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move a bunch of code out of the sdisel pass into its own opt pass "codegenprepare".

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llvm-svn: 35529
This commit is contained in:
Chris Lattner 2007-03-31 04:18:03 +00:00
parent 579b1c63d5
commit f01b0a800b
2 changed files with 21 additions and 485 deletions
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22
lib/CodeGen/LLVMTargetMachine.cpp
View File

@ -23,7 +23,7 @@
using namespace llvm;
static cl::opt<bool> PrintLSR("print-lsr-output");
static cl::opt<bool> PrintISelInput("print-isel-input");
FileModel::Model
LLVMTargetMachine::addPassesToEmitFile(FunctionPassManager &PM,
std::ostream &Out,
@ -48,6 +48,13 @@ LLVMTargetMachine::addPassesToEmitFile(FunctionPassManager &PM,
// Make sure that no unreachable blocks are instruction selected.
PM.add(createUnreachableBlockEliminationPass());
if (!Fast)
PM.add(createCodeGenPreparePass(getTargetLowering()));
if (PrintISelInput)
PM.add(new PrintFunctionPass("\n\n*** Final LLVM Code input to ISel *** \n",
&cerr));
// Ask the target for an isel.
if (addInstSelector(PM, Fast))
return FileModel::Error;
@ -126,7 +133,11 @@ bool LLVMTargetMachine::addPassesToEmitMachineCode(FunctionPassManager &PM,
// Standard LLVM-Level Passes.
// Run loop strength reduction before anything else.
if (!Fast) PM.add(createLoopStrengthReducePass(getTargetLowering()));
if (!Fast) {
PM.add(createLoopStrengthReducePass(getTargetLowering()));
if (PrintLSR)
PM.add(new PrintFunctionPass("\n\n*** Code after LSR *** \n", &cerr));
}
// FIXME: Implement efficient support for garbage collection intrinsics.
PM.add(createLowerGCPass());
@ -137,6 +148,13 @@ bool LLVMTargetMachine::addPassesToEmitMachineCode(FunctionPassManager &PM,
// Make sure that no unreachable blocks are instruction selected.
PM.add(createUnreachableBlockEliminationPass());
if (!Fast)
PM.add(createCodeGenPreparePass(getTargetLowering()));
if (PrintISelInput)
PM.add(new PrintFunctionPass("\n\n*** Final LLVM Code input to ISel *** \n",
&cerr));
// Ask the target for an isel.
if (addInstSelector(PM, Fast))
return true;

484
lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
View File

@ -16,7 +16,6 @@
#include "llvm/CodeGen/SelectionDAGISel.h"
#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/CallingConv.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/GlobalVariable.h"
@ -33,14 +32,12 @@
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/SSARegMap.h"
#include "llvm/Target/MRegisterInfo.h"
#include "llvm/Target/TargetAsmInfo.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetFrameInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Compiler.h"
@ -3830,496 +3827,17 @@ unsigned SelectionDAGISel::MakeReg(MVT::ValueType VT) {
}
void SelectionDAGISel::getAnalysisUsage(AnalysisUsage &AU) const {
// FIXME: we only modify the CFG to split critical edges. This
// updates dom and loop info.
AU.addRequired<AliasAnalysis>();
AU.setPreservesAll();
}
/// OptimizeNoopCopyExpression - We have determined that the specified cast
/// instruction is a noop copy (e.g. it's casting from one pointer type to
/// another, int->uint, or int->sbyte on PPC.
///
/// Return true if any changes are made.
static bool OptimizeNoopCopyExpression(CastInst *CI) {
BasicBlock *DefBB = CI->getParent();
/// InsertedCasts - Only insert a cast in each block once.
std::map<BasicBlock*, CastInst*> InsertedCasts;
bool MadeChange = false;
for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
UI != E; ) {
Use &TheUse = UI.getUse();
Instruction *User = cast<Instruction>(*UI);
// Figure out which BB this cast is used in. For PHI's this is the
// appropriate predecessor block.
