C Compiler generates wrong code for while loop

[gopherbot]

by [email protected]:

Before filing a bug, please check whether it has been fixed since
the latest release: run "hg pull -u" and retry what you did to
reproduce the problem.  Thanks.

What steps will reproduce the problem?
1. 6c -S this.c
--SNIP--
typedef unsigned long long uint64;
typedef char int8;
static void
puthex(uint64 n, uint64 l, int8* t) {
        static int8 hexdigits[] = "0123456789ABCDEF";
        while(l--) {
                *--t = hexdigits[n & 0xF];
                n >>= 4;
        }
}
--SNAP--
2. inspect output code
3. notice that an infinite loop (no conditional jump!) is generated

What is the expected output?
A conditional jump.

What do you see instead?
An infinite loop.

Which compiler are you using (5g, 6g, 8g, gccgo)?
6c

Which operating system are you using?
Linux toshiba 2.6.34-12-default #1 SMP 2010-06-29 02:39:08 +0200 i686 i686 i386 GNU/Linux


Which revision are you using?  (hg identify)
09ab865d875c+

Please provide any additional information below.
This code can be used to actually run it.
--SNIP--
void main·main(int argc, char** argv) {
        int8 buf[3] = {0, 0, 0};
        runtime·prints("Hello, World\n");
        puthex(0x42, 2, buf+2);
        runtime·prints(buf);
}

void main·init() {
}
--SNAP--
No surprise, it crashes.
A similar program works fine with GCC (ugh feels bad to say that).

[gopherbot]

Comment 1 by [email protected]:

I just noticed that a simple
        while(x) {x--;}
is sufficient to trigger the bug.

[gopherbot]

Comment 2 by [email protected]:

I just noticed that a simple
        while(x) {x--;}
with uint64 x is sufficient to trigger the bug.

[robpike]

Comment 3:

Owner changed to [email protected].

Status changed to Accepted.

[gopherbot]

Comment 4 by ejsherry:

I think this has been fixed.
http://code.google.com/p/go/source/detail?r=bb2d8b3cdc

[gopherbot]

Comment 5 by [email protected]:

Indeed, this seems to be fixed.
I apologize for the inconvenience

[rsc]

Comment 6:

Status changed to Retracted.