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Implement bottom-up fast-isel. This has the advantage of not requiring

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a separate DCE pass over MachineInstrs.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107804 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-07-07 19:20:32 +00:00
parent f423a69839
commit 4df83ed159
9 changed files with 157 additions and 113 deletions
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11
include/llvm/CodeGen/FastISel.h
View File

@ -19,6 +19,7 @@
#include "llvm/ADT/SmallSet.h"
#endif
#include "llvm/CodeGen/ValueTypes.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
namespace llvm {
@ -55,15 +56,17 @@ protected:
const TargetInstrInfo &TII;
const TargetLowering &TLI;
const TargetRegisterInfo &TRI;
bool IsBottomUp;
MachineBasicBlock::iterator LastLocalValue;
public:
/// getLastLocalValue - Return the position of the last instruction
/// emitted for materializing constants for use in the current block.
MachineBasicBlock::iterator getLastLocalValue() { return LastLocalValue; }
/// startNewBlock - Set the current block to which generated machine
/// instructions will be appended, and clear the local CSE map.
///
void startNewBlock() {
LocalValueMap.clear();
}
void startNewBlock();
/// getCurDebugLoc() - Return current debug location information.
DebugLoc getCurDebugLoc() const { return DL; }

20
lib/CodeGen/LLVMTargetMachine.cpp
View File

@ -329,19 +329,15 @@ bool LLVMTargetMachine::addCommonCodeGenPasses(PassManagerBase &PM,
if (OptLevel != CodeGenOpt::None)
PM.add(createOptimizePHIsPass());
// Delete dead machine instructions regardless of optimization level.
//
// At -O0, fast-isel frequently creates dead instructions.
//
// With optimization, dead code should already be eliminated. However
// there is one known exception: lowered code for arguments that are only
// used by tail calls, where the tail calls reuse the incoming stack
// arguments directly (see t11 in test/CodeGen/X86/sibcall.ll).
PM.add(createDeadMachineInstructionElimPass());
printAndVerify(PM, "After codegen DCE pass",
/* allowDoubleDefs= */ true);
if (OptLevel != CodeGenOpt::None) {
// With optimization, dead code should already be eliminated. However
// there is one known exception: lowered code for arguments that are only
// used by tail calls, where the tail calls reuse the incoming stack
// arguments directly (see t11 in test/CodeGen/X86/sibcall.ll).
PM.add(createDeadMachineInstructionElimPass());
printAndVerify(PM, "After codegen DCE pass",
/* allowDoubleDefs= */ true);
PM.add(createOptimizeExtsPass());
if (!DisableMachineLICM)
PM.add(createMachineLICMPass());

43
lib/CodeGen/SelectionDAG/FastISel.cpp
View File

@ -57,6 +57,17 @@
#include "llvm/Support/ErrorHandling.h"
