[NFC] Factor out guard utility methods into a separate file

This patch creates file GuardUtils which will contain logic for work with guards
that can be shared across different passes.

Differential Revision: https://reviews.llvm.org/D51151
Reviewed By: fedor.sergeev

llvm-svn: 340914

1 files changed, 64 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/GuardUtils.cpp b/llvm/lib/Transforms/Utils/GuardUtils.cpp
new file mode 100644
index 0000000..08de0a4
--- /dev/null
+++ b/llvm/lib/Transforms/Utils/GuardUtils.cpp
@@ -0,0 +1,64 @@
+//===-- GuardUtils.cpp - Utils for work with guards -------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// Utils that are used to perform transformations related to guards and their
+// conditions.
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/GuardUtils.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/MDBuilder.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+
+using namespace llvm;
+
+static cl::opt<uint32_t> PredicatePassBranchWeight(
+    "guards-predicate-pass-branch-weight", cl::Hidden, cl::init(1 << 20),
+    cl::desc("The probability of a guard failing is assumed to be the "
+             "reciprocal of this value (default = 1 << 20)"));
+
+void llvm::makeGuardControlFlowExplicit(Function *DeoptIntrinsic,
+                                        CallInst *Guard) {
+  OperandBundleDef DeoptOB(*Guard->getOperandBundle(LLVMContext::OB_deopt));
+  SmallVector<Value *, 4> Args(std::next(Guard->arg_begin()), Guard->arg_end());
+
+  auto *CheckBB = Guard->getParent();
+  auto *DeoptBlockTerm =
+      SplitBlockAndInsertIfThen(Guard->getArgOperand(0), Guard, true);
+
+  auto *CheckBI = cast<BranchInst>(CheckBB->getTerminator());
+
+  // SplitBlockAndInsertIfThen inserts control flow that branches to
+  // DeoptBlockTerm if the condition is true.  We want the opposite.
+  CheckBI->swapSuccessors();
+
+  CheckBI->getSuccessor(0)->setName("guarded");
+  CheckBI->getSuccessor(1)->setName("deopt");
+
+  if (auto *MD = Guard->getMetadata(LLVMContext::MD_make_implicit))
+    CheckBI->setMetadata(LLVMContext::MD_make_implicit, MD);
+
+  MDBuilder MDB(Guard->getContext());
+  CheckBI->setMetadata(LLVMContext::MD_prof,
+                       MDB.createBranchWeights(PredicatePassBranchWeight, 1));
+
+  IRBuilder<> B(DeoptBlockTerm);
+  auto *DeoptCall = B.CreateCall(DeoptIntrinsic, Args, {DeoptOB}, "");
+
+  if (DeoptIntrinsic->getReturnType()->isVoidTy()) {
+    B.CreateRetVoid();
+  } else {
+    DeoptCall->setName("deoptcall");
+    B.CreateRet(DeoptCall);
+  }
+
+  DeoptCall->setCallingConv(Guard->getCallingConv());
+  DeoptBlockTerm->eraseFromParent();
+}