@Override
public void cleanUpAndInsertEpilogue() {
Instruction inst = ir.firstInstructionInCodeOrder().nextInstructionInCodeOrder();
for (; inst != null; inst = inst.nextInstructionInCodeOrder()) {
switch (inst.getOpcode()) {
case IA32_MOV_opcode:
// remove frivolous moves
Operand result = MIR_Move.getResult(inst);
Operand val = MIR_Move.getValue(inst);
if (result.similar(val)) {
inst = inst.remove();
}
break;
case IA32_FMOV_opcode:
case IA32_MOVSS_opcode:
case IA32_MOVSD_opcode:
// remove frivolous moves
result = MIR_Move.getResult(inst);
val = MIR_Move.getValue(inst);
if (result.similar(val)) {
inst = inst.remove();
}
break;
case IA32_RET_opcode:
if (frameIsRequired()) {
insertEpilogue(inst);
}
default:
break;
}
}
// now that the frame size is fixed, fix up the spill location code
rewriteStackLocations();
}
private boolean canModifyEFLAGS(Instruction s) {
if (PhysicalDefUse.usesEFLAGS(s.operator())) {
return false;
}
if (PhysicalDefUse.definesEFLAGS(s.operator())) {
return true;
}
if (s.operator() == BBEND) return true;
return canModifyEFLAGS(s.nextInstructionInCodeOrder());
}
/**
* Perform optimizations for an inline guard.
*
* <p>Precondition: InlineGuard.conforms(cb)
*
* @param ir the governing IR
* @param cb the instruction to optimize
* @param bb the basic block holding if
* @return {@code true} iff made a transformation
*/
private boolean processInlineGuard(IR ir, Instruction cb, BasicBlock bb) {
BasicBlock targetBlock = cb.getBranchTarget();
Instruction targetLabel = targetBlock.firstInstruction();
// get the first real instruction at the branch target
// NOTE: this instruction is not necessarily in targetBlock,
// iff targetBlock has no real instructions
Instruction targetInst = firstRealInstructionFollowing(targetLabel);
if (targetInst == null || targetInst == cb) {
return false;
}
boolean endsBlock = cb.nextInstructionInCodeOrder().operator() == BBEND;
if (endsBlock) {
Instruction nextLabel = firstLabelFollowing(cb);
if (targetLabel == nextLabel) {
// found a conditional branch to the next instruction. just remove it.
cb.remove();
return true;
}
Instruction nextI = firstRealInstructionFollowing(nextLabel);
if (nextI != null && Goto.conforms(nextI)) {
// replicate Goto
cb.insertAfter(nextI.copyWithoutLinks());
bb.recomputeNormalOut(ir); // fix the CFG
return true;
}
}
// do we fall through to a block that has only a goto?
BasicBlock fallThrough = bb.getFallThroughBlock();
if (fallThrough != null) {
Instruction fallThroughInstruction = fallThrough.firstRealInstruction();
if ((fallThroughInstruction != null) && Goto.conforms(fallThroughInstruction)) {
// copy goto to bb
bb.appendInstruction(fallThroughInstruction.copyWithoutLinks());
bb.recomputeNormalOut(ir);
}
}
if (Goto.conforms(targetInst)) {
// conditional branch to unconditional branch.
// change conditional branch target to latter's target
InlineGuard.setTarget(cb, (BranchOperand) Goto.getTarget(targetInst).copy());
bb.recomputeNormalOut(ir); // fix the CFG
return true;
}
if (targetBlock.isEmpty()) {
// branch to an empty block. Change target to the next block.
BasicBlock nextBlock = targetBlock.getFallThroughBlock();
InlineGuard.setTarget(cb, nextBlock.makeJumpTarget());
bb.recomputeNormalOut(ir); // fix the CFG
return true;
}
return false;
}
/**
* Flip a conditional branch and remove the trailing goto. See comment 3) of
* processConditionalBranch
*
* <p>Precondition isFlipCandidate(cb)
*
* @param cb the conditional branch instruction
*/
private void flipConditionalBranch(Instruction cb) {
// get the trailing GOTO instruction
Instruction g = cb.nextInstructionInCodeOrder();
BranchOperand gTarget = (BranchOperand) (Goto.getTarget(g).copy());
// now flip the test and set the new target
IfCmp.setCond(cb, IfCmp.getCond(cb).flipCode());
IfCmp.setTarget(cb, gTarget);
// Update the branch probability. It is now the opposite
cb.flipBranchProbability();
// finally, remove the trailing GOTO instruction
g.remove();
}
/**
* Is a conditional branch a candidate to be flipped? See comment 3) of processConditionalBranch
*
* <p>Precondition: IfCmp.conforms(cb)
*
* @param cb the conditional branch instruction
* @param target the target instruction (real instruction) of the conditional branch
* @return boolean result
*/
private boolean isFlipCandidate(Instruction cb, Instruction target) {
// condition 1: is next instruction a GOTO?
