https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102239
luoxhu at gcc dot gnu.org changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |luoxhu at gcc dot gnu.org --- Comment #2 from luoxhu at gcc dot gnu.org --- (In reply to Segher Boessenkool from comment #1) > Confirmed. > > So the relevant insn > > (parallel [(set (reg:CC 123) > (compare:CC (and:DI (reg:DI 124) > (const_int 25769803776 [0x600000000])) > (const_int 0 [0]))) > (clobber (scratch:DI))]) > > is matched by *and<mode>3_2insn but not by any pattern that ends up as just > one insn. Not *and<mode>3_mask_dot, because that doesn't do a shift first, > is just an AND and there are no machine insns to do that; but there is no > pattern for what we can do. > > *rotl<mode>3_mask_dot cannot do this either; the base and the dot2 of that > cannot be done, they return a shifted result, but that doesn't matter for > comparing it to 0. So we should add a specialised version. Seems different with what you describe, in combine, it was combined to anddi3_2insn_dot: (insn 9 8 10 2 (parallel [ (set (reg:CC 122) (compare:CC (and:DI (reg:DI 123) (const_int 25769803776 [0x600000000])) (const_int 0 [0]))) (clobber (scratch:DI)) ]) "pr102239.c":3:6 210 {*anddi3_2insn_dot} (expr_list:REG_DEAD (reg:DI 123) (nil))) (jump_insn 10 9 11 2 (set (pc) (if_then_else (eq (reg:CC 122) (const_int 0 [0])) (label_ref 15) (pc))) "pr102239.c":3:6 868 {*cbranch} (expr_list:REG_DEAD (reg:CC 122) (int_list:REG_BR_PROB 536870916 (nil))) Then in pr102239.c.302r.split2, it is split by "*and<mode>3_2insn_dot" to rotldi3_mask+lshrdi3_dot: Splitting with gen_split_80 (rs6000.md:3721) (insn 32 8 33 2 (set (reg:DI 3 3 [124]) (and:DI (ashift:DI (reg:DI 3 3 [123]) (const_int 29 [0x1d])) (const_int -4611686018427387904 [0xc000000000000000]))) "pr102239.c":3:6 236 {*rotldi3_mask} (nil)) (insn 33 32 10 2 (parallel [ (set (reg:CC 100 0 [122]) (compare:CC (lshiftrt:DI (reg:DI 3 3 [124]) (const_int 29 [0x1d])) (const_int 0 [0]))) (clobber (reg:DI 3 3 [124])) ]) "pr102239.c":3:6 281 {*lshrdi3_dot} (nil)) Why this difference happens? 0x600000000 is not a valid mask for anddi3_2insn_dot: "(<MODE>mode == Pmode || UINTVAL (operands[2]) <= 0x7fffffff) && rs6000_is_valid_2insn_and (operands[2], <MODE>mode) && !(rs6000_is_valid_and_mask (operands[2], <MODE>mode) || logical_const_operand (operands[2], <MODE>mode))" (gdb) p UINTVAL (operands[2]) <= 0x7fffffff $84 = false (gdb) p rs6000_is_valid_2insn_and (operands[2], E_DImode) $85 = true (gdb) p logical_const_operand (operands[2], E_DImode) $86 = false (gdb) p rs6000_is_valid_and_mask (operands[2], E_DImode) $87 = false (gdb) p Pmode $88 = DImode