1 files changed, 30 insertions, 0 deletions
diff --git a/test/Transforms/LoopUnroll/tripcount-overflow.ll b/test/Transforms/LoopUnroll/tripcount-overflow.ll
new file mode 100644
index 0000000..d593685
--- /dev/null
+++ b/test/Transforms/LoopUnroll/tripcount-overflow.ll
@@ -0,0 +1,30 @@
+; RUN: opt < %s -S -unroll-runtime -unroll-count=2 -loop-unroll | FileCheck %s
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+; When prologue is fully unrolled, the branch on its end is unconditional.
+; Unrolling it is illegal if we can't prove that trip-count+1 doesn't overflow,
+; like in this example, where it comes from an argument.
+;
+; This test is based on an example from here:
+; http://stackoverflow.com/questions/23838661/why-is-clang-optimizing-this-code-out
+;
+; CHECK: while.body.prol:
+; CHECK: br i1
+; CHECK: entry.split:
+
+; Function Attrs: nounwind readnone ssp uwtable
+define i32 @foo(i32 %N) #0 {
+entry:
+  br label %while.body
+
+while.body:                                       ; preds = %while.body, %entry
+  %i = phi i32 [ 0, %entry ], [ %inc, %while.body ]
+  %cmp = icmp eq i32 %i, %N
+  %inc = add i32 %i, 1
+  br i1 %cmp, label %while.end, label %while.body
+
+while.end:                                        ; preds = %while.body
+  ret i32 %i
+}
+
+attributes #0 = { nounwind readnone ssp uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }