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From: "luoxhu at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/102239] powerpc suboptimal boolean test of contiguous bits
Date: Wed, 01 Dec 2021 07:46:45 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102239

--- Comment #11 from luoxhu at gcc dot gnu.org ---


+(define_insn_and_split "*anddi3_insn_dot"
+ [(set (pc)
+    (if_then_else (eq (and:DI (match_operand:DI 1 "gpc_reg_operand" "%r,r")
+                             (match_operand:DI 2 "const_int_operand" "n,n"=
))
+                     (const_int 0))
+                 (label_ref (match_operand 3 ""))
+                 (pc)))
+  (clobber (match_scratch:DI 0 "=3Dr,r"))]
+  "rs6000_is_valid_2insn_and (operands[2], DImode)
+   && !(rs6000_is_valid_and_mask (operands[2], DImode)
+       || logical_const_operand (operands[2], DImode))"
+  "#"
+  "&& reload_completed"
+  [(pc)]
+{
+   int nb, ne;
+   if (rs6000_is_valid_mask (operands[2], &nb, &ne, DImode) && nb >=3D ne)
+     {
+       unsigned HOST_WIDE_INT val =3D INTVAL (operands[2]);
+       int shift =3D 63 - nb;
+       rtx tmp =3D gen_rtx_ASHIFT (DImode, operands[1], GEN_INT (shift));
+       tmp =3D gen_rtx_AND (DImode, tmp, GEN_INT (val << shift));
+       rtx cr0 =3D gen_rtx_REG (CCmode, CR0_REGNO);
+       rs6000_emit_dot_insn (operands[0], tmp, 1, cr0);
+       rtx loc_ref =3D gen_rtx_LABEL_REF (VOIDmode, operands[3]);
+       rtx cond =3D gen_rtx_EQ (CCEQmode, cr0, const0_rtx);
+       rtx ite =3D gen_rtx_IF_THEN_ELSE (VOIDmode, cond, loc_ref, pc_rtx);
+       emit_jump_insn (gen_rtx_SET (pc_rtx, ite));
+       DONE;
+     }
+   else
+     FAIL;
+}
+  [(set_attr "type" "shift")
+   (set_attr "dot" "yes")
+   (set_attr "length" "8,12")])
+


This pattern could combine the two instructions from

     9: {r123:CC=3Dcmp(r124:DI&0x600000000,0);clobber scratch;}
           REG_DEAD r124:DI
     10: pc=3D{(r123:CC=3D=3D0)?L15:pc}
          REG_DEAD r123:CC

to:

     10: {pc=3D{(r124:DI&0x600000000=3D=3D0)?L15:pc};clobber scratch;}

then split2 will split it to one rotate dot instruction, is this OK?


(insn 32 9 33 2 (parallel [
            (set (reg:CC 100 0)
                (compare:CC (and:DI (ashift:DI (reg:DI 3 3 [124])
                            (const_int 29 [0x1d]))
                        (const_int -4611686018427387904 [0xc000000000000000=
]))
                    (const_int 0 [0])))
            (clobber (reg:DI 3 3 [125]))
        ]) "pr102239.c":4:6 239 {*rotldi3_mask_dot}
     (nil))
(jump_insn 33 32 11 2 (set (pc)
        (if_then_else (eq:CCEQ (reg:CC 100 0)
                (const_int 0 [0]))
            (label_ref 15)
            (pc))) "pr102239.c":4:6 869 {*cbranch}
     (int_list:REG_BR_PROB 536870916 (nil))
 -> 15)=