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/*
* Copyright (C) 2007 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.snapscript.dx.ssa;
import java.util.ArrayList;
import java.util.BitSet;
import java.util.Collections;
import java.util.List;
import java.util.Set;
import java.util.Stack;
import org.snapscript.dx.rop.code.BasicBlockList;
import org.snapscript.dx.rop.code.Insn;
import org.snapscript.dx.rop.code.PlainInsn;
import org.snapscript.dx.rop.code.RegOps;
import org.snapscript.dx.rop.code.RegisterSpec;
import org.snapscript.dx.rop.code.RegisterSpecList;
import org.snapscript.dx.rop.code.Rop;
import org.snapscript.dx.rop.code.RopMethod;
import org.snapscript.dx.rop.code.Rops;
import org.snapscript.dx.rop.code.SourcePosition;
import org.snapscript.dx.util.IntList;
/**
* A method in SSA form.
*/
public final class SsaMethod {
/** basic blocks, indexed by block index */
private ArrayList blocks;
/** Index of first executed block in method */
private int entryBlockIndex;
/**
* Index of exit block, which exists only in SSA form,
* or or {@code -1} if there is none
*/
private int exitBlockIndex;
/** total number of registers required */
private int registerCount;
/** first register number to use for any temporary "spares" */
private int spareRegisterBase;
/** current count of spare registers used */
private int borrowedSpareRegisters;
/** really one greater than the max label */
private int maxLabel;
/** the total width, in register-units, of the method's parameters */
private final int paramWidth;
/** true if this method has no {@code this} pointer argument */
private final boolean isStatic;
/**
* indexed by register: the insn where said register is defined or null
* if undefined. null until (lazily) created.
*/
private SsaInsn[] definitionList;
/** indexed by register: the list of all insns that use a register */
private ArrayList[] useList;
/** A version of useList with each List unmodifiable */
private List[] unmodifiableUseList;
/**
* "back-convert mode". Set during back-conversion when registers
* are about to be mapped into a non-SSA namespace. When true,
* use and def lists are unavailable.
*
* TODO: Remove this mode, and place the functionality elsewhere
*/
private boolean backMode;
/**
* @param ropMethod rop-form method to convert from
* @param paramWidth the total width, in register-units, of the
* method's parameters
* @param isStatic {@code true} if this method has no {@code this}
* pointer argument
*/
public static SsaMethod newFromRopMethod(RopMethod ropMethod,
int paramWidth, boolean isStatic) {
SsaMethod result = new SsaMethod(ropMethod, paramWidth, isStatic);
result.convertRopToSsaBlocks(ropMethod);
return result;
}
/**
* Constructs an instance.
*
* @param ropMethod {@code non-null;} the original rop-form method that
* this instance is based on
* @param paramWidth the total width, in register-units, of the
* method's parameters
* @param isStatic {@code true} if this method has no {@code this}
* pointer argument
*/
private SsaMethod(RopMethod ropMethod, int paramWidth, boolean isStatic) {
this.paramWidth = paramWidth;
this.isStatic = isStatic;
this.backMode = false;
this.maxLabel = ropMethod.getBlocks().getMaxLabel();
this.registerCount = ropMethod.getBlocks().getRegCount();
this.spareRegisterBase = registerCount;
}
/**
* Builds a BitSet of block indices from a basic block list and a list
* of labels taken from Rop form.
*
* @param blocks Rop blocks
* @param labelList list of rop block labels
* @return BitSet of block indices
*/
static BitSet bitSetFromLabelList(BasicBlockList blocks,
IntList labelList) {
BitSet result = new BitSet(blocks.size());
for (int i = 0, sz = labelList.size(); i < sz; i++) {
result.set(blocks.indexOfLabel(labelList.get(i)));
}
return result;
}
/**
* Builds an IntList of block indices from a basic block list and a list
* of labels taken from Rop form.
*
* @param ropBlocks Rop blocks
* @param labelList list of rop block labels
* @return IntList of block indices
*/
public static IntList indexListFromLabelList(BasicBlockList ropBlocks,
IntList labelList) {
IntList result = new IntList(labelList.size());
for (int i = 0, sz = labelList.size(); i < sz; i++) {
result.add(ropBlocks.indexOfLabel(labelList.get(i)));
}
return result;
}
private void convertRopToSsaBlocks(RopMethod rmeth) {
BasicBlockList ropBlocks = rmeth.getBlocks();
int sz = ropBlocks.size();
blocks = new ArrayList(sz + 2);
for (int i = 0; i < sz; i++) {
SsaBasicBlock sbb = SsaBasicBlock.newFromRop(rmeth, i, this);
blocks.add(sbb);
}
// Add an no-op entry block.
int origEntryBlockIndex = rmeth.getBlocks()
.indexOfLabel(rmeth.getFirstLabel());
SsaBasicBlock entryBlock
= blocks.get(origEntryBlockIndex).insertNewPredecessor();
entryBlockIndex = entryBlock.getIndex();
exitBlockIndex = -1; // This gets made later.
