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Implement a little hack for parity with GCC on crafty. This speeds up
186.crafty by about 16% (from 15.109s to 13.045s) on my system.
This turns allocas with unions/casts into scalars. For example crafty has
something like this:
union doub {
unsigned short i[4];
long long d;
};
int f(long long a) {
return ((union doub){.d=a}).i[1];
}
Instead of generating loads and stores to an alloca, we now promote the
whole thing to a scalar long value.
This implements: Transforms/ScalarRepl/AggregatePromote.ll
llvm-svn: 24667
This commit is contained in:
Chris Lattner
parent
20ac616376
commit
d61c654e67
@ -26,9 +26,10 @@
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#include "llvm/Pass.h"
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#include "llvm/Instructions.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Support/GetElementPtrTypeIterator.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Transforms/Utils/PromoteMemToReg.h"
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#include "llvm/Support/GetElementPtrTypeIterator.h"
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#include "llvm/Support/MathExtras.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/StringExtras.h"
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@ -37,6 +38,8 @@ using namespace llvm;
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namespace {
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Statistic<> NumReplaced("scalarrepl", "Number of allocas broken up");
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Statistic<> NumPromoted("scalarrepl", "Number of allocas promoted");
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Statistic<> NumConverted("scalarrepl",
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"Number of aggregates converted to scalar");
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struct SROA : public FunctionPass {
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bool runOnFunction(Function &F);
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@ -59,6 +62,10 @@ namespace {
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int isSafeAllocaToScalarRepl(AllocationInst *AI);
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void CanonicalizeAllocaUsers(AllocationInst *AI);
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AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base);
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const Type *CanConvertToScalar(Value *V, bool &IsNotTrivial);
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void ConvertToScalar(AllocationInst *AI, const Type *Ty);
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void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, unsigned Offset);
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};
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RegisterOpt<SROA> X("scalarrepl", "Scalar Replacement of Aggregates");
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@ -112,7 +119,6 @@ bool SROA::performPromotion(Function &F) {
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return Changed;
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}
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// performScalarRepl - This algorithm is a simple worklist driven algorithm,
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// which runs on all of the malloc/alloca instructions in the function, removing
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// them if they are only used by getelementptr instructions.
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@ -131,6 +137,16 @@ bool SROA::performScalarRepl(Function &F) {
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while (!WorkList.empty()) {
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AllocationInst *AI = WorkList.back();
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WorkList.pop_back();
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// If we can turn this aggregate value (potentially with casts) into a
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// simple scalar value that can be mem2reg'd into a register value.
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bool IsNotTrivial = false;
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if (const Type *ActualType = CanConvertToScalar(AI, IsNotTrivial))
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if (IsNotTrivial) {
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ConvertToScalar(AI, ActualType);
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Changed = true;
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continue;
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}
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// We cannot transform the allocation instruction if it is an array
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// allocation (allocations OF arrays are ok though), and an allocation of a
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@ -378,3 +394,262 @@ void SROA::CanonicalizeAllocaUsers(AllocationInst *AI) {
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}
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}
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}
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/// MergeInType - Add the 'In' type to the accumulated type so far. If the
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/// types are incompatible, return true, otherwise update Accum and return
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/// false.
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static bool MergeInType(const Type *In, const Type *&Accum) {
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if (!In->isIntegral()) return true;
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// If this is our first type, just use it.
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if (Accum == Type::VoidTy) {
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Accum = In;
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} else {
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// Otherwise pick whichever type is larger.
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if (In->getTypeID() > Accum->getTypeID())
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Accum = In;
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}
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return false;
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}
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/// getUIntAtLeastAsBitAs - Return an unsigned integer type that is at least
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/// as big as the specified type. If there is no suitable type, this returns
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/// null.
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const Type *getUIntAtLeastAsBitAs(unsigned NumBits) {
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if (NumBits > 64) return 0;
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if (NumBits > 32) return Type::ULongTy;
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if (NumBits > 16) return Type::UIntTy;
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if (NumBits > 8) return Type::UShortTy;
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return Type::UByteTy;
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}
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/// CanConvertToScalar - V is a pointer. If we can convert the pointee to a
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/// single scalar integer type, return that type. Further, if the use is not
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/// a completely trivial use that mem2reg could promote, set IsNotTrivial. If
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/// there are no uses of this pointer, return Type::VoidTy to differentiate from
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/// failure.
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///
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const Type *SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial) {
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const Type *UsedType = Type::VoidTy; // No uses, no forced type.
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const TargetData &TD = getAnalysis<TargetData>();
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const PointerType *PTy = cast<PointerType>(V->getType());
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for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
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Instruction *User = cast<Instruction>(*UI);
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if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
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if (MergeInType(LI->getType(), UsedType))
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return 0;
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} else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
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// Storing the pointer, not the into the value?
