Fix an oversight in isPotentiallyReachable where we wouldn't do any CFG-walking

to find loops if the From and To instructions were in the same block.

Refactor the code a little now that we need to fill to start the CFG-walking
algorithm with more than one starting basic block sometimes.

Special thanks to Andrew Trick for catching an error in my understanding of
natural loops in code review.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188236 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 0 deletions

diff --git a/unittests/Analysis/CFGTest.cpp b/unittests/Analysis/CFGTest.cpp
index 23588037784..e931709620f 100644
--- a/unittests/Analysis/CFGTest.cpp
+++ b/unittests/Analysis/CFGTest.cpp
@@ -147,6 +147,23 @@ TEST_F(IsPotentiallyReachableTest, SameBlockPath) {
   ExpectPath(true);
 }
 
+TEST_F(IsPotentiallyReachableTest, SameBlockNoLoop) {
+  ParseAssembly(
+      "define void @test() {\n"
+      "entry:\n"
+      "  br label %middle\n"
+      "middle:\n"
+      "  %B = bitcast i8 undef to i8\n"
+      "  bitcast i8 undef to i8\n"
+      "  bitcast i8 undef to i8\n"
+      "  %A = bitcast i8 undef to i8\n"
+      "  br label %nextblock\n"
+      "nextblock:\n"
+      "  ret void\n"
+      "}\n");
+  ExpectPath(false);
+}
+
 TEST_F(IsPotentiallyReachableTest, StraightNoPath) {
   ParseAssembly(
       "define void @test() {\n"