}
/**
* Creates an exit block and attaches it to the CFG if this method
* exits. Methods that never exit will not have an exit block. This
* is called after edge-splitting and phi insertion, since the edges
* going into the exit block should not be considered in those steps.
*/
/*package*/ void makeExitBlock() {
if (exitBlockIndex >= 0) {
throw new RuntimeException("must be called at most once");
}
exitBlockIndex = blocks.size();
SsaBasicBlock exitBlock
= new SsaBasicBlock(exitBlockIndex, maxLabel++, this);
blocks.add(exitBlock);
for (SsaBasicBlock block : blocks) {
block.exitBlockFixup(exitBlock);
}
if (exitBlock.getPredecessors().cardinality() == 0) {
// In cases where there is no exit...
blocks.remove(exitBlockIndex);
exitBlockIndex = -1;
maxLabel--;
}
}
/**
* Gets a new {@code GOTO} insn.
*
* @param block block to which this GOTO will be added
* (not it's destination!)
* @return an appropriately-constructed instance.
*/
private static SsaInsn getGoto(SsaBasicBlock block) {
return new NormalSsaInsn (
new PlainInsn(Rops.GOTO, SourcePosition.NO_INFO,
null, RegisterSpecList.EMPTY), block);
}
/**
* Makes a new basic block for this method, which is empty besides
* a single {@code GOTO}. Successors and predecessors are not yet
* set.
*
* @return new block
*/
public SsaBasicBlock makeNewGotoBlock() {
int newIndex = blocks.size();
SsaBasicBlock newBlock = new SsaBasicBlock(newIndex, maxLabel++, this);
newBlock.getInsns().add(getGoto(newBlock));
blocks.add(newBlock);
return newBlock;
}
/**
* @return block index of first execution block
*/
public int getEntryBlockIndex() {
return entryBlockIndex;
}
/**
* @return first execution block
*/
public SsaBasicBlock getEntryBlock() {
return blocks.get(entryBlockIndex);
}
/**
* @return block index of exit block or {@code -1} if there is none
*/
public int getExitBlockIndex() {
return exitBlockIndex;
}
/**
* @return {@code null-ok;} block of exit block or {@code null} if
* there is none
*/
public SsaBasicBlock getExitBlock() {
return exitBlockIndex < 0 ? null : blocks.get(exitBlockIndex);
}
/**
* @param bi block index or {@code -1} for none
* @return rop label or {code -1} if {@code bi} was {@code -1}
*/
public int blockIndexToRopLabel(int bi) {
if (bi < 0) {
return -1;
}
return blocks.get(bi).getRopLabel();
}
/**
* @return count of registers used in this method
*/
public int getRegCount() {
return registerCount;
}
/**
* @return the total width, in register units, of the method's
* parameters
*/
public int getParamWidth() {
return paramWidth;
}
/**
* Returns {@code true} if this is a static method.
*
* @return {@code true} if this is a static method
*/
public boolean isStatic() {
return isStatic;
}
/**
* Borrows a register to use as a temp. Used in the phi removal process.
* Call returnSpareRegisters() when done.
*
* @param category width (1 or 2) of the register
* @return register number to use
*/
public int borrowSpareRegister(int category) {
int result = spareRegisterBase + borrowedSpareRegisters;
borrowedSpareRegisters += category;
registerCount = Math.max(registerCount, result + category);
return result;
}
/**
* Returns all borrowed registers.
*/
public void returnSpareRegisters() {
borrowedSpareRegisters = 0;
}
/**
* @return {@code non-null;} basic block list. Do not modify.
*/
public ArrayList getBlocks() {
return blocks;
}
/**
* Returns the count of reachable blocks in this method: blocks that have
* predecessors (or are the start block)
*
* @return {@code >= 0;} number of reachable basic blocks
*/
public int getCountReachableBlocks() {
int ret = 0;
for (SsaBasicBlock b : blocks) {
// Blocks that have been disconnected don't count.
if (b.isReachable()) {
ret++;
}
}
return ret;
}
/**
* Computes reachability for all blocks in the method. First clears old
* values from all blocks, then starts with the entry block and walks down
* the control flow graph, marking all blocks it finds as reachable.
