1; RUN: opt < %s -S -unroll-runtime -unroll-count=2 -loop-unroll | FileCheck %s
2target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
3
4; This test case documents how runtime loop unrolling handles the case
5; when the backedge-count is -1.
6
7; If %N, the backedge-taken count, is -1 then %0 unsigned-overflows
8; and is 0.  %xtraiter too is 0, signifying that the total trip-count
9; is divisible by 2.  The prologue then branches to the unrolled loop
10; and executes the 2^32 iterations there, in groups of 2.
11
12
13; CHECK: entry:
14; CHECK-NEXT: %0 = add i32 %N, 1
15; CHECK-NEXT: %xtraiter = and i32 %0, 1
16; CHECK-NEXT: %lcmp.mod = icmp ne i32 %xtraiter, 0
17; CHECK-NEXT: br i1 %lcmp.mod, label %while.body.prol, label %entry.split
18
19; CHECK: while.body.prol:
20; CHECK: br label %entry.split
21
22; CHECK: entry.split:
23
24; Function Attrs: nounwind readnone ssp uwtable
25define i32 @foo(i32 %N) {
26entry:
27  br label %while.body
28
29while.body:                                       ; preds = %while.body, %entry
30  %i = phi i32 [ 0, %entry ], [ %inc, %while.body ]
31  %cmp = icmp eq i32 %i, %N
32  %inc = add i32 %i, 1
33  br i1 %cmp, label %while.end, label %while.body
34
35while.end:                                        ; preds = %while.body
36  ret i32 %i
37}
38