1 files changed, 174 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Transforms/Utils/LowerExpectIntrinsic.cpp b/contrib/llvm/lib/Transforms/Utils/LowerExpectIntrinsic.cpp
new file mode 100644
index 0000000..02bdcda
--- /dev/null
+++ b/contrib/llvm/lib/Transforms/Utils/LowerExpectIntrinsic.cpp
@@ -0,0 +1,174 @@
+//===- LowerExpectIntrinsic.cpp - Lower expect intrinsic ------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass lowers the 'expect' intrinsic to LLVM metadata.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "lower-expect-intrinsic"
+#include "llvm/BasicBlock.h"
+#include "llvm/Constants.h"
+#include "llvm/Function.h"
+#include "llvm/Instructions.h"
+#include "llvm/Intrinsics.h"
+#include "llvm/LLVMContext.h"
+#include "llvm/MDBuilder.h"
+#include "llvm/Metadata.h"
+#include "llvm/Pass.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include <vector>
+
+using namespace llvm;
+
+STATISTIC(IfHandled, "Number of 'expect' intrinsic intructions handled");
+
+static cl::opt<uint32_t>
+LikelyBranchWeight("likely-branch-weight", cl::Hidden, cl::init(64),
+                   cl::desc("Weight of the branch likely to be taken (default = 64)"));
+static cl::opt<uint32_t>
+UnlikelyBranchWeight("unlikely-branch-weight", cl::Hidden, cl::init(4),
+                   cl::desc("Weight of the branch unlikely to be taken (default = 4)"));
+
+namespace {
+
+  class LowerExpectIntrinsic : public FunctionPass {
+
+    bool HandleSwitchExpect(SwitchInst *SI);
+
+    bool HandleIfExpect(BranchInst *BI);
+
+  public:
+    static char ID;
+    LowerExpectIntrinsic() : FunctionPass(ID) {
+      initializeLowerExpectIntrinsicPass(*PassRegistry::getPassRegistry());
+    }
+
+    bool runOnFunction(Function &F);
+  };
+}
+
+
+bool LowerExpectIntrinsic::HandleSwitchExpect(SwitchInst *SI) {
+  CallInst *CI = dyn_cast<CallInst>(SI->getCondition());
+  if (!CI)
+    return false;
+
+  Function *Fn = CI->getCalledFunction();
+  if (!Fn || Fn->getIntrinsicID() != Intrinsic::expect)
+    return false;
+
+  Value *ArgValue = CI->getArgOperand(0);
+  ConstantInt *ExpectedValue = dyn_cast<ConstantInt>(CI->getArgOperand(1));
+  if (!ExpectedValue)
+    return false;
+
+  SwitchInst::CaseIt Case = SI->findCaseValue(ExpectedValue);
+  unsigned n = SI->getNumCases(); // +1 for default case.
+  std::vector<uint32_t> Weights(n + 1);
+
+  Weights[0] = Case == SI->case_default() ? LikelyBranchWeight
+                                          : UnlikelyBranchWeight;
+  for (unsigned i = 0; i != n; ++i)
+    Weights[i + 1] = i == Case.getCaseIndex() ? LikelyBranchWeight
+                                              : UnlikelyBranchWeight;
+
+  SI->setMetadata(LLVMContext::MD_prof,
+                  MDBuilder(CI->getContext()).createBranchWeights(Weights));
+
+  SI->setCondition(ArgValue);
+  return true;
+}
+
+
+bool LowerExpectIntrinsic::HandleIfExpect(BranchInst *BI) {
+  if (BI->isUnconditional())
+    return false;
+
+  // Handle non-optimized IR code like:
+  //   %expval = call i64 @llvm.expect.i64.i64(i64 %conv1, i64 1)
+  //   %tobool = icmp ne i64 %expval, 0
+  //   br i1 %tobool, label %if.then, label %if.end
+
+  ICmpInst *CmpI = dyn_cast<ICmpInst>(BI->getCondition());
+  if (!CmpI || CmpI->getPredicate() != CmpInst::ICMP_NE)
+    return false;
+
+  CallInst *CI = dyn_cast<CallInst>(CmpI->getOperand(0));
+  if (!CI)
+    return false;
+
+  Function *Fn = CI->getCalledFunction();
+  if (!Fn || Fn->getIntrinsicID() != Intrinsic::expect)
+    return false;
+
+  Value *ArgValue = CI->getArgOperand(0);
+  ConstantInt *ExpectedValue = dyn_cast<ConstantInt>(CI->getArgOperand(1));
+  if (!ExpectedValue)
+    return false;
+
+  MDBuilder MDB(CI->getContext());
+  MDNode *Node;
+
+  // If expect value is equal to 1 it means that we are more likely to take
+  // branch 0, in other case more likely is branch 1.
+  if (ExpectedValue->isOne())
+    Node = MDB.createBranchWeights(LikelyBranchWeight, UnlikelyBranchWeight);
+  else
+    Node = MDB.createBranchWeights(UnlikelyBranchWeight, LikelyBranchWeight);
+
+  BI->setMetadata(LLVMContext::MD_prof, Node);
+
+  CmpI->setOperand(0, ArgValue);
+  return true;
+}
+
+
+bool LowerExpectIntrinsic::runOnFunction(Function &F) {
+  for (Function::iterator I = F.begin(), E = F.end(); I != E;) {
+    BasicBlock *BB = I++;
+
+    // Create "block_weights" metadata.
+    if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator())) {
+      if (HandleIfExpect(BI))
+        IfHandled++;
+    } else if (SwitchInst *SI = dyn_cast<SwitchInst>(BB->getTerminator())) {
+      if (HandleSwitchExpect(SI))
+        IfHandled++;
+    }
+
+    // remove llvm.expect intrinsics.
+    for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
+         BI != BE; ) {
+      CallInst *CI = dyn_cast<CallInst>(BI++);
+      if (!CI)
+        continue;
+
+      Function *Fn = CI->getCalledFunction();
+      if (Fn && Fn->getIntrinsicID() == Intrinsic::expect) {
+        Value *Exp = CI->getArgOperand(0);
+        CI->replaceAllUsesWith(Exp);
+        CI->eraseFromParent();
+      }
+    }
+  }
+
+  return false;
+}
+
+
+char LowerExpectIntrinsic::ID = 0;
+INITIALIZE_PASS(LowerExpectIntrinsic, "lower-expect", "Lower 'expect' "
+                "Intrinsics", false, false)
+
+FunctionPass *llvm::createLowerExpectIntrinsicPass() {
+  return new LowerExpectIntrinsic();
+}