diff --git a/lib/Analysis/IPA/InlineCost.cpp b/lib/Analysis/IPA/InlineCost.cpp
index c43b5ca2506..358f61fd523 100644
--- a/lib/Analysis/IPA/InlineCost.cpp
+++ b/lib/Analysis/IPA/InlineCost.cpp
@@ -808,9 +808,29 @@ bool CallAnalyzer::visitBranchInst(BranchInst &BI) {
 bool CallAnalyzer::visitSwitchInst(SwitchInst &SI) {
   // We model unconditional switches as free, see the comments on handling
   // branches.
-  return isa<ConstantInt>(SI.getCondition()) ||
-         dyn_cast_or_null<ConstantInt>(
-             SimplifiedValues.lookup(SI.getCondition()));
+  if (isa<ConstantInt>(SI.getCondition()))
+    return true;
+  if (Value *V = SimplifiedValues.lookup(SI.getCondition()))
+    if (isa<ConstantInt>(V))
+      return true;
+
+  // Otherwise, we need to accumulate a cost proportional to the number of
+  // distinct successor blocks. This fan-out in the CFG cannot be represented
+  // for free even if we can represent the core switch as a jumptable that
+  // takes a single instruction.
+  //
+  // NB: We convert large switches which are just used to initialize large phi
+  // nodes to lookup tables instead in simplify-cfg, so this shouldn't prevent
+  // inlining those. It will prevent inlining in cases where the optimization
+  // does not (yet) fire.
+  SmallPtrSet<BasicBlock *, 8> SuccessorBlocks;
+  SuccessorBlocks.insert(SI.getDefaultDest());
+  for (auto I = SI.case_begin(), E = SI.case_end(); I != E; ++I)
+    SuccessorBlocks.insert(I.getCaseSuccessor());
+  // Add cost corresponding to the number of distinct destinations. The first
+  // we model as free because of fallthrough.
+  Cost += (SuccessorBlocks.size() - 1) * InlineConstants::InstrCost;
+  return false;
 }
 
 bool CallAnalyzer::visitIndirectBrInst(IndirectBrInst &IBI) {
diff --git a/test/Transforms/Inline/switch.ll b/test/Transforms/Inline/switch.ll
new file mode 100644
index 00000000000..c5dab53e8b6
--- /dev/null
+++ b/test/Transforms/Inline/switch.ll
@@ -0,0 +1,60 @@
+; RUN: opt < %s -inline -inline-threshold=20 -S | FileCheck %s
+
+define i32 @callee(i32 %a) {
+  switch i32 %a, label %sw.default [
+    i32 0, label %sw.bb0
+    i32 1, label %sw.bb1
+    i32 2, label %sw.bb2
+    i32 3, label %sw.bb3
+    i32 4, label %sw.bb4
+    i32 5, label %sw.bb5
+    i32 6, label %sw.bb6
+    i32 7, label %sw.bb7
+    i32 8, label %sw.bb8
+    i32 9, label %sw.bb9
+  ]
+
+sw.default:
+  br label %return
+
+sw.bb0:
+  br label %return
+
+sw.bb1:
+  br label %return
+
+sw.bb2:
+  br label %return
+
+sw.bb3:
+  br label %return
+
+sw.bb4:
+  br label %return
+
+sw.bb5:
+  br label %return
+
+sw.bb6:
+  br label %return
+
+sw.bb7:
+  br label %return
+
+sw.bb8:
+  br label %return
+
+sw.bb9:
+  br label %return
+
+return:
+  ret i32 42
+}
+
+define i32 @caller(i32 %a) {
+; CHECK-LABEL: @caller(
+; CHECK: call i32 @callee(
+
+  %result = call i32 @callee(i32 %a)
+  ret i32 %result
+}