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