using namespace llvm;
/// startNewBlock - Set the current block to which generated machine
/// instructions will be appended, and clear the local CSE map.
///
void FastISel::startNewBlock() {
LocalValueMap.clear();
// Start out as end(), meaining no local-value instructions have
// been emitted.
LastLocalValue = FuncInfo.MBB->end();
}
bool FastISel::hasTrivialKill(const Value *V) const {
// Don't consider constants or arguments to have trivial kills.
const Instruction *I = dyn_cast<Instruction>(V);
@ -109,12 +120,9 @@ unsigned FastISel::getRegForValue(const Value *V) {
// In bottom-up mode, just create the virtual register which will be used
// to hold the value. It will be materialized later.
if (IsBottomUp) {
if (isa<Instruction>(V)) {
Reg = createResultReg(TLI.getRegClassFor(VT));
if (isa<Instruction>(V))
FuncInfo.ValueMap[V] = Reg;
else
LocalValueMap[V] = Reg;
FuncInfo.ValueMap[V] = Reg;
return Reg;
}
@ -180,8 +188,10 @@ unsigned FastISel::materializeRegForValue(const Value *V, MVT VT) {
// Don't cache constant materializations in the general ValueMap.
// To do so would require tracking what uses they dominate.
if (Reg != 0)
if (Reg != 0) {
LocalValueMap[V] = Reg;
LastLocalValue = MRI.getVRegDef(Reg);
}
return Reg;
}
@ -210,12 +220,20 @@ unsigned FastISel::UpdateValueMap(const Value *I, unsigned Reg) {
unsigned &AssignedReg = FuncInfo.ValueMap[I];
if (AssignedReg == 0)
// Use the new register.
AssignedReg = Reg;
else if (Reg != AssignedReg) {
const TargetRegisterClass *RegClass = MRI.getRegClass(Reg);
TII.copyRegToReg(*FuncInfo.MBB, FuncInfo.InsertPt, AssignedReg,
Reg, RegClass, RegClass, DL);
// We already have a register for this value. Replace uses of
// the existing register with uses of the new one.
MRI.replaceRegWith(AssignedReg, Reg);
// Replace uses of the existing register in PHINodesToUpdate too.
for (unsigned i = 0, e = FuncInfo.PHINodesToUpdate.size(); i != e; ++i)
if (FuncInfo.PHINodesToUpdate[i].second == AssignedReg)
FuncInfo.PHINodesToUpdate[i].second = Reg;
// And update the ValueMap.
AssignedReg = Reg;
}
return AssignedReg;
}
@ -736,11 +754,15 @@ FastISel::SelectLoad(const User *I) {
BasicBlock::iterator ScanFrom = LI;
if (const Value *V = FindAvailableLoadedValue(LI->getPointerOperand(),
LI->getParent(), ScanFrom)) {
if (!isa<Instruction>(V) ||
cast<Instruction>(V)->getParent() == LI->getParent() ||
(isa<AllocaInst>(V) && FuncInfo.StaticAllocaMap.count(cast<AllocaInst>(V)))) {
unsigned ResultReg = getRegForValue(V);
if (ResultReg != 0) {
UpdateValueMap(I, ResultReg);
return true;
}
}
}
}
@ -871,8 +893,7 @@ FastISel::FastISel(FunctionLoweringInfo &funcInfo)
TD(*TM.getTargetData()),
TII(*TM.getInstrInfo()),
TLI(*TM.getTargetLowering()),
TRI(*TM.getRegisterInfo()),
IsBottomUp(false) {
TRI(*TM.getRegisterInfo()) {
}
FastISel::~FastISel() {}

