llvm/tools/llvm-reduce/deltas/ReduceOperands.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "ReduceOperands.h"
  10 #include "llvm/IR/Constants.h"
  11 #include "llvm/IR/InstIterator.h"
  12 #include "llvm/IR/InstrTypes.h"
  13 #include "llvm/IR/Operator.h"
  14 #include "llvm/IR/PatternMatch.h"
  15 #include "llvm/IR/Type.h"
  16
  17 using namespace llvm;
  18 using namespace PatternMatch;
  19
  20 static void
  21 extractOperandsFromModule(Oracle &O, ReducerWorkItem &WorkItem,
  22                           function_ref<Value *(Use &)> ReduceValue) {
  23   Module &Program = WorkItem.getModule();
  24
  25   for (auto &F : Program.functions()) {
  26     for (auto &I : instructions(&F)) {
  27       if (PHINode *Phi = dyn_cast<PHINode>(&I)) {
  28         for (auto &Op : Phi->incoming_values()) {
  29           if (!O.shouldKeep()) {
  30             if (Value *Reduced = ReduceValue(Op))
  31               Phi->setIncomingValueForBlock(Phi->getIncomingBlock(Op), Reduced);
  32           }
  33         }
  34
  35         continue;
  36       }
  37
  38       for (auto &Op : I.operands()) {
  39         if (Value *Reduced = ReduceValue(Op)) {
  40           if (!O.shouldKeep())
  41             Op.set(Reduced);
  42         }
  43       }
  44     }
  45   }
  46 }
  47
  48 static bool isOne(Use &Op) {
  49   auto *C = dyn_cast<Constant>(Op);
  50   return C && C->isOneValue();
  51 }
  52
  53 static bool isZero(Use &Op) {
  54   auto *C = dyn_cast<Constant>(Op);
  55   return C && C->isNullValue();
  56 }
  57
  58 static bool isZeroOrOneFP(Value *Op) {
  59   const APFloat *C;
  60   return match(Op, m_APFloat(C)) &&
  61          ((C->isZero() && !C->isNegative()) || C->isExactlyValue(1.0));
  62 }
  63
  64 static bool shouldReduceOperand(Use &Op) {
  65   Type *Ty = Op->getType();
  66   if (Ty->isLabelTy() || Ty->isMetadataTy())
  67     return false;
  68   // TODO: be more precise about which GEP operands we can reduce (e.g. array
  69   // indexes)
  70   if (isa<GEPOperator>(Op.getUser()))
  71     return false;
  72   if (auto *CB = dyn_cast<CallBase>(Op.getUser())) {
  73     if (&CB->getCalledOperandUse() == &Op)
  74       return false;
  75   }
  76   return true;
  77 }
  78
  79 static bool switchCaseExists(Use &Op, ConstantInt *CI) {
  80   SwitchInst *SI = dyn_cast<SwitchInst>(Op.getUser());
  81   if (!SI)
  82     return false;
  83   return SI->findCaseValue(CI) != SI->case_default();
  84 }
  85
  86 void llvm::reduceOperandsOneDeltaPass(TestRunner &Test) {
  87   auto ReduceValue = [](Use &Op) -> Value * {
  88     if (!shouldReduceOperand(Op))
  89       return nullptr;
  90
  91     Type *Ty = Op->getType();
  92     if (auto *IntTy = dyn_cast<IntegerType>(Ty)) {
  93       // Don't duplicate an existing switch case.
  94       if (switchCaseExists(Op, ConstantInt::get(IntTy, 1)))
  95         return nullptr;
  96       // Don't replace existing ones and zeroes.
  97       return (isOne(Op) || isZero(Op)) ? nullptr : ConstantInt::get(IntTy, 1);
  98     }
  99
 100     if (Ty->isFloatingPointTy())
 101       return isZeroOrOneFP(Op) ? nullptr : ConstantFP::get(Ty, 1.0);
 102
 103     if (VectorType *VT = dyn_cast<VectorType>(Ty)) {
 104       if (isOne(Op) || isZero(Op) || isZeroOrOneFP(Op))
 105         return nullptr;
 106
 107       Type *ElementType = VT->getElementType();
 108       Constant *C;
 109       if (ElementType->isFloatingPointTy()) {
 110         C = ConstantFP::get(ElementType, 1.0);
 111       } else if (IntegerType *IntTy = dyn_cast<IntegerType>(ElementType)) {
 112         C = ConstantInt::get(IntTy, 1);
 113       } else {
 114         return nullptr;
 115       }
 116       return ConstantVector::getSplat(VT->getElementCount(), C);
 117     }
 118
 119     return nullptr;
 120   };
 121   runDeltaPass(
 122       Test,
 123       [ReduceValue](Oracle &O, ReducerWorkItem &WorkItem) {
 124         extractOperandsFromModule(O, WorkItem, ReduceValue);
 125       },
 126       "Reducing Operands to one");
 127 }
 128
 129 void llvm::reduceOperandsZeroDeltaPass(TestRunner &Test) {
 130   auto ReduceValue = [](Use &Op) -> Value * {
 131     if (!shouldReduceOperand(Op))
 132       return nullptr;
 133     // Don't duplicate an existing switch case.
 134     if (auto *IntTy = dyn_cast<IntegerType>(Op->getType()))
 135       if (switchCaseExists(Op, ConstantInt::get(IntTy, 0)))
 136         return nullptr;
 137     // Don't replace existing zeroes.
 138     return isZero(Op) ? nullptr : Constant::getNullValue(Op->getType());
 139   };
 140   runDeltaPass(
 141       Test,
 142       [ReduceValue](Oracle &O, ReducerWorkItem &Program) {
 143         extractOperandsFromModule(O, Program, ReduceValue);
 144       },
 145       "Reducing Operands to zero");
 146 }
 147
 148 void llvm::reduceOperandsNaNDeltaPass(TestRunner &Test) {
 149   auto ReduceValue = [](Use &Op) -> Value * {
 150     Type *Ty = Op->getType();
 151     if (!Ty->isFPOrFPVectorTy())
 152       return nullptr;
 153
 154     // Prefer 0.0 or 1.0 over NaN.
 155     //
 156     // TODO: Preferring NaN may make more sense because FP operations are more
 157     // universally foldable.
 158     if (match(Op.get(), m_NaN()) || isZeroOrOneFP(Op.get()))
 159       return nullptr;
 160
 161     if (VectorType *VT = dyn_cast<VectorType>(Ty)) {
 162       return ConstantVector::getSplat(VT->getElementCount(),
 163                                       ConstantFP::getQNaN(VT->getElementType()));
 164     }
 165
 166     return ConstantFP::getQNaN(Ty);
 167   };
 168   runDeltaPass(
 169       Test,
 170       [ReduceValue](Oracle &O, ReducerWorkItem &Program) {
 171         extractOperandsFromModule(O, Program, ReduceValue);
 172       },
 173       "Reducing Operands to NaN");
 174 }