Index: lib/Transforms/Scalar/CallSiteSplitting.cpp
===================================================================
--- lib/Transforms/Scalar/CallSiteSplitting.cpp
+++ lib/Transforms/Scalar/CallSiteSplitting.cpp
@@ -321,20 +321,9 @@
   splitCallSite(CS, Preds[0], Preds[1], nullptr, nullptr);
   return true;
 }
-// Check if one of the predecessors is a single predecessors of the other.
-// This is a requirement for control flow modeling an OR. HeaderBB points to
-// the single predecessor and OrBB points to other node. HeaderBB potentially
-// contains the first compare of the OR and OrBB the second.
-static bool isOrHeader(BasicBlock *HeaderBB, BasicBlock *OrBB) {
-  return OrBB->getSinglePredecessor() == HeaderBB &&
-         HeaderBB->getTerminator()->getNumSuccessors() == 2;
-}
 
 static bool tryToSplitOnOrPredicatedArgument(CallSite CS) {
   auto Preds = getTwoPredecessors(CS.getInstruction()->getParent());
-  if (!isOrHeader(Preds[0], Preds[1]) && !isOrHeader(Preds[1], Preds[0]))
-    return false;
-
   SmallVector<std::pair<ICmpInst*, unsigned>, 2> C1, C2;
   recordConditions(CS, Preds[0], C1);
   recordConditions(CS, Preds[1], C2);
Index: test/Transforms/CallSiteSplitting/callsite-split-or-phi.ll
===================================================================
--- test/Transforms/CallSiteSplitting/callsite-split-or-phi.ll
+++ test/Transforms/CallSiteSplitting/callsite-split-or-phi.ll
@@ -166,6 +166,99 @@
   ret i32 %v
 }
 
+;CHECK-LABEL: @test_eq_eq_eq_untaken
+;CHECK-LABEL: Tail.predBB1.split:
+;CHECK: %[[CALL1:.*]] = call i32 @callee(i32* nonnull %a, i32 %v, i32 %p)
+;CHECK-LABEL: Tail.predBB2.split:
+;CHECK: %[[CALL2:.*]] = call i32 @callee(i32* null, i32 1, i32 99)
+;CHECK-LABEL: Tail
+;CHECK: %[[MERGED:.*]] = phi i32 [ %[[CALL1]], %Tail.predBB1.split ], [ %[[CALL2]], %Tail.predBB2.split ]
+;CHECK: ret i32 %[[MERGED]]
+define i32 @test_eq_eq_eq_untaken(i32* %a, i32 %v, i32 %p) {
+Header:
+  %tobool1 = icmp eq i32* %a, null
+  br i1 %tobool1, label %TBB1, label %Tail
+
+TBB1:
+  %cmp1 = icmp eq i32 %v, 1
+  br i1 %cmp1, label %TBB2, label %End
+
+TBB2:
+  %cmp2 = icmp eq i32 %p, 99
+  br i1 %cmp2, label %Tail, label %End
+
+Tail:
+  %r = call i32 @callee(i32* %a, i32 %v, i32 %p)
+  ret i32 %r
+
+End:
+  ret i32 %v
+}
+
+;CHECK-LABEL: @test_eq_ne_eq_untaken
+;CHECK-LABEL: Tail.predBB1.split:
+;CHECK: %[[CALL1:.*]] = call i32 @callee(i32* nonnull %a, i32 %v, i32 %p)
+;CHECK-LABEL: Tail.predBB2.split:
+;CHECK: %[[CALL2:.*]] = call i32 @callee(i32* null, i32 %v, i32 99)
+;CHECK-LABEL: Tail
+;CHECK: %[[MERGED:.*]] = phi i32 [ %[[CALL1]], %Tail.predBB1.split ], [ %[[CALL2]], %Tail.predBB2.split ]
+;CHECK: ret i32 %[[MERGED]]
+define i32 @test_eq_ne_eq_untaken(i32* %a, i32 %v, i32 %p) {
+Header:
+  %tobool1 = icmp eq i32* %a, null
+  br i1 %tobool1, label %TBB1, label %Tail
+
+TBB1:
+  %cmp1 = icmp ne i32 %v, 1
+  br i1 %cmp1, label %TBB2, label %End
+
+TBB2:
+  %cmp2 = icmp eq i32 %p, 99
+  br i1 %cmp2, label %Tail, label %End
+
+Tail:
+  %r = call i32 @callee(i32* %a, i32 %v, i32 %p)
+  ret i32 %r
+
+End:
+  ret i32 %v
+}
+
+;CHECK-LABEL: @test_eq_eq_eq_eq_untaken
+;CHECK-LABEL: Tail.predBB1.split:
+;CHECK: %[[CALL1:.*]] = call i32 @callee(i32* nonnull %a, i32 %v, i32 10)
+;CHECK-LABEL: Tail.predBB2.split:
+; NOTE: CallSiteSplitting cannot infer that %a is null here, as it currently
+;       only supports recording conditions along a single predecessor path.
+;CHECK: %[[CALL2:.*]] = call i32 @callee(i32* %a, i32 1, i32 99)
+;CHECK-LABEL: Tail
+;CHECK: %[[MERGED:.*]] = phi i32 [ %[[CALL1]], %Tail.predBB1.split ], [ %[[CALL2]], %Tail.predBB2.split ]
+;CHECK: ret i32 %[[MERGED]]
+define i32 @test_eq_eq_eq_eq_untaken(i32* %a, i32 %v, i32 %p) {
+Header:
+  %tobool1 = icmp eq i32* %a, null
+  br i1 %tobool1, label %TBB1, label %Header2
+
+Header2:
+  %tobool2 = icmp eq i32 %p, 10
+  br i1 %tobool2, label %Tail, label %TBB1
+
+TBB1:
+  %cmp1 = icmp eq i32 %v, 1
+  br i1 %cmp1, label %TBB2, label %End
+
+TBB2:
+  %cmp2 = icmp eq i32 %p, 99
+  br i1 %cmp2, label %Tail, label %End
+
+Tail:
+  %r = call i32 @callee(i32* %a, i32 %v, i32 %p)
+  ret i32 %r
+
+End:
+  ret i32 %v
+}
+
 ;CHECK-LABEL: @test_nonconst_const_phi
 ;CHECK-LABEL: Tail.predBB1.split:
 ;CHECK: %[[CALL1:.*]] = call i32 @callee(i32* %a, i32 %v, i32 1)
@@ -343,7 +436,7 @@
 }
 
 
-;CHECK-LABEL: @test_eq_eq_eq_untaken
+;CHECK-LABEL: @test_header_header2_tbb
 ;CHECK-LABEL: Tail.predBB1.split:
 ;CHECK: %[[CALL1:.*]] = call i32 @callee(i32* nonnull %a, i32 %v, i32 10)
 ;CHECK-LABEL: Tail.predBB2.split:
@@ -351,7 +444,7 @@
 ;CHECK-LABEL: Tail
 ;CHECK: %[[MERGED:.*]] = phi i32 [ %[[CALL1]], %Tail.predBB1.split ], [ %[[CALL2]], %Tail.predBB2.split ]
 ;CHECK: ret i32 %[[MERGED]]
-define i32 @test_eq_eq_eq_untaken(i32* %a, i32 %v, i32 %p) {
+define i32 @test_header_header2_tbb(i32* %a, i32 %v, i32 %p) {
 Header:
   %tobool1 = icmp eq i32* %a, null
   br i1 %tobool1, label %End, label %Header2