Closed
Description
In this example, LIR will remove the nuw/exact flags on %dist and %len, even though it does not actually perform any transform:
; RUN: opt -S -passes=loop-idiom < %s
define void @test(ptr %p.end, ptr %p.start) {
entry:
%p.end.int = ptrtoint ptr %p.end to i64
%p.start.int = ptrtoint ptr %p.start to i64
%dist = sub nuw i64 %p.end.int, %p.start.int
%len = lshr exact i64 %dist, 5
%cmp = icmp eq ptr %p.end, %p.start
br i1 %cmp, label %exit, label %preheader
preheader:
br label %loop
loop:
%iv = phi i64 [ %len, %preheader ], [ %iv.dec, %loop ]
%iv.neg = sub nsw i64 0, %iv
%src = getelementptr inbounds [32 x i8], ptr %p.end, i64 %iv.neg
%v = load <4 x i64>, ptr %src, align 8
%dst = getelementptr inbounds [32 x i8], ptr %p.start, i64 %iv.neg
store <4 x i64> %v, ptr %dst, align 8
%iv.dec = add i64 %iv, -1
%cmp2 = icmp eq i64 %iv.dec, 0
br i1 %cmp2, label %loop.exit, label %loop
loop.exit:
br label %exit
exit:
ret void
}