1 files changed, 45 insertions, 0 deletions
diff --git a/test/Transforms/GVN/PRE/pre-single-pred.ll b/test/Transforms/GVN/PRE/pre-single-pred.ll
new file mode 100644
index 000000000000..0df45cf5c1c0
--- /dev/null
+++ b/test/Transforms/GVN/PRE/pre-single-pred.ll
@@ -0,0 +1,45 @@
+; RUN: opt < %s -gvn -enable-load-pre -S | FileCheck %s
+; This testcase assumed we'll PRE the load into %for.cond, but we don't actually
+; verify that doing so is safe.  If there didn't _happen_ to be a load in
+; %for.end, we would actually be lengthening the execution on some paths, and
+; we were never actually checking that case.  Now we actually do perform some
+; conservative checking to make sure we don't make paths longer, but we don't
+; currently get this case, which we got lucky on previously.
+;
+; Now that that faulty assumption is corrected, test that we DON'T incorrectly
+; hoist the load.  Doing the right thing for the wrong reasons is still a bug.
+
+@p = external global i32
+define i32 @f(i32 %n) nounwind {
+entry:
+	br label %for.cond
+
+for.cond:		; preds = %for.inc, %entry
+	%i.0 = phi i32 [ 0, %entry ], [ %indvar.next, %for.inc ]		; <i32> [#uses=2]
+	%cmp = icmp slt i32 %i.0, %n		; <i1> [#uses=1]
+	br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge
+
+for.cond.for.end_crit_edge:		; preds = %for.cond
+	br label %for.end
+
+; CHECK: for.body:
+; CHECK-NEXT: %tmp3 = load i32, i32* @p
+for.body:		; preds = %for.cond
+	%tmp3 = load i32, i32* @p		; <i32> [#uses=1]
+	%dec = add i32 %tmp3, -1		; <i32> [#uses=2]
+	store i32 %dec, i32* @p
+	%cmp6 = icmp slt i32 %dec, 0		; <i1> [#uses=1]
+	br i1 %cmp6, label %for.body.for.end_crit_edge, label %for.inc
+
+; CHECK: for.body.for.end_crit_edge:
+for.body.for.end_crit_edge:		; preds = %for.body
+	br label %for.end
+
+for.inc:		; preds = %for.body
+	%indvar.next = add i32 %i.0, 1		; <i32> [#uses=1]
+	br label %for.cond
+
+for.end:		; preds = %for.body.for.end_crit_edge, %for.cond.for.end_crit_edge
+	%tmp9 = load i32, i32* @p		; <i32> [#uses=1]
+	ret i32 %tmp9
+}