i64 OR instruction elimination

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1

for.body: ; preds = %for.body.lr.ph, %for.body

%ACC.sroa.0.013 = phi i64 [ 0, %for.body.lr.ph ], [ %phitmp9, %for.body ]

%ACC.sroa.4.012 = phi i64 [ 0, %for.body.lr.ph ], [ %tmp.sroa.2.0.extract.shift, %for.body ]

%i.011 = phi i32 [ 0, %for.body.lr.ph ], [ %inc, %for.body ]

%arrayidx = getelementptr inbounds i16* %ary, i32 %i.011

%0 = load i16* %arrayidx, align 2, !tbaa !1

%add = add i32 %i.011, 8

%arrayidx1 = getelementptr inbounds i16* %ary, i32 %add

%1 = load i16* %arrayidx1, align 2, !tbaa !1

%2 = tail call i64 @llvm.arc.ACC40.GUARD.MUL.SQ15.SQ15(i16 %0, i16 %1) #1

%L.sroa.0.0.insert.insert.i = or i64 %ACC.sroa.0.013, %ACC.sroa.4.012

%3 = tail call i64 @llvm.arc.ADD.ACC40(i64 %L.sroa.0.0.insert.insert.i, i64 %2) #1

%tmp.sroa.2.0.extract.shift = and i64 %3, -4294967296

%inc = add i32 %i.011, 1

%phitmp9 = and i64 %3, 4294967295

%cmp = icmp ult i32 %inc, %limit

br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge

The value of the OR is simply the PHI of %3 and 0. Nobody detects this and it generates pretty ugly code in a loop. Can you tell me what phase should handle this simple transform? That is, what phase does this kind of transformation belong in?

Thanks

2

I would suggest you file a bug for this if you haven’t already.

This is rather odd code to be generating. Is this coming from another opto pass or the frontend? I might be tempted to see if the source is easy to tweak.

Philip