mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-17 21:29:20 +00:00
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37126 91177308-0d34-0410-b5e6-96231b3b80d8
317 lines
10 KiB
C++
317 lines
10 KiB
C++
//===-- IfConversion.cpp - Machine code if conversion pass. ---------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file was developed by the Evan Cheng and is distributed under
|
|
// the University of Illinois Open Source License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements the machine instruction level if-conversion pass.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#define DEBUG_TYPE "ifconversion"
|
|
#include "llvm/CodeGen/Passes.h"
|
|
#include "llvm/CodeGen/MachineModuleInfo.h"
|
|
#include "llvm/CodeGen/MachineFunctionPass.h"
|
|
#include "llvm/Target/TargetInstrInfo.h"
|
|
#include "llvm/Target/TargetMachine.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/ADT/Statistic.h"
|
|
using namespace llvm;
|
|
|
|
STATISTIC(NumIfConvBBs, "Number of if-converted blocks");
|
|
|
|
namespace {
|
|
class IfConverter : public MachineFunctionPass {
|
|
enum BBICKind {
|
|
ICInvalid, // BB data invalid.
|
|
ICNotClassfied, // BB data valid, but not classified.
|
|
ICTriangle, // BB is part of a triangle sub-CFG.
|
|
ICDiamond, // BB is part of a diamond sub-CFG.
|
|
ICTriangleEntry, // BB is entry of a triangle sub-CFG.
|
|
ICDiamondEntry // BB is entry of a diamond sub-CFG.
|
|
};
|
|
|
|
/// BBInfo - One per MachineBasicBlock, this is used to cache the result
|
|
/// if-conversion feasibility analysis. This includes results from
|
|
/// TargetInstrInfo::AnalyzeBranch() (i.e. TBB, FBB, and Cond), and its
|
|
/// classification, and common merge block of its successors (if it's a
|
|
/// diamond shape).
|
|
struct BBInfo {
|
|
BBICKind Kind;
|
|
MachineBasicBlock *EBB;
|
|
MachineBasicBlock *TBB;
|
|
MachineBasicBlock *FBB;
|
|
MachineBasicBlock *CMBB;
|
|
std::vector<MachineOperand> Cond;
|
|
BBInfo() : Kind(ICInvalid), EBB(0), TBB(0), FBB(0), CMBB(0) {}
|
|
};
|
|
|
|
/// BBAnalysis - Results of if-conversion feasibility analysis indexed by
|
|
/// basic block number.
|
|
std::vector<BBInfo> BBAnalysis;
|
|
|
|
const TargetInstrInfo *TII;
|
|
bool MadeChange;
|
|
public:
|
|
static char ID;
|
|
IfConverter() : MachineFunctionPass((intptr_t)&ID) {}
|
|
|
|
virtual bool runOnMachineFunction(MachineFunction &MF);
|
|
virtual const char *getPassName() const { return "If converter"; }
|
|
|
|
private:
|
|
void AnalyzeBlock(MachineBasicBlock *BB);
|
|
void InitialFunctionAnalysis(MachineFunction &MF,
|
|
std::vector<int> &Candidates);
|
|
bool IfConvertDiamond(BBInfo &BBI);
|
|
bool IfConvertTriangle(BBInfo &BBI);
|
|
bool isBlockPredicable(MachineBasicBlock *BB) const;
|
|
void PredicateBlock(MachineBasicBlock *BB,
|
|
std::vector<MachineOperand> &Cond,
|
|
bool IgnoreTerm = false);
|
|
void MergeBlocks(MachineBasicBlock *TBB, MachineBasicBlock *FBB);
|
|
};
|
|
char IfConverter::ID = 0;
|
|
}
|
|
|
|
FunctionPass *llvm::createIfConverterPass() { return new IfConverter(); }
|
|
|
|
bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
|
|
TII = MF.getTarget().getInstrInfo();
|
|
if (!TII) return false;
|
|
|
|
MadeChange = false;
|
|
|
|
MF.RenumberBlocks();
|
|
unsigned NumBBs = MF.getNumBlockIDs();
|
|
BBAnalysis.resize(NumBBs);
|
|
|
|
std::vector<int> Candidates;
|
|
// Do an intial analysis for each basic block and finding all the potential
|
|
// candidates to perform if-convesion.
