Debugging Tools for Windows

x64 Instructions

Most x86 instructions continue to be valid for x64 in 64-bit mode. Some rarely-used operations are no longer supported in 64-bit mode, such as:

binary-coded decimal arithmetic instructions: AAA, AAD, AAM, AAS, DAA, DAS
BOUND
PUSHAD and POPAD
most operations that dealt with segment registers, such as PUSH DS and POP DS. (Operations that use the FS or GS segment registers are still valid.)

The x64 instruction set includes recent additions to the x86, such as SSE 2. Programs compiled for x64 can freely use these instructions.

The x64 provides new variants of the MOV instruction that can handle 64-bit immediate constants or memory addresses.

MOV	r,#n	r = #n
MOV	rax, m	Move contents at 64-bit address to rax.
MOV	m, rax	Move contents of rax to 64-bit address.

The x64 also provides a new instruction to sign-extend 32-bit operands to 64 bits.

MOVSXD

r1, r/m

Move DWORD with sign extension to QWORD.

Ordinary MOV operations into 32-bit subregisters automatically zero extend to 64 bits, so there is no MOVZXD instruction.

Two SSE instructions can be used to move 128-bit values (such as GUIDs) from memory to an xmmn register or vice versa.

MOVDQA	r1/m, r2/m	Move 128-bit aligned value to xmmn register, or vice versa.
MOVDQU	r1/m, r2/m	Move 128-bit value (not necessarily aligned) to register, or vice versa.

CDQE	Convert dword (eax) to qword (rax).
CQO	convert qword (rax) to oword (rdx:rax).

MOVSQ	Move qword from rsi to rdi.
CMPSQ	Compare qword at rsi with rdi.
SCASQ	Scan qword at rdi. Compares qword at rdi to rax.
LODSQ	Load qword from rsi into rax.
STOSQ	Store qword to rdi from rax.

Build machine: CAPEBUILD