CodeGen support for x86_64 SEH catch handlers in LLVM
This adds handling for ExceptionHandling::MSVC, used by the
x86_64-pc-windows-msvc triple. It assumes that filter functions have
already been outlined in either the frontend or the backend. Filter
functions are used in place of the landingpad catch clause type info
operands. In catch clause order, the first filter to return true will
catch the exception.
The C specific handler table expects the landing pad to be split into
one block per handler, but LLVM IR uses a single landing pad for all
possible unwind actions. This patch papers over the mismatch by
synthesizing single instruction BBs for every catch clause to fill in
the EH selector that the landing pad block expects.
Missing functionality:
- Accessing data in the parent frame from outlined filters
- Cleanups (from __finally) are unsupported, as they will require
outlining and parent frame access
- Filter clauses are unsupported, as there's no clear analogue in SEH
In other words, this is the minimal set of changes needed to write IR to
catch arbitrary exceptions and resume normal execution.
Reviewers: majnemer
Differential Revision: http://reviews.llvm.org/D6300
llvm-svn: 225904
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 151bc72..86a63ee 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2071,10 +2071,14 @@
// Get the two live-in registers as SDValues. The physregs have already been
// copied into virtual registers.
SDValue Ops[2];
- Ops[0] = DAG.getZExtOrTrunc(
- DAG.getCopyFromReg(DAG.getEntryNode(), getCurSDLoc(),
- FuncInfo.ExceptionPointerVirtReg, TLI.getPointerTy()),
- getCurSDLoc(), ValueVTs[0]);
+ if (FuncInfo.ExceptionPointerVirtReg) {
+ Ops[0] = DAG.getZExtOrTrunc(
+ DAG.getCopyFromReg(DAG.getEntryNode(), getCurSDLoc(),
+ FuncInfo.ExceptionPointerVirtReg, TLI.getPointerTy()),
+ getCurSDLoc(), ValueVTs[0]);
+ } else {
+ Ops[0] = DAG.getConstant(0, TLI.getPointerTy());
+ }
Ops[1] = DAG.getZExtOrTrunc(
DAG.getCopyFromReg(DAG.getEntryNode(), getCurSDLoc(),
FuncInfo.ExceptionSelectorVirtReg, TLI.getPointerTy()),
@@ -2086,6 +2090,27 @@
setValue(&LP, Res);
}
+unsigned
+SelectionDAGBuilder::visitLandingPadClauseBB(GlobalValue *ClauseGV,
+ MachineBasicBlock *LPadBB) {
+ SDValue Chain = getControlRoot();
+
+ // Get the typeid that we will dispatch on later.
+ const TargetLowering &TLI = DAG.getTargetLoweringInfo();
+ const TargetRegisterClass *RC = TLI.getRegClassFor(TLI.getPointerTy());
+ unsigned VReg = FuncInfo.MF->getRegInfo().createVirtualRegister(RC);
+ unsigned TypeID = DAG.getMachineFunction().getMMI().getTypeIDFor(ClauseGV);
+ SDValue Sel = DAG.getConstant(TypeID, TLI.getPointerTy());
+ Chain = DAG.getCopyToReg(Chain, getCurSDLoc(), VReg, Sel);
+
+ // Branch to the main landing pad block.
+ MachineBasicBlock *ClauseMBB = FuncInfo.MBB;
+ ClauseMBB->addSuccessor(LPadBB);
+ DAG.setRoot(DAG.getNode(ISD::BR, getCurSDLoc(), MVT::Other, Chain,
+ DAG.getBasicBlock(LPadBB)));
+ return VReg;
+}
+
/// handleSmallSwitchCaseRange - Emit a series of specific tests (suitable for
/// small case ranges).
bool SelectionDAGBuilder::handleSmallSwitchRange(CaseRec& CR,