Vendor import of llvm trunk r256633:

https://llvm.org/svn/llvm-project/llvm/trunk@256633

1 files changed, 253 insertions, 0 deletions

diff --git a/lib/Target/PowerPC/PPCBoolRetToInt.cpp b/lib/Target/PowerPC/PPCBoolRetToInt.cpp
new file mode 100644
index 000000000000..7920240bc2b9
--- /dev/null
+++ b/lib/Target/PowerPC/PPCBoolRetToInt.cpp
@@ -0,0 +1,253 @@
+//===- PPCBoolRetToInt.cpp - Convert bool literals to i32 if they are returned ==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements converting i1 values to i32 if they could be more
+// profitably allocated as GPRs rather than CRs. This pass will become totally
+// unnecessary if Register Bank Allocation and Global Instruction Selection ever
+// go upstream.
+//
+// Presently, the pass converts i1 Constants, and Arguments to i32 if the
+// transitive closure of their uses includes only PHINodes, CallInsts, and
+// ReturnInsts. The rational is that arguments are generally passed and returned
+// in GPRs rather than CRs, so casting them to i32 at the LLVM IR level will
+// actually save casts at the Machine Instruction level.
+//
+// It might be useful to expand this pass to add bit-wise operations to the list
+// of safe transitive closure types. Also, we miss some opportunities when LLVM
+// represents logical AND and OR operations with control flow rather than data
+// flow. For example by lowering the expression: return (A && B && C)
+//
+// as: return A ? true : B && C.
+//
+// There's code in SimplifyCFG that code be used to turn control flow in data
+// flow using SelectInsts. Selects are slow on some architectures (P7/P8), so
+// this probably isn't good in general, but for the special case of i1, the
+// Selects could be further lowered to bit operations that are fast everywhere.
+//
+//===----------------------------------------------------------------------===//
+
+#include "PPC.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Pass.h"
+
+using namespace llvm;
+
+namespace {
+
+#define DEBUG_TYPE "bool-ret-to-int"
+
+STATISTIC(NumBoolRetPromotion,
+          "Number of times a bool feeding a RetInst was promoted to an int");
+STATISTIC(NumBoolCallPromotion,
+          "Number of times a bool feeding a CallInst was promoted to an int");
+STATISTIC(NumBoolToIntPromotion,
+          "Total number of times a bool was promoted to an int");
+
+class PPCBoolRetToInt : public FunctionPass {
+
+  static SmallPtrSet<Value *, 8> findAllDefs(Value *V) {
+    SmallPtrSet<Value *, 8> Defs;
+    SmallVector<Value *, 8> WorkList;
+    WorkList.push_back(V);
+    Defs.insert(V);
+    while (!WorkList.empty()) {
+      Value *Curr = WorkList.back();
+      WorkList.pop_back();
+      if (User *CurrUser = dyn_cast<User>(Curr))
+        for (auto &Op : CurrUser->operands())
+          if (Defs.insert(Op).second)
+            WorkList.push_back(Op);
+    }
+    return Defs;
+  }
+
+  // Translate a i1 value to an equivalent i32 value:
+  static Value *translate(Value *V) {
+    Type *Int32Ty = Type::getInt32Ty(V->getContext());
+    if (Constant *C = dyn_cast<Constant>(V))
+      return ConstantExpr::getZExt(C, Int32Ty);
+    if (PHINode *P = dyn_cast<PHINode>(V)) {
+      // Temporarily set the operands to 0. We'll fix this later in
+      // runOnUse.
+      Value *Zero = Constant::getNullValue(Int32Ty);
+      PHINode *Q =
+        PHINode::Create(Int32Ty, P->getNumIncomingValues(), P->getName(), P);
+      for (unsigned i = 0; i < P->getNumOperands(); ++i)
+        Q->addIncoming(Zero, P->getIncomingBlock(i));
+      return Q;
+    }
+
+    Argument *A = dyn_cast<Argument>(V);
+    Instruction *I = dyn_cast<Instruction>(V);
+    assert((A || I) && "Unknown value type");
+
+    auto InstPt =
+      A ? &*A->getParent()->getEntryBlock().begin() : I->getNextNode();
+    return new ZExtInst(V, Int32Ty, "", InstPt);
+  }
+
+  typedef SmallPtrSet<const PHINode *, 8> PHINodeSet;
+
+  // A PHINode is Promotable if:
+  // 1. Its type is i1 AND
+  // 2. All of its uses are ReturnInt, CallInst, PHINode, or DbgInfoIntrinsic
+  // AND
+  // 3. All of its operands are Constant or Argument or
+  //    CallInst or PHINode AND
+  // 4. All of its PHINode uses are Promotable AND
+  // 5. All of its PHINode operands are Promotable
+  static PHINodeSet getPromotablePHINodes(const Function &F) {
+    PHINodeSet Promotable;
+    // Condition 1
+    for (auto &BB : F)
+      for (auto &I : BB)
+        if (const PHINode *P = dyn_cast<PHINode>(&I))
+          if (P->getType()->isIntegerTy(1))
+            Promotable.insert(P);
+
+    SmallVector<const PHINode *, 8> ToRemove;
