Hi, when combine deals with (xor (x) (const_int -1)) it turns it into a (not (x)) first. This seems to be a disadvantage for targets not providing (not ..) patterns since it prevents intermediate steps from matching.
If noticed this for the builtin-bswap-8/9 testcases which are fixed with the attached patch. Bootstrap and regtest clean on s390x. Bye, -Andreas- 2014-04-04 Andreas Krebbel <andreas.kreb...@de.ibm.com> * config/s390/s390.md: Add a splitter for NOT rtx. diff --git a/gcc/config/s390/s390.md b/gcc/config/s390/s390.md index 7d9d1ad..b17c1fa 100644 --- a/gcc/config/s390/s390.md +++ b/gcc/config/s390/s390.md @@ -7001,6 +7001,21 @@ "" "s390_expand_logical_operator (XOR, <MODE>mode, operands); DONE;") +; Combine replaces (xor (x) (const_int -1)) with (not (x)) when doing +; simplifications. So its better to have something matching. +(define_split + [(set (match_operand:INT 0 "nonimmediate_operand" "") + (not:INT (match_operand:INT 1 "nonimmediate_operand" "")))] + "" + [(parallel + [(set (match_dup 0) (xor:INT (match_dup 1) (match_dup 2))) + (clobber (reg:CC CC_REGNUM))])] +{ + operands[2] = constm1_rtx; + if (!s390_logical_operator_ok_p (operands)) + FAIL; +}) + ; ; xordi3 instruction pattern(s). ;