BasicBlock *UserBB = User->getParent();
if (PHINode *PN = dyn_cast<PHINode>(User)) {
unsigned OpVal = UI.getOperandNo()/2;
UserBB = PN->getIncomingBlock(OpVal);
}
// Preincrement use iterator so we don't invalidate it.
++UI;
// If this user is in the same block as the cast, don't change the cast.
if (UserBB == DefBB) continue;
// If we have already inserted a cast into this block, use it.
CastInst *&InsertedCast = InsertedCasts[UserBB];
if (!InsertedCast) {
BasicBlock::iterator InsertPt = UserBB->begin();
while (isa<PHINode>(InsertPt)) ++InsertPt;
InsertedCast =
CastInst::create(CI->getOpcode(), CI->getOperand(0), CI->getType(), "",
InsertPt);
MadeChange = true;
}
// Replace a use of the cast with a use of the new casat.
TheUse = InsertedCast;
}
// If we removed all uses, nuke the cast.
if (CI->use_empty())
CI->eraseFromParent();
return MadeChange;
}
/// InsertGEPComputeCode - Insert code into BB to compute Ptr+PtrOffset,
/// casting to the type of GEPI.
static Instruction *InsertGEPComputeCode(Instruction *&V, BasicBlock *BB,
Instruction *GEPI, Value *Ptr,
Value *PtrOffset) {
if (V) return V; // Already computed.
// Figure out the insertion point
BasicBlock::iterator InsertPt;
if (BB == GEPI->getParent()) {
// If GEP is already inserted into BB, insert right after the GEP.
InsertPt = GEPI;
++InsertPt;
} else {
// Otherwise, insert at the top of BB, after any PHI nodes
InsertPt = BB->begin();
while (isa<PHINode>(InsertPt)) ++InsertPt;
}
// If Ptr is itself a cast, but in some other BB, emit a copy of the cast into
// BB so that there is only one value live across basic blocks (the cast
// operand).
if (CastInst *CI = dyn_cast<CastInst>(Ptr))
if (CI->getParent() != BB && isa<PointerType>(CI->getOperand(0)->getType()))
Ptr = CastInst::create(CI->getOpcode(), CI->getOperand(0), CI->getType(),
"", InsertPt);
// Add the offset, cast it to the right type.
Ptr = BinaryOperator::createAdd(Ptr, PtrOffset, "", InsertPt);
// Ptr is an integer type, GEPI is pointer type ==> IntToPtr
return V = CastInst::create(Instruction::IntToPtr, Ptr, GEPI->getType(),
"", InsertPt);
}
/// ReplaceUsesOfGEPInst - Replace all uses of RepPtr with inserted code to
/// compute its value. The RepPtr value can be computed with Ptr+PtrOffset. One
/// trivial way of doing this would be to evaluate Ptr+PtrOffset in RepPtr's
/// block, then ReplaceAllUsesWith'ing everything. However, we would prefer to
/// sink PtrOffset into user blocks where doing so will likely allow us to fold
/// the constant add into a load or store instruction. Additionally, if a user
/// is a pointer-pointer cast, we look through it to find its users.
static void ReplaceUsesOfGEPInst(Instruction *RepPtr, Value *Ptr,
Constant *PtrOffset, BasicBlock *DefBB,
GetElementPtrInst *GEPI,
std::map<BasicBlock*,Instruction*> &InsertedExprs) {
while (!RepPtr->use_empty()) {
Instruction *User = cast<Instruction>(RepPtr->use_back());
// If the user is a Pointer-Pointer cast, recurse. Only BitCast can be
// used for a Pointer-Pointer cast.
if (isa<BitCastInst>(User)) {
ReplaceUsesOfGEPInst(User, Ptr, PtrOffset, DefBB, GEPI, InsertedExprs);
// Drop the use of RepPtr. The cast is dead. Don't delete it now, else we
// could invalidate an iterator.
