#include <stdio.h>
/* compiled in gcc with options -g -Wall */
int main(){
    float a=1.1;
    printf("%lf\n",a);
    return 0;
}
    

format ELF64 executable 3
entry start

include 'import64.inc'

interpreter '/lib64/ld-linux-x86-64.so.2'
needed 'libc.so.6'
import printf,exit

segment readable executable

start:
push   rbp
mov    rbp,rsp
sub    rsp,0x10
mov    eax,0x3f8ccccd  ; = 1.1
mov    DWORD  [rbp-0x4],eax
movss  xmm0,DWORD  [rbp-0x4]
cvtps2pd xmm0,xmm0
mov    eax,pf
mov    rdi,rax
mov    eax,0x0  ; This was 0x1 in the disassembly, but that caused SIGSEGV
call   [printf]
mov    eax,0x0  
call [exit]

segment readable writeable
pf db '%lf',0xa,0
    

format elf64 executable 3
include 'import64.inc'

interpreter '/lib64/ld-linux-x86-64.so.2'
needed 'libc.so.6'
import printf,exit

segment readable executable
entry start

start:
push   rbp
mov    rbp,rsp
sub    rsp,0x8 ; stack has to be 16 byte aligned for printf
mov    eax,0x3f8ccccd  ; = 1.1 
mov    DWORD  [rbp-0x4],eax
movss  xmm0,DWORD  [rbp-0x4]
cvtps2pd xmm0,xmm0
mov    eax,pf
mov    rdi,rax
mov    eax,1  ; eax -> number of float arguments
call   [printf]
xor    edi,edi
call [exit]

segment readable writeable
pf db '%lf',0xa,0

    

mov eax,1.1    

Maybe he is just paranoid like me and want to be extremely sure the value is correct.

How do you know that 0x3f8ccccd is "correct"? Are you just trusting the C compiler to always give you "correct" values? Why trust it more than fasm, or Windows calculator?