//
//===----------------------------------------------------------------------===//
+#include "llvm/ADT/EquivalenceClasses.h"
+#include "llvm/Analysis/DemandedBits.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ScalarEvolution.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/VectorUtils.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/PatternMatch.h"
}
/// \brief Get splat value if the input is a splat vector or return nullptr.
-/// The value may be extracted from a splat constants vector or from
-/// a sequence of instructions that broadcast a single value into a vector.
+/// This function is not fully general. It checks only 2 cases:
+/// the input value is (1) a splat constants vector or (2) a sequence
+/// of instructions that broadcast a single value into a vector.
+///
llvm::Value *llvm::getSplatValue(Value *V) {
- llvm::ConstantDataVector *CV = dyn_cast<llvm::ConstantDataVector>(V);
- if (CV)
+ if (auto *CV = dyn_cast<ConstantDataVector>(V))
return CV->getSplatValue();
- llvm::ShuffleVectorInst *ShuffleInst = dyn_cast<llvm::ShuffleVectorInst>(V);
+
+ auto *ShuffleInst = dyn_cast<ShuffleVectorInst>(V);
if (!ShuffleInst)
return nullptr;
- // All-zero (our undef) shuffle mask elements.
- for (int i : ShuffleInst->getShuffleMask())
- if (i != 0 && i != -1)
+ // All-zero (or undef) shuffle mask elements.
+ for (int MaskElt : ShuffleInst->getShuffleMask())
+ if (MaskElt != 0 && MaskElt != -1)
return nullptr;
// The first shuffle source is 'insertelement' with index 0.
- llvm::InsertElementInst *InsertEltInst =
- dyn_cast<llvm::InsertElementInst>(ShuffleInst->getOperand(0));
+ auto *InsertEltInst =
+ dyn_cast<InsertElementInst>(ShuffleInst->getOperand(0));
if (!InsertEltInst || !isa<ConstantInt>(InsertEltInst->getOperand(2)) ||
!cast<ConstantInt>(InsertEltInst->getOperand(2))->isNullValue())
return nullptr;
return InsertEltInst->getOperand(1);
}
+
+DenseMap<Instruction*, uint64_t> llvm::computeMinimumValueSizes(
+ ArrayRef<BasicBlock*> Blocks, DemandedBits &DB,
+ const TargetTransformInfo *TTI) {
+
+ // DemandedBits will give us every value's live-out bits. But we want
+ // to ensure no extra casts would need to be inserted, so every DAG
+ // of connected values must have the same minimum bitwidth.
+ EquivalenceClasses<Value*> ECs;
+ SmallVector<Value*,16> Worklist;
+ SmallPtrSet<Value*,4> Roots;
+ SmallPtrSet<Value*,16> Visited;
+ DenseMap<Value*,uint64_t> DBits;
+ SmallPtrSet<Instruction*,4> InstructionSet;
+ DenseMap<Instruction*, uint64_t> MinBWs;
+
+ // Determine the roots. We work bottom-up, from truncs or icmps.
+ bool SeenExtFromIllegalType = false;
+ for (auto *BB : Blocks)
+ for (auto &I : *BB) {
+ InstructionSet.insert(&I);
+
+ if (TTI && (isa<ZExtInst>(&I) || isa<SExtInst>(&I)) &&
+ !TTI->isTypeLegal(I.getOperand(0)->getType()))
+ SeenExtFromIllegalType = true;
+
+ // Only deal with non-vector integers up to 64-bits wide.
+ if ((isa<TruncInst>(&I) || isa<ICmpInst>(&I)) &&
+ !I.getType()->isVectorTy() &&
+ I.getOperand(0)->getType()->getScalarSizeInBits() <= 64) {
+ // Don't make work for ourselves. If we know the loaded type is legal,
+ // don't add it to the worklist.