|
|
InitialFunctionAnalysis(MF, Candidates);
|
|
|
|
for (unsigned i = 0, e = Candidates.size(); i != e; ++i) {
|
|
BBInfo &BBI = BBAnalysis[i];
|
|
switch (BBI.Kind) {
|
|
default: assert(false && "Unexpected!");
|
|
break;
|
|
case ICTriangleEntry:
|
|
MadeChange |= IfConvertTriangle(BBI);
|
|
break;
|
|
case ICDiamondEntry:
|
|
MadeChange |= IfConvertDiamond(BBI);
|
|
break;
|
|
}
|
|
}
|
|
return MadeChange;
|
|
}
|
|
|
|
static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB,
|
|
MachineBasicBlock *TBB) {
|
|
for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
|
|
E = BB->succ_end(); SI != E; ++SI) {
|
|
MachineBasicBlock *SuccBB = *SI;
|
|
if (SuccBB != TBB)
|
|
return SuccBB;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
void IfConverter::AnalyzeBlock(MachineBasicBlock *BB) {
|
|
BBInfo &BBI = BBAnalysis[BB->getNumber()];
|
|
|
|
if (BBI.Kind != ICInvalid)
|
|
return; // Always analyzed.
|
|
BBI.EBB = BB;
|
|
|
|
// Look for 'root' of a simple (non-nested) triangle or diamond.
|
|
BBI.Kind = ICNotClassfied;
|
|
if (TII->AnalyzeBranch(*BB, BBI.TBB, BBI.FBB, BBI.Cond)
|
|
|| !BBI.TBB || BBI.Cond.size() == 0)
|
|
return;
|
|
// Can't do it if 'true' block is already marked as to be if-converted.
|
|
AnalyzeBlock(BBI.TBB);
|
|
BBInfo &TBBI = BBAnalysis[BBI.TBB->getNumber()];
|
|
if (TBBI.Kind != ICNotClassfied)
|
|
return;
|
|
|
|
// No false branch. This BB must end with a conditional branch and a
|
|
// fallthrough.
|
|
if (!BBI.FBB)
|
|
BBI.FBB = findFalseBlock(BB, BBI.TBB);
|
|
assert(BBI.FBB && "Expected to find the fallthrough block!");
|
|
|
|
// Can't do it if 'false' block is already marked as to be if-converted.
|
|
AnalyzeBlock(BBI.FBB);
|
|
BBInfo &FBBI = BBAnalysis[BBI.FBB->getNumber()];
|
|
if (FBBI.Kind != ICNotClassfied)
|
|
return;
|
|
|
|
// TODO: Only handle very simple cases for now.
|
|
if (TBBI.FBB || FBBI.FBB || TBBI.Cond.size() > 1 || FBBI.Cond.size() > 1)
|
|
return;
|
|
|
|
if (TBBI.TBB && TBBI.TBB == BBI.FBB) {
|
|
// Triangle:
|
|
// EBB
|
|
// | \_
|
|
// | |
|
|
// | TBB
|
|
// | /
|
|
// FBB
|
|
BBI.Kind = ICTriangleEntry;
|
|
TBBI.Kind = FBBI.Kind = ICTriangle;
|
|
} else if (TBBI.TBB == FBBI.TBB) {
|
|
// Diamond:
|
|
// EBB
|
|
// / \_
|
|
// | |
|
|
// TBB FBB
|
|
// \ /
|
|
// MBB
|
|
// Note MBB can be empty in case both TBB and FBB are return blocks.
|
|
BBI.Kind = ICDiamondEntry;
|
|
TBBI.Kind = FBBI.Kind = ICDiamond;
|
|
BBI.CMBB = TBBI.TBB;
|
|
}
|
|
return;
|
|
}
|
|
|
|
/// InitialFunctionAnalysis - Analyze all blocks and find entries for all
|
|
/// if-conversion candidates.
|
|
void IfConverter::InitialFunctionAnalysis(MachineFunction &MF,
|
|
std::vector<int> &Candidates) {
|
|
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
|
|
MachineBasicBlock *BB = I;
|
|
AnalyzeBlock(BB);
|
|
BBInfo &BBI = BBAnalysis[BB->getNumber()];
|
|
if (BBI.Kind == ICTriangleEntry || BBI.Kind == ICDiamondEntry)
|
|
Candidates.push_back(BB->getNumber());
|
|
}
|
|
}
|
|
|
|
/// IfConvertTriangle - If convert a triangle sub-CFG.
|
|
///
|
|
bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
|
|
if (isBlockPredicable(BBI.TBB)) {
|
|
// Predicate the 'true' block after removing its branch.
|
|
TII->RemoveBranch(*BBI.TBB);
|
|
PredicateBlock(BBI.TBB, BBI.Cond);
|
|
|
|
// Join the 'true' and 'false' blocks by copying the instructions
|
|
// from the 'false' block to the 'true' block.
|
|
MergeBlocks(BBI.TBB, BBI.FBB);
|
|
|
|
// Adjust entry block, it should have but a single unconditional
|
|
// branch.
