--- /dev/null
+//===- LevelRaise.cpp - Code to change LLVM to higher level -----------------=//
+//
+// This file implements the 'raising' part of the LevelChange API. This is
+// useful because, in general, it makes the LLVM code terser and easier to
+// analyze. Note that it is good to run DCE after doing this transformation.
+//
+// Eliminate silly things in the source that do not effect the level, but do
+// clean up the code:
+// * Casts of casts
+// - getelementptr/load & getelementptr/store are folded into a direct
+// load or store
+// - Convert this code (for both alloca and malloc):
+// %reg110 = shl uint %n, ubyte 2 ;;<uint>
+// %reg108 = alloca ubyte, uint %reg110 ;;<ubyte*>
+// %cast76 = cast ubyte* %reg108 to uint* ;;<uint*>
+// To: %cast76 = alloca uint, uint %n
+// Convert explicit addressing to use getelementptr instruction where possible
+// - ...
+//
+// Convert explicit addressing on pointers to use getelementptr instruction.
+// - If a pointer is used by arithmetic operation, insert an array casted
+// version into the source program, only for the following pointer types:
+// * Method argument pointers
+// - Pointers returned by alloca or malloc
+// - Pointers returned by function calls
+// - If a pointer is indexed with a value scaled by a constant size equal
+// to the element size of the array, the expression is replaced with a
+// getelementptr instruction.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/LevelChange.h"
+#include "llvm/Method.h"
+#include "llvm/Support/STLExtras.h"
+#include "llvm/iOther.h"
+#include "llvm/iMemory.h"
+#include "llvm/ConstPoolVals.h"
+#include "llvm/Target/TargetData.h"
+#include <map>
+#include <algorithm>
+
+#include "llvm/Assembly/Writer.h"
+
+//#define DEBUG_PEEPHOLE_INSTS 1
+
+#ifdef DEBUG_PEEPHOLE_INSTS
+#define PRINT_PEEPHOLE(ID, NUM, I) \
+ cerr << "Inst P/H " << ID << "[" << NUM << "] " << I;
+#else
+#define PRINT_PEEPHOLE(ID, NUM, I)
+#endif
+
+#define PRINT_PEEPHOLE1(ID, I1) do { PRINT_PEEPHOLE(ID, 0, I1); } while (0)
+#define PRINT_PEEPHOLE2(ID, I1, I2) \
+ do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); } while (0)
+#define PRINT_PEEPHOLE3(ID, I1, I2, I3) \
+ do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); \
+ PRINT_PEEPHOLE(ID, 2, I3); } while (0)
+
+
+// TargetData Hack: Eventually we will have annotations given to us by the
+// backend so that we know stuff about type size and alignments. For now
+// though, just use this, because it happens to match the model that GCC uses.
+//
+const TargetData TD("LevelRaise: Should be GCC though!");
+
+
+// losslessCastableTypes - Return true if the types are bitwise equivalent.
+// This predicate returns true if it is possible to cast from one type to
+// another without gaining or losing precision, or altering the bits in any way.
+//
+static bool losslessCastableTypes(const Type *T1, const Type *T2) {
+ assert(T1->isPrimitiveType() || isa<PointerType>(T1));
+ assert(T2->isPrimitiveType() || isa<PointerType>(T2));
+
+ if (T1->getPrimitiveID() == T2->getPrimitiveID())
+ return true; // Handles identity cast, and cast of differing pointer types
+
+ // Now we know that they are two differing primitive or pointer types
+ switch (T1->getPrimitiveID()) {
+ case Type::UByteTyID: return T2 == Type::SByteTy;
+ case Type::SByteTyID: return T2 == Type::UByteTy;
+ case Type::UShortTyID: return T2 == Type::ShortTy;
+ case Type::ShortTyID: return T2 == Type::UShortTy;
+ case Type::UIntTyID: return T2 == Type::IntTy;
+ case Type::IntTyID: return T2 == Type::UIntTy;
+ case Type::ULongTyID:
+ case Type::LongTyID:
+ case Type::PointerTyID:
+ return T2 == Type::ULongTy || T2 == Type::LongTy ||
+ T2->getPrimitiveID() == Type::PointerTyID;
+ default:
+ return false; // Other types have no identity values
+ }
+}
+
+
+// isReinterpretingCast - Return true if the cast instruction specified will
+// cause the operand to be "reinterpreted". A value is reinterpreted if the
+// cast instruction would cause the underlying bits to change.
