LivePhysRegs: Skip reserved regs in computeLiveIns; NFCI

We do not track liveness of reserved registers so adding them to the
liveins list in computeLiveIns() was completely unnecessary.

llvm-svn: 303937

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/LivePhysRegs.cpp b/llvm/lib/CodeGen/LivePhysRegs.cpp
index 9f7d7cf5484..10d9406a27e 100644
--- a/llvm/lib/CodeGen/LivePhysRegs.cpp
+++ b/llvm/lib/CodeGen/LivePhysRegs.cpp
@@ -200,8 +200,10 @@ void LivePhysRegs::addLiveIns(const MachineBasicBlock &MBB) {
   addBlockLiveIns(MBB);
 }
 
-void llvm::computeLiveIns(LivePhysRegs &LiveRegs, const TargetRegisterInfo &TRI,
+void llvm::computeLiveIns(LivePhysRegs &LiveRegs,
+                          const MachineRegisterInfo &MRI,
                           MachineBasicBlock &MBB) {
+  const TargetRegisterInfo &TRI = *MRI.getTargetRegisterInfo();
   assert(MBB.livein_empty());
   LiveRegs.init(TRI);
   LiveRegs.addLiveOutsNoPristines(MBB);
@@ -209,6 +211,8 @@ void llvm::computeLiveIns(LivePhysRegs &LiveRegs, const TargetRegisterInfo &TRI,
     LiveRegs.stepBackward(MI);
 
   for (unsigned Reg : LiveRegs) {
+    if (MRI.isReserved(Reg))
+      continue;
     // Skip the register if we are about to add one of its super registers.
     bool ContainsSuperReg = false;
     for (MCSuperRegIterator SReg(Reg, &TRI); SReg.isValid(); ++SReg) {