Instruction next = cb.nextInstructionInCodeOrder();
if (!Goto.conforms(next)) {
return false;
}
// condition 2: is the target of the conditional branch the
// next instruction after the GOTO?
next = firstRealInstructionFollowing(next);
if (next != target) {
return false;
}
// got this far. It's a candidate.
return true;
}
/** Transform cb into a GOTO, updating PHI nodes to maintain SSA form. */
private void takeCondBranch(BasicBlock source, Instruction cb, IR ir) {
if (DEBUG) VM.sysWrite("Eliminating definitely taken branch " + cb + "\n");
BasicBlock deadBB = source.nextBasicBlockInCodeOrder();
Instruction next = cb.nextInstructionInCodeOrder();
if (Goto.conforms(next)) {
deadBB = next.getBranchTarget();
next.remove();
}
Goto.mutate(cb, GOTO, cb.getBranchTarget().makeJumpTarget());
source.recomputeNormalOut(ir);
if (!source.pointsOut(deadBB)) {
// there is no longer an edge from source to target;
// update any PHIs in target to reflect this.
SSA.purgeBlockFromPHIs(source, deadBB);
}
}
/**
* Insert the prologue for a normal method.
*
* <p>Assume we are inserting the prologue for method B called from method A.
*
* <ul>
* <li>Perform a stack overflow check.
* <li>Store a back pointer to A's frame
* <li>Store B's compiled method id
* <li>Adjust frame pointer to point to B's frame
* <li>Save any used non-volatile registers
* </ul>
*/
@Override
public void insertNormalPrologue() {
PhysicalRegisterSet phys = (PhysicalRegisterSet) ir.regpool.getPhysicalRegisterSet();
Register ESP = phys.getESP();
MemoryOperand fpHome =
MemoryOperand.BD(
ir.regpool.makeTROp(),
ArchEntrypoints.framePointerField.getOffset(),
(byte) WORDSIZE,
null,
null);
// the prologue instruction
Instruction plg = ir.firstInstructionInCodeOrder().nextInstructionInCodeOrder();
// inst is the instruction immediately after the IR_PROLOGUE
// instruction
Instruction inst = plg.nextInstructionInCodeOrder();
int frameFixedSize = getFrameFixedSize();
ir.compiledMethod.setFrameFixedSize(frameFixedSize);
// I. Buy a stackframe (including overflow check)
// NOTE: We play a little game here. If the frame we are buying is
// very small (less than 256) then we can be sloppy with the
// stackoverflow check and actually allocate the frame in the guard
// region. We'll notice when this frame calls someone and take the
// stackoverflow in the callee. We can't do this if the frame is too big,
// because growing the stack in the callee and/or handling a hardware trap
// in this frame will require most of the guard region to complete.
// See libvm.C.
if (frameFixedSize >= 256) {
// 1. Insert Stack overflow check.
insertBigFrameStackOverflowCheck(plg);
// 2. Save caller's frame pointer
inst.insertBefore(MIR_UnaryNoRes.create(IA32_PUSH, fpHome));
// 3. Set my frame pointer to current value of stackpointer
inst.insertBefore(
MIR_Move.create(
IA32_MOV, fpHome.copy(), new RegisterOperand(ESP, PRIMITIVE_TYPE_FOR_WORD)));
// 4. Store my compiled method id
int cmid = ir.compiledMethod.getId();
inst.insertBefore(MIR_UnaryNoRes.create(IA32_PUSH, VM.BuildFor32Addr ? IC(cmid) : LC(cmid)));
} else {
// 1. Save caller's frame pointer
inst.insertBefore(MIR_UnaryNoRes.create(IA32_PUSH, fpHome));
// 2. Set my frame pointer to current value of stackpointer
inst.insertBefore(
MIR_Move.create(
IA32_MOV, fpHome.copy(), new RegisterOperand(ESP, PRIMITIVE_TYPE_FOR_WORD)));
// 3. Store my compiled method id
int cmid = ir.compiledMethod.getId();
inst.insertBefore(MIR_UnaryNoRes.create(IA32_PUSH, VM.BuildFor32Addr ? IC(cmid) : LC(cmid)));
// 4. Insert Stack overflow check.
insertNormalStackOverflowCheck(plg);
}
// II. Save any used volatile and non-volatile registers
if (ir.compiledMethod.isSaveVolatile()) {
saveVolatiles(inst);
saveFloatingPointState(inst);
}
saveNonVolatiles(inst);
}
/**
* Perform optimizations for a two way conditional branch.
