//
//===----------------------------------------------------------------------===//
-#include "llvm/Transforms/Scalar.h"
+#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/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
-#include <vector>
+#include "llvm/Transforms/Scalar.h"
using namespace llvm;
#define DEBUG_TYPE "lower-expect-intrinsic"
-STATISTIC(IfHandled, "Number of 'expect' intrinsic instructions handled");
+STATISTIC(ExpectIntrinsicsHandled,
+ "Number of 'expect' intrinsic instructions handled");
static cl::opt<uint32_t>
LikelyBranchWeight("likely-branch-weight", cl::Hidden, cl::init(64),
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) override;
-};
-}
-
-bool LowerExpectIntrinsic::HandleSwitchExpect(SwitchInst *SI) {
- CallInst *CI = dyn_cast<CallInst>(SI->getCondition());
+static bool handleSwitchExpect(SwitchInst &SI) {
+ CallInst *CI = dyn_cast<CallInst>(SI.getCondition());
if (!CI)
return false;
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);
+ SwitchInst::CaseIt Case = SI.findCaseValue(ExpectedValue);
+ unsigned n = SI.getNumCases(); // +1 for default case.
+ SmallVector<uint32_t, 16> Weights(n + 1, UnlikelyBranchWeight);
- Weights[0] =
- Case == SI->case_default() ? LikelyBranchWeight : UnlikelyBranchWeight;
- for (unsigned i = 0; i != n; ++i)
- Weights[i + 1] =
- i == Case.getCaseIndex() ? LikelyBranchWeight : 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.setMetadata(LLVMContext::MD_prof,
+ MDBuilder(CI->getContext()).createBranchWeights(Weights));
- SI->setCondition(ArgValue);
+ SI.setCondition(ArgValue);
return true;
}
-bool LowerExpectIntrinsic::HandleIfExpect(BranchInst *BI) {
- if (BI->isUnconditional())
+static bool handleBranchExpect(BranchInst &BI) {
+ if (BI.isUnconditional())
return false;
// Handle non-optimized IR code like:
CallInst *CI;
- ICmpInst *CmpI = dyn_cast<ICmpInst>(BI->getCondition());
+ ICmpInst *CmpI = dyn_cast<ICmpInst>(BI.getCondition());
if (!CmpI) {
- CI = dyn_cast<CallInst>(BI->getCondition());
+ CI = dyn_cast<CallInst>(BI.getCondition());
} else {
if (CmpI->getPredicate() != CmpInst::ICMP_NE)
return false;
else
Node = MDB.createBranchWeights(UnlikelyBranchWeight, LikelyBranchWeight);
- BI->setMetadata(LLVMContext::MD_prof, Node);
+ BI.setMetadata(LLVMContext::MD_prof, Node);
if (CmpI)
CmpI->setOperand(0, ArgValue);
else
- BI->setCondition(ArgValue);
+ BI.setCondition(ArgValue);
return true;
}
-bool LowerExpectIntrinsic::runOnFunction(Function &F) {
- for (Function::iterator I = F.begin(), E = F.end(); I != E;) {
- BasicBlock *BB = I++;
+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 (HandleIfExpect(BI))
- IfHandled++;
- } else if (SwitchInst *SI = dyn_cast<SwitchInst>(BB->getTerminator())) {
- if (HandleSwitchExpect(SI))
- IfHandled++;
+ 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;) {
+ for (BasicBlock::iterator BI = BB.begin(), BE = BB.end(); BI != BE;) {
CallInst *CI = dyn_cast<CallInst>(BI++);
if (!CI)
continue;
Value *Exp = CI->getArgOperand(0);
CI->replaceAllUsesWith(Exp);
CI->eraseFromParent();
+ Changed = true;
}
}
}
- return false;
+ 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;