Merge "Update aosp/master LLVM for rebase to r230699."

1 files changed, 192 insertions, 0 deletions

diff --git a/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp b/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp
new file mode 100644
index 0000000..0c47cbd
--- /dev/null
+++ b/lib/Transforms/Scalar/LowerExpectIntrinsic.cpp
@@ -0,0 +1,192 @@
+//===- 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.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar/LowerExpectIntrinsic.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/MDBuilder.h"
+#include "llvm/IR/Metadata.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Transforms/Scalar.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "lower-expect-intrinsic"
+
+STATISTIC(ExpectIntrinsicsHandled,
+          "Number of 'expect' intrinsic instructions 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)"));
+
+static bool 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.
+  SmallVector<uint32_t, 16> Weights(n + 1, UnlikelyBranchWeight);
+
+  if (Case == SI.case_default())
+    Weights[0] = LikelyBranchWeight;
+  else
+    Weights[Case.getCaseIndex() + 1] = LikelyBranchWeight;
+
+  SI.setMetadata(LLVMContext::MD_prof,
+                 MDBuilder(CI->getContext()).createBranchWeights(Weights));
+
+  SI.setCondition(ArgValue);
+  return true;
+}
+
+static bool handleBranchExpect(BranchInst &BI) {
+  if (BI.isUnconditional())
+    return false;
+
+  // Handle non-optimized IR code like:
+  //   %expval = call i64 @llvm.expect.i64(i64 %conv1, i64 1)
+  //   %tobool = icmp ne i64 %expval, 0
+  //   br i1 %tobool, label %if.then, label %if.end
+  //
+  // Or the following simpler case:
+  //   %expval = call i1 @llvm.expect.i1(i1 %cmp, i1 1)
+  //   br i1 %expval, label %if.then, label %if.end
+
+  CallInst *CI;
+
+  ICmpInst *CmpI = dyn_cast<ICmpInst>(BI.getCondition());
+  if (!CmpI) {
+    CI = dyn_cast<CallInst>(BI.getCondition());
+  } else {
+    if (CmpI->getPredicate() != CmpInst::ICMP_NE)
+      return false;
+    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);
+
+  if (CmpI)
+    CmpI->setOperand(0, ArgValue);
+  else
+    BI.setCondition(ArgValue);
+  return true;
+}
+
+static bool lowerExpectIntrinsic(Function &F) {
+  bool Changed = false;
+
+  for (BasicBlock &BB : F) {
+    // Create "block_weights" metadata.
+    if (BranchInst *BI = dyn_cast<BranchInst>(BB.getTerminator())) {
+      if (handleBranchExpect(*BI))
+        ExpectIntrinsicsHandled++;
+    } else if (SwitchInst *SI = dyn_cast<SwitchInst>(BB.getTerminator())) {
+      if (handleSwitchExpect(*SI))
+        ExpectIntrinsicsHandled++;
+    }
+
+    // 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();
+        Changed = true;
+      }
+    }
+  }
+
+  return Changed;
+}
+
+PreservedAnalyses LowerExpectIntrinsicPass::run(Function &F) {
+  if (lowerExpectIntrinsic(F))
+    return PreservedAnalyses::none();
+
+  return PreservedAnalyses::all();
+}
+
+namespace {
+/// \brief Legacy pass for lowering expect intrinsics out of the IR.
+///
+/// When this pass is run over a function it uses expect intrinsics which feed
+/// branches and switches to provide branch weight metadata for those
+/// terminators. It then removes the expect intrinsics from the IR so the rest
+/// of the optimizer can ignore them.
+class LowerExpectIntrinsic : public FunctionPass {
+public:
+  static char ID;
+  LowerExpectIntrinsic() : FunctionPass(ID) {
+    initializeLowerExpectIntrinsicPass(*PassRegistry::getPassRegistry());
+  }
+
+  bool runOnFunction(Function &F) override { return lowerExpectIntrinsic(F); }
+};
+}
+
+char LowerExpectIntrinsic::ID = 0;
+INITIALIZE_PASS(LowerExpectIntrinsic, "lower-expect",
+                "Lower 'expect' Intrinsics", false, false)
+
+FunctionPass *llvm::createLowerExpectIntrinsicPass() {
+  return new LowerExpectIntrinsic();
+}