*
* <p>Precondition: IfCmp2.conforms(cb)
*
* @param ir the governing IR
* @param cb the instruction to optimize
* @param bb the basic block holding if
* @return {@code true} iff made a transformation
*/
private boolean processTwoTargetConditionalBranch(IR ir, Instruction cb, BasicBlock bb) {
// First condition/target
Instruction target1Label = IfCmp2.getTarget1(cb).target;
Instruction target1Inst = firstRealInstructionFollowing(target1Label);
Instruction nextLabel = firstLabelFollowing(cb);
boolean endsBlock = cb.nextInstructionInCodeOrder().operator() == BBEND;
if (target1Inst != null && target1Inst != cb) {
if (Goto.conforms(target1Inst)) {
// conditional branch to unconditional branch.
// change conditional branch target to latter's target
IfCmp2.setTarget1(cb, (BranchOperand) Goto.getTarget(target1Inst).copy());
bb.recomputeNormalOut(ir); // fix CFG
return true;
}
BasicBlock target1Block = target1Label.getBasicBlock();
if (target1Block.isEmpty()) {
// branch to an empty block. Change target to the next block.
BasicBlock nextBlock = target1Block.getFallThroughBlock();
IfCmp2.setTarget1(cb, nextBlock.makeJumpTarget());
bb.recomputeNormalOut(ir); // fix the CFG
return true;
}
}
// Second condition/target
Instruction target2Label = IfCmp2.getTarget2(cb).target;
Instruction target2Inst = firstRealInstructionFollowing(target2Label);
if (target2Inst != null && target2Inst != cb) {
if (Goto.conforms(target2Inst)) {
// conditional branch to unconditional branch.
// change conditional branch target to latter's target
IfCmp2.setTarget2(cb, (BranchOperand) Goto.getTarget(target2Inst).copy());
bb.recomputeNormalOut(ir); // fix CFG
return true;
}
if ((target2Label == nextLabel) && endsBlock) {
// found a conditional branch to the next instruction. Reduce to IfCmp
if (VM.VerifyAssertions) VM._assert(cb.operator() == INT_IFCMP2);
IfCmp.mutate(
cb,
INT_IFCMP,
IfCmp2.getGuardResult(cb),
IfCmp2.getVal1(cb),
IfCmp2.getVal2(cb),
IfCmp2.getCond1(cb),
IfCmp2.getTarget1(cb),
IfCmp2.getBranchProfile1(cb));
return true;
}
BasicBlock target2Block = target2Label.getBasicBlock();
if (target2Block.isEmpty()) {
// branch to an empty block. Change target to the next block.
BasicBlock nextBlock = target2Block.getFallThroughBlock();
IfCmp2.setTarget2(cb, nextBlock.makeJumpTarget());
bb.recomputeNormalOut(ir); // fix the CFG
return true;
}
}
// if fall through to a goto; replicate the goto
if (endsBlock) {
Instruction nextI = firstRealInstructionFollowing(nextLabel);
if (nextI != null && Goto.conforms(nextI)) {
// replicate Goto
cb.insertAfter(nextI.copyWithoutLinks());
bb.recomputeNormalOut(ir); // fix the CFG
return true;
}
}
return false;
}
/**
* Perform optimizations for a conditional branch.
*
* <pre>
* 1) IF .. GOTO A replaced by IF .. GOTO B
* ...
* A: GOTO B
* 2) conditional branch to next instruction eliminated
* 3) IF (condition) GOTO A replaced by IF (!condition) GOTO B
* GOTO B A: ...
* A: ...
* 4) special case to generate Boolean compare opcode
* 5) special case to generate conditional move sequence
* 6) IF .. GOTO A replaced by IF .. GOTO B
* A: LABEL
* BBEND
* B:
* 7) fallthrough to a goto: replicate goto to enable other optimizations.
