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How to explicitly state in md pattern that I expect bitwise zero target?
- From: Konstantin Vladimirov <konstantin dot vladimirov at gmail dot com>
- To: gcc at gcc dot gnu dot org
- Date: Fri, 26 Oct 2012 12:49:17 +0400
- Subject: How to explicitly state in md pattern that I expect bitwise zero target?
Consider I have pattern like:
[(set (match_operand:SI 0 ...)
(ior:SI (and:SI (lshiftrt:SI (match_operand:SI 1 ...)
(match_operand:SI 2 ...))
(match_operand:SI 3 ...))
(and:SI (lshiftrt:SI (match_dup 1)
(match_operand:SI 4 ...))
(match_operand:SI 5 ...))))]
I can match it as one instruction, only if target operand is proven to
be bitwise zero, that is very often case for this pattern.
But how can I decide if it is so?
With best regards, Konstantin