3 files changed, 24 insertions, 14 deletions

diff --git a/llvm/include/llvm/Transforms/Utils/CodeMoverUtils.h b/llvm/include/llvm/Transforms/Utils/CodeMoverUtils.h
index 4cf30e3899a..0d2ea8c6ff7 100644
--- a/llvm/include/llvm/Transforms/Utils/CodeMoverUtils.h
+++ b/llvm/include/llvm/Transforms/Utils/CodeMoverUtils.h
@@ -16,6 +16,7 @@
 
 namespace llvm {
 
+class BasicBlock;
 class DependenceInfo;
 class DominatorTree;
 class Instruction;
@@ -30,6 +31,15 @@ bool isControlFlowEquivalent(const Instruction &I0, const Instruction &I1,
                              const DominatorTree &DT,
                              const PostDominatorTree &PDT);
 
+/// Return true if \p BB0 and \p BB1 are control flow equivalent.
+/// Two basic blocks are control flow equivalent if when one executes, the other
+/// is guaranteed to execute. This is determined using dominators and
+/// post-dominators: if A dominates B and B post-dominates A then A and B are
+/// control-flow equivalent.
+bool isControlFlowEquivalent(const BasicBlock &BB0, const BasicBlock &BB1,
+                             const DominatorTree &DT,
+                             const PostDominatorTree &PDT);
+
 /// Return true if \p I can be safely moved before \p InsertPoint.
 bool isSafeToMoveBefore(Instruction &I, Instruction &InsertPoint,
                         const DominatorTree &DT, const PostDominatorTree &PDT,
diff --git a/llvm/lib/Transforms/Scalar/LoopFuse.cpp b/llvm/lib/Transforms/Scalar/LoopFuse.cpp
index 7e9e5a470cd..2bbbd7c73e6 100644
--- a/llvm/lib/Transforms/Scalar/LoopFuse.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopFuse.cpp
@@ -63,6 +63,7 @@
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Utils.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/CodeMoverUtils.h"
 
 using namespace llvm;
 
@@ -593,16 +594,8 @@ private:
                                const FusionCandidate &FC1) const {
     assert(FC0.Preheader && FC1.Preheader && "Expecting valid preheaders");
 
-    BasicBlock *FC0EntryBlock = FC0.getEntryBlock();
-    BasicBlock *FC1EntryBlock = FC1.getEntryBlock();
-
-    if (DT.dominates(FC0EntryBlock, FC1EntryBlock))
-      return PDT.dominates(FC1EntryBlock, FC0EntryBlock);
-
-    if (DT.dominates(FC1EntryBlock, FC0EntryBlock))
-      return PDT.dominates(FC0EntryBlock, FC1EntryBlock);
-
-    return false;
+    return ::isControlFlowEquivalent(*FC0.getEntryBlock(), *FC1.getEntryBlock(),
+                                     DT, PDT);
   }
 
   /// Iterate over all loops in the given loop set and identify the loops that
diff --git a/llvm/lib/Transforms/Utils/CodeMoverUtils.cpp b/llvm/lib/Transforms/Utils/CodeMoverUtils.cpp
index 5aab27fa094..7a3a8adfea8 100644
--- a/llvm/lib/Transforms/Utils/CodeMoverUtils.cpp
+++ b/llvm/lib/Transforms/Utils/CodeMoverUtils.cpp
@@ -33,10 +33,17 @@ STATISTIC(NotMovedTerminator, "Movement of Terminator are not supported");
 bool llvm::isControlFlowEquivalent(const Instruction &I0, const Instruction &I1,
                                    const DominatorTree &DT,
                                    const PostDominatorTree &PDT) {
-  const BasicBlock *BB0 = I0.getParent();
-  const BasicBlock *BB1 = I1.getParent();
-  return ((DT.dominates(BB0, BB1) && PDT.dominates(BB1, BB0)) ||
-          (PDT.dominates(BB0, BB1) && DT.dominates(BB1, BB0)));
+  return isControlFlowEquivalent(*I0.getParent(), *I1.getParent(), DT, PDT);
+}
+
+bool llvm::isControlFlowEquivalent(const BasicBlock &BB0, const BasicBlock &BB1,
+                                   const DominatorTree &DT,
+                                   const PostDominatorTree &PDT) {
+  if (&BB0 == &BB1)
+    return true;
+
+  return ((DT.dominates(&BB0, &BB1) && PDT.dominates(&BB1, &BB0)) ||
+          (PDT.dominates(&BB0, &BB1) && DT.dominates(&BB1, &BB0)));
 }
 
 static bool reportInvalidCandidate(const Instruction &I,