Index: llvm/trunk/lib/Target/X86/X86ExpandPseudo.cpp
===================================================================
--- llvm/trunk/lib/Target/X86/X86ExpandPseudo.cpp
+++ llvm/trunk/lib/Target/X86/X86ExpandPseudo.cpp
@@ -122,8 +122,9 @@
         Op = X86::TAILJMPd_CC;
         break;
       case X86::TCRETURNdi64cc:
-        assert(!IsWin64 && "Conditional tail calls confuse the Win64 unwinder.");
-        // TODO: We could do it for Win64 "leaf" functions though; PR30337.
+        assert(!MBB.getParent()->hasWinCFI() &&
+               "Conditional tail calls confuse "
+               "the Win64 unwinder.");
         Op = X86::TAILJMPd64_CC;
         break;
       default:
Index: llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
===================================================================
--- llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
+++ llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
@@ -4240,9 +4240,9 @@
     return false;
   }
 
-  if (Subtarget.isTargetWin64()) {
+  const MachineFunction *MF = TailCall.getParent()->getParent();
+  if (Subtarget.isTargetWin64() && MF->hasWinCFI()) {
     // Conditional tail calls confuse the Win64 unwinder.
-    // TODO: Allow them for "leaf" functions; PR30337.
     return false;
   }
 
@@ -4252,8 +4252,7 @@
     return false;
   }
 
-  const X86MachineFunctionInfo *X86FI =
-      TailCall.getParent()->getParent()->getInfo<X86MachineFunctionInfo>();
+  const X86MachineFunctionInfo *X86FI = MF->getInfo<X86MachineFunctionInfo>();
   if (X86FI->getTCReturnAddrDelta() != 0 ||
       TailCall.getOperand(1).getImm() != 0) {
     // A conditional tail call cannot do any stack adjustment.
Index: llvm/trunk/test/CodeGen/X86/conditional-tailcall.ll
===================================================================
--- llvm/trunk/test/CodeGen/X86/conditional-tailcall.ll
+++ llvm/trunk/test/CodeGen/X86/conditional-tailcall.ll
@@ -1,5 +1,6 @@
-; RUN: llc < %s -mtriple=i686-linux -show-mc-encoding | FileCheck %s
-; RUN: llc < %s -mtriple=x86_64-linux -show-mc-encoding | FileCheck %s
+; RUN: llc < %s -mtriple=i686-linux -show-mc-encoding | FileCheck -check-prefix=CHECK %s
+; RUN: llc < %s -mtriple=x86_64-linux -show-mc-encoding | FileCheck -check-prefix=CHECK %s
+; RUN: llc < %s -mtriple=x86_64-win32 -show-mc-encoding | FileCheck -check-prefix=CHECK -check-prefix=WIN64 %s
 
 declare void @foo()
 declare void @bar()
@@ -23,6 +24,28 @@
 ; CHECK: jmp foo
 }
 
+define void @f_non_leaf(i32 %x, i32 %y) optsize {
+entry:
+  ; Force %ebx to be spilled on the stack, turning this into
+  ; not a "leaf" function for Win64.
+  tail call void asm sideeffect "", "~{ebx}"()
+
+	%p = icmp eq i32 %x, %y
+  br i1 %p, label %bb1, label %bb2
+bb1:
+  tail call void @foo()
+  ret void
+bb2:
+  tail call void @bar()
+  ret void
+
+; CHECK-LABEL: f_non_leaf:
+; WIN64-NOT: je foo
+; WIN64-NOT: jne bar
+; WIN64: jne
+; WIN64: jmp foo
+; WIN64: jmp bar
+}
 
 declare x86_thiscallcc zeroext i1 @baz(i8*, i32)
 define x86_thiscallcc zeroext i1 @BlockPlacementTest(i8* %this, i32 %x) optsize {