https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116815
--- Comment #17 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Kyrylo Tkachov <[email protected]>: https://gcc.gnu.org/g:c62176c0ea0d8139161ebb82fabfa0a02e493e2e commit r17-2923-gc62176c0ea0d8139161ebb82fabfa0a02e493e2e Author: Kyrylo Tkachov <[email protected]> Date: Thu Jul 30 10:36:40 2026 -0700 aarch64: Add missing CC clobber to max/min-of-add/sub patterns [PR116815] *aarch64_plus_within_<optab><mode>3_<ovf_commutate> and *aarch64_minus_within_<optab><mode>3 split into a flag-setting ADDS or SUBS followed by a CSEL, but their insn patterns do not say that they write the condition codes. For unsigned f (unsigned a, unsigned b, unsigned c, unsigned d) { unsigned s = a + b; unsigned m = s > a ? s : a; return (c < d && a < b) ? m : d; } combine produces (parallel [(set (reg:SI 0 x0) (umax:SI (plus:SI (reg:SI 107) (reg:SI 108)) (reg:SI 107))) (clobber (scratch:SI))]) which claims to leave the flags alone. The compare feeding the enclosing CCMP chain is therefore treated as still live and is removed, and split1 then emits an ADDS that overwrites the flags the outer CSEL reads: adds w1, w0, w1 csel w1, w1, w0, cc csel w0, w1, w3, cc so f (5, 7, 9, 2) returns 12 rather than 2. Add the (clobber (reg:CC CC_REGNUM)) that the neighbouring *aarch64_minmax_plus pattern already carries. The comparison is then kept: cmp w2, w3 ccmp w0, w1, 2, cc bcs .L2 adds w1, w0, w1 csel w3, w1, w0, cc Bootstrapped and tested on aarch64-none-linux-gnu. gcc/ChangeLog: PR middle-end/116815 * config/aarch64/aarch64.md (*aarch64_plus_within_<optab><mode>3_<ovf_commutate>): Add a clobber of CC_REGNUM. (*aarch64_minus_within_<optab><mode>3): Likewise. gcc/testsuite/ChangeLog: PR middle-end/116815 * gcc.target/aarch64/pr116815-4.c: New test. Signed-off-by: Kyrylo Tkachov <[email protected]>
