GNU Info

(as.info)i386-Regs

---

Next: i386-Prefixes Prev: i386-Mnemonics Up: i386-Dependent

---

Enter node , (file) or (file)node

Register Naming
---------------

   Register operands are always prefixed with `%'.  The 80386 registers
consist of

   * the 8 32-bit registers `%eax' (the accumulator), `%ebx', `%ecx',
     `%edx', `%edi', `%esi', `%ebp' (the frame pointer), and `%esp'
     (the stack pointer).

   * the 8 16-bit low-ends of these: `%ax', `%bx', `%cx', `%dx', `%di',
     `%si', `%bp', and `%sp'.

   * the 8 8-bit registers: `%ah', `%al', `%bh', `%bl', `%ch', `%cl',
     `%dh', and `%dl' (These are the high-bytes and low-bytes of `%ax',
     `%bx', `%cx', and `%dx')

   * the 6 section registers `%cs' (code section), `%ds' (data
     section), `%ss' (stack section), `%es', `%fs', and `%gs'.

   * the 3 processor control registers `%cr0', `%cr2', and `%cr3'.

   * the 6 debug registers `%db0', `%db1', `%db2', `%db3', `%db6', and
     `%db7'.

   * the 2 test registers `%tr6' and `%tr7'.

   * the 8 floating point register stack `%st' or equivalently
     `%st(0)', `%st(1)', `%st(2)', `%st(3)', `%st(4)', `%st(5)',
     `%st(6)', and `%st(7)'.  These registers are overloaded by 8 MMX
     registers `%mm0', `%mm1', `%mm2', `%mm3', `%mm4', `%mm5', `%mm6'
     and `%mm7'.

   * the 8 SSE registers registers `%xmm0', `%xmm1', `%xmm2', `%xmm3',
     `%xmm4', `%xmm5', `%xmm6' and `%xmm7'.

   The AMD x86-64 architecture extends the register set by:

   * enhancing the 8 32-bit registers to 64-bit: `%rax' (the
     accumulator), `%rbx', `%rcx', `%rdx', `%rdi', `%rsi', `%rbp' (the
     frame pointer), `%rsp' (the stack pointer)

   * the 8 extended registers `%r8'-`%r15'.

   * the 8 32-bit low ends of the extended registers: `%r8d'-`%r15d'

   * the 8 16-bit low ends of the extended registers: `%r8w'-`%r15w'

   * the 8 8-bit low ends of the extended registers: `%r8b'-`%r15b'

   * the 4 8-bit registers: `%sil', `%dil', `%bpl', `%spl'.

   * the 8 debug registers: `%db8'-`%db15'.

   * the 8 SSE registers: `%xmm8'-`%xmm15'.