User->setOperand(0, UndefValue::get(RepPtr->getType()));
continue;
}
// If this is a load of the pointer, or a store through the pointer, emit
// the increment into the load/store block.
Instruction *NewVal;
if (isa<LoadInst>(User) ||
(isa<StoreInst>(User) && User->getOperand(0) != RepPtr)) {
NewVal = InsertGEPComputeCode(InsertedExprs[User->getParent()],
User->getParent(), GEPI,
Ptr, PtrOffset);
} else {
// If this use is not foldable into the addressing mode, use a version
// emitted in the GEP block.
NewVal = InsertGEPComputeCode(InsertedExprs[DefBB], DefBB, GEPI,
Ptr, PtrOffset);
}
if (GEPI->getType() != RepPtr->getType()) {
BasicBlock::iterator IP = NewVal;
++IP;
// NewVal must be a GEP which must be pointer type, so BitCast
NewVal = new BitCastInst(NewVal, RepPtr->getType(), "", IP);
}
User->replaceUsesOfWith(RepPtr, NewVal);
}
}
/// OptimizeGEPExpression - Since we are doing basic-block-at-a-time instruction
/// selection, we want to be a bit careful about some things. In particular, if
/// we have a GEP instruction that is used in a different block than it is
/// defined, the addressing expression of the GEP cannot be folded into loads or
/// stores that use it. In this case, decompose the GEP and move constant
/// indices into blocks that use it.
static bool OptimizeGEPExpression(GetElementPtrInst *GEPI,
const TargetData *TD) {
// If this GEP is only used inside the block it is defined in, there is no
// need to rewrite it.
bool isUsedOutsideDefBB = false;
BasicBlock *DefBB = GEPI->getParent();
for (Value::use_iterator UI = GEPI->use_begin(), E = GEPI->use_end();
UI != E; ++UI) {
if (cast<Instruction>(*UI)->getParent() != DefBB) {
isUsedOutsideDefBB = true;
break;
}
}
if (!isUsedOutsideDefBB) return false;
// If this GEP has no non-zero constant indices, there is nothing we can do,
// ignore it.
bool hasConstantIndex = false;
bool hasVariableIndex = false;
for (GetElementPtrInst::op_iterator OI = GEPI->op_begin()+1,
E = GEPI->op_end(); OI != E; ++OI) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(*OI)) {
if (CI->getZExtValue()) {
hasConstantIndex = true;
break;
}
} else {
hasVariableIndex = true;
}
}
// If this is a "GEP X, 0, 0, 0", turn this into a cast.
if (!hasConstantIndex && !hasVariableIndex) {
/// The GEP operand must be a pointer, so must its result -> BitCast
Value *NC = new BitCastInst(GEPI->getOperand(0), GEPI->getType(),
GEPI->getName(), GEPI);
GEPI->replaceAllUsesWith(NC);
GEPI->eraseFromParent();
return true;
}
// If this is a GEP &Alloca, 0, 0, forward subst the frame index into uses.
if (!hasConstantIndex && !isa<AllocaInst>(GEPI->getOperand(0)))
return false;
// Otherwise, decompose the GEP instruction into multiplies and adds. Sum the
// constant offset (which we now know is non-zero) and deal with it later.
uint64_t ConstantOffset = 0;
const Type *UIntPtrTy = TD->getIntPtrType();
Value *Ptr = new PtrToIntInst(GEPI->getOperand(0), UIntPtrTy, "", GEPI);
const Type *Ty = GEPI->getOperand(0)->getType();
for (GetElementPtrInst::op_iterator OI = GEPI->op_begin()+1,
E = GEPI->op_end(); OI != E; ++OI) {
Value *Idx = *OI;
if (const StructType *StTy = dyn_cast<StructType>(Ty)) {
unsigned Field = cast<ConstantInt>(Idx)->getZExtValue();
if (Field)
ConstantOffset += TD->getStructLayout(StTy)->getElementOffset(Field);
Ty = StTy->getElementType(Field);
} else {
Ty = cast<SequentialType>(Ty)->getElementType();
// Handle constant subscripts.
if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx)) {
if (CI->getZExtValue() == 0) continue;
ConstantOffset += (int64_t)TD->getTypeSize(Ty)*CI->getSExtValue();
continue;
}
// Ptr = Ptr + Idx * ElementSize;
// Cast Idx to UIntPtrTy if needed.
