On Sun, Nov 16, 2003 at 09:41:58PM -0500, Albert Cahalan wrote: > Using 16-byte stack alignment? More?
We've had 16 byte stack alignment on ppc64 forever. > Keeping .text in the low 2 GB? Other stuff? -maddr32 does the text and static data in -2G..2G thing. Not in mainline gcc because the powerpc maintainers didn't like it. Anton is messing around with it in the kernel at the moment, but results so far are discouraging. We're probably hitting some cache problems due to mapping the kernel at -2G as well as 0xc << 60. Then again, it might be that David Edelsohn was right all along, and -maddr32 doesn't give us any performance increase. > Keeping anything in a 48-bit range? > (One less opcode than full 64-bit) No. ppc64 loads 64 bit addresses from the TOC. We don't build up 64 bit addresses from multiple insns each setting 16 bits at a time. > That TOC? CVS ld supports generation of multiple TOCs and stubs to adjust r2 as necessary. -mminimal-toc shouldn't be needed except in extreme cases. In some ways the TOC is a good thing. Think of it as a compiler generated GOT. Then realize that the compiler can do better than the linker in placing entries for good cache performance. On other Linux architectures, ld generates the GOT via a hash table traversal, which means entries are fairly well randomized. > Still using "funtion pointers" that aren't? I'm not sure what you mean here. > Anything left to improve? Plenty. For starters, I'd like to get rid of those pesky dot symbols. ie. A ".foo" symbol defined as well as a "foo" symbol for each function "foo". -- Alan Modra IBM OzLabs - Linux Technology Centre
