optimization/8204: gcj -O2 to native reorders certain instructions improperly.

[rsdio@metastatic.org]

>Number:         8204
>Category:       optimization
>Synopsis:       gcj -O2 to native reorders certain instructions improperly.
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Oct 11 18:36:00 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     rsdio@metastatic.org
>Release:        gcc-3.2
>Organization:
>Environment:
linux-2.4.18-i686.
gcc-3.2 Configured with: ../gcc-3.2/configure --enable-languages=c,c++,f77,java,objc
>Description:
A statement such as:

String s; int i;
while (i < s.length) {
   result[j++] = (byte) ((f(s.charAt(i++)) << 4) | (f(s.charAt(i++))));
}

(f is e.g. a method to turn a hex digit [0-9A-Fa-f] into an integer)

inverts the calls to 'f()' such that the result from the SECOND call is shifted left, not the first as expected.

This bug only appears with native compilation with level 2 optimization or above. It appears only within loops and only with the two method calls.
>How-To-Repeat:
gcj -O2 --classpath=/path/to/libgcj.jar --main=bug -o bug bug.java ; ./bug

Where 'bug.java' is the attached sample. This should print out 8 lines that all say 'false'. The expected behavior is 8 lines that say 'true'.
>Fix:
Unknown.
>Release-Note:
>Audit-Trail:
>Unformatted:
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