Index: lib/Transforms/Scalar/CallSiteSplitting.cpp
===================================================================
--- lib/Transforms/Scalar/CallSiteSplitting.cpp
+++ lib/Transforms/Scalar/CallSiteSplitting.cpp
@@ -332,18 +332,10 @@
   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]))
+  if (Preds[0] == Preds[1])
     return false;
 
   SmallVector<std::pair<ICmpInst *, unsigned>, 2> C1, C2;
Index: test/Transforms/CallSiteSplitting/callsite-no-or-structure.ll
===================================================================
--- /dev/null
+++ test/Transforms/CallSiteSplitting/callsite-no-or-structure.ll
@@ -0,0 +1,139 @@
+; RUN: opt < %s -callsite-splitting -S | FileCheck %s
+; RUN: opt < %s  -passes='function(callsite-splitting)' -S | FileCheck %s
+
+; CHECK-LABEL: @test_simple
+; CHECK-LABEL: Header:
+; CHECK-NEXT: br i1 undef, label %Tail.predBB1.split
+; CHECK-LABEL: TBB:
+; CHECK: br i1 %cmp, label %Tail.predBB2.split
+; CHECK-LABEL: Tail.predBB1.split:
+; CHECK: %[[CALL1:.*]] = call i32 @callee(i32* %a, i32 %v, i32 %p)
+; CHECK-LABEL: Tail.predBB2.split:
+; CHECK: %[[CALL2:.*]] = call i32 @callee(i32* null, i32 %v, i32 %p)
+; CHECK-LABEL: Tail
+; CHECK: %[[MERGED:.*]] = phi i32 [ %[[CALL1]], %Tail.predBB1.split ], [ %[[CALL2]], %Tail.predBB2.split ]
+; CHECK: ret i32 %[[MERGED]]
+define i32 @test_simple(i32* %a, i32 %v, i32 %p) {
+Header:
+  br i1 undef, label %Tail, label %End
+
+TBB:
+  %cmp = icmp eq i32* %a, null
+  br i1 %cmp, 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_untaken
+; CHECK-LABEL: Header:
+; CHECK: br i1 %tobool1, label %TBB1, label %Tail.predBB1.split
+; CHECK-LABEL: TBB2:
+; CHECK: br i1 %cmp2, label %Tail.predBB2.split, label %End
+; 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_untaken2(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: Header:
+; CHECK: br i1 %tobool1, label %TBB1, label %Tail.predBB1.split
+; CHECK-LABEL: TBB2:
+; CHECK: br i1 %cmp2, label %Tail.predBB2.split, label %End
+; 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_header_header2_tbb
+; CHECK: Header2:
+; CHECK:br i1 %tobool2, label %Tail.predBB1.split, label %TBB1
+; CHECK-LABEL: TBB2:
+; CHECK: br i1 %cmp2, label %Tail.predBB2.split, label %End
+; 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_header_header2_tbb(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
+}
+
+define i32 @callee(i32* %a, i32 %v, i32 %p) {
+  ret i32 10
+}
Index: test/Transforms/CallSiteSplitting/callsite-no-splitting.ll
===================================================================
--- /dev/null
+++ test/Transforms/CallSiteSplitting/callsite-no-splitting.ll
@@ -0,0 +1,18 @@
+; RUN: opt < %s -callsite-splitting -S | FileCheck %s
+; RUN: opt < %s  -passes='function(callsite-splitting)' -S | FileCheck %s
+
+define i32 @callee(i32*, i32, i32) {
+  ret i32 10
+}
+
+; CHECK-LABEL: @test_preds_equal
+; CHECK-NOT: split
+; CHECK: br i1 %cmp, label %Tail, label %Tail
+define i32 @test_preds_equal(i32* %a, i32 %v, i32 %p) {
+TBB:
+  %cmp = icmp eq i32* %a, null
+  br i1 %cmp, label %Tail, label %Tail
+Tail:
+  %r = call i32 @callee(i32* %a, i32 %v, i32 %p)
+  ret i32 %r
+}