* </pre>
*
* <p>Precondition: IfCmp.conforms(cb)
*
* @param ir the governing IR
* @param cb the instruction to optimize
* @param bb the basic block holding if
* @return {@code true} iff made a transformation
*/
private boolean processConditionalBranch(IR ir, Instruction cb, BasicBlock bb) {
BasicBlock targetBlock = cb.getBranchTarget();
// don't optimize jumps to a code motion landing pad
if (targetBlock.getLandingPad()) return false;
Instruction targetLabel = targetBlock.firstInstruction();
// get the first real instruction at the branch target
// NOTE: this instruction is not necessarily in targetBlock,
// iff targetBlock has no real instructions
Instruction targetInst = firstRealInstructionFollowing(targetLabel);
if (targetInst == null || targetInst == cb) {
return false;
}
boolean endsBlock = cb.nextInstructionInCodeOrder().operator() == BBEND;
if (endsBlock) {
Instruction nextLabel = firstLabelFollowing(cb);
if (targetLabel == nextLabel) {
// found a conditional branch to the next instruction. just remove it.
cb.remove();
return true;
}
Instruction nextI = firstRealInstructionFollowing(nextLabel);
if (nextI != null && Goto.conforms(nextI)) {
// Check that the target is not the fall through (the goto itself).
// If we add a goto to the next block, it will be removed by
// processGoto and we will loop indefinitely.
// This can be tripped by (strange) code such as:
// if (condition) while (true);
BasicBlock gotoTarget = nextI.getBranchTarget();
Instruction gotoLabel = gotoTarget.firstInstruction();
Instruction gotoInst = firstRealInstructionFollowing(gotoLabel);
if (gotoInst != nextI) {
// replicate Goto
cb.insertAfter(nextI.copyWithoutLinks());
bb.recomputeNormalOut(ir); // fix the CFG
return true;
}
}
}
// attempt to generate boolean compare.
if (generateBooleanCompare(ir, bb, cb, targetBlock)) {
// generateBooleanCompare does all necessary CFG fixup.
return true;
}
// attempt to generate a sequence using conditional moves
if (generateCondMove(ir, bb, cb)) {
// generateCondMove does all necessary CFG fixup.
return true;
}
// do we fall through to a block that has only a goto?
BasicBlock fallThrough = bb.getFallThroughBlock();
if (fallThrough != null) {
Instruction fallThroughInstruction = fallThrough.firstRealInstruction();
if ((fallThroughInstruction != null) && Goto.conforms(fallThroughInstruction)) {
// copy goto to bb
bb.appendInstruction(fallThroughInstruction.copyWithoutLinks());
bb.recomputeNormalOut(ir);
}
}
if (Goto.conforms(targetInst)) {
// conditional branch to unconditional branch.
// change conditional branch target to latter's target
Instruction target2 =
firstRealInstructionFollowing(targetInst.getBranchTarget().firstInstruction());
if (target2 == targetInst) {
// Avoid an infinite recursion in the following scenario:
// g: if (...) goto L
// ...
// L: goto L
// This happens in GCUtil in some systems due to a while(true) {}
return false;
}
IfCmp.setTarget(cb, (BranchOperand) Goto.getTarget(targetInst).copy());
bb.recomputeNormalOut(ir); // fix the CFG
return true;
}
if (targetBlock.isEmpty()) {
// branch to an empty block. Change target to the next block.
BasicBlock nextBlock = targetBlock.getFallThroughBlock();
IfCmp.setTarget(cb, nextBlock.makeJumpTarget());
bb.recomputeNormalOut(ir); // fix the CFG
return true;
}
if (isFlipCandidate(cb, targetInst)) {
flipConditionalBranch(cb);
bb.recomputeNormalOut(ir); // fix the CFG
return true;
}
return false;
}
/**
* Perform optimizations for a Goto.
*
* <p> Patterns:
* <pre>
* 1) GOTO A replaced by GOTO B
* A: GOTO B
*
* 2) GOTO A replaced by IF .. GOTO B
* A: IF .. GOTO B GOTO C
* C: ...
