@FiloSottile suggested that a recent mailing list post be moved to an issue, so here goes:

Jan Mercl reports that this code will miscompile on ARM:

package main

import "fmt"

var x = [4]int32{((-0x7fffffff - 1) / 2), 0x7fffffff, 2, 4} /* 20041210-1.c:5:5 */

func main() { /* 20041210-1.c:8:1: */
        if x[0] < x[1] {
                if x[2]&x[3] < 0 {
                        panic(fmt.Errorf("%v & %v = %v, < 0 ? %v", x[2], x[3], x[2]&x[3], x[2]&x[3] < 0))
                }
        }
}

Running the same code on 386 vs arm shows success on 386 and panics on arm. I've confirmed this is the case with 1.15.5, and Meng Zhuo confirmed it to be happening on 1.13, so it is at least a somewhat oldish bug.

The current issue title is vague because I haven't looked into what's actually happening yet. And I haven't yet assessed the security implications, either, but one can start imagining worrisome corner cases.

CC @rsc @cherrymui @ianlancetaylor @aclements