+    for (const auto &P : Promotable) {
+      // Condition 2 and 3
+      auto IsValidUser = [] (const Value *V) -> bool {
+        return isa<ReturnInst>(V) || isa<CallInst>(V) || isa<PHINode>(V) ||
+        isa<DbgInfoIntrinsic>(V);
+      };
+      auto IsValidOperand = [] (const Value *V) -> bool {
+        return isa<Constant>(V) || isa<Argument>(V) || isa<CallInst>(V) ||
+        isa<PHINode>(V);
+      };
+      const auto &Users = P->users();
+      const auto &Operands = P->operands();
+      if (!std::all_of(Users.begin(), Users.end(), IsValidUser) ||
+          !std::all_of(Operands.begin(), Operands.end(), IsValidOperand))
+        ToRemove.push_back(P);
+    }
+
+    // Iterate to convergence
+    auto IsPromotable = [&Promotable] (const Value *V) -> bool {
+      const PHINode *Phi = dyn_cast<PHINode>(V);
+      return !Phi || Promotable.count(Phi);
+    };
+    while (!ToRemove.empty()) {
+      for (auto &User : ToRemove)
+        Promotable.erase(User);
+      ToRemove.clear();
+
+      for (const auto &P : Promotable) {
+        // Condition 4 and 5
+        const auto &Users = P->users();
+        const auto &Operands = P->operands();
+        if (!std::all_of(Users.begin(), Users.end(), IsPromotable) ||
+            !std::all_of(Operands.begin(), Operands.end(), IsPromotable))
+          ToRemove.push_back(P);
+      }
+    }
+
+    return Promotable;
+  }
+
+  typedef DenseMap<Value *, Value *> B2IMap;
+
+ public:
+  static char ID;
+  PPCBoolRetToInt() : FunctionPass(ID) {
+    initializePPCBoolRetToIntPass(*PassRegistry::getPassRegistry());
+  }
+
+  bool runOnFunction(Function &F) {
+    PHINodeSet PromotablePHINodes = getPromotablePHINodes(F);
+    B2IMap Bool2IntMap;
+    bool Changed = false;
+    for (auto &BB : F) {
+      for (auto &I : BB) {
+        if (ReturnInst *R = dyn_cast<ReturnInst>(&I))
+          if (F.getReturnType()->isIntegerTy(1))
+            Changed |=
+              runOnUse(R->getOperandUse(0), PromotablePHINodes, Bool2IntMap);
+
+        if (CallInst *CI = dyn_cast<CallInst>(&I))
+          for (auto &U : CI->operands())
+            if (U->getType()->isIntegerTy(1))
+              Changed |= runOnUse(U, PromotablePHINodes, Bool2IntMap);
+      }
+    }
+
+    return Changed;
+  }
+
+  static bool runOnUse(Use &U, const PHINodeSet &PromotablePHINodes,
+                       B2IMap &BoolToIntMap) {
+    auto Defs = findAllDefs(U);
+
+    // If the values are all Constants or Arguments, don't bother
+    if (!std::any_of(Defs.begin(), Defs.end(), isa<Instruction, Value *>))
+      return false;
+
+    // Presently, we only know how to handle PHINode, Constant, and Arguments.
+    // Potentially, bitwise operations (AND, OR, XOR, NOT) and sign extension
+    // could also be handled in the future.
+    for (const auto &V : Defs)
+      if (!isa<PHINode>(V) && !isa<Constant>(V) && !isa<Argument>(V))
+        return false;
+
+    for (const auto &V : Defs)
+      if (const PHINode *P = dyn_cast<PHINode>(V))
+        if (!PromotablePHINodes.count(P))
+          return false;
+
+    if (isa<ReturnInst>(U.getUser()))
+      ++NumBoolRetPromotion;
+    if (isa<CallInst>(U.getUser()))
+      ++NumBoolCallPromotion;
+    ++NumBoolToIntPromotion;
+
+    for (const auto &V : Defs)
+      if (!BoolToIntMap.count(V))
+        BoolToIntMap[V] = translate(V);
+
+    // Replace the operands of the translated instructions. There were set to
+    // zero in the translate function.
+    for (auto &Pair : BoolToIntMap) {
+      User *First = dyn_cast<User>(Pair.first);
+      User *Second = dyn_cast<User>(Pair.second);
+      assert((!First || Second) && "translated from user to non-user!?");
+      if (First)
+        for (unsigned i = 0; i < First->getNumOperands(); ++i)
+          Second->setOperand(i, BoolToIntMap[First->getOperand(i)]);
+    }
+
+    Value *IntRetVal = BoolToIntMap[U];
+    Type *Int1Ty = Type::getInt1Ty(U->getContext());
+    Instruction *I = cast<Instruction>(U.getUser());
+    Value *BackToBool = new TruncInst(IntRetVal, Int1Ty, "backToBool", I);
+    U.set(BackToBool);
+
+    return true;
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const {
+    AU.addPreserved<DominatorTreeWrapperPass>();
+    FunctionPass::getAnalysisUsage(AU);
+  }
+};
+}
+
+char PPCBoolRetToInt::ID = 0;
+INITIALIZE_PASS(PPCBoolRetToInt, "bool-ret-to-int",
+                "Convert i1 constants to i32 if they are returned",
+                false, false)
+
+FunctionPass *llvm::createPPCBoolRetToIntPass() { return new PPCBoolRetToInt(); }