1 files changed, 88 insertions, 0 deletions

diff --git a/contrib/llvm/lib/CodeGen/PatchableFunction.cpp b/contrib/llvm/lib/CodeGen/PatchableFunction.cpp
new file mode 100644
index 000000000000..32468c90b864
--- /dev/null
+++ b/contrib/llvm/lib/CodeGen/PatchableFunction.cpp
@@ -0,0 +1,88 @@
+//===-- PatchableFunction.cpp - Patchable prologues for LLVM -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements edits function bodies in place to support the
+// "patchable-function" attribute.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/Target/TargetFrameLowering.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
+
+using namespace llvm;
+
+namespace {
+struct PatchableFunction : public MachineFunctionPass {
+  static char ID; // Pass identification, replacement for typeid
+  PatchableFunction() : MachineFunctionPass(ID) {
+    initializePatchableFunctionPass(*PassRegistry::getPassRegistry());
+  }
+
+  bool runOnMachineFunction(MachineFunction &F) override;
+   MachineFunctionProperties getRequiredProperties() const override {
+    return MachineFunctionProperties().set(
+        MachineFunctionProperties::Property::AllVRegsAllocated);
+  }
+};
+}
+
+/// Returns true if instruction \p MI will not result in actual machine code
+/// instructions.
+static bool doesNotGeneratecode(const MachineInstr &MI) {
+  // TODO: Introduce an MCInstrDesc flag for this
+  switch (MI.getOpcode()) {
+  default: return false;
+  case TargetOpcode::IMPLICIT_DEF:
+  case TargetOpcode::KILL:
+  case TargetOpcode::CFI_INSTRUCTION:
+  case TargetOpcode::EH_LABEL:
+  case TargetOpcode::GC_LABEL:
+  case TargetOpcode::DBG_VALUE:
+    return true;
+  }
+}
+
+bool PatchableFunction::runOnMachineFunction(MachineFunction &MF) {
+  if (!MF.getFunction()->hasFnAttribute("patchable-function"))
+    return false;
+
+#ifndef NDEBUG
+  Attribute PatchAttr = MF.getFunction()->getFnAttribute("patchable-function");
+  StringRef PatchType = PatchAttr.getValueAsString();
+  assert(PatchType == "prologue-short-redirect" && "Only possibility today!");
+#endif
+
+  auto &FirstMBB = *MF.begin();
+  MachineBasicBlock::iterator FirstActualI = FirstMBB.begin();
+  for (; doesNotGeneratecode(*FirstActualI); ++FirstActualI)
+    assert(FirstActualI != FirstMBB.end());
+
+  auto *TII = MF.getSubtarget().getInstrInfo();
+  auto MIB = BuildMI(FirstMBB, FirstActualI, FirstActualI->getDebugLoc(),
+                     TII->get(TargetOpcode::PATCHABLE_OP))
+                 .addImm(2)
+                 .addImm(FirstActualI->getOpcode());
+
+  for (auto &MO : FirstActualI->operands())
+    MIB.addOperand(MO);
+
+  FirstActualI->eraseFromParent();
+  MF.ensureAlignment(4);
+  return true;
+}
+
+char PatchableFunction::ID = 0;
+char &llvm::PatchableFunctionID = PatchableFunction::ID;
+INITIALIZE_PASS(PatchableFunction, "patchable-function",
+                "Implement the 'patchable-function' attribute", false, false)