llvm-6502/lib/Transforms/Utils/AddrModeMatcher.cpp
Eric Christopher 551754c495 Revert 101465, it broke internal OpenGL testing.
Probably the best way to know that all getOperand() calls have been handled
is to replace that API instead of updating.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101579 91177308-0d34-0410-b5e6-96231b3b80d8
2010-04-16 23:37:20 +00:00

600 lines
22 KiB
C++

//===- AddrModeMatcher.cpp - Addressing mode matching facility --*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements target addressing mode matcher class.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/AddrModeMatcher.h"
#include "llvm/DerivedTypes.h"
#include "llvm/GlobalValue.h"
#include "llvm/Instruction.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/PatternMatch.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
using namespace llvm::PatternMatch;
void ExtAddrMode::print(raw_ostream &OS) const {
bool NeedPlus = false;
OS << "[";
if (BaseGV) {
OS << (NeedPlus ? " + " : "")
<< "GV:";
WriteAsOperand(OS, BaseGV, /*PrintType=*/false);
NeedPlus = true;
}
if (BaseOffs)
OS << (NeedPlus ? " + " : "") << BaseOffs, NeedPlus = true;
if (BaseReg) {
OS << (NeedPlus ? " + " : "")
<< "Base:";
WriteAsOperand(OS, BaseReg, /*PrintType=*/false);
NeedPlus = true;
}
if (Scale) {
OS << (NeedPlus ? " + " : "")
<< Scale << "*";
WriteAsOperand(OS, ScaledReg, /*PrintType=*/false);
NeedPlus = true;
}
OS << ']';
}
void ExtAddrMode::dump() const {
print(dbgs());
dbgs() << '\n';
}
/// MatchScaledValue - Try adding ScaleReg*Scale to the current addressing mode.
/// Return true and update AddrMode if this addr mode is legal for the target,
/// false if not.
bool AddressingModeMatcher::MatchScaledValue(Value *ScaleReg, int64_t Scale,
unsigned Depth) {
// If Scale is 1, then this is the same as adding ScaleReg to the addressing
// mode. Just process that directly.
if (Scale == 1)
return MatchAddr(ScaleReg, Depth);
// If the scale is 0, it takes nothing to add this.
if (Scale == 0)
return true;
// If we already have a scale of this value, we can add to it, otherwise, we
// need an available scale field.
if (AddrMode.Scale != 0 && AddrMode.ScaledReg != ScaleReg)
return false;
ExtAddrMode TestAddrMode = AddrMode;
// Add scale to turn X*4+X*3 -> X*7. This could also do things like
// [A+B + A*7] -> [B+A*8].
TestAddrMode.Scale += Scale;
TestAddrMode.ScaledReg = ScaleReg;
// If the new address isn't legal, bail out.
if (!TLI.isLegalAddressingMode(TestAddrMode, AccessTy))
return false;
// It was legal, so commit it.
AddrMode = TestAddrMode;
// Okay, we decided that we can add ScaleReg+Scale to AddrMode. Check now
// to see if ScaleReg is actually X+C. If so, we can turn this into adding
// X*Scale + C*Scale to addr mode.
ConstantInt *CI = 0; Value *AddLHS = 0;
if (isa<Instruction>(ScaleReg) && // not a constant expr.
match(ScaleReg, m_Add(m_Value(AddLHS), m_ConstantInt(CI)))) {
TestAddrMode.ScaledReg = AddLHS;
TestAddrMode.BaseOffs += CI->getSExtValue()*TestAddrMode.Scale;
// If this addressing mode is legal, commit it and remember that we folded
// this instruction.
if (TLI.isLegalAddressingMode(TestAddrMode, AccessTy)) {
AddrModeInsts.push_back(cast<Instruction>(ScaleReg));
AddrMode = TestAddrMode;
return true;
}
}
// Otherwise, not (x+c)*scale, just return what we have.
return true;
}
/// MightBeFoldableInst - This is a little filter, which returns true if an
/// addressing computation involving I might be folded into a load/store
/// accessing it. This doesn't need to be perfect, but needs to accept at least
/// the set of instructions that MatchOperationAddr can.
static bool MightBeFoldableInst(Instruction *I) {
switch (I->getOpcode()) {
case Instruction::BitCast:
// Don't touch identity bitcasts.