7
lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
View File

@ -78,6 +78,13 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf) {
MF = &mf;
RegInfo = &MF->getRegInfo();
// Check whether the function can return without sret-demotion.
SmallVector<ISD::OutputArg, 4> Outs;
GetReturnInfo(Fn->getReturnType(),
Fn->getAttributes().getRetAttributes(), Outs, TLI);
CanLowerReturn = TLI.CanLowerReturn(Fn->getCallingConv(), Fn->isVarArg(),
Outs, Fn->getContext());
// Create a vreg for each argument register that is not dead and is used
// outside of the entry block for the function.
for (Function::const_arg_iterator AI = Fn->arg_begin(), E = Fn->arg_end();

29
lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
View File

@ -951,12 +951,10 @@ SDValue SelectionDAGBuilder::getValueImpl(const Value *V) {
// If this is an instruction which fast-isel has deferred, select it now.
if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
assert(Inst->isSafeToSpeculativelyExecute() &&
"Instruction with side effects deferred!");
visit(*Inst);
DenseMap<const Value *, SDValue>::iterator NIt = NodeMap.find(Inst);
if (NIt != NodeMap.end() && NIt->second.getNode())
return NIt->second;
unsigned InReg = FuncInfo.InitializeRegForValue(Inst);
RegsForValue RFV(*DAG.getContext(), TLI, InReg, Inst->getType());
SDValue Chain = DAG.getEntryNode();
return RFV.getCopyFromRegs(DAG, FuncInfo, getCurDebugLoc(), Chain, NULL);
}
llvm_unreachable("Can't get register for value!");
@ -1259,7 +1257,7 @@ SelectionDAGBuilder::ShouldEmitAsBranches(const std::vector<CaseBlock> &Cases){
}
void SelectionDAGBuilder::visitBr(const BranchInst &I) {
MachineBasicBlock *BrMBB = FuncInfo.MBBMap[I.getParent()];
MachineBasicBlock *BrMBB = FuncInfo.MBB;
// Update machine-CFG edges.
MachineBasicBlock *Succ0MBB = FuncInfo.MBBMap[I.getSuccessor(0)];
@ -1585,7 +1583,7 @@ void SelectionDAGBuilder::visitBitTestCase(MachineBasicBlock* NextMBB,
}
void SelectionDAGBuilder::visitInvoke(const InvokeInst &I) {
MachineBasicBlock *InvokeMBB = FuncInfo.MBBMap[I.getParent()];
MachineBasicBlock *InvokeMBB = FuncInfo.MBB;
// Retrieve successors.
MachineBasicBlock *Return = FuncInfo.MBBMap[I.getSuccessor(0)];
@ -2113,7 +2111,7 @@ size_t SelectionDAGBuilder::Clusterify(CaseVector& Cases,
}
void SelectionDAGBuilder::visitSwitch(const SwitchInst &SI) {
MachineBasicBlock *SwitchMBB = FuncInfo.MBBMap[SI.getParent()];
MachineBasicBlock *SwitchMBB = FuncInfo.MBB;
// Figure out which block is immediately after the current one.
MachineBasicBlock *NextBlock = 0;
@ -2179,7 +2177,7 @@ void SelectionDAGBuilder::visitSwitch(const SwitchInst &SI) {
}
void SelectionDAGBuilder::visitIndirectBr(const IndirectBrInst &I) {
MachineBasicBlock *IndirectBrMBB = FuncInfo.MBBMap[I.getParent()];
MachineBasicBlock *IndirectBrMBB = FuncInfo.MBB;
// Update machine-CFG edges with unique successors.
SmallVector<BasicBlock*, 32> succs;
@ -3839,7 +3837,7 @@ SelectionDAGBuilder::EmitFuncArgumentDbgValue(const DbgValueInst &DI,
if (DV.isInlinedFnArgument(MF.getFunction()))
return false;
MachineBasicBlock *MBB = FuncInfo.MBBMap[DI.getParent()];
MachineBasicBlock *MBB = FuncInfo.MBB;
if (MBB != &MF.front())
return false;
@ -4102,7 +4100,7 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
}
case Intrinsic::eh_exception: {
// Insert the EXCEPTIONADDR instruction.
assert(FuncInfo.MBBMap[I.getParent()]->isLandingPad() &&
assert(FuncInfo.MBB->isLandingPad() &&
"Call to eh.exception not in landing pad!");
SDVTList VTs = DAG.getVTList(TLI.getPointerTy(), MVT::Other);
SDValue Ops[1];
@ -4114,7 +4112,7 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
}
case Intrinsic::eh_selector: {
MachineBasicBlock *CallMBB = FuncInfo.MBBMap[I.getParent()];
MachineBasicBlock *CallMBB = FuncInfo.MBB;
MachineModuleInfo &MMI = DAG.getMachineFunction().getMMI();
if (CallMBB->isLandingPad())
AddCatchInfo(I, &MMI, CallMBB);
@ -4124,7 +4122,7 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
#endif
// FIXME: Mark exception selector register as live in. Hack for PR1508.
unsigned Reg = TLI.getExceptionSelectorRegister();
if (Reg) FuncInfo.MBBMap[I.getParent()]->addLiveIn(Reg);
if (Reg) FuncInfo.MBB->addLiveIn(Reg);
}
// Insert the EHSELECTION instruction.
@ -5901,9 +5899,6 @@ void SelectionDAGISel::LowerArguments(const BasicBlock *LLVMBB) {
GetReturnInfo(F.getReturnType(), F.getAttributes().getRetAttributes(),
Outs, TLI);
FuncInfo->CanLowerReturn = TLI.CanLowerReturn(F.getCallingConv(),
F.isVarArg(),
Outs, F.getContext());
if (!FuncInfo->CanLowerReturn) {
// Put in an sret pointer parameter before all the other parameters.
SmallVector<EVT, 1> ValueVTs;

