Hello, for the reduced code below, its second loop is redundant. There seems to be a missed optimization.

https://godbolt.org/z/McqeYdnfY

int a[1024];
int b[1024];

void func()
{
    for (int i = 0; i < 1024; i+=1) {
        a[i] = b[i] * 2;
    }

    for (int i = 0; i < 1024; i+=1) {
        a[i] = b[i] * 2;
    }
}

GCC -O3:
func:
        xor     eax, eax
.L2:
        movdqa  xmm0, XMMWORD PTR b[rax]
        add     rax, 16
        pslld   xmm0, 1
        movaps  XMMWORD PTR a[rax-16], xmm0
        cmp     rax, 4096
        jne     .L2
        xor     eax, eax
.L3:
        movdqa  xmm0, XMMWORD PTR b[rax]
        add     rax, 16
        pslld   xmm0, 1
        movaps  XMMWORD PTR a[rax-16], xmm0
        cmp     rax, 4096
        jne     .L3
        ret

Expected code:
func:
        xor     eax, eax
.L2:
        movdqa  xmm0, XMMWORD PTR b[rax]
        add     rax, 16
        pslld   xmm0, 1
        movaps  XMMWORD PTR a[rax-16], xmm0
        cmp     rax, 4096
        jne     .L2
        ret

Thank you very much for your time and effort! We look forward to hearing from you.