if (I->getType() == I->getOperand(0)->getType())
return false;
return I->getType()->isPointerTy() || I->getType()->isIntegerTy();
case Instruction::PtrToInt:
// PtrToInt is always a noop, as we know that the int type is pointer sized.
return true;
case Instruction::IntToPtr:
// We know the input is intptr_t, so this is foldable.
return true;
case Instruction::Add:
return true;
case Instruction::Mul:
case Instruction::Shl:
// Can only handle X*C and X << C.
return isa<ConstantInt>(I->getOperand(1));
case Instruction::GetElementPtr:
return true;
default:
return false;
}
}
/// MatchOperationAddr - Given an instruction or constant expr, see if we can
/// fold the operation into the addressing mode. If so, update the addressing
/// mode and return true, otherwise return false without modifying AddrMode.
bool AddressingModeMatcher::MatchOperationAddr(User *AddrInst, unsigned Opcode,
unsigned Depth) {
// Avoid exponential behavior on extremely deep expression trees.
if (Depth >= 5) return false;
switch (Opcode) {
case Instruction::PtrToInt:
// PtrToInt is always a noop, as we know that the int type is pointer sized.
return MatchAddr(AddrInst->getOperand(0), Depth);
case Instruction::IntToPtr:
// This inttoptr is a no-op if the integer type is pointer sized.
if (TLI.getValueType(AddrInst->getOperand(0)->getType()) ==
TLI.getPointerTy())
return MatchAddr(AddrInst->getOperand(0), Depth);
return false;
case Instruction::BitCast:
// BitCast is always a noop, and we can handle it as long as it is
// int->int or pointer->pointer (we don't want int<->fp or something).
if ((AddrInst->getOperand(0)->getType()->isPointerTy() ||
AddrInst->getOperand(0)->getType()->isIntegerTy()) &&
// Don't touch identity bitcasts. These were probably put here by LSR,
// and we don't want to mess around with them. Assume it knows what it
// is doing.
AddrInst->getOperand(0)->getType() != AddrInst->getType())
return MatchAddr(AddrInst->getOperand(0), Depth);
return false;
case Instruction::Add: {
// Check to see if we can merge in the RHS then the LHS. If so, we win.
ExtAddrMode BackupAddrMode = AddrMode;
unsigned OldSize = AddrModeInsts.size();
if (MatchAddr(AddrInst->getOperand(1), Depth+1) &&
MatchAddr(AddrInst->getOperand(0), Depth+1))
return true;
// Restore the old addr mode info.
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
// Otherwise this was over-aggressive. Try merging in the LHS then the RHS.
if (MatchAddr(AddrInst->getOperand(0), Depth+1) &&
MatchAddr(AddrInst->getOperand(1), Depth+1))
return true;
// Otherwise we definitely can't merge the ADD in.
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
break;
}
//case Instruction::Or:
// TODO: We can handle "Or Val, Imm" iff this OR is equivalent to an ADD.
//break;
case Instruction::Mul:
case Instruction::Shl: {
// Can only handle X*C and X << C.
ConstantInt *RHS = dyn_cast<ConstantInt>(AddrInst->getOperand(1));
if (!RHS) return false;
int64_t Scale = RHS->getSExtValue();
if (Opcode == Instruction::Shl)
Scale = 1LL << Scale;
return MatchScaledValue(AddrInst->getOperand(0), Scale, Depth);
}
case Instruction::GetElementPtr: {
// Scan the GEP. We check it if it contains constant offsets and at most
// one variable offset.
int VariableOperand = -1;
unsigned VariableScale = 0;
int64_t ConstantOffset = 0;
const TargetData *TD = TLI.getTargetData();
gep_type_iterator GTI = gep_type_begin(AddrInst);
for (unsigned i = 1, e = AddrInst->getNumOperands(); i != e; ++i, ++GTI) {
if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
const StructLayout *SL = TD->getStructLayout(STy);
unsigned Idx =
cast<ConstantInt>(AddrInst->getOperand(i))->getZExtValue();
ConstantOffset += SL->getElementOffset(Idx);
} else {
uint64_t TypeSize = TD->getTypeAllocSize(GTI.getIndexedType());
if (ConstantInt *CI = dyn_cast<ConstantInt>(AddrInst->getOperand(i))) {
ConstantOffset += CI->getSExtValue()*TypeSize;
} else if (TypeSize) { // Scales of zero don't do anything.
// We only allow one variable index at the moment.
if (VariableOperand != -1)
return false;
// Remember the variable index.
