29.6. x86 shift and rotate instructions
Intel 64 and IA-32 Architectures Software Developer’s Manuals Volume 1 5.1.5 "Shift and Rotate Instructions"
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SHift left or Right and insert 0.
CF == the bit that got shifted out.
Application: quick unsigned multiply and divide by powers of 2.
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Application: signed multiply and divide by powers of 2.
Mnemonics: Shift Arithmetic Left and Right
Keeps the same sign on right shift.
Not directly exposed in C, for which signed shift is undetermined behavior, but does exist in Java via the
>>>operator. C compilers can omit it however.SHL and SAL are exactly the same and have the same encoding: https://stackoverflow.com/questions/8373415/difference-between-shl-and-sal-in-80x86/56621271#56621271
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userland/arch/x86_64/rol.S: ROL and ROR
Rotates the bit that is going out around to the other side.
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userland/arch/x86_64/rol.S: RCL and RCR
Like ROL and ROR, but insert the carry bit instead, which effectively generates a rotation of 8 + 1 bits. TODO application.