* 3) GOTO next instruction eliminated
* 4) GOTO A replaced by GOTO B
* A: LABEL
* BBEND
* B:
* 5) GOTO BBn where BBn has exactly one in edge
* - move BBn immediately after the GOTO in the code order,
* so that pattern 3) will create a fallthrough
* <pre>
*
* <p> Precondition: Goto.conforms(g)
*
* @param ir governing IR
* @param g the instruction to optimize
* @param bb the basic block holding g
* @return {@code true} if made a transformation
*/
private boolean processGoto(IR ir, Instruction g, BasicBlock bb) {
BasicBlock targetBlock = g.getBranchTarget();
// don't optimize jumps to a code motion landing pad
if (targetBlock.getLandingPad()) return false;
Instruction targetLabel = targetBlock.firstInstruction();
// get the first real instruction at the g target
// NOTE: this instruction is not necessarily in targetBlock,
// iff targetBlock has no real instructions
Instruction targetInst = firstRealInstructionFollowing(targetLabel);
if (targetInst == null || targetInst == g) {
return false;
}
Instruction nextLabel = firstLabelFollowing(g);
if (targetLabel == nextLabel) {
// found a GOTO to the next instruction. just remove it.
g.remove();
return true;
}
if (Goto.conforms(targetInst)) {
// unconditional branch to unconditional branch.
// replace g with goto to targetInst's target
Instruction target2 =
firstRealInstructionFollowing(targetInst.getBranchTarget().firstInstruction());
if (target2 == targetInst) {
// Avoid an infinite recursion in the following bizarre scenario:
// g: goto L
// ...
// L: goto L
// This happens in jByteMark.EmFloatPnt.denormalize() due to a while(true) {}
return false;
}
Goto.setTarget(g, (BranchOperand) Goto.getTarget(targetInst).copy());
bb.recomputeNormalOut(ir); // fix the CFG
return true;
}
if (targetBlock.isEmpty()) {
// GOTO an empty basic block. Change target to the
// next block.
BasicBlock nextBlock = targetBlock.getFallThroughBlock();
Goto.setTarget(g, nextBlock.makeJumpTarget());
bb.recomputeNormalOut(ir); // fix the CFG
return true;
}
if (mayDuplicateCondBranches && IfCmp.conforms(targetInst)) {
// unconditional branch to a conditional branch.
// If the Goto is the only branch instruction in its basic block
// and the IfCmp is the only non-GOTO branch instruction
// in its basic block then replace the goto with a copy of
// targetInst and append another GOTO to the not-taken
// target of targetInst's block.
// We impose these additional restrictions to avoid getting
// multiple conditional branches in a single basic block.
if (!g.prevInstructionInCodeOrder().isBranch()
&& (targetInst.nextInstructionInCodeOrder().operator == BBEND
|| targetInst.nextInstructionInCodeOrder().operator == GOTO)) {
Instruction copy = targetInst.copyWithoutLinks();
g.replace(copy);
Instruction newGoto = targetInst.getBasicBlock().getNotTakenNextBlock().makeGOTO();
copy.insertAfter(newGoto);
bb.recomputeNormalOut(ir); // fix the CFG
return true;
}
}
// try to create a fallthrough
if (mayReorderCode && targetBlock.getNumberOfIn() == 1) {
BasicBlock ftBlock = targetBlock.getFallThroughBlock();
if (ftBlock != null) {
BranchOperand ftTarget = ftBlock.makeJumpTarget();
targetBlock.appendInstruction(CPOS(g, Goto.create(GOTO, ftTarget)));
}
ir.cfg.removeFromCodeOrder(targetBlock);
ir.cfg.insertAfterInCodeOrder(bb, targetBlock);
targetBlock.recomputeNormalOut(ir); // fix the CFG
return true;
}
return false;
}
/**
* Attempt to generate a boolean compare opcode from a conditional branch.
*
* <pre>
* 1) IF .. GOTO A replaced by BOOLEAN_CMP x=..
* x = 0
* GOTO B
* A: x = 1
* B: ...
* </pre>
*
* <p>Precondition: <code>IfCmp.conforms(<i>cb</i>)</code>
*
* @param ir governing IR
* @param bb basic block of cb
* @param cb conditional branch instruction
* @return true if the transformation succeeds, false otherwise
*/
private boolean generateBooleanCompare(IR ir, BasicBlock bb, Instruction cb, BasicBlock tb) {
if ((cb.operator() != INT_IFCMP) && (cb.operator() != REF_IFCMP)) {
return false;
}
// make sure this is the last branch in the block
if (cb.nextInstructionInCodeOrder().operator() != BBEND) {
return false;
}
Operand val1 = IfCmp.getVal1(cb);
Operand val2 = IfCmp.getVal2(cb);
ConditionOperand condition = IfCmp.getCond(cb);
// "not taken" path
BasicBlock fb = cb.getBasicBlock().getNotTakenNextBlock();
// make sure it's a diamond
if (tb.getNumberOfNormalOut() != 1) {
return false;
}
if (fb.getNumberOfNormalOut() != 1) {
return false;
}
BasicBlock jb = fb.getNormalOut().nextElement(); // join block
// make sure it's a diamond
if (!tb.pointsOut(jb)) {
return false;
}
Instruction ti = tb.firstRealInstruction();
Instruction fi = fb.firstRealInstruction();
// make sure the instructions in target blocks are either both moves
// or both returns
if (ti == null || fi == null) {
return false;
}
if (ti.operator() != fi.operator()) {
return false;
}
if (ti.operator != RETURN && ti.operator() != INT_MOVE) {
return false;
}
//
// WARNING: This code is currently NOT exercised!