VariableOperand = i;
VariableScale = TypeSize;
}
}
}
// A common case is for the GEP to only do a constant offset. In this case,
// just add it to the disp field and check validity.
if (VariableOperand == -1) {
AddrMode.BaseOffs += ConstantOffset;
if (ConstantOffset == 0 || TLI.isLegalAddressingMode(AddrMode, AccessTy)){
// Check to see if we can fold the base pointer in too.
if (MatchAddr(AddrInst->getOperand(0), Depth+1))
return true;
}
AddrMode.BaseOffs -= ConstantOffset;
return false;
}
// Save the valid addressing mode in case we can't match.
ExtAddrMode BackupAddrMode = AddrMode;
unsigned OldSize = AddrModeInsts.size();
// See if the scale and offset amount is valid for this target.
AddrMode.BaseOffs += ConstantOffset;
// Match the base operand of the GEP.
if (!MatchAddr(AddrInst->getOperand(0), Depth+1)) {
// If it couldn't be matched, just stuff the value in a register.
if (AddrMode.HasBaseReg) {
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
return false;
}
AddrMode.HasBaseReg = true;
AddrMode.BaseReg = AddrInst->getOperand(0);
}
// Match the remaining variable portion of the GEP.
if (!MatchScaledValue(AddrInst->getOperand(VariableOperand), VariableScale,
Depth)) {
// If it couldn't be matched, try stuffing the base into a register
// instead of matching it, and retrying the match of the scale.
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
if (AddrMode.HasBaseReg)
return false;
AddrMode.HasBaseReg = true;
AddrMode.BaseReg = AddrInst->getOperand(0);
AddrMode.BaseOffs += ConstantOffset;
if (!MatchScaledValue(AddrInst->getOperand(VariableOperand),
VariableScale, Depth)) {
// If even that didn't work, bail.
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
return false;
}
}
return true;
}
}
return false;
}
/// MatchAddr - If we can, try to add the value of 'Addr' into the current
/// addressing mode. If Addr can't be added to AddrMode this returns false and
/// leaves AddrMode unmodified. This assumes that Addr is either a pointer type
/// or intptr_t for the target.
///
bool AddressingModeMatcher::MatchAddr(Value *Addr, unsigned Depth) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(Addr)) {
// Fold in immediates if legal for the target.
AddrMode.BaseOffs += CI->getSExtValue();
if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
return true;
AddrMode.BaseOffs -= CI->getSExtValue();
} else if (GlobalValue *GV = dyn_cast<GlobalValue>(Addr)) {
// If this is a global variable, try to fold it into the addressing mode.
if (AddrMode.BaseGV == 0) {
AddrMode.BaseGV = GV;
if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
return true;
AddrMode.BaseGV = 0;
}
} else if (Instruction *I = dyn_cast<Instruction>(Addr)) {
ExtAddrMode BackupAddrMode = AddrMode;
unsigned OldSize = AddrModeInsts.size();
// Check to see if it is possible to fold this operation.
if (MatchOperationAddr(I, I->getOpcode(), Depth)) {
// Okay, it's possible to fold this. Check to see if it is actually
// *profitable* to do so. We use a simple cost model to avoid increasing
// register pressure too much.
if (I->hasOneUse() ||
IsProfitableToFoldIntoAddressingMode(I, BackupAddrMode, AddrMode)) {
AddrModeInsts.push_back(I);
return true;
}
// It isn't profitable to do this, roll back.
//cerr << "NOT FOLDING: " << *I;
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
}
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Addr)) {
if (MatchOperationAddr(CE, CE->getOpcode(), Depth))
return true;
} else if (isa<ConstantPointerNull>(Addr)) {
// Null pointer gets folded without affecting the addressing mode.
return true;
}
// Worse case, the target should support [reg] addressing modes. :)
if (!AddrMode.HasBaseReg) {
AddrMode.HasBaseReg = true;
AddrMode.BaseReg = Addr;
// Still check for legality in case the target supports [imm] but not [i+r].
if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
return true;
AddrMode.HasBaseReg = false;
AddrMode.BaseReg = 0;
}
// If the base register is already taken, see if we can do [r+r].
if (AddrMode.Scale == 0) {
AddrMode.Scale = 1;
AddrMode.ScaledReg = Addr;
if (TLI.isLegalAddressingMode(AddrMode, AccessTy))
return true;
AddrMode.Scale = 0;
AddrMode.ScaledReg = 0;
}
// Couldn't match.
