[CodeGenPrepare] Hoist all getSubtargetImpl calls to the beginning of the pass

[igor-laevsky]

Summary

Calls to the getSubtargetImpl on X86 tend to have non trivial execution cost. Usually it's negligible but it becomes noticeable when we try to request subtarget from the frequently executed methods, i.e like optimizeMemoryInst. This change saves subtarget, target lowering and target register info at the beginning of the pass and reuses this values during pass execution.

On one of our internal benchmarks this change reduces time spent in the llc by ~20%.

[echristo]

LGTM.

Thanks!

-eric

lib/CodeGen/CodeGenPrepare.cpp

 namespace {
 typedef SmallPtrSet<Instruction *, 16> SetOfInstrs;
 typedef PointerIntPair<Type *, 1, bool> TypeIsSExt;
 typedef DenseMap<Instruction *, TypeIsSExt> InstrToOrigTy;
 class TypePromotionTransaction;
 
   class CodeGenPrepare : public FunctionPass {
     const TargetMachine *TM;
+    const TargetSubtargetInfo *SubtargetInfo;
     const TargetLowering *TLI;
+    const TargetRegisterInfo *TRI;
     const TargetTransformInfo *TTI;
     const TargetLibraryInfo *TLInfo;
     const LoopInfo *LI;
     std::unique_ptr<BlockFrequencyInfo> BFI;
     std::unique_ptr<BranchProbabilityInfo> BPI;
 
     /// As we scan instructions optimizing them, this is the next instruction
     /// to optimize. Transforms that can invalidate this should update it.
bool CodeGenPrepare::runOnFunction(Function &F) {
   bool EverMadeChange = false;
   // Clear per function information.
   InsertedInsts.clear();
   PromotedInsts.clear();
   BFI.reset();
   BPI.reset();
 
   ModifiedDT = false;
-  if (TM)
-    TLI = TM->getSubtargetImpl(F)->getTargetLowering();
+  if (TM) {
+    SubtargetInfo = TM->getSubtargetImpl(F);
+    TLI = SubtargetInfo->getTargetLowering();
+    TRI = SubtargetInfo->getRegisterInfo();
+  }
   TLInfo = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
   TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
   LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
   OptSize = F.optForSize();
 
   if (ProfileGuidedSectionPrefix) {
     ProfileSummaryInfo *PSI =
         getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
void TypePromotionTransaction::rollback(
   }
 }
 
 /// \brief A helper class for matching addressing modes.
 ///
 /// This encapsulates the logic for matching the target-legal addressing modes.
 class AddressingModeMatcher {
   SmallVectorImpl<Instruction*> &AddrModeInsts;
-  const TargetMachine &TM;
   const TargetLowering &TLI;
+  const TargetRegisterInfo &TRI;
   const DataLayout &DL;
 
   /// AccessTy/MemoryInst - This is the type for the access (e.g. double) and
   /// the memory instruction that we're computing this address for.
   Type *AccessTy;
   unsigned AddrSpace;
   Instruction *MemoryInst;
 
   /// This is the addressing mode that we're building up. This is
   /// part of the return value of this addressing mode matching stuff.
   ExtAddrMode &AddrMode;
 
   /// The instructions inserted by other CodeGenPrepare optimizations.
   const SetOfInstrs &InsertedInsts;
   /// A map from the instructions to their type before promotion.
   InstrToOrigTy &PromotedInsts;
   /// The ongoing transaction where every action should be registered.
   TypePromotionTransaction &TPT;
 
   /// This is set to true when we should not do profitability checks.
   /// When true, IsProfitableToFoldIntoAddressingMode always returns true.
   bool IgnoreProfitability;
 
   AddressingModeMatcher(SmallVectorImpl<Instruction *> &AMI,
-                        const TargetMachine &TM, Type *AT, unsigned AS,
+                        const TargetLowering &TLI,
+                        const TargetRegisterInfo &TRI,
+                        Type *AT, unsigned AS,
                         Instruction *MI, ExtAddrMode &AM,
                         const SetOfInstrs &InsertedInsts,
                         InstrToOrigTy &PromotedInsts,
                         TypePromotionTransaction &TPT)
-      : AddrModeInsts(AMI), TM(TM),
-        TLI(*TM.getSubtargetImpl(*MI->getParent()->getParent())
-                 ->getTargetLowering()),
+      : AddrModeInsts(AMI), TLI(TLI), TRI(TRI),
         DL(MI->getModule()->getDataLayout()), AccessTy(AT), AddrSpace(AS),
         MemoryInst(MI), AddrMode(AM), InsertedInsts(InsertedInsts),
         PromotedInsts(PromotedInsts), TPT(TPT) {
     IgnoreProfitability = false;
   }
 public:
 
