloc_off" fixups:
1) Top of mainline on XPedite5370: text data bss dec hex filename 308612 24488 33172 366272 596c0 u-boot
2) Top of "reloc" branch on XPedite5370 (ie -mrelocatable): text data bss dec hex filename 303704 28644 33156 365504 593c0 u-boot
For fun: 3) #2 but with s/-mrelocatable/-fpic/ (probably doesn't boot): text data bss dec hex filename 303704 24472 33156 361332 58374 u-boot
There may be some other changes that affect the size between mainline and "reloc", but their sizes are in the same general ballpark.
Best, Peter