[WinEH] Add a funclet layout pass
Windows EH funclets need to be contiguous. The FuncletLayout pass will
ensure that the funclets are together and begin with a funclet entry MBB.
Differential Revision: http://reviews.llvm.org/D12943
llvm-svn: 247937
diff --git a/llvm/lib/CodeGen/FuncletLayout.cpp b/llvm/lib/CodeGen/FuncletLayout.cpp
new file mode 100644
index 0000000..9b40a1a
--- /dev/null
+++ b/llvm/lib/CodeGen/FuncletLayout.cpp
@@ -0,0 +1,97 @@
+//===-- FuncletLayout.cpp - Contiguously lay out funclets -----------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements basic block placement transformations which result in
+// funclets being contiguous.
+//
+//===----------------------------------------------------------------------===//
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/ADT/MapVector.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "funclet-layout"
+
+namespace {
+class FuncletLayout : public MachineFunctionPass {
+public:
+ static char ID; // Pass identification, replacement for typeid
+ FuncletLayout() : MachineFunctionPass(ID) {
+ initializeFuncletLayoutPass(*PassRegistry::getPassRegistry());
+ }
+
+ bool runOnMachineFunction(MachineFunction &F) override;
+};
+}
+
+static void
+collectFuncletMembers(MapVector<MachineBasicBlock *, int> &FuncletMembership,
+ int Funclet, MachineBasicBlock *MBB) {
+ // Don't revisit blocks.
+ if (FuncletMembership.count(MBB) > 0)
+ return;
+
+ // Add this MBB to our funclet.
+ FuncletMembership[MBB] = Funclet;
+
+ bool IsReturn = false;
+ int NumTerminators = 0;
+ for (MachineInstr &MI : MBB->terminators()) {
+ IsReturn |= MI.isReturn();
+ ++NumTerminators;
+ }
+ assert((!IsReturn || NumTerminators == 1) &&
+ "Expected only one terminator when a return is present!");
+
+ // Returns are boundaries where funclet transfer can occur, don't follow
+ // successors.
+ if (IsReturn)
+ return;
+
+ for (MachineBasicBlock *SMBB : MBB->successors())
+ if (!SMBB->isEHPad())
+ collectFuncletMembers(FuncletMembership, Funclet, SMBB);
+}
+
+char FuncletLayout::ID = 0;
+char &llvm::FuncletLayoutID = FuncletLayout::ID;
+INITIALIZE_PASS(FuncletLayout, "funclet-layout",
+ "Contiguously Lay Out Funclets", false, false)
+
+bool FuncletLayout::runOnMachineFunction(MachineFunction &F) {
+ // We don't have anything to do if there aren't any EH pads.
+ if (!F.getMMI().hasEHFunclets())
+ return false;
+
+ SmallVector<MachineBasicBlock *, 16> FuncletBlocks;
+ for (MachineBasicBlock &MBB : F)
+ if (MBB.isEHFuncletEntry())
+ FuncletBlocks.push_back(&MBB);
+
+ // We don't have anything to do if there aren't any EH pads.
+ if (FuncletBlocks.empty())
+ return false;
+
+ MapVector<MachineBasicBlock *, int> FuncletMembership;
+ for (MachineBasicBlock *MBB : FuncletBlocks)
+ collectFuncletMembers(FuncletMembership, MBB->getNumber(), MBB);
+
+ for (std::pair<llvm::MachineBasicBlock *, int> &FuncletMember :
+ FuncletMembership) {
+ // Move this block to the end of the function.
+ MachineBasicBlock *MBB = FuncletMember.first;
+ MBB->moveAfter(--F.end());
+ }
+
+ // Conservatively assume we changed something.
+ return true;
+}