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if (SI->getOperand(0) == V) return 0;
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// NOTE: We could handle storing of FP imms here!
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if (MergeInType(SI->getOperand(0)->getType(), UsedType))
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return 0;
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} else if (CastInst *CI = dyn_cast<CastInst>(User)) {
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if (!isa<PointerType>(CI->getType())) return 0;
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IsNotTrivial = true;
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const Type *SubTy = CanConvertToScalar(CI, IsNotTrivial);
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if (!SubTy || MergeInType(SubTy, UsedType)) return 0;
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} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
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// Check to see if this is stepping over an element: GEP Ptr, int C
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if (GEP->getNumOperands() == 2 && isa<ConstantInt>(GEP->getOperand(1))) {
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unsigned Idx = cast<ConstantInt>(GEP->getOperand(1))->getRawValue();
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unsigned ElSize = TD.getTypeSize(PTy->getElementType());
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unsigned BitOffset = Idx*ElSize*8;
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if (BitOffset > 64 || !isPowerOf2_32(ElSize)) return 0;
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IsNotTrivial = true;
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const Type *SubElt = CanConvertToScalar(GEP, IsNotTrivial);
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if (SubElt == 0) return 0;
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if (SubElt != Type::VoidTy) {
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const Type *NewTy =
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getUIntAtLeastAsBitAs(SubElt->getPrimitiveSizeInBits()+BitOffset);
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if (NewTy == 0 || MergeInType(NewTy, UsedType)) return 0;
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continue;
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}
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} else if (GEP->getNumOperands() == 3 &&
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isa<ConstantInt>(GEP->getOperand(1)) &&
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isa<ConstantInt>(GEP->getOperand(2)) &&
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cast<Constant>(GEP->getOperand(1))->isNullValue()) {
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// We are stepping into an element, e.g. a structure or an array:
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// GEP Ptr, int 0, uint C
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const Type *AggTy = PTy->getElementType();
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unsigned Idx = cast<ConstantInt>(GEP->getOperand(2))->getRawValue();
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if (const ArrayType *ATy = dyn_cast<ArrayType>(AggTy)) {
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if (Idx >= ATy->getNumElements()) return 0; // Out of range.
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} else if (const PackedType *PTy = dyn_cast<PackedType>(AggTy)) {
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if (Idx >= PTy->getNumElements()) return 0; // Out of range.
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} else if (isa<StructType>(AggTy)) {
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// Structs are always ok.
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} else {
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return 0;
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}
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const Type *NTy = getUIntAtLeastAsBitAs(TD.getTypeSize(AggTy)*8);
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if (NTy == 0 || MergeInType(NTy, UsedType)) return 0;
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const Type *SubTy = CanConvertToScalar(GEP, IsNotTrivial);
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if (SubTy == 0) return 0;
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if (SubTy != Type::VoidTy && MergeInType(SubTy, UsedType))
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return 0;
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continue; // Everything looks ok
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}
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return 0;
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} else {
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// Cannot handle this!
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return 0;
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}
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}
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return UsedType;
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}
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/// ConvertToScalar - The specified alloca passes the CanConvertToScalar
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/// predicate and is non-trivial. Convert it to something that can be trivially
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/// promoted into a register by mem2reg.
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void SROA::ConvertToScalar(AllocationInst *AI, const Type *ActualTy) {
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DEBUG(std::cerr << "CONVERT TO SCALAR: " << *AI << " TYPE = "
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<< *ActualTy << "\n");
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++NumConverted;
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BasicBlock *EntryBlock = AI->getParent();
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assert(EntryBlock == &EntryBlock->getParent()->front() &&
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"Not in the entry block!");
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EntryBlock->getInstList().remove(AI); // Take the alloca out of the program.
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// Create and insert the alloca.
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AllocaInst *NewAI = new AllocaInst(ActualTy->getUnsignedVersion(), 0,
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AI->getName(), EntryBlock->begin());
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ConvertUsesToScalar(AI, NewAI, 0);
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delete AI;
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}
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/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
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/// directly. Offset is an offset from the original alloca, in bits that need
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/// to be shifted to the right. By the end of this, there should be no uses of
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/// Ptr.
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void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, unsigned Offset) {
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while (!Ptr->use_empty()) {
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Instruction *User = cast<Instruction>(Ptr->use_back());
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if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
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// The load is a bit extract from NewAI shifted right by Offset bits.
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Value *NV = new LoadInst(NewAI, LI->getName(), LI);
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if (Offset)
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NV = new ShiftInst(Instruction::Shr, NV,
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ConstantUInt::get(Type::UByteTy, Offset),
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LI->getName(), LI);
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if (NV->getType() != LI->getType())
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NV = new CastInst(NV, LI->getType(), LI->getName(), LI);
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LI->replaceAllUsesWith(NV);
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LI->eraseFromParent();
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} else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
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assert(SI->getOperand(0) != Ptr && "Consistency error!");
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// Convert the stored type to the actual type, shift it left to insert
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// then 'or' into place.
