[llvm] r276886 - [Hexagon] Add saved callee-saved registers as live-in in non-wrapped blocks

[Krzysztof Parzyszek via llvm-commits]

Author: kparzysz
Date: Wed Jul 27 11:26:39 2016
New Revision: 276886

URL: http://llvm.org/viewvc/llvm-project?rev=276886&view=rev
Log:
[Hexagon] Add saved callee-saved registers as live-in in non-wrapped blocks

The callee-saved registers that are saved in a function are not pristine,
and so they can be defined and used. In case of shrink-wrapping though,
there are blocks that are outside of the save/restore range, and in those
blocks the saved registers must be treated as pristine. To avoid any uses
of these registers, add them as live-in in all those blocks.
This was already done for blocks reaching function exits after restore,
add code that does the same for blocks reached from the function entry
before save.

Modified:
    llvm/trunk/lib/Target/Hexagon/HexagonFrameLowering.cpp
    llvm/trunk/lib/Target/Hexagon/HexagonFrameLowering.h

Modified: llvm/trunk/lib/Target/Hexagon/HexagonFrameLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Hexagon/HexagonFrameLowering.cpp?rev=276886&r1=276885&r2=276886&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Hexagon/HexagonFrameLowering.cpp (original)
+++ llvm/trunk/lib/Target/Hexagon/HexagonFrameLowering.cpp Wed Jul 27 11:26:39 2016
@@ -457,6 +457,7 @@ void HexagonFrameLowering::emitPrologue(
   bool PrologueStubs = false;
   insertCSRSpillsInBlock(*PrologB, CSI, HRI, PrologueStubs);
   insertPrologueInBlock(*PrologB, PrologueStubs);
+  updateEntryPaths(MF, *PrologB);
 
   if (EpilogB) {
     insertCSRRestoresInBlock(*EpilogB, CSI, HRI);
@@ -485,12 +486,9 @@ void HexagonFrameLowering::emitPrologue(
     // If there is an epilog block, it may not have a return instruction.
     // In such case, we need to add the callee-saved registers as live-ins
     // in all blocks on all paths from the epilog to any return block.
-    unsigned MaxBN = 0;
-    for (auto &B : MF)
-      if (B.getNumber() >= 0)
-        MaxBN = std::max(MaxBN, unsigned(B.getNumber()));
+    unsigned MaxBN = MF.getNumBlockIDs();
     BitVector DoneT(MaxBN+1), DoneF(MaxBN+1), Path(MaxBN+1);
-    updateExitPaths(*EpilogB, EpilogB, DoneT, DoneF, Path);
+    updateExitPaths(*EpilogB, *EpilogB, DoneT, DoneF, Path);
   }
 }
 
@@ -653,9 +651,30 @@ void HexagonFrameLowering::insertEpilogu
   MBB.erase(RetI);
 }
 
+void HexagonFrameLowering::updateEntryPaths(MachineFunction &MF,
+      MachineBasicBlock &SaveB) const {
+  SetVector<unsigned> Worklist;
+
+  MachineBasicBlock &EntryB = MF.front();
+  Worklist.insert(EntryB.getNumber());
+
+  unsigned SaveN = SaveB.getNumber();
+  auto &CSI = MF.getFrameInfo()->getCalleeSavedInfo();
+
+  for (unsigned i = 0; i < Worklist.size(); ++i) {
+    unsigned BN = Worklist[i];
+    MachineBasicBlock &MBB = *MF.getBlockNumbered(BN);
+    for (auto &R : CSI)
+      if (!MBB.isLiveIn(R.getReg()))
+        MBB.addLiveIn(R.getReg());
+    if (BN != SaveN)
+      for (auto &SB : MBB.successors())
+        Worklist.insert(SB->getNumber());
+  }
+}
 
 bool HexagonFrameLowering::updateExitPaths(MachineBasicBlock &MBB,
-      MachineBasicBlock *RestoreB, BitVector &DoneT, BitVector &DoneF,
+      MachineBasicBlock &RestoreB, BitVector &DoneT, BitVector &DoneF,
       BitVector &Path) const {
   assert(MBB.getNumber() >= 0);
   unsigned BN = MBB.getNumber();
@@ -685,7 +704,7 @@ bool HexagonFrameLowering::updateExitPat
   // We don't want to add unnecessary live-ins to the restore block: since
   // the callee-saved registers are being defined in it, the entry of the
   // restore block cannot be on the path from the definitions to any exit.
-  if (ReachedExit && &MBB != RestoreB) {
+  if (ReachedExit && &MBB != &RestoreB) {
     for (auto &R : CSI)
       if (!MBB.isLiveIn(R.getReg()))
         MBB.addLiveIn(R.getReg());

Modified: llvm/trunk/lib/Target/Hexagon/HexagonFrameLowering.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Hexagon/HexagonFrameLowering.h?rev=276886&r1=276885&r2=276886&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Hexagon/HexagonFrameLowering.h (original)
+++ llvm/trunk/lib/Target/Hexagon/HexagonFrameLowering.h Wed Jul 27 11:26:39 2016
@@ -91,7 +91,8 @@ private:
       const HexagonRegisterInfo &HRI, bool &PrologueStubs) const;
   bool insertCSRRestoresInBlock(MachineBasicBlock &MBB, const CSIVect &CSI,
       const HexagonRegisterInfo &HRI) const;
-  bool updateExitPaths(MachineBasicBlock &MBB, MachineBasicBlock *RestoreB,
+  void updateEntryPaths(MachineFunction &MF, MachineBasicBlock &SaveB) const;
+  bool updateExitPaths(MachineBasicBlock &MBB, MachineBasicBlock &RestoreB,
       BitVector &DoneT, BitVector &DoneF, BitVector &Path) const;
   void insertCFIInstructionsAt(MachineBasicBlock &MBB,
       MachineBasicBlock::iterator At) const;