return false;
}
/// IsOperandAMemoryOperand - Check to see if all uses of OpVal by the specified
/// inline asm call are due to memory operands. If so, return true, otherwise
/// return false.
static bool IsOperandAMemoryOperand(CallInst *CI, InlineAsm *IA, Value *OpVal,
const TargetLowering &TLI) {
std::vector<InlineAsm::ConstraintInfo>
Constraints = IA->ParseConstraints();
unsigned ArgNo = 1; // ArgNo - The operand of the CallInst.
for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
TargetLowering::AsmOperandInfo OpInfo(Constraints[i]);
// Compute the value type for each operand.
switch (OpInfo.Type) {
case InlineAsm::isOutput:
if (OpInfo.isIndirect)
OpInfo.CallOperandVal = CI->getOperand(ArgNo++);
break;
case InlineAsm::isInput:
OpInfo.CallOperandVal = CI->getOperand(ArgNo++);
break;
case InlineAsm::isClobber:
// Nothing to do.
break;
}
// Compute the constraint code and ConstraintType to use.
TLI.ComputeConstraintToUse(OpInfo, SDValue(),
OpInfo.ConstraintType == TargetLowering::C_Memory);
// If this asm operand is our Value*, and if it isn't an indirect memory
// operand, we can't fold it!
if (OpInfo.CallOperandVal == OpVal &&
(OpInfo.ConstraintType != TargetLowering::C_Memory ||
!OpInfo.isIndirect))
return false;
}
return true;
}
/// FindAllMemoryUses - Recursively walk all the uses of I until we find a
/// memory use. If we find an obviously non-foldable instruction, return true.
/// Add the ultimately found memory instructions to MemoryUses.
static bool FindAllMemoryUses(Instruction *I,
SmallVectorImpl<std::pair<Instruction*,unsigned> > &MemoryUses,
SmallPtrSet<Instruction*, 16> &ConsideredInsts,
const TargetLowering &TLI) {
// If we already considered this instruction, we're done.
if (!ConsideredInsts.insert(I))
return false;
// If this is an obviously unfoldable instruction, bail out.
if (!MightBeFoldableInst(I))
return true;
// Loop over all the uses, recursively processing them.
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI) {
User *U = *UI;
if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
MemoryUses.push_back(std::make_pair(LI, UI.getOperandNo()));
continue;
}
if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
unsigned opNo = UI.getOperandNo();
if (opNo == 0) return true; // Storing addr, not into addr.
MemoryUses.push_back(std::make_pair(SI, opNo));
continue;
}
if (CallInst *CI = dyn_cast<CallInst>(U)) {
InlineAsm *IA = dyn_cast<InlineAsm>(CI->getCalledValue());
if (IA == 0) return true;
// If this is a memory operand, we're cool, otherwise bail out.
if (!IsOperandAMemoryOperand(CI, IA, I, TLI))
return true;
continue;
}
if (FindAllMemoryUses(cast<Instruction>(U), MemoryUses, ConsideredInsts,
TLI))
return true;
}
return false;
}
/// ValueAlreadyLiveAtInst - Retrn true if Val is already known to be live at
/// the use site that we're folding it into. If so, there is no cost to
/// include it in the addressing mode. KnownLive1 and KnownLive2 are two values
/// that we know are live at the instruction already.
bool AddressingModeMatcher::ValueAlreadyLiveAtInst(Value *Val,Value *KnownLive1,
Value *KnownLive2) {
// If Val is either of the known-live values, we know it is live!
if (Val == 0 || Val == KnownLive1 || Val == KnownLive2)
return true;
// All values other than instructions and arguments (e.g. constants) are live.
if (!isa<Instruction>(Val) && !isa<Argument>(Val)) return true;
// If Val is a constant sized alloca in the entry block, it is live, this is
// true because it is just a reference to the stack/frame pointer, which is
// live for the whole function.
if (AllocaInst *AI = dyn_cast<AllocaInst>(Val))
if (AI->isStaticAlloca())
return true;
// Check to see if this value is already used in the memory instruction's
// block. If so, it's already live into the block at the very least, so we
// can reasonably fold it.
