1 //===- PreSelection.cpp - Specialize LLVM code for target machine ---------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the PreSelection pass which specializes LLVM code for a
11 // target machine, while remaining in legal portable LLVM form and
12 // preserving type information and type safety. This is meant to enable
13 // dataflow optimizations on target-specific operations such as accesses to
14 // constants, globals, and array indexing.
16 //===----------------------------------------------------------------------===//
18 #include "SparcV9Internals.h"
19 #include "llvm/Constants.h"
20 #include "llvm/DerivedTypes.h"
21 #include "llvm/iMemory.h"
22 #include "llvm/iPHINode.h"
23 #include "llvm/iOther.h"
24 #include "llvm/Module.h"
25 #include "llvm/Pass.h"
26 #include "llvm/Support/InstVisitor.h"
27 #include "llvm/Support/GetElementPtrTypeIterator.h"
28 #include "llvm/Target/TargetInstrInfo.h"
29 #include "llvm/Target/TargetMachine.h"
30 #include "llvm/Transforms/Scalar.h"
36 //===--------------------------------------------------------------------===//
37 // PreSelection Pass - Specialize LLVM code for the current target machine.
39 class PreSelection : public FunctionPass, public InstVisitor<PreSelection> {
40 const TargetInstrInfo &instrInfo;
43 PreSelection(const TargetMachine &T)
44 : instrInfo(T.getInstrInfo()) {}
46 // runOnFunction - apply this pass to each Function
47 bool runOnFunction(Function &F) {
51 const char *getPassName() const { return "SparcV9 Instr. Pre-selection"; }
53 // These methods do the actual work of specializing code
54 void visitInstruction(Instruction &I); // common work for every instr.
55 void visitGetElementPtrInst(GetElementPtrInst &I);
56 void visitCallInst(CallInst &I);
57 void visitPHINode(PHINode &PN);
59 // Helper functions for visiting operands of every instruction
61 // visitOperands() works on every operand in [firstOp, lastOp-1].
62 // If lastOp==0, lastOp defaults to #operands or #incoming Phi values.
64 // visitOneOperand() does all the work for one operand.
66 void visitOperands(Instruction &I, int firstOp=0);
67 void visitOneOperand(Instruction &I, Value* Op, unsigned opNum,
68 Instruction& insertBefore);
72 // Register the pass...
73 RegisterPass<PreSelection> X("preselect",
74 "Specialize LLVM code for a target machine"
75 createPreselectionPass);
78 } // end anonymous namespace
81 //------------------------------------------------------------------------------
82 // Helper functions used by methods of class PreSelection
83 //------------------------------------------------------------------------------
86 // getGlobalAddr(): Put address of a global into a v. register.
87 static GetElementPtrInst* getGlobalAddr(Value* ptr, Instruction& insertBefore) {
88 if (isa<ConstantPointerRef>(ptr))
89 ptr = cast<ConstantPointerRef>(ptr)->getValue();
91 return (isa<GlobalVariable>(ptr))
92 ? new GetElementPtrInst(ptr,
93 std::vector<Value*>(1, ConstantSInt::get(Type::LongTy, 0U)),
94 "addrOfGlobal", &insertBefore)
98 // Wrapper on Constant::classof to use in find_if
99 inline static bool nonConstant(const Use& U) {
100 return ! isa<Constant>(U);
103 static Instruction* DecomposeConstantExpr(ConstantExpr* CE,
104 Instruction& insertBefore)
106 Value *getArg1, *getArg2;
108 switch(CE->getOpcode())
110 case Instruction::Cast:
111 getArg1 = CE->getOperand(0);
112 if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg1))
113 getArg1 = DecomposeConstantExpr(CEarg, insertBefore);
114 return new CastInst(getArg1, CE->getType(), "constantCast",&insertBefore);
116 case Instruction::GetElementPtr:
117 assert(find_if(CE->op_begin()+1, CE->op_end(),nonConstant) == CE->op_end()
118 && "All indices in ConstantExpr getelementptr must be constant!");
119 getArg1 = CE->getOperand(0);
120 if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg1))
121 getArg1 = DecomposeConstantExpr(CEarg, insertBefore);
122 else if (GetElementPtrInst* gep = getGlobalAddr(getArg1, insertBefore))
124 return new GetElementPtrInst(getArg1,
125 std::vector<Value*>(CE->op_begin()+1, CE->op_end()),
126 "constantGEP", &insertBefore);
128 case Instruction::Select: {
130 C = CE->getOperand (0);
131 if (ConstantExpr* CEarg = dyn_cast<ConstantExpr> (C))
132 C = DecomposeConstantExpr (CEarg, insertBefore);
133 S1 = CE->getOperand (1);
134 if (ConstantExpr* CEarg = dyn_cast<ConstantExpr> (S1))
135 S1 = DecomposeConstantExpr (CEarg, insertBefore);
136 S2 = CE->getOperand (2);
137 if (ConstantExpr* CEarg = dyn_cast<ConstantExpr> (S2))
138 S2 = DecomposeConstantExpr (CEarg, insertBefore);
139 return new SelectInst (C, S1, S2);
142 default: // must be a binary operator
143 assert(CE->getOpcode() >= Instruction::BinaryOpsBegin &&
144 CE->getOpcode() < Instruction::BinaryOpsEnd &&
145 "Unhandled opcode in ConstantExpr");
146 getArg1 = CE->getOperand(0);
147 if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg1))
148 getArg1 = DecomposeConstantExpr(CEarg, insertBefore);
149 getArg2 = CE->getOperand(1);
150 if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg2))
151 getArg2 = DecomposeConstantExpr(CEarg, insertBefore);
152 return BinaryOperator::create((Instruction::BinaryOps) CE->getOpcode(),
154 "constantBinaryOp", &insertBefore);
159 //------------------------------------------------------------------------------
160 // Instruction visitor methods to perform instruction-specific operations
161 //------------------------------------------------------------------------------
163 PreSelection::visitOneOperand(Instruction &I, Value* Op, unsigned opNum,
164 Instruction& insertBefore)
166 assert(&insertBefore != NULL && "Must have instruction to insert before.");
168 if (GetElementPtrInst* gep = getGlobalAddr(Op, insertBefore)) {
169 I.setOperand(opNum, gep); // replace global operand
170 return; // nothing more to do for this op.