Idx = CastInst::createIntegerCast(Idx, UIntPtrTy, true/*SExt*/, "", GEPI);
uint64_t ElementSize = TD->getTypeSize(Ty);
// Mask off bits that should not be set.
ElementSize &= ~0ULL >> (64-UIntPtrTy->getPrimitiveSizeInBits());
Constant *SizeCst = ConstantInt::get(UIntPtrTy, ElementSize);
// Multiply by the element size and add to the base.
Idx = BinaryOperator::createMul(Idx, SizeCst, "", GEPI);
Ptr = BinaryOperator::createAdd(Ptr, Idx, "", GEPI);
}
}
// Make sure that the offset fits in uintptr_t.
ConstantOffset &= ~0ULL >> (64-UIntPtrTy->getPrimitiveSizeInBits());
Constant *PtrOffset = ConstantInt::get(UIntPtrTy, ConstantOffset);
// Okay, we have now emitted all of the variable index parts to the BB that
// the GEP is defined in. Loop over all of the using instructions, inserting
// an "add Ptr, ConstantOffset" into each block that uses it and update the
// instruction to use the newly computed value, making GEPI dead. When the
// user is a load or store instruction address, we emit the add into the user
// block, otherwise we use a canonical version right next to the gep (these
// won't be foldable as addresses, so we might as well share the computation).
std::map<BasicBlock*,Instruction*> InsertedExprs;
ReplaceUsesOfGEPInst(GEPI, Ptr, PtrOffset, DefBB, GEPI, InsertedExprs);
// Finally, the GEP is dead, remove it.
GEPI->eraseFromParent();
return true;
}
/// SinkInvariantGEPIndex - If a GEP instruction has a variable index that has
/// been hoisted out of the loop by LICM pass, sink it back into the use BB
/// if it can be determined that the index computation can be folded into the
/// addressing mode of the load / store uses.
static bool SinkInvariantGEPIndex(BinaryOperator *BinOp,
const TargetLowering &TLI) {
// Only look at Add.
if (BinOp->getOpcode() != Instruction::Add)
return false;
// DestBBs - These are the blocks where a copy of BinOp will be inserted.
SmallSet<BasicBlock*, 8> DestBBs;
BasicBlock *DefBB = BinOp->getParent();
bool MadeChange = false;
for (Value::use_iterator UI = BinOp->use_begin(), E = BinOp->use_end();
UI != E; ++UI) {
Instruction *GEPI = cast<Instruction>(*UI);
// Only look for GEP use in another block.
if (GEPI->getParent() == DefBB) continue;
if (isa<GetElementPtrInst>(GEPI)) {
// If the GEP has another variable index, abondon.
bool hasVariableIndex = false;
for (GetElementPtrInst::op_iterator OI = GEPI->op_begin()+1,
OE = GEPI->op_end(); OI != OE; ++OI)
if (*OI != BinOp && !isa<ConstantInt>(*OI)) {
hasVariableIndex = true;
break;
}
if (hasVariableIndex)
break;
BasicBlock *GEPIBB = GEPI->getParent();
for (Value::use_iterator UUI = GEPI->use_begin(), UE = GEPI->use_end();
UUI != UE; ++UUI) {
Instruction *GEPIUser = cast<Instruction>(*UUI);
const Type *UseTy = NULL;
if (LoadInst *Load = dyn_cast<LoadInst>(GEPIUser))
UseTy = Load->getType();
else if (StoreInst *Store = dyn_cast<StoreInst>(GEPIUser))
UseTy = Store->getOperand(0)->getType();
// Check if it is possible to fold the expression to address mode.
