[Bug rtl-optimization/42258] [4.5 Regression] redundant register move around mul instruction

[bernds at codesourcery dot com]

------- Comment #5 from bernds at codesourcery dot com  2010-03-17 11:44 -------
Created an attachment (id=20123)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=20123&action=view)
A patch to fix it.

Okay, so the pattern is written strangely because it's a two-operand mul where
the input and output may not be the same register.
It may be better to write this using an earlyclobbered in-out operand, but you
can't show anymore that the operation is commutative.

It can be fixed with a simple peephole optimization, at least for this
testcase.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42258