173 Constant* CV = dyn_cast<Constant>(Op);
177 if (ConstantExpr* CE = dyn_cast<ConstantExpr>(CV)) {
178 // load-time constant: factor it out so we optimize as best we can
179 Instruction* computeConst = DecomposeConstantExpr(CE, insertBefore);
180 I.setOperand(opNum, computeConst); // replace expr operand with result
181 } else if (instrInfo.ConstantTypeMustBeLoaded(CV)) {
182 // load address of constant into a register, then load the constant
183 // this is now done during instruction selection
184 // the constant will live in the MachineConstantPool later on
185 } else if (instrInfo.ConstantMayNotFitInImmedField(CV, &I)) {
186 // put the constant into a virtual register using a cast
187 CastInst* castI = new CastInst(CV, CV->getType(), "copyConst",
189 I.setOperand(opNum, castI); // replace operand with copy in v.reg.
193 /// visitOperands - transform individual operands of all instructions:
194 /// -- Load "large" int constants into a virtual register. What is large
195 /// depends on the type of instruction and on the target architecture.
196 /// -- For any constants that cannot be put in an immediate field,
197 /// load address into virtual register first, and then load the constant.
199 /// firstOp and lastOp can be used to skip leading and trailing operands.
200 /// If lastOp is 0, it defaults to #operands or #incoming Phi values.
202 inline void PreSelection::visitOperands(Instruction &I, int firstOp) {
203 // For any instruction other than PHI, copies go just before the instr.
204 for (unsigned i = firstOp, e = I.getNumOperands(); i != e; ++i)
205 visitOneOperand(I, I.getOperand(i), i, I);
209 void PreSelection::visitPHINode(PHINode &PN) {
210 // For a PHI, operand copies must be before the terminator of the
211 // appropriate predecessor basic block. Remaining logic is simple
212 // so just handle PHIs and other instructions separately.
214 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
215 visitOneOperand(PN, PN.getIncomingValue(i),
216 PN.getOperandNumForIncomingValue(i),
217 *PN.getIncomingBlock(i)->getTerminator());
218 // do not call visitOperands!
221 // Common work for *all* instructions. This needs to be called explicitly
222 // by other visit<InstructionType> functions.
223 inline void PreSelection::visitInstruction(Instruction &I) {
224 visitOperands(I); // Perform operand transformations
227 // GetElementPtr instructions: check if pointer is a global
228 void PreSelection::visitGetElementPtrInst(GetElementPtrInst &I) {
229 Instruction* curI = &I;
231 // The Sparc backend doesn't handle array indexes that are not long types, so
232 // insert a cast from whatever it is to long, if the sequential type index is
233 // not a long already.
235 for (gep_type_iterator TI = gep_type_begin(I), E = gep_type_end(I); TI != E;
237 if (isa<SequentialType>(*TI) &&
238 I.getOperand(Idx)->getType() != Type::LongTy) {
239 Value *Op = I.getOperand(Idx);
240 if (Op->getType()->isUnsigned()) // Must sign extend!
241 Op = new CastInst(Op, Op->getType()->getSignedVersion(), "v9", &I);
242 if (Op->getType() != Type::LongTy)
243 Op = new CastInst(Op, Type::LongTy, "v9", &I);
244 I.setOperand(Idx, Op);
248 // Decompose multidimensional array references
249 if (I.getNumIndices() >= 2) {
250 // DecomposeArrayRef() replaces I and deletes it, if successful,
251 // so remember predecessor in order to find the replacement instruction.
252 // Also remember the basic block in case there is no predecessor.
253 Instruction* prevI = I.getPrev();
254 BasicBlock* bb = I.getParent();
255 if (DecomposeArrayRef(&I))
256 // first instr. replacing I
257 curI = cast<GetElementPtrInst>(prevI? prevI->getNext() : &bb->front());
260 // Perform other transformations common to all instructions
261 visitInstruction(*curI);
264 void PreSelection::visitCallInst(CallInst &I) {
265 // Tell visitOperands to ignore the function name if this is a direct call.
266 visitOperands(I, (/*firstOp=*/ I.getCalledFunction()? 1 : 0));
269 /// createPreSelectionPass - Public entry point for the PreSelection pass
271 FunctionPass* llvm::createPreSelectionPass(const TargetMachine &TM) {
272 return new PreSelection(TM);