path: root/src/setjmp/x32
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2020-08-12setjmp: optimize longjmp prologuesAlexander Monakov-5/+3
Use a branchless sequence that is one byte shorter on 64-bit, same size on 32-bit. Thanks to Pete Cawley for suggesting this variant.
2020-08-11setjmp: optimize x86 longjmp epiloguesAlexander Monakov-4/+2
2020-08-11setjmp: avoid useless REX-prefix on xor %eax, %eaxAlexander Monakov-1/+1
2020-08-11setjmp: fix x86-64 longjmp argument adjustmentAlexander Monakov-3/+3
longjmp 'val' argument is an int, but the assembly is referencing 64-bit registers as if the argument was a long, or the caller was responsible for extending the argument. Though the psABI is not clear on this, the interpretation in GCC is that high bits may be arbitrary and the callee is responsible for sign/zero-extending the value as needed (likewise for return values: callers must anticipate that high bits may be garbage). Therefore testing %rax is a functional bug: setjmp would wrongly return zero if longjmp was called with val==0, but high bits of %rsi happened to be non-zero. Rewrite the prologue to refer to 32-bit registers. In passing, change 'test' to use %rsi, as there's no advantage to using %rax and the new form is cheaper on processors that do not perform move elimination.
2014-02-23import vanilla x86_64 code as x32rofl0r-0/+44