+//
+static inline bool isReinterpretingCast(const CastInst *CI) {
+ return !losslessCastableTypes(CI->getOperand(0)->getType(), CI->getType());
+}
+
+
+// getPointedToStruct - If the argument is a pointer type, and the pointed to
+// value is a struct type, return the struct type, else return null.
+//
+static const StructType *getPointedToStruct(const Type *Ty) {
+ const PointerType *PT = dyn_cast<PointerType>(Ty);
+ return PT ? dyn_cast<StructType>(PT->getValueType()) : 0;
+}
+
+
+// getStructOffsetType - Return a vector of offsets that are to be used to index
+// into the specified struct type to get as close as possible to index as we
+// can. Note that it is possible that we cannot get exactly to Offset, in which
+// case we update offset to be the offset we actually obtained. The resultant
+// leaf type is returned.
+//
+static const Type *getStructOffsetType(const Type *Ty, unsigned &Offset,
+ vector<ConstPoolVal*> &Offsets) {
+ if (!isa<StructType>(Ty)) {
+ Offset = 0; // Return the offset that we were able to acheive
+ return Ty; // Return the leaf type
+ }
+
+ assert(Offset < TD.getTypeSize(Ty) && "Offset not in struct!");
+ const StructType *STy = cast<StructType>(Ty);
+ const StructLayout *SL = TD.getStructLayout(STy);
+
+ // This loop terminates always on a 0 <= i < MemberOffsets.size()
+ unsigned i;
+ for (i = 0; i < SL->MemberOffsets.size()-1; ++i)
+ if (Offset >= SL->MemberOffsets[i] && Offset < SL->MemberOffsets[i+1])
+ break;
+
+ assert(Offset >= SL->MemberOffsets[i] && Offset < SL->MemberOffsets[i+1]);
+
+ // Make sure to save the current index...
+ Offsets.push_back(ConstPoolUInt::get(Type::UByteTy, i));
+
+ unsigned SubOffs = Offset - SL->MemberOffsets[i];
+ const Type *LeafTy = getStructOffsetType(STy->getElementTypes()[i], SubOffs,
+ Offsets);
+ Offset = SL->MemberOffsets[i] + SubOffs;
+ return LeafTy;
+}
+
+
+
+// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
+// with a value, then remove and delete the original instruction.
+//
+static void ReplaceInstWithValue(BasicBlock::InstListType &BIL,
+ BasicBlock::iterator &BI, Value *V) {
+ Instruction *I = *BI;
+ // Replaces all of the uses of the instruction with uses of the value
+ I->replaceAllUsesWith(V);
+
+ // Remove the unneccesary instruction now...
+ BIL.remove(BI);
+
+ // Make sure to propogate a name if there is one already...
+ if (I->hasName() && !V->hasName())
+ V->setName(I->getName(), BIL.getParent()->getSymbolTable());
+
+ // Remove the dead instruction now...
+ delete I;
+}
+
+
+// ReplaceInstWithInst - Replace the instruction specified by BI with the
+// instruction specified by I. The original instruction is deleted and BI is
+// updated to point to the new instruction.
+//
+static void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
+ BasicBlock::iterator &BI, Instruction *I) {
+ assert(I->getParent() == 0 &&
+ "ReplaceInstWithInst: Instruction already inserted into basic block!");
+
+ // Insert the new instruction into the basic block...
+ BI = BIL.insert(BI, I)+1;
+
+ // Replace all uses of the old instruction, and delete it.
+ ReplaceInstWithValue(BIL, BI, I);
+
+ // Reexamine the instruction just inserted next time around the cleanup pass
+ // loop.
+ --BI;
+}
+
+
+// ExpressionConvertableToType - Return true if it is possible
+static bool ExpressionConvertableToType(Value *V, const Type *Ty) {
+ Instruction *I = dyn_cast<Instruction>(V);
+ if (I == 0) return false; // Noninstructions can't convert
+ if (I->getType() == Ty) return false; // Expression already correct type!