+ if (TTI && isa<TruncInst>(&I) && TTI->isTypeLegal(I.getType()))
+ continue;
+
+ Worklist.push_back(&I);
+ Roots.insert(&I);
+ }
+ }
+ // Early exit.
+ if (Worklist.empty() || (TTI && !SeenExtFromIllegalType))
+ return MinBWs;
+
+ // Now proceed breadth-first, unioning values together.
+ while (!Worklist.empty()) {
+ Value *Val = Worklist.pop_back_val();
+ Value *Leader = ECs.getOrInsertLeaderValue(Val);
+
+ if (Visited.count(Val))
+ continue;
+ Visited.insert(Val);
+
+ // Non-instructions terminate a chain successfully.
+ if (!isa<Instruction>(Val))
+ continue;
+ Instruction *I = cast<Instruction>(Val);
+
+ // If we encounter a type that is larger than 64 bits, we can't represent
+ // it so bail out.
+ if (DB.getDemandedBits(I).getBitWidth() > 64)
+ return DenseMap<Instruction*,uint64_t>();
+
+ uint64_t V = DB.getDemandedBits(I).getZExtValue();
+ DBits[Leader] |= V;
+
+ // Casts, loads and instructions outside of our range terminate a chain
+ // successfully.
+ if (isa<SExtInst>(I) || isa<ZExtInst>(I) || isa<LoadInst>(I) ||
+ !InstructionSet.count(I))
+ continue;
+
+ // Unsafe casts terminate a chain unsuccessfully. We can't do anything
+ // useful with bitcasts, ptrtoints or inttoptrs and it'd be unsafe to
+ // transform anything that relies on them.
+ if (isa<BitCastInst>(I) || isa<PtrToIntInst>(I) || isa<IntToPtrInst>(I) ||
+ !I->getType()->isIntegerTy()) {
+ DBits[Leader] |= ~0ULL;
+ continue;
+ }
+
+ // We don't modify the types of PHIs. Reductions will already have been
+ // truncated if possible, and inductions' sizes will have been chosen by
+ // indvars.
+ if (isa<PHINode>(I))
+ continue;
+
+ if (DBits[Leader] == ~0ULL)
+ // All bits demanded, no point continuing.
+ continue;
+
+ for (Value *O : cast<User>(I)->operands()) {
+ ECs.unionSets(Leader, O);
+ Worklist.push_back(O);
+ }
+ }
+
+ // Now we've discovered all values, walk them to see if there are
+ // any users we didn't see. If there are, we can't optimize that
+ // chain.
+ for (auto &I : DBits)
+ for (auto *U : I.first->users())
+ if (U->getType()->isIntegerTy() && DBits.count(U) == 0)
+ DBits[ECs.getOrInsertLeaderValue(I.first)] |= ~0ULL;
+
+ for (auto I = ECs.begin(), E = ECs.end(); I != E; ++I) {
+ uint64_t LeaderDemandedBits = 0;
+ for (auto MI = ECs.member_begin(I), ME = ECs.member_end(); MI != ME; ++MI)
+ LeaderDemandedBits |= DBits[*MI];
+
+ uint64_t MinBW = (sizeof(LeaderDemandedBits) * 8) -
+ llvm::countLeadingZeros(LeaderDemandedBits);
+ // Round up to a power of 2
+ if (!isPowerOf2_64((uint64_t)MinBW))
+ MinBW = NextPowerOf2(MinBW);
+ for (auto MI = ECs.member_begin(I), ME = ECs.member_end(); MI != ME; ++MI) {
+ if (!isa<Instruction>(*MI))
+ continue;
+ Type *Ty = (*MI)->getType();
+ if (Roots.count(*MI))
+ Ty = cast<Instruction>(*MI)->getOperand(0)->getType();
+ if (MinBW < Ty->getScalarSizeInBits())
+ MinBWs[cast<Instruction>(*MI)] = MinBW;
+ }
+ }
+
+ return MinBWs;
+}
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