if (UseTy && isa<ConstantInt>(BinOp->getOperand(1))) {
uint64_t Scale = TLI.getTargetData()->getTypeSize(UseTy);
int64_t Cst = cast<ConstantInt>(BinOp->getOperand(1))->getSExtValue();
// e.g. load (gep i32 * %P, (X+42)) => load (%P + X*4 + 168).
if (TLI.isLegalAddressImmediate(Cst*Scale, UseTy) &&
(Scale == 1 || TLI.isLegalAddressScale(Scale, UseTy))) {
DestBBs.insert(GEPIBB);
MadeChange = true;
break;
}
}
}
}
}
// Nothing to do.
if (!MadeChange)
return false;
/// InsertedOps - Only insert a duplicate in each block once.
std::map<BasicBlock*, BinaryOperator*> InsertedOps;
for (Value::use_iterator UI = BinOp->use_begin(), E = BinOp->use_end();
UI != E; ) {
Instruction *User = cast<Instruction>(*UI);
BasicBlock *UserBB = User->getParent();
// Preincrement use iterator so we don't invalidate it.
++UI;
// If any user in this BB wants it, replace all the uses in the BB.
if (DestBBs.count(UserBB)) {
// Sink it into user block.
BinaryOperator *&InsertedOp = InsertedOps[UserBB];
if (!InsertedOp) {
BasicBlock::iterator InsertPt = UserBB->begin();
while (isa<PHINode>(InsertPt)) ++InsertPt;
InsertedOp =
BinaryOperator::create(BinOp->getOpcode(), BinOp->getOperand(0),
BinOp->getOperand(1), "", InsertPt);
}
User->replaceUsesOfWith(BinOp, InsertedOp);
}
}
if (BinOp->use_empty())
BinOp->eraseFromParent();
return true;
}
/// SplitEdgeNicely - Split the critical edge from TI to it's specified
/// successor if it will improve codegen. We only do this if the successor has
/// phi nodes (otherwise critical edges are ok). If there is already another
/// predecessor of the succ that is empty (and thus has no phi nodes), use it
/// instead of introducing a new block.
static void SplitEdgeNicely(TerminatorInst *TI, unsigned SuccNum, Pass *P) {
BasicBlock *TIBB = TI->getParent();
BasicBlock *Dest = TI->getSuccessor(SuccNum);
assert(isa<PHINode>(Dest->begin()) &&
"This should only be called if Dest has a PHI!");
/// TIPHIValues - This array is lazily computed to determine the values of
/// PHIs in Dest that TI would provide.
std::vector<Value*> TIPHIValues;
// Check to see if Dest has any blocks that can be used as a split edge for
// this terminator.
for (pred_iterator PI = pred_begin(Dest), E = pred_end(Dest); PI != E; ++PI) {
BasicBlock *Pred = *PI;
// To be usable, the pred has to end with an uncond branch to the dest.
BranchInst *PredBr = dyn_cast<BranchInst>(Pred->getTerminator());
if (!PredBr || !PredBr->isUnconditional() ||
// Must be empty other than the branch.
&Pred->front() != PredBr)
continue;
// Finally, since we know that Dest has phi nodes in it, we have to make
// sure that jumping to Pred will have the same affect as going to Dest in
// terms of PHI values.
