diff --git a/llvm/lib/Target/X86/X86FloatingPoint.cpp b/llvm/lib/Target/X86/X86FloatingPoint.cpp
index a4ea1a9eab04..48470da0164a 100644
--- a/llvm/lib/Target/X86/X86FloatingPoint.cpp
+++ b/llvm/lib/Target/X86/X86FloatingPoint.cpp
@@ -1662,6 +1662,7 @@ void FPS::handleSpecialFP(MachineBasicBlock::iterator &I) {
     BuildMI(*MBB, I, MI->getDebugLoc(), TII->get(X86::CALLpcrel32))
       .addExternalSymbol("_ftol2")
       .addReg(X86::ST0, RegState::ImplicitKill)
+      .addReg(X86::ECX, RegState::ImplicitDefine)
       .addReg(X86::EAX, RegState::Define | RegState::Implicit)
       .addReg(X86::EDX, RegState::Define | RegState::Implicit)
       .addReg(X86::EFLAGS, RegState::Define | RegState::Implicit);
diff --git a/llvm/lib/Target/X86/X86InstrCompiler.td b/llvm/lib/Target/X86/X86InstrCompiler.td
index 8a7ee7d077fc..896994629824 100644
--- a/llvm/lib/Target/X86/X86InstrCompiler.td
+++ b/llvm/lib/Target/X86/X86InstrCompiler.td
@@ -129,12 +129,13 @@ def SEG_ALLOCA_64 : I<0, Pseudo, (outs GR64:$dst), (ins GR64:$size),
 
 // The MSVC runtime contains an _ftol2 routine for converting floating-point
 // to integer values. It has a strange calling convention: the input is
-// popped from the x87 stack, and the return value is given in EDX:EAX. No
-// other registers (aside from flags) are touched.
+// popped from the x87 stack, and the return value is given in EDX:EAX. ECX is
+// used as a temporary register. No other registers (aside from flags) are
+// touched.
 // Microsoft toolchains do not support 80-bit precision, so a WIN_FTOL_80
 // variant is unnecessary.
 
-let Defs = [EAX, EDX, EFLAGS], FPForm = SpecialFP in {
+let Defs = [EAX, EDX, ECX, EFLAGS], FPForm = SpecialFP in {
   def WIN_FTOL_32 : I<0, Pseudo, (outs), (ins RFP32:$src),
                       "# win32 fptoui",
                       [(X86WinFTOL RFP32:$src)]>,