https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100056
--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:39d23b7960e4efb11bbe1eff056ae9da0884c539 commit r11-8188-g39d23b7960e4efb11bbe1eff056ae9da0884c539 Author: Jakub Jelinek <ja...@redhat.com> Date: Thu Apr 15 10:45:09 2021 +0200 aarch64: Fix several *<LOGICAL:optab>_ashl<mode>3 related regressions [PR100056] Before combiner added 2 to 2 combinations, the following testcase functions have been all compiled into 2 instructions, zero/sign extensions or and followed by orr with lsl, e.g. for the first function Trying 7 -> 8: 7: r96:SI=r94:SI<<0xb 8: r95:SI=r96:SI|r94:SI REG_DEAD r96:SI REG_DEAD r94:SI Successfully matched this instruction: (set (reg:SI 95) (ior:SI (ashift:SI (reg/v:SI 94 [ i ]) (const_int 11 [0xb])) (reg/v:SI 94 [ i ]))) is the important successful try_combine and so we end up with and w0, w0, 255 orr w0, w0, w0, lsl 11 in the body. With 2 to 2 combination, before that can trigger, another successful combination: Trying 2 -> 7: 2: r94:SI=zero_extend(x0:QI) REG_DEAD x0:QI 7: r96:SI=r94:SI<<0xb is replaced with: (set (reg/v:SI 94 [ i ]) (zero_extend:SI (reg:QI 0 x0 [ i ]))) and (set (reg:SI 96) (and:SI (ashift:SI (reg:SI 0 x0 [ i ]) (const_int 11 [0xb])) (const_int 522240 [0x7f800]))) and in the end results in 3 instructions in the body: and w1, w0, 255 ubfiz w0, w0, 11, 8 orr w0, w0, w1 The following combine splitters help undo that when combiner tries to combine 3 instructions - the zero/sign extend or and, the other insn from the 2 to 2 combination ([us]bfiz) and the logical op, the CPUs don't have an insn to do everything in one op, but we can split it back into the zero/sign extend or and followed by logical with lsl. 2021-04-15 Jakub Jelinek <ja...@redhat.com> PR target/100056 * config/aarch64/aarch64.md (*<LOGICAL:optab>_<SHIFT:optab><mode>3): Add combine splitters for *<LOGICAL:optab>_ashl<mode>3 with ZERO_EXTEND, SIGN_EXTEND or AND. * gcc.target/aarch64/pr100056.c: New test.
