https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114929

--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Gaius Mulley <ga...@gcc.gnu.org>:

https://gcc.gnu.org/g:a561dc0f6c7085e102fe9e9b6abd7f2138512576

commit r15-122-ga561dc0f6c7085e102fe9e9b6abd7f2138512576
Author: Gaius Mulley <gaiusm...@gmail.com>
Date:   Fri May 3 01:22:10 2024 +0100

    PR modula2/114929 for loop fails to iterate down to zero when using a
cardinal type

    There is a bug in the for loop control code which is exposed when an
    unsigned type is used in the iterator variable.  See
    gm2/pim/run/pass/testforloopzero[234].mod.  The bug is in the
    calculation of the last iterator value.  The bug fix is to avoid using
    negative expressions when calculating the last iterator value with a
    negative step value.  This patch detects if e1, e2, step value are all
    constant, in which case the ztype is used internally and there is no
    overflow.  If the last iterator value is held in a variable then it
    uses a different method to calculate the last iterator depending upon
    the sign of the step value.

    gcc/m2/ChangeLog:

            PR modula2/114929
            * gm2-compiler/M2LangDump.mod (GenQualidentSymString): Add
            missing return result into identstr.
            * gm2-compiler/M2Quads.mod (ForLoopLastIteratorVariable): New
            procedure.
            (ForLoopLastIteratorConstant): Ditto.
            (ForLoopLastIterator): Ditto.
            (BuildForToByDo): Remove LastIterator calculation and call
            ForLoopLastIterator instead.
            (FinalValue): Replace with ...
            (LastIterator): ... this.

    gcc/testsuite/ChangeLog:

            PR modula2/114929
            * gm2/pim/run/pass/testforloopzero.mod: New test.
            * gm2/pim/run/pass/testforloopzero2.mod: New test.
            * gm2/pim/run/pass/testforloopzero3.mod: New test.
            * gm2/pim/run/pass/testforloopzero4.mod: New test.

    Signed-off-by: Gaius Mulley <gaiusm...@gmail.com>

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