1 files changed, 39 insertions, 4 deletions
diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index 08a51b9b0242..1cb57a4fa425 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -606,6 +606,26 @@ void MachineBasicBlock::removeLiveIn(MCRegister Reg, LaneBitmask LaneMask) {
     LiveIns.erase(I);
 }
 
+void MachineBasicBlock::removeLiveInOverlappedWith(MCRegister Reg) {
+  const MachineFunction *MF = getParent();
+  const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
+  // Remove Reg and its subregs from live in set.
+  for (MCPhysReg S : TRI->subregs_inclusive(Reg))
+    removeLiveIn(S);
+
+  // Remove live-in bitmask in super registers as well.
+  for (MCPhysReg Super : TRI->superregs(Reg)) {
+    for (MCSubRegIndexIterator SRI(Super, TRI); SRI.isValid(); ++SRI) {
+      if (Reg == SRI.getSubReg()) {
+        unsigned SubRegIndex = SRI.getSubRegIndex();
+        LaneBitmask SubRegLaneMask = TRI->getSubRegIndexLaneMask(SubRegIndex);
+        removeLiveIn(Super, SubRegLaneMask);
+        break;
+      }
+    }
+  }
+}
+
 MachineBasicBlock::livein_iterator
 MachineBasicBlock::removeLiveIn(MachineBasicBlock::livein_iterator I) {
   // Get non-const version of iterator.
@@ -1160,7 +1180,7 @@ MachineBasicBlock *MachineBasicBlock::SplitCriticalEdge(
 MachineBasicBlock *MachineBasicBlock::SplitCriticalEdge(
     MachineBasicBlock *Succ, const SplitCriticalEdgeAnalyses &Analyses,
     std::vector<SparseBitVector<>> *LiveInSets, MachineDomTreeUpdater *MDTU) {
-  if (!canSplitCriticalEdge(Succ))
+  if (!canSplitCriticalEdge(Succ, Analyses.MLI))
     return nullptr;
 
   MachineFunction *MF = getParent();
@@ -1388,8 +1408,8 @@ MachineBasicBlock *MachineBasicBlock::SplitCriticalEdge(
   return NMBB;
 }
 
-bool MachineBasicBlock::canSplitCriticalEdge(
-    const MachineBasicBlock *Succ) const {
+bool MachineBasicBlock::canSplitCriticalEdge(const MachineBasicBlock *Succ,
+                                             const MachineLoopInfo *MLI) const {
   // Splitting the critical edge to a landing pad block is non-trivial. Don't do
   // it in this generic function.
   if (Succ->isEHPad())
@@ -1403,8 +1423,17 @@ bool MachineBasicBlock::canSplitCriticalEdge(
   const MachineFunction *MF = getParent();
   // Performance might be harmed on HW that implements branching using exec mask
   // where both sides of the branches are always executed.
-  if (MF->getTarget().requiresStructuredCFG())
+
+  if (MF->getTarget().requiresStructuredCFG()) {
+    // If `Succ` is a loop header, splitting the critical edge will not
+    // break structured CFG.
+    if (MLI) {
+      const MachineLoop *L = MLI->getLoopFor(Succ);
+      return L && L->getHeader() == Succ;
+    }
+
     return false;
+  }
 
   // Do we have an Indirect jump with a jumptable that we can rewrite?
   int JTI = findJumpTableIndex(*this);
@@ -1802,6 +1831,12 @@ bool MachineBasicBlock::sizeWithoutDebugLargerThan(unsigned Limit) const {
   return false;
 }
 
+void MachineBasicBlock::removePHIsIncomingValuesForPredecessor(
+    const MachineBasicBlock &PredMBB) {
+  for (MachineInstr &Phi : phis())
+    Phi.removePHIIncomingValueFor(PredMBB);
+}
+
 const MBBSectionID MBBSectionID::ColdSectionID(MBBSectionID::SectionType::Cold);
 const MBBSectionID
     MBBSectionID::ExceptionSectionID(MBBSectionID::SectionType::Exception);