mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-12-23 12:08:25 +00:00
232 lines
8.7 KiB
C++
232 lines
8.7 KiB
C++
//===- ScalarEvolutionExpander.cpp - Scalar Evolution Analysis --*- C++ -*-===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file was developed by the LLVM research group and is distributed under
|
|
// the University of Illinois Open Source License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file contains the implementation of the scalar evolution expander,
|
|
// which is used to generate the code corresponding to a given scalar evolution
|
|
// expression.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Analysis/ScalarEvolutionExpander.h"
|
|
#include "llvm/Analysis/LoopInfo.h"
|
|
using namespace llvm;
|
|
|
|
/// InsertCastOfTo - Insert a cast of V to the specified type, doing what
|
|
/// we can to share the casts.
|
|
Value *SCEVExpander::InsertCastOfTo(Instruction::CastOps opcode, Value *V,
|
|
const Type *Ty) {
|
|
// FIXME: keep track of the cast instruction.
|
|
if (Constant *C = dyn_cast<Constant>(V))
|
|
return ConstantExpr::getCast(opcode, C, Ty);
|
|
|
|
if (Argument *A = dyn_cast<Argument>(V)) {
|
|
// Check to see if there is already a cast!
|
|
for (Value::use_iterator UI = A->use_begin(), E = A->use_end();
|
|
UI != E; ++UI) {
|
|
if ((*UI)->getType() == Ty)
|
|
if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI))) {
|
|
// If the cast isn't the first instruction of the function, move it.
|
|
if (BasicBlock::iterator(CI) !=
|
|
A->getParent()->getEntryBlock().begin()) {
|
|
CI->moveBefore(A->getParent()->getEntryBlock().begin());
|
|
}
|
|
return CI;
|
|
}
|
|
}
|
|
return CastInst::create(opcode, V, Ty, V->getName(),
|
|
A->getParent()->getEntryBlock().begin());
|
|
}
|
|
|
|
Instruction *I = cast<Instruction>(V);
|
|
|
|
// Check to see if there is already a cast. If there is, use it.
|
|
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
|
|
UI != E; ++UI) {
|
|
if ((*UI)->getType() == Ty)
|
|
if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI))) {
|
|
BasicBlock::iterator It = I; ++It;
|
|
if (isa<InvokeInst>(I))
|
|
It = cast<InvokeInst>(I)->getNormalDest()->begin();
|
|
while (isa<PHINode>(It)) ++It;
|
|
if (It != BasicBlock::iterator(CI)) {
|
|
// Splice the cast immediately after the operand in question.
|
|
CI->moveBefore(It);
|
|
}
|
|
return CI;
|
|
}
|
|
}
|
|
BasicBlock::iterator IP = I; ++IP;
|
|
if (InvokeInst *II = dyn_cast<InvokeInst>(I))
|
|
IP = II->getNormalDest()->begin();
|
|
while (isa<PHINode>(IP)) ++IP;
|
|
return CastInst::create(opcode, V, Ty, V->getName(), IP);
|
|
}
|
|
|
|
/// InsertBinop - Insert the specified binary operator, doing a small amount
|
|
/// of work to avoid inserting an obviously redundant operation.
|
|
Value *SCEVExpander::InsertBinop(Instruction::BinaryOps Opcode, Value *LHS,
|
|
Value *RHS, Instruction *&InsertPt) {
|
|
// Fold a binop with constant operands.
|
|
if (Constant *CLHS = dyn_cast<Constant>(LHS))
|
|
if (Constant *CRHS = dyn_cast<Constant>(RHS))
|
|
return ConstantExpr::get(Opcode, CLHS, CRHS);
|
|
|
|
// Do a quick scan to see if we have this binop nearby. If so, reuse it.
|
|
unsigned ScanLimit = 6;
|
|
for (BasicBlock::iterator IP = InsertPt, E = InsertPt->getParent()->begin();
|
|
ScanLimit; --IP, --ScanLimit) {
|
|
if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(IP))
|
|
if (BinOp->getOpcode() == Opcode && BinOp->getOperand(0) == LHS &&
|
|
BinOp->getOperand(1) == RHS) {
|
|
// If we found the instruction *at* the insert point, insert later
|
|
// instructions after it.
|
|
if (BinOp == InsertPt)
|
|
InsertPt = ++IP;
|
|
return BinOp;
|
|
}
|
|
if (IP == E) break;
|
|
}
|
|
|
|
// If we don't have
|
|
return BinaryOperator::create(Opcode, LHS, RHS, "tmp", InsertPt);
|
|
}
|
|
|
|
Value *SCEVExpander::visitMulExpr(SCEVMulExpr *S) {
|
|
int FirstOp = 0; // Set if we should emit a subtract.
|
|
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getOperand(0)))
|
|
if (SC->getValue()->isAllOnesValue())
|
|
FirstOp = 1;
|
|
|
|
int i = S->getNumOperands()-2;
|
|
Value *V = expand(S->getOperand(i+1));
|
|
|
|
// Emit a bunch of multiply instructions
|
|
for (; i >= FirstOp; --i)
|
|
V = InsertBinop(Instruction::Mul, V, expand(S->getOperand(i)),
|
|
InsertPt);
|
|
// -1 * ... ---> 0 - ...