*/
public void computeReachability() {
for (SsaBasicBlock block : blocks) {
block.setReachable(0);
}
ArrayList blockList = new ArrayList();
blockList.add(this.getEntryBlock());
while (!blockList.isEmpty()) {
SsaBasicBlock block = blockList.remove(0);
if (block.isReachable()) continue;
block.setReachable(1);
BitSet succs = block.getSuccessors();
for (int i = succs.nextSetBit(0); i >= 0;
i = succs.nextSetBit(i + 1)) {
blockList.add(blocks.get(i));
}
}
}
/**
* Remaps unversioned registers.
*
* @param mapper maps old registers to new.
*/
public void mapRegisters(RegisterMapper mapper) {
for (SsaBasicBlock block : getBlocks()) {
for (SsaInsn insn : block.getInsns()) {
insn.mapRegisters(mapper);
}
}
registerCount = mapper.getNewRegisterCount();
spareRegisterBase = registerCount;
}
/**
* Returns the insn that defines the given register
* @param reg register in question
* @return insn (actual instance from code) that defined this reg or null
* if reg is not defined.
*/
public SsaInsn getDefinitionForRegister(int reg) {
if (backMode) {
throw new RuntimeException("No def list in back mode");
}
if (definitionList != null) {
return definitionList[reg];
}
definitionList = new SsaInsn[getRegCount()];
forEachInsn(new SsaInsn.Visitor() {
public void visitMoveInsn (NormalSsaInsn insn) {
definitionList[insn.getResult().getReg()] = insn;
}
public void visitPhiInsn (PhiInsn phi) {
definitionList[phi.getResult().getReg()] = phi;
}
public void visitNonMoveInsn (NormalSsaInsn insn) {
RegisterSpec result = insn.getResult();
if (result != null) {
definitionList[insn.getResult().getReg()] = insn;
}
}
});
return definitionList[reg];
}
/**
* Builds useList and unmodifiableUseList.
*/
private void buildUseList() {
if (backMode) {
throw new RuntimeException("No use list in back mode");
}
useList = new ArrayList[registerCount];
for (int i = 0; i < registerCount; i++) {
useList[i] = new ArrayList();
}
forEachInsn(new SsaInsn.Visitor() {
/** {@inheritDoc} */
public void visitMoveInsn (NormalSsaInsn insn) {
addToUses(insn);
}
/** {@inheritDoc} */
public void visitPhiInsn (PhiInsn phi) {
addToUses(phi);
}
/** {@inheritDoc} */
public void visitNonMoveInsn (NormalSsaInsn insn) {
addToUses(insn);
}
/**
* Adds specified insn to the uses list for all of its sources.
* @param insn {@code non-null;} insn to process
*/
private void addToUses(SsaInsn insn) {
RegisterSpecList rl = insn.getSources();
int sz = rl.size();
for (int i = 0; i < sz; i++) {
useList[rl.get(i).getReg()].add(insn);
}
}
});
unmodifiableUseList = new List[registerCount];
for (int i = 0; i < registerCount; i++) {
unmodifiableUseList[i] = Collections.unmodifiableList(useList[i]);
}
}
/**
* Updates the use list for a single change in source register.
*
* @param insn {@code non-null;} insn being changed
* @param oldSource {@code null-ok;} The source that was used, if
* applicable
* @param newSource {@code non-null;} the new source being used
*/
/*package*/ void onSourceChanged(SsaInsn insn,
RegisterSpec oldSource, RegisterSpec newSource) {
if (useList == null) return;
if (oldSource != null) {
int reg = oldSource.getReg();
useList[reg].remove(insn);
}
int reg = newSource.getReg();
if (useList.length <= reg) {
useList = null;
return;
}
useList[reg].add(insn);
}
/**
* Updates the use list for a source list change.
*
* @param insn {@code insn non-null;} insn being changed.
* {@code insn.getSources()} must return the new source list.
* @param oldSources {@code null-ok;} list of sources that were
* previously used
*/
/*package*/ void onSourcesChanged(SsaInsn insn,
RegisterSpecList oldSources) {
if (useList == null) return;
if (oldSources != null) {
removeFromUseList(insn, oldSources);
}
RegisterSpecList sources = insn.getSources();
int szNew = sources.size();
for (int i = 0; i < szNew; i++) {
int reg = sources.get(i).getReg();
useList[reg].add(insn);
}
}
/**
* Removes a given {@code insn} from the use lists for the given
* {@code oldSources} (rather than the sources currently
* returned by insn.getSources()).