|
|
BBI.EBB->removeSuccessor(BBI.FBB);
|
|
TII->RemoveBranch(*BBI.EBB);
|
|
std::vector<MachineOperand> NoCond;
|
|
TII->InsertBranch(*BBI.EBB, BBI.TBB, NULL, NoCond);
|
|
|
|
// FIXME: Must maintain LiveIns.
|
|
NumIfConvBBs++;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// IfConvertDiamond - If convert a diamond sub-CFG.
|
|
///
|
|
bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
|
|
if (isBlockPredicable(BBI.TBB) && isBlockPredicable(BBI.FBB)) {
|
|
std::vector<MachineInstr*> Dups;
|
|
if (!BBI.CMBB) {
|
|
// No common merge block. Check if the terminators (e.g. return) are
|
|
// the same or predicable.
|
|
MachineBasicBlock::iterator TT = BBI.TBB->getFirstTerminator();
|
|
MachineBasicBlock::iterator FT = BBI.FBB->getFirstTerminator();
|
|
while (TT != BBI.TBB->end() && FT != BBI.FBB->end()) {
|
|
if (TT->isIdenticalTo(FT))
|
|
Dups.push_back(TT); // Will erase these later.
|
|
else if (!TT->isPredicable() && !FT->isPredicable())
|
|
return false; // Can't if-convert. Abort!
|
|
++TT;
|
|
++FT;
|
|
}
|
|
// One of the two pathes have more terminators, make sure they are all
|
|
// predicable.
|
|
while (TT != BBI.TBB->end())
|
|
if (!TT->isPredicable())
|
|
return false; // Can't if-convert. Abort!
|
|
while (FT != BBI.FBB->end())
|
|
if (!FT->isPredicable())
|
|
return false; // Can't if-convert. Abort!
|
|
}
|
|
|
|
// Remove the duplicated instructions from the 'true' block.
|
|
for (unsigned i = 0, e = Dups.size(); i != e; ++i)
|
|
Dups[i]->eraseFromParent();
|
|
|
|
// Predicate the 'true' block after removing its branch.
|
|
TII->RemoveBranch(*BBI.TBB);
|
|
PredicateBlock(BBI.TBB, BBI.Cond);
|
|
|
|
// Predicate the 'false' block.
|
|
std::vector<MachineOperand> NewCond(BBI.Cond);
|
|
TII->ReverseBranchCondition(NewCond);
|
|
PredicateBlock(BBI.FBB, NewCond, true);
|
|
|
|
// Join the 'true' and 'false' blocks by copying the instructions
|
|
// from the 'false' block to the 'true' block.
|
|
MergeBlocks(BBI.TBB, BBI.FBB);
|
|
|
|
// Adjust entry block, it should have but a single unconditional
|
|
// branch .
|
|
BBI.EBB->removeSuccessor(BBI.FBB);
|
|
TII->RemoveBranch(*BBI.EBB);
|
|
std::vector<MachineOperand> NoCond;
|
|
TII->InsertBranch(*BBI.EBB, BBI.TBB, NULL, NoCond);
|
|
|
|
// FIXME: Must maintain LiveIns.
|
|
NumIfConvBBs += 2;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// isBlockPredicable - Returns true if the block is predicable. In most
|
|
/// cases, that means all the instructions in the block has M_PREDICABLE flag.
|
|
/// It assume all the terminator instructions can be converted or deleted.
|
|
bool IfConverter::isBlockPredicable(MachineBasicBlock *BB) const {
|
|
for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end();
|
|
I != E; ++I) {
|
|
if (TII->isTerminatorInstr(I->getOpcode()))
|
|
continue;
|
|
if (!I->isPredicable())
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// PredicateBlock - Predicate every instruction in the block with the specified
|
|
/// condition. If IgnoreTerm is true, skip over all terminator instructions.
|
|
void IfConverter::PredicateBlock(MachineBasicBlock *BB,
|
|
std::vector<MachineOperand> &Cond,
|
|
bool IgnoreTerm) {
|
|
for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end();
|
|
I != E; ++I) {
|
|
if (IgnoreTerm && TII->isTerminatorInstr(I->getOpcode()))
|
|
continue;
|
|
if (!TII->PredicateInstruction(&*I, Cond)) {
|
|
cerr << "Unable to predication " << *I << "!\n";
|
|
abort();
|
|
}
|
|
}
|
|
}
|
|
|
|
/// MergeBlocks - Move all instructions from FBB to the end of TBB.
|
|
///
|
|
void IfConverter::MergeBlocks(MachineBasicBlock *TBB, MachineBasicBlock *FBB) {
|
|
TBB->splice(TBB->end(), FBB, FBB->begin(), FBB->end());
|
|
}
|