BasicBlock *MemBB = MemoryInst->getParent();
for (Value::use_iterator UI = Val->use_begin(), E = Val->use_end();
UI != E; ++UI)
// We know that uses of arguments and instructions have to be instructions.
if (cast<Instruction>(*UI)->getParent() == MemBB)
return true;
return false;
}
/// IsProfitableToFoldIntoAddressingMode - It is possible for the addressing
/// mode of the machine to fold the specified instruction into a load or store
/// that ultimately uses it. However, the specified instruction has multiple
/// uses. Given this, it may actually increase register pressure to fold it
/// into the load. For example, consider this code:
///
/// X = ...
/// Y = X+1
/// use(Y) -> nonload/store
/// Z = Y+1
/// load Z
///
/// In this case, Y has multiple uses, and can be folded into the load of Z
/// (yielding load [X+2]). However, doing this will cause both "X" and "X+1" to
/// be live at the use(Y) line. If we don't fold Y into load Z, we use one
/// fewer register. Since Y can't be folded into "use(Y)" we don't increase the
/// number of computations either.
///
/// Note that this (like most of CodeGenPrepare) is just a rough heuristic. If
/// X was live across 'load Z' for other reasons, we actually *would* want to
/// fold the addressing mode in the Z case. This would make Y die earlier.
bool AddressingModeMatcher::
IsProfitableToFoldIntoAddressingMode(Instruction *I, ExtAddrMode &AMBefore,
ExtAddrMode &AMAfter) {
if (IgnoreProfitability) return true;
// AMBefore is the addressing mode before this instruction was folded into it,
// and AMAfter is the addressing mode after the instruction was folded. Get
// the set of registers referenced by AMAfter and subtract out those
// referenced by AMBefore: this is the set of values which folding in this
// address extends the lifetime of.
//
// Note that there are only two potential values being referenced here,
// BaseReg and ScaleReg (global addresses are always available, as are any
// folded immediates).
Value *BaseReg = AMAfter.BaseReg, *ScaledReg = AMAfter.ScaledReg;
// If the BaseReg or ScaledReg was referenced by the previous addrmode, their
// lifetime wasn't extended by adding this instruction.
if (ValueAlreadyLiveAtInst(BaseReg, AMBefore.BaseReg, AMBefore.ScaledReg))
BaseReg = 0;
if (ValueAlreadyLiveAtInst(ScaledReg, AMBefore.BaseReg, AMBefore.ScaledReg))
ScaledReg = 0;
// If folding this instruction (and it's subexprs) didn't extend any live
// ranges, we're ok with it.
if (BaseReg == 0 && ScaledReg == 0)
return true;
// If all uses of this instruction are ultimately load/store/inlineasm's,
// check to see if their addressing modes will include this instruction. If
// so, we can fold it into all uses, so it doesn't matter if it has multiple
// uses.
SmallVector<std::pair<Instruction*,unsigned>, 16> MemoryUses;
SmallPtrSet<Instruction*, 16> ConsideredInsts;
if (FindAllMemoryUses(I, MemoryUses, ConsideredInsts, TLI))
return false; // Has a non-memory, non-foldable use!
// Now that we know that all uses of this instruction are part of a chain of
// computation involving only operations that could theoretically be folded
// into a memory use, loop over each of these uses and see if they could
// *actually* fold the instruction.
SmallVector<Instruction*, 32> MatchedAddrModeInsts;
for (unsigned i = 0, e = MemoryUses.size(); i != e; ++i) {
Instruction *User = MemoryUses[i].first;
unsigned OpNo = MemoryUses[i].second;
// Get the access type of this use. If the use isn't a pointer, we don't
// know what it accesses.
Value *Address = User->getOperand(OpNo);
if (!Address->getType()->isPointerTy())
return false;
const Type *AddressAccessTy =
cast<PointerType>(Address->getType())->getElementType();
// Do a match against the root of this address, ignoring profitability. This
// will tell us if the addressing mode for the memory operation will
// *actually* cover the shared instruction.
ExtAddrMode Result;
AddressingModeMatcher Matcher(MatchedAddrModeInsts, TLI, AddressAccessTy,
MemoryInst, Result);
Matcher.IgnoreProfitability = true;
bool Success = Matcher.MatchAddr(Address, 0);
Success = Success; assert(Success && "Couldn't select *anything*?");
// If the match didn't cover I, then it won't be shared by it.
if (std::find(MatchedAddrModeInsts.begin(), MatchedAddrModeInsts.end(),
I) == MatchedAddrModeInsts.end())
return false;
MatchedAddrModeInsts.clear();
}
return true;
}