[Issue 9844] DMD (-m64) int->long conversion bug

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=9844


John Colvin <john.loughran.colvin at gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |john.loughran.colvin at gmail.
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--- Comment #3 from John Colvin <john.loughran.colvin at gmail.com> 2013-04-03 20:05:58 BST ---
A simplified test:

import std.stdio;
void foo() {
    int a = -1;
    long b = -1;
    writeln(a); // -1
    writeln(b); // (2^32)-1
}

The mistake only happens when a and b are initialised to the same negative
value.

In light of that and after some perusing of the asm generated, it appears that
dmd goes "-1 == -1" and uses the same value for a as for b, except of course
that doesn't work because of the different sign bit positions for int and long.

e.g.

mov    eax,0xffffffff              //rax is now 0x00000000ffffffff
mov    DWORD PTR [rbp-0x10],eax
mov    QWORD PTR [rbp-0x8],rax


I don't get any bug with ldc, so it's probably either a recent regression or a
backend problem.

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