https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114211
--- Comment #10 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-13 branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:df3994a1be3565ad450d552dc94b696748a7807a commit r13-8447-gdf3994a1be3565ad450d552dc94b696748a7807a Author: Jakub Jelinek <ja...@redhat.com> Date: Tue Mar 5 10:32:38 2024 +0100 lower-subreg: Fix ROTATE handling [PR114211] On the following testcase, we have (insn 10 7 11 2 (set (reg/v:TI 106 [ h ]) (rotate:TI (reg/v:TI 106 [ h ]) (const_int 64 [0x40]))) "pr114211.c":8:5 1042 {rotl64ti2_doubleword} (nil)) before subreg1 and the pass decides to use (reg:DI 127 [ h ]) / (reg:DI 128 [ h+8 ]) register pair instead of (reg/v:TI 106 [ h ]). resolve_operand_for_swap_move_operator implements it by pretending it is an assignment from (concatn (reg:DI 127 [ h ]) (reg:DI 128 [ h+8 ])) to (concatn (reg:DI 128 [ h+8 ]) (reg:DI 127 [ h ])) The problem is that if the rotate argument is the same as destination or if there is even an overlap between the first half of the destination with second half of the source we emit incorrect code, because the store to (reg:DI 128 [ h+8 ]) overwrites what we need for source of the second move. The following patch detects that case and uses a temporary pseudo to hold the original (reg:DI 128 [ h+8 ]) value across the first store. 2024-03-05 Jakub Jelinek <ja...@redhat.com> PR rtl-optimization/114211 * lower-subreg.cc (resolve_simple_move): For double-word rotates by BITS_PER_WORD if there is overlap between source and destination use a temporary. * gcc.dg/pr114211.c: New test. (cherry picked from commit aed445b0fd0c7ed16124c61e7eb732992426f103)