*
* @param insn {@code non-null;} insn in question
* @param oldSources {@code null-ok;} registers whose use lists
* {@code insn} should be removed form
*/
private void removeFromUseList(SsaInsn insn, RegisterSpecList oldSources) {
if (oldSources == null) {
return;
}
int szNew = oldSources.size();
for (int i = 0; i < szNew; i++) {
if (!useList[oldSources.get(i).getReg()].remove(insn)) {
throw new RuntimeException("use not found");
}
}
}
/**
* Adds an insn to both the use and def lists. For use when adding
* a new insn to the method.
*
* @param insn {@code non-null;} insn to add
*/
/*package*/ void onInsnAdded(SsaInsn insn) {
onSourcesChanged(insn, null);
updateOneDefinition(insn, null);
}
/**
* Removes an instruction from use and def lists. For use during
* instruction removal.
*
* @param insn {@code non-null;} insn to remove
*/
/*package*/ void onInsnRemoved(SsaInsn insn) {
if (useList != null) {
removeFromUseList(insn, insn.getSources());
}
RegisterSpec resultReg = insn.getResult();
if (definitionList != null && resultReg != null) {
definitionList[resultReg.getReg()] = null;
}
}
/**
* Indicates that the instruction list has changed or the SSA register
* count has increased, so that internal datastructures that rely on
* it should be rebuild. In general, the various other on* methods
* should be called in preference when changes occur if they are
* applicable.
*/
public void onInsnsChanged() {
// Definition list will need to be recomputed
definitionList = null;
// Use list will need to be recomputed
useList = null;
unmodifiableUseList = null;
}
/**
* Updates a single definition.
*
* @param insn {@code non-null;} insn who's result should be recorded as
* a definition
* @param oldResult {@code null-ok;} a previous result that should
* be no longer considered a definition by this insn
*/
/*package*/ void updateOneDefinition(SsaInsn insn,
RegisterSpec oldResult) {
if (definitionList == null) return;
if (oldResult != null) {
int reg = oldResult.getReg();
definitionList[reg] = null;
}
RegisterSpec resultReg = insn.getResult();
if (resultReg != null) {
int reg = resultReg.getReg();
if (definitionList[reg] != null) {
throw new RuntimeException("Duplicate add of insn");
} else {
definitionList[resultReg.getReg()] = insn;
}
}
}
/**
* Returns the list of all source uses (not results) for a register.
*
* @param reg register in question
* @return unmodifiable instruction list
*/
public List getUseListForRegister(int reg) {
if (unmodifiableUseList == null) {
buildUseList();
}
return unmodifiableUseList[reg];
}
/**
* Returns a modifiable copy of the register use list.
*
* @return modifiable copy of the use-list, indexed by register
*/
public ArrayList[] getUseListCopy() {
if (useList == null) {
buildUseList();
}
ArrayList[] useListCopy
= (ArrayList[])(new ArrayList[registerCount]);
for (int i = 0; i < registerCount; i++) {
useListCopy[i] = (ArrayList)(new ArrayList(useList[i]));
}
return useListCopy;
}
/**
* Checks to see if the given SSA reg is ever associated with a local
* local variable. Each SSA reg may be associated with at most one
* local var.
*
* @param spec {@code non-null;} ssa reg
* @return true if reg is ever associated with a local
*/
public boolean isRegALocal(RegisterSpec spec) {
SsaInsn defn = getDefinitionForRegister(spec.getReg());
if (defn == null) {
// version 0 registers are never used as locals
return false;
}
// Does the definition have a local associated with it?
if (defn.getLocalAssignment() != null) return true;
// If not, is there a mark-local insn?
for (SsaInsn use : getUseListForRegister(spec.getReg())) {
Insn insn = use.getOriginalRopInsn();
if (insn != null
&& insn.getOpcode().getOpcode() == RegOps.MARK_LOCAL) {
return true;
}
}
return false;
}
/**
* Sets the new register count after renaming.
*
* @param newRegCount new register count
*/
/*package*/ void setNewRegCount(int newRegCount) {
registerCount = newRegCount;
spareRegisterBase = registerCount;
onInsnsChanged();
}
/**
* Makes a new SSA register. For use after renaming has completed.
*
* @return {@code >=0;} new SSA register.
