This page is focused on the less common x86 instructions. The less common instructions are infrequently used simply because they are not in a programmer's rapidly accessible knowledge bank. Enjoy these instructions. (This is a work in progress. Occasionally I add to this collect of instructions.)
movsxd Copies an integer from a 32-bit GPR to a 64-bit GPR. Preserves sign and numeric value.
Example: movsxd r14, ecx
bt Copies a single bit from a GPR to carry flag CF
Example: bt rbx, 13
bts Sets the numbered bit to 1
Example: bts rdx, 23
btr Clears the numbered bit to 0
Example: btr rbx, 9
rol rotate the data in a GPR a certain number of places to the left
Example: rol r8, 6
ror rotate the data in a GPR a certain number of places to the right
Example: ror rdi, 20
shl shift all bits to the left a given number of bits; may result in loss of sign
Example: shl rdi, 40
shr shift all bits to the right a given number of bits; may result in loss of sign
Example: shr rsi, 6
lea returns the physical address of something in memory
Example: Let scores resw 500 be an array of word-size cells.
Then mov [scores+362*2], 189 copies 189 into cell number 362.
lea rax, [scores+362*2] places the physical address of the cell number 362 into rax.