path: root/src/math/x86_64/asinl.s
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authorRich Felker <>2012-04-04 00:37:33 -0400
committerRich Felker <>2012-04-04 00:37:33 -0400
commit5bd0ab8af66829af74ed80cac767ce1c041fd767 (patch)
tree0e4c9ae49ee2aea74348ae866a2cdb0197ce2315 /src/math/x86_64/asinl.s
parent450f2c4a8515f2c5c9f469082bf69fdef009d26a (diff)
work around nasty gcc bug in the i386 syscall asm
when the "r" (register) constraint is used to let gcc choose a register, gcc will sometimes assign the same register that was used for one of the other fixed-register operands, if it knows the values are the same. one common case is multiple zero arguments to a syscall. this horribly breaks the intended usage, which is swapping the GOT pointer from ebx into the temp register and back to perform the syscall. presumably there is a way to fix this with advanced usage of register constaints on the inline asm, but having bad memories about hellish compatibility issues with different gcc versions, for the time being i'm just going to hard-code specific registers to be used. this may hurt the compiler's ability to optimize, but it will fix serious miscompilation issues. so far the only function i know what compiled incorrectly is getrlimit.c, and naturally the bug only applies to shared (PIC) builds, but it may be more extensive and may have gone undetected..
Diffstat (limited to 'src/math/x86_64/asinl.s')
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