1 files changed, 89 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Scalar/LowerGuardIntrinsic.cpp b/llvm/lib/Transforms/Scalar/LowerGuardIntrinsic.cpp
new file mode 100644
index 000000000000..9489e01774d6
--- /dev/null
+++ b/llvm/lib/Transforms/Scalar/LowerGuardIntrinsic.cpp
@@ -0,0 +1,89 @@
+//===- LowerGuardIntrinsic.cpp - Lower the guard intrinsic ---------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass lowers the llvm.experimental.guard intrinsic to a conditional call
+// to @llvm.experimental.deoptimize.  Once this happens, the guard can no longer
+// be widened.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar/LowerGuardIntrinsic.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Analysis/GuardUtils.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/InstIterator.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/GuardUtils.h"
+
+using namespace llvm;
+
+namespace {
+struct LowerGuardIntrinsicLegacyPass : public FunctionPass {
+  static char ID;
+  LowerGuardIntrinsicLegacyPass() : FunctionPass(ID) {
+    initializeLowerGuardIntrinsicLegacyPassPass(
+        *PassRegistry::getPassRegistry());
+  }
+
+  bool runOnFunction(Function &F) override;
+};
+}
+
+static bool lowerGuardIntrinsic(Function &F) {
+  // Check if we can cheaply rule out the possibility of not having any work to
+  // do.
+  auto *GuardDecl = F.getParent()->getFunction(
+      Intrinsic::getName(Intrinsic::experimental_guard));
+  if (!GuardDecl || GuardDecl->use_empty())
+    return false;
+
+  SmallVector<CallInst *, 8> ToLower;
+  for (auto &I : instructions(F))
+    if (isGuard(&I))
+      ToLower.push_back(cast<CallInst>(&I));
+
+  if (ToLower.empty())
+    return false;
+
+  auto *DeoptIntrinsic = Intrinsic::getDeclaration(
+      F.getParent(), Intrinsic::experimental_deoptimize, {F.getReturnType()});
+  DeoptIntrinsic->setCallingConv(GuardDecl->getCallingConv());
+
+  for (auto *CI : ToLower) {
+    makeGuardControlFlowExplicit(DeoptIntrinsic, CI);
+    CI->eraseFromParent();
+  }
+
+  return true;
+}
+
+bool LowerGuardIntrinsicLegacyPass::runOnFunction(Function &F) {
+  return lowerGuardIntrinsic(F);
+}
+
+char LowerGuardIntrinsicLegacyPass::ID = 0;
+INITIALIZE_PASS(LowerGuardIntrinsicLegacyPass, "lower-guard-intrinsic",
+                "Lower the guard intrinsic to normal control flow", false,
+                false)
+
+Pass *llvm::createLowerGuardIntrinsicPass() {
+  return new LowerGuardIntrinsicLegacyPass();
+}
+
+PreservedAnalyses LowerGuardIntrinsicPass::run(Function &F,
+                                               FunctionAnalysisManager &AM) {
+  if (lowerGuardIntrinsic(F))
+    return PreservedAnalyses::none();
+
+  return PreservedAnalyses::all();
+}