   /// Find the maximal addressing mode that a load/store of V can fold,
   /// give an access type of AccessTy.  This returns a list of involved
   /// instructions in AddrModeInsts.
   /// \p InsertedInsts The instructions inserted by other CodeGenPrepare
   /// optimizations.
   /// \p PromotedInsts maps the instructions to their type before promotion.
   /// \p The ongoing transaction where every action should be registered.
   static ExtAddrMode Match(Value *V, Type *AccessTy, unsigned AS,
                            Instruction *MemoryInst,
                            SmallVectorImpl<Instruction*> &AddrModeInsts,
-                           const TargetMachine &TM,
+                           const TargetLowering &TLI,
+                           const TargetRegisterInfo &TRI,
                            const SetOfInstrs &InsertedInsts,
                            InstrToOrigTy &PromotedInsts,
                            TypePromotionTransaction &TPT) {
     ExtAddrMode Result;
 
-    bool Success = AddressingModeMatcher(AddrModeInsts, TM, AccessTy, AS,
+    bool Success = AddressingModeMatcher(AddrModeInsts, TLI, TRI,
+                                         AccessTy, AS,
                                          MemoryInst, Result, InsertedInsts,
                                          PromotedInsts, TPT).matchAddr(V, 0);
     (void)Success; assert(Success && "Couldn't select *anything*?");
     return Result;
   }
 private:
   bool matchScaledValue(Value *ScaleReg, int64_t Scale, unsigned Depth);
   bool matchAddr(Value *V, unsigned Depth);
bool AddressingModeMatcher::matchAddr(Value *Addr, unsigned Depth) {
   // Couldn't match.
   TPT.rollback(LastKnownGood);
   return false;
 }
 
 /// Check to see if all uses of OpVal by the specified inline asm call are due
 /// to memory operands. If so, return true, otherwise return false.
 static bool IsOperandAMemoryOperand(CallInst *CI, InlineAsm *IA, Value *OpVal,
-                                    const TargetMachine &TM) {
+                                    const TargetLowering &TLI,
+                                    const TargetRegisterInfo &TRI) {
   const Function *F = CI->getParent()->getParent();
-  const TargetLowering *TLI = TM.getSubtargetImpl(*F)->getTargetLowering();
-  const TargetRegisterInfo *TRI = TM.getSubtargetImpl(*F)->getRegisterInfo();
   TargetLowering::AsmOperandInfoVector TargetConstraints =
-      TLI->ParseConstraints(F->getParent()->getDataLayout(), TRI,
+      TLI.ParseConstraints(F->getParent()->getDataLayout(), &TRI,
                             ImmutableCallSite(CI));
+
   for (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) {
     TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i];
 
     // Compute the constraint code and ConstraintType to use.
-    TLI->ComputeConstraintToUse(OpInfo, SDValue());
+    TLI.ComputeConstraintToUse(OpInfo, SDValue());
 
     // If this asm operand is our Value*, and if it isn't an indirect memory
     // operand, we can't fold it!
     if (OpInfo.CallOperandVal == OpVal &&
         (OpInfo.ConstraintType != TargetLowering::C_Memory ||
          !OpInfo.isIndirect))
       return false;
   }
 
   return true;
 }
 
 /// Recursively walk all the uses of I until we find a memory use.
 /// If we find an obviously non-foldable instruction, return true.
 /// Add the ultimately found memory instructions to MemoryUses.
 static bool FindAllMemoryUses(
     Instruction *I,
     SmallVectorImpl<std::pair<Instruction *, unsigned>> &MemoryUses,
-    SmallPtrSetImpl<Instruction *> &ConsideredInsts, const TargetMachine &TM) {
+    SmallPtrSetImpl<Instruction *> &ConsideredInsts,
+    const TargetLowering &TLI, const TargetRegisterInfo &TRI) {
   // If we already considered this instruction, we're done.
   if (!ConsideredInsts.insert(I).second)
     return false;
 
   // If this is an obviously unfoldable instruction, bail out.
   if (!MightBeFoldableInst(I))
     return true;
 
if (CallInst *CI = dyn_cast<CallInst>(UserI)) {
       // the cold path.  See optimizeCallInst
       if (!OptSize && CI->hasFnAttr(Attribute::Cold))
         continue;
 
       InlineAsm *IA = dyn_cast<InlineAsm>(CI->getCalledValue());
       if (!IA) return true;
 
       // If this is a memory operand, we're cool, otherwise bail out.
-      if (!IsOperandAMemoryOperand(CI, IA, I, TM))
+      if (!IsOperandAMemoryOperand(CI, IA, I, TLI, TRI))
         return true;
       continue;
     }
 
