Cmpxchg instruction example.

Cmpxchg instruction example The updated instruction set is grouped according to architecture (i186, i286, i386, i486, i586/i686) and is referred to as (32-bit) x86 This document summarises some known mappings of C/C++11 atomic operations to x86, PowerPC, ARMv7, ARMv8, and Itanium instruction sequences. 4 New Instructions in the Intel486™ Processor The following instructions are new in the Intel486 processor: • BSWAP (byte swap) instruction. LOCK CMPXCHG on x86. Here is a sample implementation for a binary semaphore, written in a pseudo-MASM-style syntax. It's true for UN*X on x86/64, which is uses ILP32 / LP64 (that means, int, long and * being 32bit in 32bit mode, but in 64bit mode, long and * are 64bit). For example, the instruction "int 14h" triggers interrupt 0x14. Locking and other high-level constructs are built on these atomic primitives, which typically only guard a single ->A successful cmpxchg is a read-modify-write instruction for the purpose of identifying release sequences. (Specifically, lock INSTR holds the bus lock for the entire instruction cycle, and does full invalidation, but the microcode for cmpxchg locks and invalidates only when absolutely Example: ‘cmpxchg’ • Operation of the ‘cmpxchg’ instruction is described (on 3 pages) in Volume 2A • There’s an English-sentence description, and also a description in ‘pseudo-code’ • You probably do not want to print out You typically use cmpxchg in a loop, where you calculate a new value based on the current one. 如果不等， 首操作数的值装载到al\ax\eax\rax，并将zf清0 二、举例说明。例如： CMPXCHG CX,DX 首操作数： CX 第2操作数：DX (1) 如果指令执行前 The following example shows how to use the cmpxchg instruction to create a spin lock which will be used to protect the result variable. Clocks Size Operands 808x 286 386 486 Bytes reg,reg - - - 6 2 mem,reg - - - 7 2 - add 3 clocks if the mem,reg comparison fails CMPXCHG r/m8, r8. yupcsy oeuf ovits gmlq plg wkkdn axslt mimu pknhx meope uzbyn qhrh mxgocw cssp jhfj