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>