+
+ switch (I->getOpcode()) {
+ case Instruction::Cast:
+ // We can convert the expr if the cast destination type is losslessly
+ // convertable to the requested type.
+ return losslessCastableTypes(Ty, I->getType());
+
+ case Instruction::Add:
+ case Instruction::Sub:
+ return ExpressionConvertableToType(I->getOperand(0), Ty) &&
+ ExpressionConvertableToType(I->getOperand(1), Ty);
+ case Instruction::Shl:
+ case Instruction::Shr:
+ return ExpressionConvertableToType(I->getOperand(0), Ty);
+ }
+ return false;
+}
+
+
+static Instruction *ConvertExpressionToType(Value *V, const Type *Ty) {
+ Instruction *I = cast<Instruction>(V);
+ assert(ExpressionConvertableToType(I, Ty) && "Inst is not convertable!");
+ BasicBlock *BB = I->getParent();
+ BasicBlock::InstListType &BIL = BB->getInstList();
+ string Name = I->getName(); if (!Name.empty()) I->setName("");
+ Instruction *Res; // Result of conversion
+
+ //cerr << endl << endl << "Type:\t" << Ty << "\nInst: " << I << "BB Before: " << BB << endl;
+
+ switch (I->getOpcode()) {
+ case Instruction::Cast:
+ Res = new CastInst(I->getOperand(0), Ty, Name);
+ break;
+
+ case Instruction::Add:
+ case Instruction::Sub:
+ Res = BinaryOperator::create(cast<BinaryOperator>(I)->getOpcode(),
+ ConvertExpressionToType(I->getOperand(0), Ty),
+ ConvertExpressionToType(I->getOperand(1), Ty),
+ Name);
+ break;
+
+ case Instruction::Shl:
+ case Instruction::Shr:
+ Res = new ShiftInst(cast<ShiftInst>(I)->getOpcode(),
+ ConvertExpressionToType(I->getOperand(0), Ty),
+ I->getOperand(1), Name);
+ break;
+
+ default:
+ assert(0 && "Expression convertable, but don't know how to convert?");
+ return 0;
+ }
+
+ BasicBlock::iterator It = find(BIL.begin(), BIL.end(), I);
+ assert(It != BIL.end() && "Instruction not in own basic block??");
+ BIL.insert(It, Res);
+
+ //cerr << "RInst: " << Res << "BB After: " << BB << endl << endl;
+
+ return Res;
+}
+
+
+
+// DoInsertArrayCast - If the argument value has a pointer type, and if the
+// argument value is used as an array, insert a cast before the specified
+// basic block iterator that casts the value to an array pointer. Return the
+// new cast instruction (in the CastResult var), or null if no cast is inserted.
+//
+static bool DoInsertArrayCast(Method *CurMeth, Value *V, BasicBlock *BB,
+ BasicBlock::iterator &InsertBefore,
+ CastInst *&CastResult) {
+ const PointerType *ThePtrType = dyn_cast<PointerType>(V->getType());
+ if (!ThePtrType) return false;
+ bool InsertCast = false;
+
+ for (Value::use_iterator I = V->use_begin(), E = V->use_end(); I != E; ++I) {
+ Instruction *Inst = cast<Instruction>(*I);
+ switch (Inst->getOpcode()) {
+ default: break; // Not an interesting use...
+ case Instruction::Add: // It's being used as an array index!
+ //case Instruction::Sub:
+ InsertCast = true;
+ break;
+ case Instruction::Cast: // There is already a cast instruction!
+ if (const PointerType *PT = dyn_cast<const PointerType>(Inst->getType()))
+ if (const ArrayType *AT = dyn_cast<const ArrayType>(PT->getValueType()))
+ if (AT->getElementType() == ThePtrType->getValueType()) {
+ // Cast already exists! Return the existing one!
+ CastResult = cast<CastInst>(Inst);
+ return false; // No changes made to program though...
+ }
+ break;
+ }
+ }
+
+ if (!InsertCast) return false; // There is no reason to insert a cast!
