[Issue 5581] [64-bit] Wrong code with bitwise operations on bools

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=5581



--- Comment #1 from David Simcha <dsimcha at yahoo.com> 2011-02-15 11:29:13 PST ---
I think this is actually a long-standing, hard to reproduce, non-deterministic
codegen bug that strikes on 32-bit as well, though due to the non-deterministic
nature of it, under different circumstances.  Here's some code that segfaults
on 32 with stock DMD 2.051, only with -O -inline -release enabled.  This is
slightly less reduced than the 64 version because anytime I try to reduce it
more, the bug goes away.

import std.stdio;

bool comp(long a, long b) { return a < b; }

size_t medianOf3(T)(T[] data) {
    // Removing this print statement changes the result.
    stderr.writeln(data[0], '\t', data[$ / 2], '\t', data[$ - 1]);
    immutable size_t mid = data.length / 2;
    immutable uint result = ((cast(uint) (comp(data[0], data[mid]))) << 2) |
                            ((cast(uint) (comp(data[0], data[$ - 1]))) << 1) |
                            (cast(uint) (comp(data[mid], data[$ - 1])));

    assert(result != 2 && result != 5 && result < 8); // Cases 2, 5 can't
happen.
    switch(result) {
        case 1:  // 001
        case 6:  // 110
            return data.length - 1;
        case 3:  // 011
        case 4:  // 100
            return 0;
        case 0:  // 000
        case 7:  // 111
            return mid;
        default:
            assert(0);
    }
    assert(0);
}


void main() {
    long[] stuff = [4602111750194969114, 4591797823464657051,
4579622497201165564];
    medianOf3(stuff);
}

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------