//
if (ti.operator() == RETURN) {
// make sure each of the target blocks contains only one instruction
if (ti != tb.lastRealInstruction()) {
return false;
}
if (fi != fb.lastRealInstruction()) {
return false;
}
Operand tr = Return.getVal(ti);
Operand fr = Return.getVal(fi);
// make sure we're returning constants
if (!(tr instanceof IntConstantOperand) || !(fr instanceof IntConstantOperand)) {
return false;
}
int tv = ((IntConstantOperand) tr).value;
int fv = ((IntConstantOperand) fr).value;
if (!((tv == 1 && fv == 0) || (tv == 1 && fv == 0))) {
return false;
}
RegisterOperand t = ir.regpool.makeTemp(TypeReference.Boolean);
// Cases 1) and 2)
if (tv == 0) {
condition = condition.flipCode();
}
booleanCompareHelper(cb, t, val1.copy(), val2.copy(), condition);
cb.insertAfter(Return.create(RETURN, t.copyD2U()));
} else { // (ti.operator() == INT_MOVE)
// make sure each of the target blocks only does the move
if (ti != tb.lastRealInstruction() && ti.nextInstructionInCodeOrder().operator() != GOTO) {
return false;
}
if (fi != fb.lastRealInstruction() && fi.nextInstructionInCodeOrder().operator() != GOTO) {
return false;
}
RegisterOperand t = Move.getResult(ti);
// make sure both moves are to the same register
if (t.getRegister() != Move.getResult(fi).getRegister()) {
return false;
}
Operand tr = Move.getVal(ti);
Operand fr = Move.getVal(fi);
// make sure we're assigning constants
if (!(tr instanceof IntConstantOperand) || !(fr instanceof IntConstantOperand)) {
return false;
}
int tv = ((IntConstantOperand) tr).value;
int fv = ((IntConstantOperand) fr).value;
if (!((tv == 1 && fv == 0) || (tv == 0 && fv == 1))) {
return false;
}
// Cases 3) and 4)
if (tv == 0) {
condition = condition.flipCode();
}
booleanCompareHelper(cb, t.copyRO(), val1.copy(), val2.copy(), condition);
Instruction next = cb.nextInstructionInCodeOrder();
if (next.operator() == GOTO) {
Goto.setTarget(next, jb.makeJumpTarget());
} else {
cb.insertAfter(jb.makeGOTO());
}
}
// fixup CFG
bb.deleteOut(tb);
bb.deleteOut(fb);
bb.insertOut(jb); // Note: if we processed returns,
// jb is the exit node.
return true;
}
/**
* Perform the transformation to replace conditional branch with a sequence using conditional
* moves.
*
* @param ir governing IR
* @param diamond the IR diamond structure to replace
* @param cb conditional branch instruction at the head of the diamond
*/
private void doCondMove(IR ir, Diamond diamond, Instruction cb) {
BasicBlock taken = diamond.getTaken();
BasicBlock notTaken = diamond.getNotTaken();
// for each non-branch instruction s in the diamond,
// copy s to a new instruction s'
// and store a mapping from s to s'
HashMap<Instruction, Instruction> takenInstructions = new HashMap<Instruction, Instruction>();
Instruction[] takenInstructionList = copyAndMapInstructions(taken, takenInstructions);
HashMap<Instruction, Instruction> notTakenInstructions =
new HashMap<Instruction, Instruction>();
Instruction[] notTakenInstructionList = copyAndMapInstructions(notTaken, notTakenInstructions);
// Extract the values and condition from the conditional branch.
Operand val1 = IfCmp.getVal1(cb);
Operand val2 = IfCmp.getVal2(cb);
ConditionOperand cond = IfCmp.getCond(cb);
// Copy val1 and val2 to temporaries, just in case they're defined in
// the diamond. If they're not defined in the diamond, copy prop
// should clean these moves up.
