On Wednesday 25 June 2008 18:01, Mikulas Patocka wrote: > > Ingo's suggestion to talk to gcc people to remedy > > insane call convention sounds as a more workable solution. > > > > BTW, i386 uses regparm call convention, is similar trick > > possible for sparc64? > > Sparc64 has register windows: it passes arguments in registers, but it > must allocate space for that registers. If the call stack is too deep (8 > levels), the CPU runs out of registers and starts spilling the registers > of the function 8-levels-deep to the stack. > > The stack usage could be reduced to 176 bytes with little work from gcc > developers and to 128 bytes with more work (ABI change). If you wanted to Wow, it's nearly x2 reduction. ABI change in not a problem for kernel, since it is a "freestanding application". Exactly like i386 switched to regparm, which is a different ABI. > go below 128 bytes, you could use one register to indicate number of used > registers and modify the spill/fill handlers to load only that number of > registers and reduce the stack usage even more --- that would be a big > code change in both gcc and linux. -- vda -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