+
+ // Insert a cast!
+ const Type *ElTy = ThePtrType->getValueType();
+ const PointerType *DestTy = PointerType::get(ArrayType::get(ElTy));
+
+ CastResult = new CastInst(V, DestTy);
+ BB->getInstList().insert(InsertBefore, CastResult);
+ //cerr << "Inserted cast: " << CastResult;
+ return true; // Made a change!
+}
+
+
+// DoInsertArrayCasts - Loop over all "incoming" values in the specified method,
+// inserting a cast for pointer values that are used as arrays. For our
+// purposes, an incoming value is considered to be either a value that is
+// either a method parameter, a value created by alloca or malloc, or a value
+// returned from a function call. All casts are kept attached to their original
+// values through the PtrCasts map.
+//
+static bool DoInsertArrayCasts(Method *M, map<Value*, CastInst*> &PtrCasts) {
+ assert(!M->isExternal() && "Can't handle external methods!");
+
+ // Insert casts for all arguments to the function...
+ bool Changed = false;
+ BasicBlock *CurBB = M->front();
+ BasicBlock::iterator It = CurBB->begin();
+ for (Method::ArgumentListType::iterator AI = M->getArgumentList().begin(),
+ AE = M->getArgumentList().end(); AI != AE; ++AI) {
+ CastInst *TheCast = 0;
+ if (DoInsertArrayCast(M, *AI, CurBB, It, TheCast)) {
+ It = CurBB->begin(); // We might have just invalidated the iterator!
+ Changed = true; // Yes we made a change
+ ++It; // Insert next cast AFTER this one...
+ }
+
+ if (TheCast) // Is there a cast associated with this value?
+ PtrCasts[*AI] = TheCast; // Yes, add it to the map...
+ }
+
+ // TODO: insert casts for alloca, malloc, and function call results. Also,
+ // look for pointers that already have casts, to add to the map.
+
+ return Changed;
+}
+
+
+
+
+// DoElminatePointerArithmetic - Loop over each incoming pointer variable,
+// replacing indexing arithmetic with getelementptr calls.
+//
+static bool DoEliminatePointerArithmetic(const pair<Value*, CastInst*> &Val) {
+ Value *V = Val.first; // The original pointer
+ CastInst *CV = Val.second; // The array casted version of the pointer...
+
+ for (Value::use_iterator I = V->use_begin(), E = V->use_end(); I != E; ++I) {
+ Instruction *Inst = cast<Instruction>(*I);
+ if (Inst->getOpcode() != Instruction::Add)
+ continue; // We only care about add instructions
+
+ BinaryOperator *Add = cast<BinaryOperator>(Inst);
+
+ // Make sure the array is the first operand of the add expression...
+ if (Add->getOperand(0) != V)
+ Add->swapOperands();
+
+ // Get the amount added to the pointer value...
+ Value *AddAmount = Add->getOperand(1);
+
+
+ }
+ return false;
+}
+
+
+// Peephole Malloc instructions: we take a look at the use chain of the
+// malloc instruction, and try to find out if the following conditions hold:
+// 1. The malloc is of the form: 'malloc [sbyte], uint <constant>'
+// 2. The only users of the malloc are cast instructions
+// 3. Of the cast instructions, there is only one destination pointer type
+// [RTy] where the size of the pointed to object is equal to the number
+// of bytes allocated.
+//
+// If these conditions hold, we convert the malloc to allocate an [RTy]
+// element. This should be extended in the future to handle arrays. TODO
+//
+static bool PeepholeMallocInst(BasicBlock *BB, BasicBlock::iterator &BI) {
+ MallocInst *MI = cast<MallocInst>(*BI);
+ if (!MI->isArrayAllocation()) return false; // No array allocation?
+
+ ConstPoolUInt *Amt = dyn_cast<ConstPoolUInt>(MI->getArraySize());
+ if (Amt == 0 || MI->getAllocatedType() != ArrayType::get(Type::SByteTy))
+ return false;
+
+ // Get the number of bytes allocated...
+ unsigned Size = Amt->getValue();
+ const Type *ResultTy = 0;
+
+ // Loop over all of the uses of the malloc instruction, inspecting casts.
