Comparison of escaped pointers too non-deterministic

[nunoplopes]

Here's a variant without zero-size types:

define i1 @src() {
    %a = alloca i64
    %a2 = alloca i32
    %gep = getelementptr i8, ptr %a, i64 8
    %cmp = icmp eq ptr %gep, %a2
    call void @escape(ptr %a, ptr %a2)
    ret i1 %cmp
}

define i1 @tgt() {
    %a = alloca i64
    %a2 = alloca i32
    %gep = getelementptr i8, ptr %a, i64 8
    %cmp = icmp eq ptr %gep, %a2
    call void @escape(ptr %a, ptr %a2)
    ret i1 false
}

declare void @escape(ptr, ptr)

This claims that two (non-zero-size) allocas can't have adjacent addresses.

Originally posted by @nikic in #1109 (comment)

[nunoplopes]

The issue is we related with the function call: if the pointers escape, their address may have been observed.