78
lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
View File

@ -680,60 +680,55 @@ void SelectionDAGISel::SelectAllBasicBlocks(const Function &Fn) {
BasicBlock::const_iterator const Begin = LLVMBB->getFirstNonPHI();
BasicBlock::const_iterator const End = LLVMBB->end();
BasicBlock::const_iterator BI = Begin;
BasicBlock::const_iterator BI = End;
// Lower any arguments needed in this block if this is the entry block.
if (LLVMBB == &Fn.getEntryBlock())
LowerArguments(LLVMBB);
// Setup an EH landing-pad block.
if (FuncInfo->MBB->isLandingPad())
PrepareEHLandingPad();
// Before doing SelectionDAG ISel, see if FastISel has been requested.
if (FastIS) {
// Emit code for any incoming arguments. This must happen before
// beginning FastISel on the entry block.
if (LLVMBB == &Fn.getEntryBlock()) {
CurDAG->setRoot(SDB->getControlRoot());
SDB->clear();
CodeGenAndEmitDAG();
}
FastIS->startNewBlock();
// Do FastISel on as many instructions as possible.
for (; BI != End; ++BI) {
#if 0
// Defer instructions with no side effects; they'll be emitted
// on-demand later.
if (BI->isSafeToSpeculativelyExecute() &&
!FuncInfo->isExportedInst(BI))
for (; BI != Begin; --BI) {
const Instruction *Inst = llvm::prior(BI);
// If we no longer require this instruction, skip it.
if (!Inst->mayWriteToMemory() &&
!isa<TerminatorInst>(Inst) &&
!isa<DbgInfoIntrinsic>(Inst) &&
!FuncInfo->isExportedInst(Inst))
continue;
#endif
// Bottom-up: reset the insert pos at the top, after any local-value
// instructions.
MachineBasicBlock::iterator LVIP = FastIS->getLastLocalValue();
if (LVIP != FuncInfo->MBB->end())
FuncInfo->InsertPt = next(LVIP);
else
FuncInfo->InsertPt = FuncInfo->MBB->getFirstNonPHI();
// Try to select the instruction with FastISel.
if (FastIS->SelectInstruction(BI))
if (FastIS->SelectInstruction(Inst))
continue;
// Then handle certain instructions as single-LLVM-Instruction blocks.
if (isa<CallInst>(BI)) {
if (isa<CallInst>(Inst)) {
++NumFastIselFailures;
if (EnableFastISelVerbose || EnableFastISelAbort) {
dbgs() << "FastISel missed call: ";
BI->dump();
Inst->dump();
}
if (!BI->getType()->isVoidTy() && !BI->use_empty()) {
unsigned &R = FuncInfo->ValueMap[BI];
if (!Inst->getType()->isVoidTy() && !Inst->use_empty()) {
unsigned &R = FuncInfo->ValueMap[Inst];
if (!R)
R = FuncInfo->CreateRegs(BI->getType());
R = FuncInfo->CreateRegs(Inst->getType());
}
bool HadTailCall = false;
SelectBasicBlock(BI, llvm::next(BI), HadTailCall);
SelectBasicBlock(Inst, BI, HadTailCall);
// If the call was emitted as a tail call, we're done with the block.
if (HadTailCall) {
BI = End;
--BI;
break;
}
@ -746,7 +741,7 @@ void SelectionDAGISel::SelectAllBasicBlocks(const Function &Fn) {
++NumFastIselFailures;
if (EnableFastISelVerbose || EnableFastISelAbort) {
dbgs() << "FastISel miss: ";
BI->dump();
Inst->dump();
}
if (EnableFastISelAbort)
// The "fast" selector couldn't handle something and bailed.
@ -757,13 +752,21 @@ void SelectionDAGISel::SelectAllBasicBlocks(const Function &Fn) {
}
}
FuncInfo->InsertPt = FuncInfo->MBB->getFirstNonPHI();
// Setup an EH landing-pad block.
if (FuncInfo->MBB->isLandingPad())
PrepareEHLandingPad();
// Lower any arguments needed in this block if this is the entry block.
if (LLVMBB == &Fn.getEntryBlock())
LowerArguments(LLVMBB);
// Run SelectionDAG instruction selection on the remainder of the block
// not handled by FastISel. If FastISel is not run, this is the entire
// block.
if (BI != End) {
bool HadTailCall;
SelectBasicBlock(BI, End, HadTailCall);
}
bool HadTailCall;
SelectBasicBlock(Begin, BI, HadTailCall);
FinishBasicBlock();
FuncInfo->PHINodesToUpdate.clear();
@ -963,7 +966,8 @@ SelectionDAGISel::FinishBasicBlock() {
for (unsigned i = 0, e = Succs.size(); i != e; ++i) {
FuncInfo->MBB = Succs[i];
FuncInfo->InsertPt = FuncInfo->MBB->end();
// BB may have been removed from the CFG if a branch was constant folded.
// FuncInfo->MBB may have been removed from the CFG if a branch was
// constant folded.
if (ThisBB->isSuccessor(FuncInfo->MBB)) {
for (MachineBasicBlock::iterator Phi = FuncInfo->MBB->begin();
Phi != FuncInfo->MBB->end() && Phi->isPHI();

