LLVM arbitrary precision integer

Question

LLVM language reference states that

The integer type is a very simple type that simply indicates an arbitrary bit width for the desired integer type. Any bit width from 1 bit to 2 ²³ -1 (about 8 million).

Does this mean that I can use arbitrary fixed lengths for free? To say, if I declare i100, will I have a variable with a width of 100 bits?

Answer 1

, "", LLVM . , CPU.

i100, 100 . , , CPU . 64- , IR :

define i64 @add(i64 %a, i64 %b) {
  %1 = add i64 %a, %b
  ret i64 %1
}

, :

add:                                    # @add
    .cfi_startproc
# BB#0:
    addq    %rsi, %rdi
    movq    %rdi, %rax
    ret

, , , i1024 IR:

define i1024 @add(i1024 %a, i1024 %b) {
  %1 = add i1024 %a, %b
  ret i1024 %1
}

x86-64 - , mov .

add:                                    # @add
    .cfi_startproc
# BB#0:
    pushq   %r15
.Ltmp5:
    .cfi_def_cfa_offset 16
    pushq   %r14
.Ltmp6:
    .cfi_def_cfa_offset 24
    pushq   %r12
.Ltmp7:
    .cfi_def_cfa_offset 32
    pushq   %rbx
.Ltmp8:
    .cfi_def_cfa_offset 40
.Ltmp9:
    .cfi_offset %rbx, -40
.Ltmp10:
    .cfi_offset %r12, -32
.Ltmp11:
    .cfi_offset %r14, -24
.Ltmp12:
    .cfi_offset %r15, -16
    movq    40(%rsp), %r10
    addq    128(%rsp), %rsi
    adcq    136(%rsp), %rdx
    adcq    144(%rsp), %rcx
    adcq    152(%rsp), %r8
    adcq    160(%rsp), %r9
    movq    96(%rsp), %r14
    movq    104(%rsp), %r11
    movq    80(%rsp), %r12
    movq    88(%rsp), %r15
    adcq    168(%rsp), %r10
    movq    64(%rsp), %rax
    movq    72(%rsp), %rbx
    movq    %rsi, (%rdi)
    movq    %rdx, 8(%rdi)
    movq    48(%rsp), %rsi
    movq    56(%rsp), %rdx
    movq    %rcx, 16(%rdi)
    movq    %r8, 24(%rdi)
    movq    %r9, 32(%rdi)
    movq    112(%rsp), %rcx
    movq    120(%rsp), %r8
    adcq    176(%rsp), %rsi
    adcq    184(%rsp), %rdx
    adcq    192(%rsp), %rax
    adcq    200(%rsp), %rbx
    adcq    208(%rsp), %r12
    adcq    216(%rsp), %r15
    adcq    224(%rsp), %r14
    movq    %r10, 40(%rdi)
    movq    %rsi, 48(%rdi)
    movq    %rdx, 56(%rdi)
    movq    %rax, 64(%rdi)
    movq    %rbx, 72(%rdi)
    movq    %r12, 80(%rdi)
    movq    %r15, 88(%rdi)
    movq    %r14, 96(%rdi)
    adcq    232(%rsp), %r11
    movq    %r11, 104(%rdi)
    adcq    240(%rsp), %rcx
    movq    %rcx, 112(%rdi)
    adcq    248(%rsp), %r8
    movq    %r8, 120(%rdi)
    popq    %rbx
    popq    %r12
    popq    %r14
    popq    %r15
    ret