1 files changed, 89 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/ResetMachineFunctionPass.cpp b/llvm/lib/CodeGen/ResetMachineFunctionPass.cpp
new file mode 100644
index 000000000000..019de6554d2a
--- /dev/null
+++ b/llvm/lib/CodeGen/ResetMachineFunctionPass.cpp
@@ -0,0 +1,89 @@
+//===-- ResetMachineFunctionPass.cpp - Reset Machine Function ----*- C++ -*-==//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+/// \file
+/// This file implements a pass that will conditionally reset a machine
+/// function as if it was just created. This is used to provide a fallback
+/// mechanism when GlobalISel fails, thus the condition for the reset to
+/// happen is that the MachineFunction has the FailedISel property.
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/ScopeExit.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/StackProtector.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/DiagnosticInfo.h"
+#include "llvm/Support/Debug.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "reset-machine-function"
+
+STATISTIC(NumFunctionsReset, "Number of functions reset");
+STATISTIC(NumFunctionsVisited, "Number of functions visited");
+
+namespace {
+  class ResetMachineFunction : public MachineFunctionPass {
+    /// Tells whether or not this pass should emit a fallback
+    /// diagnostic when it resets a function.
+    bool EmitFallbackDiag;
+    /// Whether we should abort immediately instead of resetting the function.
+    bool AbortOnFailedISel;
+
+  public:
+    static char ID; // Pass identification, replacement for typeid
+    ResetMachineFunction(bool EmitFallbackDiag = false,
+                         bool AbortOnFailedISel = false)
+        : MachineFunctionPass(ID), EmitFallbackDiag(EmitFallbackDiag),
+          AbortOnFailedISel(AbortOnFailedISel) {}
+
+    StringRef getPassName() const override { return "ResetMachineFunction"; }
+
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
+      AU.addPreserved<StackProtector>();
+      MachineFunctionPass::getAnalysisUsage(AU);
+    }
+
+    bool runOnMachineFunction(MachineFunction &MF) override {
+      ++NumFunctionsVisited;
+      // No matter what happened, whether we successfully selected the function
+      // or not, nothing is going to use the vreg types after us. Make sure they
+      // disappear.
+      auto ClearVRegTypesOnReturn =
+          make_scope_exit([&MF]() { MF.getRegInfo().clearVirtRegTypes(); });
+
+      if (MF.getProperties().hasProperty(
+              MachineFunctionProperties::Property::FailedISel)) {
+        if (AbortOnFailedISel)
+          report_fatal_error("Instruction selection failed");
+        LLVM_DEBUG(dbgs() << "Resetting: " << MF.getName() << '\n');
+        ++NumFunctionsReset;
+        MF.reset();
+        if (EmitFallbackDiag) {
+          const Function &F = MF.getFunction();
+          DiagnosticInfoISelFallback DiagFallback(F);
+          F.getContext().diagnose(DiagFallback);
+        }
+        return true;
+      }
+      return false;
+    }
+
+  };
+} // end anonymous namespace
+
+char ResetMachineFunction::ID = 0;
+INITIALIZE_PASS(ResetMachineFunction, DEBUG_TYPE,
+                "Reset machine function if ISel failed", false, false)
+
+MachineFunctionPass *
+llvm::createResetMachineFunctionPass(bool EmitFallbackDiag = false,
+                                     bool AbortOnFailedISel = false) {
+  return new ResetMachineFunction(EmitFallbackDiag, AbortOnFailedISel);
+}