*/
public int makeNewSsaReg() {
int reg = registerCount++;
spareRegisterBase = registerCount;
onInsnsChanged();
return reg;
}
/**
* Visits all insns in this method.
*
* @param visitor {@code non-null;} callback interface
*/
public void forEachInsn(SsaInsn.Visitor visitor) {
for (SsaBasicBlock block : blocks) {
block.forEachInsn(visitor);
}
}
/**
* Visits each phi insn in this method
* @param v {@code non-null;} callback.
*
*/
public void forEachPhiInsn(PhiInsn.Visitor v) {
for (SsaBasicBlock block : blocks) {
block.forEachPhiInsn(v);
}
}
/**
* Walks the basic block tree in depth-first order, calling the visitor
* method once for every block. This depth-first walk may be run forward
* from the method entry point or backwards from the method exit points.
*
* @param reverse true if this should walk backwards from the exit points
* @param v {@code non-null;} callback interface. {@code parent} is set
* unless this is the root node
*/
public void forEachBlockDepthFirst(boolean reverse,
SsaBasicBlock.Visitor v) {
BitSet visited = new BitSet(blocks.size());
// We push the parent first, then the child on the stack.
Stack stack = new Stack();
SsaBasicBlock rootBlock = reverse ? getExitBlock() : getEntryBlock();
if (rootBlock == null) {
// in the case there's no exit block
return;
}
stack.add(null); // Start with null parent.
stack.add(rootBlock);
while (stack.size() > 0) {
SsaBasicBlock cur = stack.pop();
SsaBasicBlock parent = stack.pop();
if (!visited.get(cur.getIndex())) {
BitSet children
= reverse ? cur.getPredecessors() : cur.getSuccessors();
for (int i = children.nextSetBit(0); i >= 0
; i = children.nextSetBit(i + 1)) {
stack.add(cur);
stack.add(blocks.get(i));
}
visited.set(cur.getIndex());
v.visitBlock(cur, parent);
}
}
}
/**
* Visits blocks in dom-tree order, starting at the current node.
* The {@code parent} parameter of the Visitor.visitBlock callback
* is currently always set to null.
*
* @param v {@code non-null;} callback interface
*/
public void forEachBlockDepthFirstDom(SsaBasicBlock.Visitor v) {
BitSet visited = new BitSet(getBlocks().size());
Stack stack = new Stack();
stack.add(getEntryBlock());
while (stack.size() > 0) {
SsaBasicBlock cur = stack.pop();
ArrayList curDomChildren = cur.getDomChildren();
if (!visited.get(cur.getIndex())) {
// We walk the tree this way for historical reasons...
for (int i = curDomChildren.size() - 1; i >= 0; i--) {
SsaBasicBlock child = curDomChildren.get(i);
stack.add(child);
}
visited.set(cur.getIndex());
v.visitBlock(cur, null);
}
}
}
/**
* Deletes all insns in the set from this method.
*
* @param deletedInsns {@code non-null;} insns to delete
*/
public void deleteInsns(Set deletedInsns) {
for (SsaBasicBlock block : getBlocks()) {
ArrayList insns = block.getInsns();
for (int i = insns.size() - 1; i >= 0; i--) {
SsaInsn insn = insns.get(i);
if (deletedInsns.contains(insn)) {
onInsnRemoved(insn);
insns.remove(i);
}
}
// Check to see if we need to add a GOTO
int insnsSz = insns.size();
SsaInsn lastInsn = (insnsSz == 0) ? null : insns.get(insnsSz - 1);
if (block != getExitBlock() && (insnsSz == 0
|| lastInsn.getOriginalRopInsn() == null
|| lastInsn.getOriginalRopInsn().getOpcode()
.getBranchingness() == Rop.BRANCH_NONE)) {
// We managed to eat a throwable insn
Insn gotoInsn = new PlainInsn(Rops.GOTO,
SourcePosition.NO_INFO, null, RegisterSpecList.EMPTY);
insns.add(SsaInsn.makeFromRop(gotoInsn, block));
// Remove secondary successors from this block
BitSet succs = block.getSuccessors();
for (int i = succs.nextSetBit(0); i >= 0;
i = succs.nextSetBit(i + 1)) {
if (i != block.getPrimarySuccessorIndex()) {
block.removeSuccessor(i);
}
}
}
}
}
/**
* Sets "back-convert mode". Set during back-conversion when registers
* are about to be mapped into a non-SSA namespace. When true,
* use and def lists are unavailable.
*/
public void setBackMode() {
backMode = true;
useList = null;
definitionList = null;
}
}