66
lib/Target/X86/X86FastISel.cpp
View File

@ -108,6 +108,7 @@ private:
bool X86SelectCall(const Instruction *I);
CCAssignFn *CCAssignFnForCall(CallingConv::ID CC, bool isTailCall = false);
CCAssignFn *CCAssignFnForRet(CallingConv::ID CC, bool isTailCall = false);
const X86InstrInfo *getInstrInfo() const {
return getTargetMachine()->getInstrInfo();
@ -181,6 +182,20 @@ CCAssignFn *X86FastISel::CCAssignFnForCall(CallingConv::ID CC,
return CC_X86_32_C;
}
/// CCAssignFnForRet - Selects the correct CCAssignFn for a given calling
/// convention.
CCAssignFn *X86FastISel::CCAssignFnForRet(CallingConv::ID CC,
bool isTaillCall) {
if (Subtarget->is64Bit()) {
if (Subtarget->isTargetWin64())
return RetCC_X86_Win64_C;
else
return RetCC_X86_64_C;
}
return RetCC_X86_32_C;
}
/// X86FastEmitLoad - Emit a machine instruction to load a value of type VT.
/// The address is either pre-computed, i.e. Ptr, or a GlobalAddress, i.e. GV.
/// Return true and the result register by reference if it is possible.
@ -689,34 +704,39 @@ bool X86FastISel::X86SelectRet(const Instruction *I) {
if (F.isVarArg())
return false;
SmallVector<ISD::OutputArg, 4> Outs;
GetReturnInfo(F.getReturnType(), F.getAttributes().getRetAttributes(),
Outs, TLI);
if (Ret->getNumOperands() > 0) {
SmallVector<ISD::OutputArg, 4> Outs;
GetReturnInfo(F.getReturnType(), F.getAttributes().getRetAttributes(),
Outs, TLI);
// Analyze operands of the call, assigning locations to each operand.
SmallVector<CCValAssign, 16> ValLocs;
CCState CCInfo(CC, F.isVarArg(), TM, ValLocs, I->getContext());
CCInfo.AnalyzeReturn(Outs, CCAssignFnForCall(CC));
// Analyze operands of the call, assigning locations to each operand.
SmallVector<CCValAssign, 16> ValLocs;
CCState CCInfo(CC, F.isVarArg(), TM, ValLocs, I->getContext());
CCInfo.AnalyzeReturn(Outs, CCAssignFnForRet(CC));
// Copy the return value into registers.
for (unsigned i = 0, e = ValLocs.size(); i != e; ++i) {
CCValAssign &VA = ValLocs[i];
// Don't bother handling odd stuff for now.
if (VA.getLocInfo() != CCValAssign::Full)
return false;
if (!VA.isRegLoc())
return false;
const Value *RV = Ret->getOperand(VA.getValNo());
const Value *RV = Ret->getOperand(0);
unsigned Reg = getRegForValue(RV);
if (Reg == 0)
return false;
TargetRegisterClass* RC = TLI.getRegClassFor(VA.getValVT());
bool Emitted = TII.copyRegToReg(*FuncInfo.MBB, FuncInfo.InsertPt,
VA.getLocReg(), Reg, RC, RC, DL);
assert(Emitted && "Failed to emit a copy instruction!"); Emitted=Emitted;
// Copy the return value into registers.
for (unsigned i = 0, e = ValLocs.size(); i != e; ++i) {
CCValAssign &VA = ValLocs[i];
// Don't bother handling odd stuff for now.
if (VA.getLocInfo() != CCValAssign::Full)
return false;
if (!VA.isRegLoc())
return false;
MRI.addLiveOut(X86::XMM0);
TargetRegisterClass* RC = TLI.getRegClassFor(VA.getValVT());
bool Emitted = TII.copyRegToReg(*FuncInfo.MBB, FuncInfo.InsertPt,
VA.getLocReg(), Reg + VA.getValNo(),
RC, RC, DL);
assert(Emitted && "Failed to emit a copy instruction!"); Emitted=Emitted;
MRI.addLiveOut(VA.getLocReg());
}
}
// Now emit the RET.

2
test/CodeGen/X86/fast-isel-loads.ll
View File

@ -5,7 +5,7 @@
; CHECK: foo:
; CHECK-NEXT: movq %rdi, -8(%rsp)
; CHECK-NEXT: movq %rsi, -16(%rsp)
; CHECK: movsd 128(%rsi,%rdi,8), %xmm0
; CHECK-NEXT: movsd 128(%rsi,%rdi,8), %xmm0
; CHECK-NEXT: ret
define double @foo(i64 %x, double* %p) nounwind {

14
test/CodeGen/X86/fast-isel.ll
View File

@ -49,9 +49,10 @@ entry:
ret i32 %tmp2
}
define i1 @ptrtoint_i1(i8* %p) nounwind {
define void @ptrtoint_i1(i8* %p, i1* %q) nounwind {
%t = ptrtoint i8* %p to i1
ret i1 %t
store i1 %t, i1* %q
ret void
}
define i8* @inttoptr_i1(i1 %p) nounwind {
%t = inttoptr i1 %p to i8*
@ -86,11 +87,8 @@ define i8 @mul_i8(i8 %a) nounwind {
ret i8 %tmp
}
define void @store_i1(i1* %p, i1 %t) nounwind {
store i1 %t, i1* %p
define void @load_store_i1(i1* %p, i1* %q) nounwind {
%t = load i1* %p
store i1 %t, i1* %q
ret void
}
define i1 @load_i1(i1* %p) nounwind {
%t = load i1* %p
ret i1 %t
}