RegisterOperand tempVal1 = ir.regpool.makeTemp(val1);
Operator op = IRTools.getMoveOp(tempVal1.getType());
cb.insertBefore(Move.create(op, tempVal1.copyRO(), val1.copy()));
RegisterOperand tempVal2 = ir.regpool.makeTemp(val2);
op = IRTools.getMoveOp(tempVal2.getType());
cb.insertBefore(Move.create(op, tempVal2.copyRO(), val2.copy()));
// For each instruction in each temporary set, rewrite it to def a new
// temporary, and insert it before the branch.
rewriteWithTemporaries(takenInstructionList, ir);
rewriteWithTemporaries(notTakenInstructionList, ir);
insertBefore(takenInstructionList, cb);
insertBefore(notTakenInstructionList, cb);
// For each register defined in the TAKEN branch, save a mapping to
// the corresponding conditional move.
HashMap<Register, Instruction> takenMap = new HashMap<Register, Instruction>();
// Now insert conditional moves to replace each instruction in the diamond.
// First handle the taken branch.
if (taken != null) {
for (Enumeration<Instruction> e = taken.forwardRealInstrEnumerator(); e.hasMoreElements(); ) {
Instruction s = e.nextElement();
if (s.isBranch()) continue;
Operand def = s.getDefs().nextElement();
// if the register does not span a basic block, it is a temporary
// that will now be dead
if (def.asRegister().getRegister().spansBasicBlock()) {
Instruction tempS = takenInstructions.get(s);
RegisterOperand temp = (RegisterOperand) tempS.getDefs().nextElement();
op = IRTools.getCondMoveOp(def.asRegister().getType());
Instruction cmov =
CondMove.create(
op,
def.asRegister(),
tempVal1.copy(),
tempVal2.copy(),
cond.copy().asCondition(),
temp.copy(),
def.copy());
takenMap.put(def.asRegister().getRegister(), cmov);
cb.insertBefore(cmov);
}
s.remove();
}
}
// For each register defined in the NOT-TAKEN branch, save a mapping to
// the corresponding conditional move.
HashMap<Register, Instruction> notTakenMap = new HashMap<Register, Instruction>();
// Next handle the not taken branch.
if (notTaken != null) {
for (Enumeration<Instruction> e = notTaken.forwardRealInstrEnumerator();
e.hasMoreElements(); ) {
Instruction s = e.nextElement();
if (s.isBranch()) continue;
Operand def = s.getDefs().nextElement();
// if the register does not span a basic block, it is a temporary
// that will now be dead
if (def.asRegister().getRegister().spansBasicBlock()) {
Instruction tempS = notTakenInstructions.get(s);
RegisterOperand temp = (RegisterOperand) tempS.getDefs().nextElement();
Instruction prevCmov = takenMap.get(def.asRegister().getRegister());
if (prevCmov != null) {
// if this register was also defined in the taken branch, change
// the previous cmov with a different 'False' Value
CondMove.setFalseValue(prevCmov, temp.copy());
notTakenMap.put(def.asRegister().getRegister(), prevCmov);
} else {
// create a new cmov instruction
op = IRTools.getCondMoveOp(def.asRegister().getType());
Instruction cmov =
CondMove.create(
op,
def.asRegister(),
tempVal1.copy(),
tempVal2.copy(),
cond.copy().asCondition(),
def.copy(),
temp.copy());
cb.insertBefore(cmov);
notTakenMap.put(def.asRegister().getRegister(), cmov);
}
}
s.remove();
}
}
// Mutate the conditional branch into a GOTO.
BranchOperand target = diamond.getBottom().makeJumpTarget();
Goto.mutate(cb, GOTO, target);
// Delete a potential GOTO after cb.
Instruction next = cb.nextInstructionInCodeOrder();
if (next.operator != BBEND) {
next.remove();
}
// Recompute the CFG.
