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bdb0817599
we have to avoid using ebx unconditionally in asm constraints for
i386, because gcc 3 and 4 and possibly other simplistic compilers
(pcc?) implement PIC via making ebx a fixed-use register, and disallow
its use for anything else. rather than hard-coding knowledge of which
compilers work (at least gcc 5+ and clang), perform a configure test;
this should give us the good codegen on any new compilers we don't yet
know about.
swapping ebx and edx is kept for 1- and 2-arg syscalls because it
avoids having any spills/stack-frame at all in small functions. for
6-arg, if ebx is directly usable, the complex shuffling introduced in
commit
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| arm | ||
| generic | ||
| i386 | ||
| m68k | ||
| microblaze | ||
| mips | ||
| mips64 | ||
| mipsn32 | ||
| or1k | ||
| powerpc | ||
| powerpc64 | ||
| s390x | ||
| sh | ||
| x32 | ||
| x86_64 | ||