|
|
if (FirstOp == 1)
|
|
V = InsertBinop(Instruction::Sub, Constant::getNullValue(V->getType()), V,
|
|
InsertPt);
|
|
return V;
|
|
}
|
|
|
|
Value *SCEVExpander::visitAddRecExpr(SCEVAddRecExpr *S) {
|
|
const Type *Ty = S->getType();
|
|
const Loop *L = S->getLoop();
|
|
// We cannot yet do fp recurrences, e.g. the xform of {X,+,F} --> X+{0,+,F}
|
|
assert(Ty->isInteger() && "Cannot expand fp recurrences yet!");
|
|
|
|
// {X,+,F} --> X + {0,+,F}
|
|
if (!isa<SCEVConstant>(S->getStart()) ||
|
|
!cast<SCEVConstant>(S->getStart())->getValue()->isZero()) {
|
|
Value *Start = expand(S->getStart());
|
|
std::vector<SCEVHandle> NewOps(S->op_begin(), S->op_end());
|
|
NewOps[0] = SE.getIntegerSCEV(0, Ty);
|
|
Value *Rest = expand(SE.getAddRecExpr(NewOps, L));
|
|
|
|
// FIXME: look for an existing add to use.
|
|
return InsertBinop(Instruction::Add, Rest, Start, InsertPt);
|
|
}
|
|
|
|
// {0,+,1} --> Insert a canonical induction variable into the loop!
|
|
if (S->getNumOperands() == 2 &&
|
|
S->getOperand(1) == SE.getIntegerSCEV(1, Ty)) {
|
|
// Create and insert the PHI node for the induction variable in the
|
|
// specified loop.
|
|
BasicBlock *Header = L->getHeader();
|
|
PHINode *PN = new PHINode(Ty, "indvar", Header->begin());
|
|
PN->addIncoming(Constant::getNullValue(Ty), L->getLoopPreheader());
|
|
|
|
pred_iterator HPI = pred_begin(Header);
|
|
assert(HPI != pred_end(Header) && "Loop with zero preds???");
|
|
if (!L->contains(*HPI)) ++HPI;
|
|
assert(HPI != pred_end(Header) && L->contains(*HPI) &&
|
|
"No backedge in loop?");
|
|
|
|
// Insert a unit add instruction right before the terminator corresponding
|
|
// to the back-edge.
|
|
Constant *One = ConstantInt::get(Ty, 1);
|
|
Instruction *Add = BinaryOperator::createAdd(PN, One, "indvar.next",
|
|
(*HPI)->getTerminator());
|
|
|
|
pred_iterator PI = pred_begin(Header);
|
|
if (*PI == L->getLoopPreheader())
|
|
++PI;
|
|
PN->addIncoming(Add, *PI);
|
|
return PN;
|
|
}
|
|
|
|
// Get the canonical induction variable I for this loop.
|
|
Value *I = getOrInsertCanonicalInductionVariable(L, Ty);
|
|
|
|
// If this is a simple linear addrec, emit it now as a special case.
|
|
if (S->getNumOperands() == 2) { // {0,+,F} --> i*F
|
|
Value *F = expand(S->getOperand(1));
|
|
|
|
// IF the step is by one, just return the inserted IV.
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(F))
|
|
if (CI->getValue() == 1)
|
|
return I;
|
|
|
|
// If the insert point is directly inside of the loop, emit the multiply at
|
|
// the insert point. Otherwise, L is a loop that is a parent of the insert
|
|
// point loop. If we can, move the multiply to the outer most loop that it
|
|
// is safe to be in.
|
|
Instruction *MulInsertPt = InsertPt;
|
|
Loop *InsertPtLoop = LI.getLoopFor(MulInsertPt->getParent());
|
|
if (InsertPtLoop != L && InsertPtLoop &&
|
|
L->contains(InsertPtLoop->getHeader())) {
|
|
while (InsertPtLoop != L) {
|
|
// If we cannot hoist the multiply out of this loop, don't.
|
|
if (!InsertPtLoop->isLoopInvariant(F)) break;
|
|
|
|
// Otherwise, move the insert point to the preheader of the loop.
|
|
MulInsertPt = InsertPtLoop->getLoopPreheader()->getTerminator();
|
|
InsertPtLoop = InsertPtLoop->getParentLoop();
|
|
}
|
|
}
|
|
|
|
return InsertBinop(Instruction::Mul, I, F, MulInsertPt);
|
|
}
|
|
|
|
// If this is a chain of recurrences, turn it into a closed form, using the
|
|
// folders, then expandCodeFor the closed form. This allows the folders to
|
|
// simplify the expression without having to build a bunch of special code
|
|
// into this folder.
|
|
SCEVHandle IH = SE.getUnknown(I); // Get I as a "symbolic" SCEV.
|
|
|
|
SCEVHandle V = S->evaluateAtIteration(IH, SE);
|
|
//cerr << "Evaluated: " << *this << "\n to: " << *V << "\n";
|
|
|
|
return expand(V);
|
|
}
|
|
|
|
Value *SCEVExpander::visitSMaxExpr(SCEVSMaxExpr *S) {
|
|
Value *LHS = expand(S->getOperand(0));
|
|
for (unsigned i = 1; i < S->getNumOperands(); ++i) {
|
|
Value *RHS = expand(S->getOperand(i));
|
|
Value *ICmp = new ICmpInst(ICmpInst::ICMP_SGT, LHS, RHS, "tmp", InsertPt);
|
|
LHS = new SelectInst(ICmp, LHS, RHS, "smax", InsertPt);
|
|
}
|
|
return LHS;
|
|
}
|
|
|
|
Value *SCEVExpander::expand(SCEV *S) {
|
|
// Check to see if we already expanded this.
|
|
std::map<SCEVHandle, Value*>::iterator I = InsertedExpressions.find(S);
|
|
if (I != InsertedExpressions.end())
|
|
return I->second;
|
|
|
|
Value *V = visit(S);
|
|
InsertedExpressions[S] = V;
|
|
return V;
|
|
}
|
|
|