https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116024
--- Comment #12 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jeff Law <l...@gcc.gnu.org>: https://gcc.gnu.org/g:52fdf1e7eb89a148a9cdd1daade524f4540ab5fa commit r15-4189-g52fdf1e7eb89a148a9cdd1daade524f4540ab5fa Author: Artemiy Volkov <artemiy.vol...@synopsys.com> Date: Tue Oct 8 18:06:23 2024 -0600 tree-optimization/116024 - simplify some cases of X +- C1 cmp C2 Whenever C1 and C2 are integer constants, X is of a wrapping type, and cmp is a relational operator, the expression X +- C1 cmp C2 can be simplified in the following cases: (a) If cmp is <= and C2 -+ C1 == +INF(1), we can transform the initial comparison in the following way: X +- C1 <= C2 -INF <= X +- C1 <= C2 (add left hand side which holds for any X, C1) -INF -+ C1 <= X <= C2 -+ C1 (add -+C1 to all 3 expressions) -INF -+ C1 <= X <= +INF (due to (1)) -INF -+ C1 <= X (eliminate the right hand side since it holds for any X) (b) By analogy, if cmp if >= and C2 -+ C1 == -INF(1), use the following sequence of transformations: X +- C1 >= C2 +INF >= X +- C1 >= C2 (add left hand side which holds for any X, C1) +INF -+ C1 >= X >= C2 -+ C1 (add -+C1 to all 3 expressions) +INF -+ C1 >= X >= -INF (due to (1)) +INF -+ C1 >= X (eliminate the right hand side since it holds for any X) (c) The > and < cases are negations of (a) and (b), respectively. This transformation allows to occasionally save add / sub instructions, for instance the expression 3 + (uint32_t)f() < 2 compiles to cmn w0, #4 cset w0, ls instead of add w0, w0, 3 cmp w0, 2 cset w0, ls on aarch64. Testcases that go together with this patch have been split into two separate files, one containing testcases for unsigned variables and the other for wrapping signed ones (and thus compiled with -fwrapv). Additionally, one aarch64 test has been adjusted since the patch has caused the generated code to change from cmn w0, #2 csinc w0, w1, wzr, cc (x < -2) to cmn w0, #3 csinc w0, w1, wzr, cs (x <= -3) This patch has been bootstrapped and regtested on aarch64, x86_64, and i386, and additionally regtested on riscv32. gcc/ChangeLog: PR tree-optimization/116024 * match.pd: New transformation around integer comparison. gcc/testsuite/ChangeLog: * gcc.dg/tree-ssa/pr116024-2.c: New test. * gcc.dg/tree-ssa/pr116024-2-fwrapv.c: Ditto. * gcc.target/aarch64/gtu_to_ltu_cmp_1.c: Adjust.
