Don't perform expensive queries checking for super and sub registers when we know that there aren't any.

This speed up LiveVariables on instcombine at -O0 -g from 0.3855s to 0.3503s.  Look for more improvements in this area soon!

llvm-svn: 52804

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index e008c9a61b9..5da6a317cb0 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -780,6 +780,7 @@ bool MachineInstr::addRegisterDead(unsigned IncomingReg,
                                    const TargetRegisterInfo *RegInfo,
                                    bool AddIfNotFound) {
   bool isPhysReg = TargetRegisterInfo::isPhysicalRegister(IncomingReg);
+  bool hasAliases = isPhysReg && RegInfo->getAliasSet(IncomingReg) == 0;
   bool Found = false;
   SmallVector<unsigned,4> DeadOps;
   for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
@@ -790,7 +791,7 @@ bool MachineInstr::addRegisterDead(unsigned IncomingReg,
     if (Reg == IncomingReg) {
       MO.setIsDead();
       Found = true;
-    } else if (isPhysReg && MO.isDead() &&
+    } else if (hasAliases && MO.isDead() &&
         TargetRegisterInfo::isPhysicalRegister(Reg)) {
       // There exists a super-register that's marked dead.
       if (RegInfo->isSuperRegister(IncomingReg, Reg))