Change eliminateCallFramePseudoInstr() to return an iterator

This will become necessary in a subsequent change to make this method
merge adjacent stack adjustments, i.e. it might erase the previous
and/or next instruction.

It also greatly simplifies the calls to this function from Prolog-
EpilogInserter. Previously, that had a bunch of logic to resume iteration
after the call; now it just continues with the returned iterator.

Note that this changes the behaviour of PEI a little. Previously,
it attempted to re-visit the new instruction created by
eliminateCallFramePseudoInstr(). That code was added in r36625,
but I can't see any reason for it: the new instructions will obviously
not be pseudo instructions, they will not have FrameIndex operands,
and we have already accounted for the stack adjustment.

Differential Revision: http://reviews.llvm.org/D18627

llvm-svn: 265036

2 files changed, 7 insertions, 6 deletions

diff --git a/llvm/lib/Target/Hexagon/HexagonFrameLowering.cpp b/llvm/lib/Target/Hexagon/HexagonFrameLowering.cpp
index ac91169a7b5..827ca99743a 100644
--- a/llvm/lib/Target/Hexagon/HexagonFrameLowering.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonFrameLowering.cpp
@@ -1060,15 +1060,15 @@ bool HexagonFrameLowering::insertCSRRestoresInBlock(MachineBasicBlock &MBB,
   return true;
 }
 
-
-void HexagonFrameLowering::eliminateCallFramePseudoInstr(MachineFunction &MF,
-      MachineBasicBlock &MBB, MachineBasicBlock::iterator I) const {
+MachineBasicBlock::iterator HexagonFrameLowering::eliminateCallFramePseudoInstr(
+    MachineFunction &MF, MachineBasicBlock &MBB,
+    MachineBasicBlock::iterator I) const {
   MachineInstr &MI = *I;
   unsigned Opc = MI.getOpcode();
   (void)Opc; // Silence compiler warning.
   assert((Opc == Hexagon::ADJCALLSTACKDOWN || Opc == Hexagon::ADJCALLSTACKUP) &&
          "Cannot handle this call frame pseudo instruction");
-  MBB.erase(I);
+  return MBB.erase(I);
 }
 
 
diff --git a/llvm/lib/Target/Hexagon/HexagonFrameLowering.h b/llvm/lib/Target/Hexagon/HexagonFrameLowering.h
index dc6b0515f0a..1f578f30c77 100644
--- a/llvm/lib/Target/Hexagon/HexagonFrameLowering.h
+++ b/llvm/lib/Target/Hexagon/HexagonFrameLowering.h
@@ -42,8 +42,9 @@ public:
     return true;
   }
 
-  void eliminateCallFramePseudoInstr(MachineFunction &MF,
-      MachineBasicBlock &MBB, MachineBasicBlock::iterator I) const override;
+  MachineBasicBlock::iterator
+  eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
+                                MachineBasicBlock::iterator I) const override;
   void processFunctionBeforeFrameFinalized(MachineFunction &MF,
       RegScavenger *RS = nullptr) const override;
   void determineCalleeSaves(MachineFunction &MF, BitVector &SavedRegs,