Simplify landing pad lowering.

Stop using the ISD::EXCEPTIONADDR and ISD::EHSELECTION when lowering
landing pad arguments. These nodes were previously legalized into
CopyFromReg nodes, but that never worked properly because the
CopyFromReg node weren't guaranteed to be  scheduled at the top of the
basic block.

This meant the exception pointer and selector registers could be
clobbered before being copied to a virtual register.

This patch copies the two physical registers to virtual registers at
the beginning of the basic block, and lowers the landingpad instruction
directly to two CopyFromReg nodes reading the *virtual* registers. This
is safe because virtual registers don't get clobbered.

A future patch will remove the ISD::EXCEPTIONADDR and ISD::EHSELECTION
nodes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185617 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/FunctionLoweringInfo.h b/include/llvm/CodeGen/FunctionLoweringInfo.h
index f1d815592f80c8dae7357b9a2ac1abb4abdf8d23..50d320f8e839d338b7f3b098bd88b8d8ad249f0d 100644 (file)
--- a/include/llvm/CodeGen/FunctionLoweringInfo.h
+++ b/include/llvm/CodeGen/FunctionLoweringInfo.h
@@ -115,6 +115,11 @@ public:
   /// there's no other convenient place for it to live right now.
   std::vector<std::pair<MachineInstr*, unsigned> > PHINodesToUpdate;
 
+  /// If the current MBB is a landing pad, the exception pointer and exception
+  /// selector registers are copied into these virtual registers by
+  /// SelectionDAGISel::PrepareEHLandingPad().
+  unsigned ExceptionPointerVirtReg, ExceptionSelectorVirtReg;
+
   explicit FunctionLoweringInfo(const TargetMachine &TM) : TM(TM) {}
 
   /// set - Initialize this FunctionLoweringInfo with the given Function

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 03696b9c39b93224e35a801fe2e26fe2d6c86f73..fe284f5c0fca8fdad246cbf3053e75eae7b58898 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1919,33 +1919,25 @@ void SelectionDAGBuilder::visitLandingPad(const LandingPadInst &LP) {
 
   SmallVector<EVT, 2> ValueVTs;
   ComputeValueVTs(*TLI, LP.getType(), ValueVTs);
+  assert(ValueVTs.size() == 2 && "Only two-valued landingpads are supported");
 
-  // Insert the EXCEPTIONADDR instruction.
-  assert(FuncInfo.MBB->isLandingPad() &&
-         "Call to eh.exception not in landing pad!");
-  SDVTList VTs = DAG.getVTList(TLI->getPointerTy(), MVT::Other);
+  // Get the two live-in registers as SDValues. The physregs have already been
+  // copied into virtual registers.
   SDValue Ops[2];
-  Ops[0] = DAG.getRoot();
-  SDValue Op1 = DAG.getNode(ISD::EXCEPTIONADDR, getCurSDLoc(), VTs, Ops, 1);
-  SDValue Chain = Op1.getValue(1);
-
-  // Insert the EHSELECTION instruction.
-  VTs = DAG.getVTList(TLI->getPointerTy(), MVT::Other);
-  Ops[0] = Op1;
-  Ops[1] = Chain;
-  SDValue Op2 = DAG.getNode(ISD::EHSELECTION, getCurSDLoc(), VTs, Ops, 2);
-  Chain = Op2.getValue(1);
-  Op2 = DAG.getSExtOrTrunc(Op2, getCurSDLoc(), MVT::i32);
-
-  Ops[0] = Op1;
-  Ops[1] = Op2;
+  Ops[0] = DAG.getZExtOrTrunc(
+    DAG.getCopyFromReg(DAG.getEntryNode(), getCurSDLoc(),
+                       FuncInfo.ExceptionPointerVirtReg, TLI->getPointerTy()),
+    getCurSDLoc(), ValueVTs[0]);
+  Ops[1] = DAG.getZExtOrTrunc(
+    DAG.getCopyFromReg(DAG.getEntryNode(), getCurSDLoc(),
+                       FuncInfo.ExceptionSelectorVirtReg, TLI->getPointerTy()),
+    getCurSDLoc(), ValueVTs[1]);
+
+  // Merge into one.
   SDValue Res = DAG.getNode(ISD::MERGE_VALUES, getCurSDLoc(),
                             DAG.getVTList(&ValueVTs[0], ValueVTs.size()),
                             &Ops[0], 2);
-
-  std::pair<SDValue, SDValue> RetPair = std::make_pair(Res, Chain);
-  setValue(&LP, RetPair.first);
-  DAG.setRoot(RetPair.second);
+  setValue(&LP, Res);
 }
 
 /// handleSmallSwitchCaseRange - Emit a series of specific tests (suitable for

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 587ea83721aeda1c6221f24aac8049508dd99093..3d490fac6b266b604c3d64eec6beec3bb4bc3258 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -829,12 +829,13 @@ void SelectionDAGISel::PrepareEHLandingPad() {
 
   // Mark exception register as live in.
   const TargetLowering *TLI = getTargetLowering();
-  unsigned Reg = TLI->getExceptionPointerRegister();
-  if (Reg) MBB->addLiveIn(Reg);
+  const TargetRegisterClass *PtrRC = TLI->getRegClassFor(TLI->getPointerTy());
+  if (unsigned Reg = TLI->getExceptionPointerRegister())
+    FuncInfo->ExceptionPointerVirtReg = MBB->addLiveIn(Reg, PtrRC);
 
   // Mark exception selector register as live in.
-  Reg = TLI->getExceptionSelectorRegister();
-  if (Reg) MBB->addLiveIn(Reg);
+  if (unsigned Reg = TLI->getExceptionSelectorRegister())
+    FuncInfo->ExceptionSelectorVirtReg = MBB->addLiveIn(Reg, PtrRC);
 }
 
 /// isFoldedOrDeadInstruction - Return true if the specified instruction is
@@ -972,6 +973,8 @@ void SelectionDAGISel::SelectAllBasicBlocks(const Function &Fn) {
     FuncInfo->InsertPt = FuncInfo->MBB->getFirstNonPHI();
 
     // Setup an EH landing-pad block.
+    FuncInfo->ExceptionPointerVirtReg = 0;
+    FuncInfo->ExceptionSelectorVirtReg = 0;
     if (FuncInfo->MBB->isLandingPad())
       PrepareEHLandingPad();