Missed optimization opportunity with duplicated conditional (JumpThreading?)

[llvmbot]

Bugzilla Link	8108
Version	trunk
OS	All
Attachments	missed.ll
Reporter	LLVM Bugzilla Contributor

Extended Description

See the attached .ll files. In particular, note this snippet:

lor.rhs.i:
%cmp9.i = icmp eq i32 %tmp2, 16
br label %_Z16sparc_floating_pPK4type.exit

_Z16sparc_floating_pPK4type.exit:
%call19 = phi i1 [ true, %sw.bb.i ], [ %cmp9.i, %lor.rhs.i ], [ true, %sw.bb.i ]
%cmp = icmp eq i32 %tmp2, 16
%or.cond = and i1 %call19, %cmp
br i1 %or.cond, label %if.end18, label %sw.bb.i24

Notice that the comparison of %tmp2 with 16 is repeated. If this edge were to be threaded by JumpThreading, GVN would pick up the duplication and get rid of it. However, because we can't actually determine a value for the comparison JumpThreading does not currently choose to thread this edge.