Add getUniqueVRegDef to MachineRegisterInfo.

This comes in handy during peephole optimization.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159453 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 16 insertions, 0 deletions

diff --git a/include/llvm/CodeGen/MachineRegisterInfo.h b/include/llvm/CodeGen/MachineRegisterInfo.h
index 5a82caa9ac..2bcd1c72ce 100644
--- a/include/llvm/CodeGen/MachineRegisterInfo.h
+++ b/include/llvm/CodeGen/MachineRegisterInfo.h
@@ -237,6 +237,11 @@ public:
   /// form, so there should only be one definition.
   MachineInstr *getVRegDef(unsigned Reg) const;
 
+  /// getUniqueVRegDef - Return the unique machine instr that defines the
+  /// specified virtual register or null if none is found.  If there are
+  /// multiple definitions or no definition, return null.
+  MachineInstr *getUniqueVRegDef(unsigned Reg) const;
+
   /// clearKillFlags - Iterate over all the uses of the given register and
   /// clear the kill flag from the MachineOperand. This function is used by
   /// optimization passes which extend register lifetimes and need only
diff --git a/lib/CodeGen/MachineRegisterInfo.cpp b/lib/CodeGen/MachineRegisterInfo.cpp
index 9c0d749a26..863da72774 100644
--- a/lib/CodeGen/MachineRegisterInfo.cpp
+++ b/lib/CodeGen/MachineRegisterInfo.cpp
@@ -165,6 +165,17 @@ MachineInstr *MachineRegisterInfo::getVRegDef(unsigned Reg) const {
   return !I.atEnd() ? &*I : 0;
 }
 
+/// getUniqueVRegDef - Return the unique machine instr that defines the
+/// specified virtual register or null if none is found.  If there are
+/// multiple definitions or no definition, return null.
+MachineInstr *MachineRegisterInfo::getUniqueVRegDef(unsigned Reg) const {
+  if (def_empty(Reg)) return 0;
+  def_iterator I = def_begin(Reg);
+  if (llvm::next(I) != def_end())
+    return 0;
+  return &*I;
+}
+
 bool MachineRegisterInfo::hasOneUse(unsigned RegNo) const {
   use_iterator UI = use_begin(RegNo);
   if (UI == use_end())