Fill out codegen SSA updater. It's not yet tested.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90395 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 0 deletions

diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp
index f73a5a3621..ba9be6a870 100644
--- a/lib/CodeGen/MachineInstr.cpp
+++ b/lib/CodeGen/MachineInstr.cpp
@@ -1058,6 +1058,20 @@ bool MachineInstr::isInvariantLoad(AliasAnalysis *AA) const {
   return true;
 }
 
+/// isConstantValuePHI - If the specified instruction is a PHI that always
+/// merges together the same virtual register, return the register, otherwise
+/// return 0.
+unsigned MachineInstr::isConstantValuePHI() const {
+  if (getOpcode() != TargetInstrInfo::PHI)
+    return 0;
+
+  unsigned Reg = getOperand(1).getReg();
+  for (unsigned i = 3, e = getNumOperands(); i < e; i += 2)
+    if (getOperand(i).getReg() != Reg)
+      return 0;
+  return Reg;
+}
+
 void MachineInstr::dump() const {
   errs() << "  " << *this;
 }