Paolo Bonzini wrote:
Compared to the slow idivl, abs could be negligible, right. However, abs
does introduce new data dependence which might add a noticeable cost.
Is there an abs instruction in the i386 instruction set?
No, the closest thing (input in eax, output in edx) is
cltq
addl %edx, %eax
xorl %eax, %edx
But the register allocations constraints are pretty heavy considering
that idivl already puts strain on the RA.
Paolo
Paolo, what does the cltq instruction do? I cannot find it in my x86
reference manuals...
