1 files changed, 31 insertions, 3 deletions
diff --git a/lib/Target/X86/X86VZeroUpper.cpp b/lib/Target/X86/X86VZeroUpper.cpp
index 477f75a..66ae9c2 100644
--- a/lib/Target/X86/X86VZeroUpper.cpp
+++ b/lib/Target/X86/X86VZeroUpper.cpp
@@ -122,11 +122,11 @@ static bool checkFnHasLiveInYmm(MachineRegisterInfo &MRI) {
 }
 
 static bool clobbersAllYmmRegs(const MachineOperand &MO) {
-  for (unsigned reg = X86::YMM0; reg < X86::YMM31; ++reg) {
+  for (unsigned reg = X86::YMM0; reg <= X86::YMM31; ++reg) {
     if (!MO.clobbersPhysReg(reg))
       return false;
   }
-  for (unsigned reg = X86::ZMM0; reg < X86::ZMM31; ++reg) {
+  for (unsigned reg = X86::ZMM0; reg <= X86::ZMM31; ++reg) {
     if (!MO.clobbersPhysReg(reg))
       return false;
   }
@@ -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) {
@@ -231,8 +250,9 @@ bool VZeroUpperInserter::processBasicBlock(MachineFunction &MF,
   bool BBHasCall = false;
 
   for (MachineBasicBlock::iterator I = BB.begin(); I != BB.end(); ++I) {
-    MachineInstr *MI = I;
     DebugLoc dl = I->getDebugLoc();
+    MachineInstr *MI = I;
+
     bool isControlFlow = MI->isCall() || MI->isReturn();
 
     // Shortcut: don't need to check regular instructions in dirty state.
@@ -251,6 +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