1 files changed, 124 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/CFIInstrInserter.cpp b/llvm/lib/CodeGen/CFIInstrInserter.cpp
new file mode 100644
index 00000000000..b83c957d7c4
--- /dev/null
+++ b/llvm/lib/CodeGen/CFIInstrInserter.cpp
@@ -0,0 +1,124 @@
+//===------ CFIInstrInserter.cpp - Insert additional CFI instructions -----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Insert CFI instructions at the beginnings of basic blocks if needed. CFI
+// instructions are inserted if basic blocks have incorrect offset or register
+// set by prevoius blocks.
+//
+//===----------------------------------------------------------------------===//
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
+using namespace llvm;
+
+namespace {
+class CFIInstrInserter : public MachineFunctionPass {
+ public:
+  CFIInstrInserter() : MachineFunctionPass(ID) {
+    initializeCFIInstrInserterPass(*PassRegistry::getPassRegistry());
+  }
+  bool runOnMachineFunction(MachineFunction &MF) override;
+  static char ID;
+
+ private:
+  StringRef getPassName() const override { return "CFI Instruction Inserter"; }
+
+  // Check if incoming CFI information of a basic block matches outgoing CFI
+  // information of the previous block. If it doesn't, insert CFI instruction at
+  // the beginning of the block that corrects the CFA calculation rule for that
+  // block.
+  void CorrectCFA(MachineFunction &MF);
+
+  // Return the cfa offset value that should be set at the beginning of MBB if
+  // needed. The negated value is needed when creating CFI instructions that set
+  // absolute offset.
+  int getCorrectCFAOffset(MachineBasicBlock &MBB) {
+    return -MBB.getIncomingCFAOffset();
+  }
+
+  // Were any CFI instructions inserted
+  bool InsertedCFIInstr = false;
+};
+}
+
+char CFIInstrInserter::ID = 0;
+INITIALIZE_PASS(CFIInstrInserter, "cfiinstrinserter",
+                "Check CFI info and insert CFI instructions if needed", false,
+                false)
+
+FunctionPass *llvm::createCFIInstrInserter() { return new CFIInstrInserter(); }
+
+bool CFIInstrInserter::runOnMachineFunction(MachineFunction &MF) {
+  bool NeedsDwarfCFI = (MF.getMMI().hasDebugInfo() ||
+                        MF.getFunction()->needsUnwindTableEntry()) &&
+                       (!MF.getTarget().getTargetTriple().isOSDarwin() &&
+                        !MF.getTarget().getTargetTriple().isOSWindows());
+
+  if (!NeedsDwarfCFI) return false;
+
+  // Insert appropriate CFI instructions for each MBB if CFA calculation rule
+  // needs to be corrected for that MBB.
+  CorrectCFA(MF);
+
+  return InsertedCFIInstr;
+}
+
+void CFIInstrInserter::CorrectCFA(MachineFunction &MF) {
+
+  MachineBasicBlock &FirstMBB = MF.front();
+  MachineBasicBlock *PrevMBB = &FirstMBB;
+  const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
+  InsertedCFIInstr = false;
+
+  for (auto &MBB : MF) {
+    // Skip the first MBB in a function
+    if (MBB.getNumber() == FirstMBB.getNumber()) continue;
+
+    auto MBBI = MBB.begin();
+    DebugLoc DL = MBB.findDebugLoc(MBBI);
+
+    if (PrevMBB->getOutgoingCFAOffset() != MBB.getIncomingCFAOffset()) {
+      // If both outgoing offset and register of a previous block don't match
+      // incoming offset and register of this block, add a def_cfa instruction
+      // with the correct offset and register for this block.
+      if (PrevMBB->getOutgoingCFARegister() != MBB.getIncomingCFARegister()) {
+        unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createDefCfa(
+            nullptr, MBB.getIncomingCFARegister(), getCorrectCFAOffset(MBB)));
+        BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
+            .addCFIIndex(CFIIndex);
+        // If outgoing offset of a previous block doesn't match incoming offset
+        // of this block, add a def_cfa_offset instruction with the correct
+        // offset for this block.
+      } else {
+        unsigned CFIIndex =
+            MF.addFrameInst(MCCFIInstruction::createDefCfaOffset(
+                nullptr, getCorrectCFAOffset(MBB)));
+        BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
+            .addCFIIndex(CFIIndex);
+      }
+      InsertedCFIInstr = true;
+      // If outgoing register of a previous block doesn't match incoming
+      // register of this block, add a def_cfa_register instruction with the
+      // correct register for this block.
+    } else if (PrevMBB->getOutgoingCFARegister() !=
+               MBB.getIncomingCFARegister()) {
+      unsigned CFIIndex =
+          MF.addFrameInst(MCCFIInstruction::createDefCfaRegister(
+              nullptr, MBB.getIncomingCFARegister()));
+      BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
+          .addCFIIndex(CFIIndex);
+      InsertedCFIInstr = true;
+    }
+    PrevMBB = &MBB;
+  }
+}