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64-Bit Architectures

64-Bit Architectures. CS 105 “Tour of the Black Holes of Computing!”. Topics 64-bit data New registers and instructions Calling conventions. Data Representations: IA32 + x86-64. Sizes of C Objects (in Bytes) C Data Type Typical 32-bit Intel IA32 x86-64 unsigned 4 4 4

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64-Bit Architectures

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  1. 64-Bit Architectures CS 105“Tour of the Black Holes of Computing!” • Topics • 64-bit data • New registers and instructions • Calling conventions

  2. Data Representations: IA32 + x86-64 Sizes of C Objects (in Bytes) C Data Type Typical 32-bit Intel IA32 x86-64 • unsigned 4 4 4 • int 4 4 4 • long int 4 4 8 • char 1 1 1 • short 2 2 2 • float 4 4 4 • double 8 8 8 • long double 8 10/12 16 • char * 4 4 8Or any other pointer

  3. x86-64 Integer Registers %rax %r8 Oh. %eax %ax ah al %r8d %r8w r8b • Extend existing registers. Add 8 new ones. • Make %ebp/%rbp general purpose %r8w %rbx %r9 %ebx %bx bh bl %r9d %r9w r9b %r9w %rcx %r10 %ecx ch %cx cl %r10d %r10w r10b %r10w My. %rdx %r11 %edx dh %dx dl %r11d %r11w r11b %dx %r11w %rsi %r12 %esi %si sil %r12d %r12w r12b %si %r12w %rdi %r13 %edi %di dil %r13d %r13w r13b %di God. %rsp %r14 %esp %sp spl %r14d %r14w r14b %sp %rbp %r15 %ebp %bp bpl %r15d %r15w r15b %bp

  4. x86-64 Integer Registers %rax %r8 %eax %r8d • Extend existing registers. Add 8 new ones. • Make %ebp/%rbp general purpose %rbx %r9 %ebx %r9d %rcx %r10 %ecx %r10d %rdx %r11 %edx %r11d %rsi %r12 %esi %r12d %rdi %r13 %edi %r13d %rsp %r14 %esp %r14d %rbp %r15 %ebp %r15d

  5. Instructions • Long word l (4 Bytes) ↔ Quad word q (8 Bytes) • New instructions: • movl → movq • addl → addq • sall → salq • movzbq, movslq • etc. • 32-bit instructions that generate 32-bit results • Set higher order bits of destination register to 0 • Example: addl, movl (thus nomovzlq)

  6. Swap in 32-bit Mode swap: pushl %ebp movl %esp,%ebp pushl %ebx movl 12(%ebp),%ecx movl 8(%ebp),%edx movl (%ecx),%eax movl (%edx),%ebx movl %eax,(%edx) movl %ebx,(%ecx) movl -4(%ebp),%ebx movl %ebp,%esp popl %ebp ret void swap(int *xp, int *yp) { int t0 = *xp; int t1 = *yp; *xp = t1; *yp = t0; } Setup Body Finish

  7. Swap in 64-bit Mode • Operands passed in registers (why useful?) • First (xp) in %rdi, second (yp) in %rsi • 64-bit pointers • No stack operations required • 32-bit data • Data held in registers %eax and %edx • movl operation void swap(int *xp, int *yp) { int t0 = *xp; int t1 = *yp; *xp = t1; *yp = t0; } swap: movl (%rdi), %edx movl (%rsi), %eax movl %eax, (%rdi) movl %edx, (%rsi) retq

  8. Swap Long Ints in 64-bit Mode • 64-bit data • Data held in registers %rax and %rdx • movq operation • Otherwise same void swap_l (long int *xp, long int *yp) { long int t0 = *xp; long int t1 = *yp; *xp = t1; *yp = t0; } swap_l: movq (%rdi), %rdx movq (%rsi), %rax movq %rax, (%rdi) movq %rdx, (%rsi) retq

  9. New Calling Conventions • Most procedures no longer need stack frame • First six arguments passed in registers • Register %rbp available for general use • Stack frame accessed via %rsp • 128 bytes below %rsp usable by function (“red zone”)

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