Extend ScalarEvolution's executesAtLeastOnce logic to be able to

continue past the first conditional branch when looking for a
relevant test. This helps it avoid using MAX expressions in
loop trip counts in more cases.

llvm-svn: 54697

1 files changed, 35 insertions, 0 deletions

diff --git a/llvm/test/Analysis/ScalarEvolution/avoid-smax.ll b/llvm/test/Analysis/ScalarEvolution/avoid-smax.ll
new file mode 100644
index 00000000000..fe4b86f21ed
--- /dev/null
+++ b/llvm/test/Analysis/ScalarEvolution/avoid-smax.ll
@@ -0,0 +1,35 @@
+; RUN: llvm-as < %s | opt -scalar-evolution -analyze | grep {Loop bb3: ( -1 +  %n) iterations!}
+
+; We don't want to use a max in the trip count expression in
+; this testcase.
+
+define void @foo(i32 %n, i32* %p, i32* %q) nounwind {
+entry:
+	icmp sgt i32 %n, 0
+	br i1 %0, label %bb, label %return
+
+bb:
+	load i32* %q, align 4
+	icmp eq i32 %1, 0
+	br i1 %2, label %return, label %bb3.preheader
+
+bb3.preheader:
+	br label %bb3
+
+bb3:
+	%i.0 = phi i32 [ %7, %bb3 ], [ 0, %bb3.preheader ]
+	getelementptr i32* %p, i32 %i.0
+	load i32* %3, align 4
+	add i32 %4, 1
+	getelementptr i32* %p, i32 %i.0
+	store i32 %5, i32* %6, align 4
+	add i32 %i.0, 1
+	icmp slt i32 %7, %n
+	br i1 %8, label %bb3, label %return.loopexit
+
+return.loopexit:
+	br label %return
+
+return:
+	ret void
+}