-    if (FindAllMemoryUses(UserI, MemoryUses, ConsideredInsts, TM))
+    if (FindAllMemoryUses(UserI, MemoryUses, ConsideredInsts, TLI, TRI))
       return true;
   }
 
   return false;
 }
 
 /// Return true if Val is already known to be live at the use site that we're
 /// folding it into. If so, there is no cost to include it in the addressing
if (!BaseReg && !ScaledReg)
     return true;
 
   // If all uses of this instruction can have the address mode sunk into them,
   // we can remove the addressing mode and effectively trade one live register
   // for another (at worst.)  In this context, folding an addressing mode into
   // the use is just a particularly nice way of sinking it.
   SmallVector<std::pair<Instruction*,unsigned>, 16> MemoryUses;
   SmallPtrSet<Instruction*, 16> ConsideredInsts;
-  if (FindAllMemoryUses(I, MemoryUses, ConsideredInsts, TM))
+  if (FindAllMemoryUses(I, MemoryUses, ConsideredInsts, TLI, TRI))
     return false;  // Has a non-memory, non-foldable use!
 
   // Now that we know that all uses of this instruction are part of a chain of
   // computation involving only operations that could theoretically be folded
   // into a memory use, loop over each of these memory operation uses and see
   // if they could  *actually* fold the instruction.  The assumption is that
   // addressing modes are cheap and that duplicating the computation involved
   // many times is worthwhile, even on a fastpath. For sinking candidates
for (unsigned i = 0, e = MemoryUses.size(); i != e; ++i) {
     unsigned AS = AddrTy->getAddressSpace();
 
     // Do a match against the root of this address, ignoring profitability. This
     // will tell us if the addressing mode for the memory operation will
     // *actually* cover the shared instruction.
     ExtAddrMode Result;
     TypePromotionTransaction::ConstRestorationPt LastKnownGood =
         TPT.getRestorationPoint();
-    AddressingModeMatcher Matcher(MatchedAddrModeInsts, TM, AddressAccessTy, AS,
+    AddressingModeMatcher Matcher(MatchedAddrModeInsts, TLI, TRI,
+                                  AddressAccessTy, AS,
                                   MemoryInst, Result, InsertedInsts,
                                   PromotedInsts, TPT);
     Matcher.IgnoreProfitability = true;
     bool Success = Matcher.matchAddr(Address, 0);
     (void)Success; assert(Success && "Couldn't select *anything*?");
 
     // The match was to check the profitability, the changes made are not
     // part of the original matcher. Therefore, they should be dropped
if (PHINode *P = dyn_cast<PHINode>(V)) {
       continue;
     }
 
     // For non-PHIs, determine the addressing mode being computed.  Note that
     // the result may differ depending on what other uses our candidate
     // addressing instructions might have.
     SmallVector<Instruction*, 16> NewAddrModeInsts;
     ExtAddrMode NewAddrMode = AddressingModeMatcher::Match(
-      V, AccessTy, AddrSpace, MemoryInst, NewAddrModeInsts, *TM,
+      V, AccessTy, AddrSpace, MemoryInst, NewAddrModeInsts, *TLI, *TRI,
       InsertedInsts, PromotedInsts, TPT);
 
     // This check is broken into two cases with very similar code to avoid using
     // getNumUses() as much as possible. Some values have a lot of uses, so
     // calling getNumUses() unconditionally caused a significant compile-time
     // regression.
     if (!Consensus) {
       Consensus = V;
bool CodeGenPrepare::optimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
   Value *&SunkAddr = SunkAddrs[Addr];
   if (SunkAddr) {
     DEBUG(dbgs() << "CGP: Reusing nonlocal addrmode: " << AddrMode << " for "
                  << *MemoryInst << "\n");
     if (SunkAddr->getType() != Addr->getType())
       SunkAddr = Builder.CreateBitCast(SunkAddr, Addr->getType());
   } else if (AddrSinkUsingGEPs ||
              (!AddrSinkUsingGEPs.getNumOccurrences() && TM &&
-              TM->getSubtargetImpl(*MemoryInst->getParent()->getParent())
-                  ->useAA())) {
+              SubtargetInfo->useAA())) {
     // By default, we use the GEP-based method when AA is used later. This
     // prevents new inttoptr/ptrtoint pairs from degrading AA capabilities.
     DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for "
                  << *MemoryInst << "\n");
     Type *IntPtrTy = DL->getIntPtrType(Addr->getType());
     Value *ResultPtr = nullptr, *ResultIndex = nullptr;
 
     // First, find the pointer.