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

4 files changed, 11 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/BranchFolding.cpp b/llvm/lib/CodeGen/BranchFolding.cpp
index 025b9fc6cd0..03ceac10bee 100644
--- a/llvm/lib/CodeGen/BranchFolding.cpp
+++ b/llvm/lib/CodeGen/BranchFolding.cpp
@@ -153,13 +153,14 @@ bool BranchFolder::OptimizeFunction(MachineFunction &MF,
 
   TriedMerging.clear();
 
+  MachineRegisterInfo &MRI = MF.getRegInfo();
   AfterBlockPlacement = AfterPlacement;
   TII = tii;
   TRI = tri;
   MMI = mmi;
   MLI = mli;
+  this->MRI = &MRI;
 
-  MachineRegisterInfo &MRI = MF.getRegInfo();
   UpdateLiveIns = MRI.tracksLiveness() && TRI->trackLivenessAfterRegAlloc(MF);
   if (!UpdateLiveIns)
     MRI.invalidateLiveness();
@@ -351,7 +352,7 @@ void BranchFolder::ReplaceTailWithBranchTo(MachineBasicBlock::iterator OldInst,
 
   if (UpdateLiveIns) {
     NewDest->clearLiveIns();
-    computeLiveIns(LiveRegs, *TRI, *NewDest);
+    computeLiveIns(LiveRegs, *MRI, *NewDest);
   }
 
   ++NumTailMerge;
@@ -388,7 +389,7 @@ MachineBasicBlock *BranchFolder::SplitMBBAt(MachineBasicBlock &CurMBB,
   MBBFreqInfo.setBlockFreq(NewMBB, MBBFreqInfo.getBlockFreq(&CurMBB));
 
   if (UpdateLiveIns)
-    computeLiveIns(LiveRegs, *TRI, *NewMBB);
+    computeLiveIns(LiveRegs, *MRI, *NewMBB);
 
   // Add the new block to the funclet.
   const auto &FuncletI = FuncletMembership.find(&CurMBB);
diff --git a/llvm/lib/CodeGen/BranchFolding.h b/llvm/lib/CodeGen/BranchFolding.h
index 4852721eea1..92681137e4c 100644
--- a/llvm/lib/CodeGen/BranchFolding.h
+++ b/llvm/lib/CodeGen/BranchFolding.h
@@ -108,6 +108,7 @@ namespace llvm {
     bool UpdateLiveIns;
     unsigned MinCommonTailLength;
     const TargetInstrInfo *TII;
+    const MachineRegisterInfo *MRI;
     const TargetRegisterInfo *TRI;
     MachineModuleInfo *MMI;
     MachineLoopInfo *MLI;
diff --git a/llvm/lib/CodeGen/BranchRelaxation.cpp b/llvm/lib/CodeGen/BranchRelaxation.cpp
index 7af13694166..feaabb44c07 100644
--- a/llvm/lib/CodeGen/BranchRelaxation.cpp
+++ b/llvm/lib/CodeGen/BranchRelaxation.cpp
@@ -259,7 +259,7 @@ MachineBasicBlock *BranchRelaxation::splitBlockBeforeInstr(MachineInstr &MI,
 
   // Need to fix live-in lists if we track liveness.
   if (TRI->trackLivenessAfterRegAlloc(*MF))
-    computeLiveIns(LiveRegs, *TRI, *NewBB);
+    computeLiveIns(LiveRegs, MF->getRegInfo(), *NewBB);
 
   ++NumSplit;
 
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) {