PHINode *PN;
unsigned PHINo = 0;
bool FoundMatch = true;
for (BasicBlock::iterator I = Dest->begin();
(PN = dyn_cast<PHINode>(I)); ++I, ++PHINo) {
if (PHINo == TIPHIValues.size())
TIPHIValues.push_back(PN->getIncomingValueForBlock(TIBB));
// If the PHI entry doesn't work, we can't use this pred.
if (TIPHIValues[PHINo] != PN->getIncomingValueForBlock(Pred)) {
FoundMatch = false;
break;
}
}
// If we found a workable predecessor, change TI to branch to Succ.
if (FoundMatch) {
Dest->removePredecessor(TIBB);
TI->setSuccessor(SuccNum, Pred);
return;
}
}
SplitCriticalEdge(TI, SuccNum, P, true);
}
bool SelectionDAGISel::runOnFunction(Function &Fn) {
MachineFunction &MF = MachineFunction::construct(&Fn, TLI.getTargetMachine());
RegMap = MF.getSSARegMap();
DOUT << "\n\n\n=== " << Fn.getName() << "\n";
//
// In this pass we also look for GEP and cast instructions that are used
// across basic blocks and rewrite them to improve basic-block-at-a-time
// selection.
//
bool MadeChange = true;
while (MadeChange) {
MadeChange = false;
for (Function::iterator FNI = Fn.begin(), E = Fn.end(); FNI != E; ++FNI) {
// Split all critical edges where the dest block has a PHI.
TerminatorInst *BBTI = FNI->getTerminator();
if (BBTI->getNumSuccessors() > 1) {
for (unsigned i = 0, e = BBTI->getNumSuccessors(); i != e; ++i)
if (isa<PHINode>(BBTI->getSuccessor(i)->begin()) &&
isCriticalEdge(BBTI, i, true))
SplitEdgeNicely(BBTI, i, this);
}
for (BasicBlock::iterator BBI = FNI->begin(), E = FNI->end(); BBI != E; ) {
Instruction *I = BBI++;
if (CallInst *CI = dyn_cast<CallInst>(I)) {
// If we found an inline asm expession, and if the target knows how to
// lower it to normal LLVM code, do so now.
if (isa<InlineAsm>(CI->getCalledValue()))
if (const TargetAsmInfo *TAI =
TLI.getTargetMachine().getTargetAsmInfo()) {
if (TAI->ExpandInlineAsm(CI))
BBI = FNI->begin();
}
} else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
MadeChange |= OptimizeGEPExpression(GEPI, TLI.getTargetData());
} else if (CastInst *CI = dyn_cast<CastInst>(I)) {
// If the source of the cast is a constant, then this should have
// already been constant folded. The only reason NOT to constant fold
// it is if something (e.g. LSR) was careful to place the constant
// evaluation in a block other than then one that uses it (e.g. to hoist
// the address of globals out of a loop). If this is the case, we don't
// want to forward-subst the cast.
if (isa<Constant>(CI->getOperand(0)))
continue;
// If this is a noop copy, sink it into user blocks to reduce the number
// of virtual registers that must be created and coallesced.
MVT::ValueType SrcVT = TLI.getValueType(CI->getOperand(0)->getType());
MVT::ValueType DstVT = TLI.getValueType(CI->getType());
// This is an fp<->int conversion?
if (MVT::isInteger(SrcVT) != MVT::isInteger(DstVT))
continue;
// If this is an extension, it will be a zero or sign extension, which
// isn't a noop.
if (SrcVT < DstVT) continue;
// If these values will be promoted, find out what they will be promoted
// to. This helps us consider truncates on PPC as noop copies when they
// are.
if (TLI.getTypeAction(SrcVT) == TargetLowering::Promote)
SrcVT = TLI.getTypeToTransformTo(SrcVT);
if (TLI.getTypeAction(DstVT) == TargetLowering::Promote)
DstVT = TLI.getTypeToTransformTo(DstVT);
// If, after promotion, these are the same types, this is a noop copy.
if (SrcVT == DstVT)
MadeChange |= OptimizeNoopCopyExpression(CI);
} else if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(I)) {
MadeChange |= SinkInvariantGEPIndex(BinOp, TLI);
}
}
}
}
FunctionLoweringInfo FuncInfo(TLI, Fn, MF);
for (Function::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I)