[llvm] r225419 - X86: VZeroUpperInserter: shortcut should not trigger if we have any function live-ins.

[Matthias Braun]

Author: matze
Date: Wed Jan  7 18:33:48 2015
New Revision: 225419

URL: http://llvm.org/viewvc/llvm-project?rev=225419&view=rev
Log:
X86: VZeroUpperInserter: shortcut should not trigger if we have any function live-ins.

Modified:
    llvm/trunk/lib/Target/X86/X86VZeroUpper.cpp

Modified: llvm/trunk/lib/Target/X86/X86VZeroUpper.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86VZeroUpper.cpp?rev=225419&r1=225418&r2=225419&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86VZeroUpper.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86VZeroUpper.cpp Wed Jan  7 18:33:48 2015
@@ -254,16 +254,20 @@ bool VZeroUpperInserter::runOnMachineFun
   MachineRegisterInfo &MRI = MF.getRegInfo();
   EverMadeChange = false;
 
+  bool FnHasLiveInYmm = checkFnHasLiveInYmm(MRI);
+
   // Fast check: if the function doesn't use any ymm registers, we don't need
   // to insert any VZEROUPPER instructions.  This is constant-time, so it is
   // cheap in the common case of no ymm use.
-  bool YMMUsed = false;
-  const TargetRegisterClass *RC = &X86::VR256RegClass;
-  for (TargetRegisterClass::iterator i = RC->begin(), e = RC->end();
-       i != e; i++) {
-    if (!MRI.reg_nodbg_empty(*i)) {
-      YMMUsed = true;
-      break;
+  bool YMMUsed = FnHasLiveInYmm;
+  if (!YMMUsed) {
+    const TargetRegisterClass *RC = &X86::VR256RegClass;
+    for (TargetRegisterClass::iterator i = RC->begin(), e = RC->end(); i != e;
+         i++) {
+      if (!MRI.reg_nodbg_empty(*i)) {
+        YMMUsed = true;
+        break;
+      }
     }
   }
   if (!YMMUsed) {
@@ -282,7 +286,7 @@ bool VZeroUpperInserter::runOnMachineFun
 
   // If any YMM regs are live in to this function, add the entry block to the
   // DirtySuccessors list
-  if (checkFnHasLiveInYmm(MRI))
+  if (FnHasLiveInYmm)
     addDirtySuccessor(MF.front());
 
   // Re-visit all blocks that are successors of EXITS_DIRTY bsocks. Add