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Value *SV = SI->getOperand(0);
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if (SV->getType() == NewAI->getType()->getElementType()) {
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assert(Offset == 0 && "Store out of bounds!");
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} else {
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Value *Old = new LoadInst(NewAI, NewAI->getName()+".in", SI);
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// If SV is signed, convert it to unsigned, so that the next cast zero
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// extends the value.
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if (SV->getType()->isSigned())
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SV = new CastInst(SV, SV->getType()->getUnsignedVersion(),
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SV->getName(), SI);
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SV = new CastInst(SV, Old->getType(), SV->getName(), SI);
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if (Offset)
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SV = new ShiftInst(Instruction::Shl, SV,
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ConstantUInt::get(Type::UByteTy, Offset),
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SV->getName()+".adj", SI);
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// Mask out the bits we are about to insert from the old value.
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unsigned TotalBits = SV->getType()->getPrimitiveSizeInBits();
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unsigned InsertBits =
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SI->getOperand(0)->getType()->getPrimitiveSizeInBits();
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if (TotalBits != InsertBits) {
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assert(TotalBits > InsertBits);
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uint64_t Mask = ~(((1ULL << InsertBits)-1) << Offset);
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if (TotalBits != 64)
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Mask = Mask & ((1ULL << TotalBits)-1);
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Old = BinaryOperator::createAnd(Old,
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ConstantUInt::get(Old->getType(), Mask),
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Old->getName()+".mask", SI);
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SV = BinaryOperator::createOr(Old, SV, SV->getName()+".ins", SI);
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}
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}
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new StoreInst(SV, NewAI, SI);
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SI->eraseFromParent();
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} else if (CastInst *CI = dyn_cast<CastInst>(User)) {
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unsigned NewOff = Offset;
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const TargetData &TD = getAnalysis<TargetData>();
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if (TD.isBigEndian()) {
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// Adjust the pointer. For example, storing 16-bits into a 32-bit
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// alloca with just a cast makes it modify the top 16-bits.
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const Type *SrcTy = cast<PointerType>(Ptr->getType())->getElementType();
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const Type *DstTy = cast<PointerType>(CI->getType())->getElementType();
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int PtrDiffBits = TD.getTypeSize(SrcTy)*8-TD.getTypeSize(DstTy)*8;
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NewOff += PtrDiffBits;
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}
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ConvertUsesToScalar(CI, NewAI, NewOff);
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CI->eraseFromParent();
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} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
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const PointerType *AggPtrTy =
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cast<PointerType>(GEP->getOperand(0)->getType());
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const TargetData &TD = getAnalysis<TargetData>();
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unsigned AggSizeInBits = TD.getTypeSize(AggPtrTy->getElementType())*8;
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// Check to see if this is stepping over an element: GEP Ptr, int C
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unsigned NewOffset = Offset;
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if (GEP->getNumOperands() == 2) {
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unsigned Idx = cast<ConstantInt>(GEP->getOperand(1))->getRawValue();
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unsigned BitOffset = Idx*AggSizeInBits;
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if (TD.isLittleEndian())
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NewOffset += BitOffset;
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else
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NewOffset -= BitOffset;
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} else if (GEP->getNumOperands() == 3) {
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// We know that operand #2 is zero.
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unsigned Idx = cast<ConstantInt>(GEP->getOperand(2))->getRawValue();
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const Type *AggTy = AggPtrTy->getElementType();
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if (const SequentialType *SeqTy = dyn_cast<SequentialType>(AggTy)) {
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unsigned ElSizeBits = TD.getTypeSize(SeqTy->getElementType())*8;
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if (TD.isLittleEndian())
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NewOffset += ElSizeBits*Idx;
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else
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NewOffset += AggSizeInBits-ElSizeBits*(Idx+1);
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} else if (const StructType *STy = dyn_cast<StructType>(AggTy)) {
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unsigned EltBitOffset = TD.getStructLayout(STy)->MemberOffsets[Idx]*8;
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if (TD.isLittleEndian())
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NewOffset += EltBitOffset;
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else {
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const PointerType *ElPtrTy = cast<PointerType>(GEP->getType());
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unsigned ElSizeBits = TD.getTypeSize(ElPtrTy->getElementType())*8;
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NewOffset += AggSizeInBits-(EltBitOffset+ElSizeBits);
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}
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} else {
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assert(0 && "Unsupported operation!");
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abort();
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}
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} else {
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assert(0 && "Unsupported operation!");
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abort();
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}
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ConvertUsesToScalar(GEP, NewAI, NewOffset);
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GEP->eraseFromParent();
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} else {
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assert(0 && "Unsupported operation!");
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abort();
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}
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}
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}
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