+ for (Value::use_iterator I = MI->use_begin(), E = MI->use_end();
+ I != E; ++I) {
+ if (!isa<CastInst>(*I)) {
+ //cerr << "\tnon" << *I;
+ return false; // A non cast user?
+ }
+ CastInst *CI = cast<CastInst>(*I);
+ //cerr << "\t" << CI;
+
+ // We only work on casts to pointer types for sure, be conservative
+ if (!isa<PointerType>(CI->getType())) {
+ cerr << "Found cast of malloc value to non pointer type:\n" << CI;
+ return false;
+ }
+
+ const Type *DestTy = cast<PointerType>(CI->getType())->getValueType();
+ if (TD.getTypeSize(DestTy) == Size && DestTy != ResultTy) {
+ // Does the size of the allocated type match the number of bytes
+ // allocated?
+ //
+ if (ResultTy == 0) {
+ ResultTy = DestTy; // Keep note of this for future uses...
+ } else {
+ // It's overdefined! We don't know which type to convert to!
+ return false;
+ }
+ }
+ }
+
+ // If we get this far, we have either found, or not, a type that is cast to
+ // that is of the same size as the malloc instruction.
+ if (!ResultTy) return false;
+
+ PRINT_PEEPHOLE1("mall-refine:in ", MI);
+ ReplaceInstWithInst(BB->getInstList(), BI,
+ MI = new MallocInst(PointerType::get(ResultTy)));
+ PRINT_PEEPHOLE1("mall-refine:out", MI);
+ return true;
+}
+
+
+
+static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
+ Instruction *I = *BI;
+ if (I->use_size() == 0) return false;
+
+ if (CastInst *CI = dyn_cast<CastInst>(I)) {
+ Value *Src = CI->getOperand(0);
+ Instruction *SrcI = dyn_cast<Instruction>(Src); // Nonnull if instr source
+ const Type *DestTy = CI->getType();
+
+ // Check for a cast of the same type as the destination!
+ if (DestTy == Src->getType()) {
+ PRINT_PEEPHOLE1("cast-of-self-ty", CI);
+ CI->replaceAllUsesWith(Src);
+ if (!Src->hasName() && CI->hasName()) {
+ string Name = CI->getName();
+ CI->setName(""); Src->setName(Name);
+ }
+ return true;
+ }
+
+ // Check for a cast of cast, where no size information is lost...
+ if (SrcI)
+ if (CastInst *CSrc = dyn_cast<CastInst>(SrcI))
+ if (isReinterpretingCast(CI) + isReinterpretingCast(CSrc) < 2) {
+ // We can only do c-c elimination if, at most, one cast does a
+ // reinterpretation of the input data.
+ //
+ // If legal, make this cast refer the the original casts argument!
+ //
+ PRINT_PEEPHOLE2("cast-cast:in ", CI, CSrc);
+ CI->setOperand(0, CSrc->getOperand(0));
+ PRINT_PEEPHOLE1("cast-cast:out", CI);
+ return true;
+ }
+
+ // Check to see if it's a cast of an instruction that does not depend on the
+ // specific type of the operands to do it's job.
+ if (SrcI && !isReinterpretingCast(CI) &&
+ ExpressionConvertableToType(SrcI, DestTy)) {
+ PRINT_PEEPHOLE2("EXPR-CONV:in ", CI, SrcI);
+ CI->setOperand(0, ConvertExpressionToType(SrcI, DestTy));
+ BI = BB->begin(); // Rescan basic block. BI might be invalidated.
