[llvm] r357425 - Not all blocks are reachable from entry. Don't assume they are.

[Nick Lewycky via llvm-commits]

Author: nicholas
Date: Mon Apr  1 13:03:16 2019
New Revision: 357425

URL: http://llvm.org/viewvc/llvm-project?rev=357425&view=rev
Log:
Not all blocks are reachable from entry. Don't assume they are.

Fixes a bug in isPotentiallyReachable, noticed by inspection.

Modified:
    llvm/trunk/lib/Analysis/CFG.cpp
    llvm/trunk/unittests/Analysis/CFGTest.cpp

Modified: llvm/trunk/lib/Analysis/CFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/CFG.cpp?rev=357425&r1=357424&r2=357425&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/CFG.cpp (original)
+++ llvm/trunk/lib/Analysis/CFG.cpp Mon Apr  1 13:03:16 2019
@@ -226,10 +226,17 @@ bool llvm::isPotentiallyReachable(const
     Worklist.push_back(const_cast<BasicBlock*>(A->getParent()));
   }
 
-  if (A->getParent() == &A->getParent()->getParent()->getEntryBlock())
-    return true;
-  if (B->getParent() == &A->getParent()->getParent()->getEntryBlock())
-    return false;
+  if (DT) {
+    if (DT->isReachableFromEntry(A->getParent()) !=
+        DT->isReachableFromEntry(B->getParent()))
+      return false;
+    if (A->getParent() == &A->getParent()->getParent()->getEntryBlock() &&
+        DT->isReachableFromEntry(B->getParent()))
+      return true;
+    if (B->getParent() == &A->getParent()->getParent()->getEntryBlock() &&
+        DT->isReachableFromEntry(A->getParent()))
+      return false;
+  }
 
   return isPotentiallyReachableFromMany(
       Worklist, const_cast<BasicBlock *>(B->getParent()), DT, LI);

Modified: llvm/trunk/unittests/Analysis/CFGTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Analysis/CFGTest.cpp?rev=357425&r1=357424&r2=357425&view=diff
==============================================================================
--- llvm/trunk/unittests/Analysis/CFGTest.cpp (original)
+++ llvm/trunk/unittests/Analysis/CFGTest.cpp Mon Apr  1 13:03:16 2019
@@ -385,3 +385,43 @@ TEST_F(IsPotentiallyReachableTest, Modif
   S[0] = OldBB;
   ExpectPath(true);
 }
+
+TEST_F(IsPotentiallyReachableTest, UnreachableFromEntryTest) {
+  ParseAssembly("define void @test() {\n"
+                "entry:\n"
+                "  %A = bitcast i8 undef to i8\n"
+                "  ret void\n"
+                "not.reachable:\n"
+                "  %B = bitcast i8 undef to i8\n"
+                "  ret void\n"
+                "}");
+  ExpectPath(false);
+}
+
+TEST_F(IsPotentiallyReachableTest, UnreachableBlocksTest1) {
+  ParseAssembly("define void @test() {\n"
+                "entry:\n"
+                "  ret void\n"
+                "not.reachable.1:\n"
+                "  %A = bitcast i8 undef to i8\n"
+                "  br label %not.reachable.2\n"
+                "not.reachable.2:\n"
+                "  %B = bitcast i8 undef to i8\n"
+                "  ret void\n"
+                "}");
+  ExpectPath(true);
+}
+
+TEST_F(IsPotentiallyReachableTest, UnreachableBlocksTest2) {
+  ParseAssembly("define void @test() {\n"
+                "entry:\n"
+                "  ret void\n"
+                "not.reachable.1:\n"
+                "  %B = bitcast i8 undef to i8\n"
+                "  br label %not.reachable.2\n"
+                "not.reachable.2:\n"
+                "  %A = bitcast i8 undef to i8\n"
+                "  ret void\n"
+                "}");
+  ExpectPath(false);
+}