diff --git a/lib/Target/X86/X86VZeroUpper.cpp b/lib/Target/X86/X86VZeroUpper.cpp
index 0d37a7d0e674..a9446529494a 100644
--- a/lib/Target/X86/X86VZeroUpper.cpp
+++ b/lib/Target/X86/X86VZeroUpper.cpp
@@ -148,6 +148,25 @@ static bool hasYmmReg(MachineInstr *MI) {
   return false;
 }
 
+/// clobbersAnyYmmReg() - Check if any YMM register will be clobbered by this
+/// instruction.
+static bool clobbersAnyYmmReg(MachineInstr *MI) {
+  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+    const MachineOperand &MO = MI->getOperand(i);
+    if (!MO.isRegMask())
+      continue;
+    for (unsigned reg = X86::YMM0; reg < X86::YMM31; ++reg) {
+      if (MO.clobbersPhysReg(reg))
+        return true;
+    }
+    for (unsigned reg = X86::ZMM0; reg < X86::ZMM31; ++reg) {
+      if (MO.clobbersPhysReg(reg))
+        return true;
+    }
+  }
+  return false;
+}
+
 /// runOnMachineFunction - Loop over all of the basic blocks, inserting
 /// vzero upper instructions before function calls.
 bool VZeroUpperInserter::runOnMachineFunction(MachineFunction &MF) {
@@ -234,14 +253,6 @@ bool VZeroUpperInserter::processBasicBlock(MachineFunction &MF,
     DebugLoc dl = I->getDebugLoc();
     MachineInstr *MI = I;
 
-    // Don't need to check instructions added in prolog.
-    // In prolog, special function calls may be added for specific targets
-    // (e.g. on Windows, a prolog helper '_chkstk' is called when the local
-    // variables exceed 4K bytes on stack.) These helpers won't use/def YMM/XMM
-    // registers.
-    if (MI->getFlag(MachineInstr::FrameSetup))
-      continue;
-
     bool isControlFlow = MI->isCall() || MI->isReturn();
 
     // Shortcut: don't need to check regular instructions in dirty state.
@@ -260,6 +271,14 @@ bool VZeroUpperInserter::processBasicBlock(MachineFunction &MF,
     if (!isControlFlow)
       continue;
 
+    // If the call won't clobber any YMM register, skip it as well. It usually
+    // happens on helper function calls (such as '_chkstk', '_ftol2') where
+    // standard calling convention is not used (RegMask is not used to mark
+    // register clobbered and register usage (def/imp-def/use) is well-dfined
+    // and explicitly specified.
+    if (MI->isCall() && !clobbersAnyYmmReg(MI))
+      continue;
+
     BBHasCall = true;
 
     // The VZEROUPPER instruction resets the upper 128 bits of all Intel AVX
diff --git a/test/CodeGen/X86/pr17631.ll b/test/CodeGen/X86/pr17631.ll
index a572ff2e3b3b..98f951f1b10c 100644
--- a/test/CodeGen/X86/pr17631.ll
+++ b/test/CodeGen/X86/pr17631.ll
@@ -1,16 +1,16 @@
 ; RUN: llc < %s -mcpu=core-avx-i -mtriple=i386-pc-win32 | FileCheck %s
- 
+
 %struct_type = type { [64 x <8 x float>], <8 x float> }
- 
+
 ; Function Attrs: nounwind readnone
 declare i32 @llvm.x86.avx.movmsk.ps.256(<8 x float>)
- 
+
 ; Function Attrs: nounwind
 define i32 @equal(<8 x i32> %A) {
 allocas:
   %first_alloc  = alloca [64 x <8 x i32>]
   %second_alloc = alloca %struct_type
- 
+
   %A1 = bitcast <8 x i32> %A to <8 x float>
   %A2 = call i32 @llvm.x86.avx.movmsk.ps.256(<8 x float> %A1)
   ret i32 %A2
@@ -20,3 +20,15 @@ allocas:
 ; CHECK-NOT: vzeroupper
 ; CHECK: _chkstk
 ; CHECK: ret
+
+define <8 x float> @foo(<8 x float> %y, i64* %p, double %x) {
+  %i = fptoui double %x to i64
+  store i64 %i, i64* %p
+  %ret = fadd <8 x float> %y, %y
+  ret <8 x float> %ret
+}
+
+; CHECK: foo
+; CHECK-NOT: vzeroupper
+; CHECK: _ftol2
+; CHECK: ret