+ PRINT_PEEPHOLE2("EXPR-CONV:out", CI, CI->getOperand(0));
+ return true;
+ }
+
+ } else if (MallocInst *MI = dyn_cast<MallocInst>(I)) {
+ if (PeepholeMallocInst(BB, BI)) return true;
+ } else if (I->getOpcode() == Instruction::Add &&
+ isa<CastInst>(I->getOperand(1))) {
+
+ // Peephole optimize the following instructions:
+ // %t1 = cast ulong <const int> to {<...>} *
+ // %t2 = add {<...>} * %SP, %t1 ;; Constant must be 2nd operand
+ //
+ // or
+ // %t1 = cast {<...>}* %SP to int*
+ // %t5 = cast ulong <const int> to int*
+ // %t2 = add int* %t1, %t5 ;; int is same size as field
+ //
+ // Into: %t3 = getelementptr {<...>} * %SP, <element indices>
+ // %t2 = cast <eltype> * %t3 to {<...>}*
+ //
+ Value *AddOp1 = I->getOperand(0);
+ CastInst *AddOp2 = cast<CastInst>(I->getOperand(1));
+ ConstPoolUInt *OffsetV = dyn_cast<ConstPoolUInt>(AddOp2->getOperand(0));
+ unsigned Offset = OffsetV ? OffsetV->getValue() : 0;
+ Value *SrcPtr; // Of type pointer to struct...
+ const StructType *StructTy;
+
+ if ((StructTy = getPointedToStruct(AddOp1->getType()))) {
+ SrcPtr = AddOp1; // Handle the first case...
+ } else if (CastInst *AddOp1c = dyn_cast<CastInst>(AddOp1)) {
+ SrcPtr = AddOp1c->getOperand(0); // Handle the second case...
+ StructTy = getPointedToStruct(SrcPtr->getType());
+ }
+
+ // Only proceed if we have detected all of our conditions successfully...
+ if (Offset && StructTy && SrcPtr && Offset < TD.getTypeSize(StructTy)) {
+ const StructLayout *SL = TD.getStructLayout(StructTy);
+ vector<ConstPoolVal*> Offsets;
+ unsigned ActualOffset = Offset;
+ const Type *ElTy = getStructOffsetType(StructTy, ActualOffset, Offsets);
+
+ if (getPointedToStruct(AddOp1->getType())) { // case 1
+ PRINT_PEEPHOLE2("add-to-gep1:in", AddOp2, I);
+ } else {
+ PRINT_PEEPHOLE3("add-to-gep2:in", AddOp1, AddOp2, I);
+ }
+
+ GetElementPtrInst *GEP = new GetElementPtrInst(SrcPtr, Offsets);
+ BI = BB->getInstList().insert(BI, GEP)+1;
+
+ assert(Offset-ActualOffset == 0 &&
+ "GEP to middle of element not implemented yet!");
+
+ ReplaceInstWithInst(BB->getInstList(), BI,
+ I = new CastInst(GEP, I->getType()));
+ PRINT_PEEPHOLE2("add-to-gep:out", GEP, I);
+ return true;
+ }
+ }
+
+ return false;
+}
+
+
+
+
+static bool DoRaisePass(Method *M) {
+ bool Changed = false;
+ for (Method::iterator MI = M->begin(), ME = M->end(); MI != ME; ++MI) {
+ BasicBlock *BB = *MI;
+ BasicBlock::InstListType &BIL = BB->getInstList();
+
+ for (BasicBlock::iterator BI = BB->begin(); BI != BB->end();) {
+ if (PeepholeOptimize(BB, BI))
+ Changed = true;
+ else
+ ++BI;
+ }
+ }
+ return Changed;
+}
+
+
+// RaisePointerReferences::doit - Raise a method representation to a higher
+// level.
+//
+bool RaisePointerReferences::doit(Method *M) {
+ if (M->isExternal()) return false;
+ bool Changed = false;
+
+ while (DoRaisePass(M)) Changed = true;
+
+ // PtrCasts - Keep a mapping between the pointer values (the key of the
+ // map), and the cast to array pointer (the value) in this map. This is
+ // used when converting pointer math into array addressing.
+ //
+ map<Value*, CastInst*> PtrCasts;
+
+ // Insert casts for all incoming pointer values. Keep track of those casts
+ // and the identified incoming values in the PtrCasts map.
+ //
+ Changed |= DoInsertArrayCasts(M, PtrCasts);
+
+ // Loop over each incoming pointer variable, replacing indexing arithmetic
+ // with getelementptr calls.
+ //
+ Changed |= reduce_apply_bool(PtrCasts.begin(), PtrCasts.end(),
+ ptr_fun(DoEliminatePointerArithmetic));
+
+ return Changed;
+}
projects / oota-llvm.git / commitdiff