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.

llvm-svn: 185617

1 files changed, 7 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 587ea83721a..3d490fac6b2 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/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();