diamond.getTop().recomputeNormalOut(ir); // fix the CFG
}
/**
* @param ir the IR to expand
* @return return value is garbage for IA32
*/
public static int expand(IR ir) {
PhysicalRegisterSet phys = ir.regpool.getPhysicalRegisterSet().asIA32();
MachineCodeOffsets mcOffsets = ir.MIRInfo.mcOffsets;
for (Instruction next, p = ir.firstInstructionInCodeOrder(); p != null; p = next) {
next = p.nextInstructionInCodeOrder();
mcOffsets.setMachineCodeOffset(p, -1);
switch (p.getOpcode()) {
case IA32_MOVAPS_opcode:
// a reg-reg move turned into a memory move where we can't guarantee alignment
if (MIR_Move.getResult(p).isMemory() || MIR_Move.getValue(p).isMemory()) {
MIR_Move.mutate(p, IA32_MOVSS, MIR_Move.getClearResult(p), MIR_Move.getClearValue(p));
}
break;
case IA32_MOVAPD_opcode:
// a reg-reg move turned into a memory move where we can't guarantee alignment
if (MIR_Move.getResult(p).isMemory() || MIR_Move.getValue(p).isMemory()) {
MIR_Move.mutate(p, IA32_MOVSD, MIR_Move.getClearResult(p), MIR_Move.getClearValue(p));
}
break;
case IA32_TEST_opcode:
// don't bother telling rest of compiler that memory operand
// must be first; we can just commute it here.
if (MIR_Test.getVal2(p).isMemory()) {
Operand tmp = MIR_Test.getClearVal1(p);
MIR_Test.setVal1(p, MIR_Test.getClearVal2(p));
MIR_Test.setVal2(p, tmp);
}
break;
case NULL_CHECK_opcode:
{
// mutate this into a TRAPIF, and then fall through to the the
// TRAP_IF case.
Operand ref = NullCheck.getRef(p);
MIR_TrapIf.mutate(
p,
IA32_TRAPIF,
null,
ref.copy(),
IC(0),
IA32ConditionOperand.EQ(),
TrapCodeOperand.NullPtr());
}
// There is no break statement here on purpose!
case IA32_TRAPIF_opcode:
{
// split the basic block right before the IA32_TRAPIF
BasicBlock thisBlock = p.getBasicBlock();
BasicBlock trap = thisBlock.createSubBlock(p.getBytecodeIndex(), ir, 0f);
thisBlock.insertOut(trap);
BasicBlock nextBlock = thisBlock.splitNodeWithLinksAt(p, ir);
thisBlock.insertOut(trap);
TrapCodeOperand tc = MIR_TrapIf.getClearTrapCode(p);
p.remove();
mcOffsets.setMachineCodeOffset(nextBlock.firstInstruction(), -1);
// add code to thisBlock to conditionally jump to trap
Instruction cmp =
MIR_Compare.create(IA32_CMP, MIR_TrapIf.getVal1(p), MIR_TrapIf.getVal2(p));
if (p.isMarkedAsPEI()) {
// The trap if was explictly marked, which means that it has
// a memory operand into which we've folded a null check.
// Actually need a GC map for both the compare and the INT.
cmp.markAsPEI();
cmp.copyPosition(p);
ir.MIRInfo.gcIRMap.insertTwin(p, cmp);
}
thisBlock.appendInstruction(cmp);
thisBlock.appendInstruction(
MIR_CondBranch.create(
IA32_JCC, MIR_TrapIf.getCond(p), trap.makeJumpTarget(), null));
// add block at end to hold trap instruction, and
// insert trap sequence
ir.cfg.addLastInCodeOrder(trap);
if (tc.isArrayBounds()) {
// attempt to store index expression in processor object for
// C trap handler
Operand index = MIR_TrapIf.getVal2(p);
if (!(index instanceof RegisterOperand || index instanceof IntConstantOperand)) {
index = IC(0xdeadbeef); // index was spilled, and
// we can't get it back here.
}
MemoryOperand mo =
MemoryOperand.BD(
ir.regpool.makeTROp(),
ArchEntrypoints.arrayIndexTrapParamField.getOffset(),
(byte) 4,
null,
null);
trap.appendInstruction(MIR_Move.create(IA32_MOV, mo, index.copy()));
}
// NOTE: must make p the trap instruction: it is the GC point!
// IMPORTANT: must also inform the GCMap that the instruction has
// been moved!!!
trap.appendInstruction(MIR_Trap.mutate(p, IA32_INT, null, tc));
ir.MIRInfo.gcIRMap.moveToEnd(p);
if (tc.isStackOverflow()) {
// only stackoverflow traps resume at next instruction.
trap.appendInstruction(MIR_Branch.create(IA32_JMP, nextBlock.makeJumpTarget()));
}
}
break;
case IA32_FMOV_ENDING_LIVE_RANGE_opcode:
{
Operand result = MIR_Move.getResult(p);
Operand value = MIR_Move.getValue(p);
if (result.isRegister() && value.isRegister()) {
if (result.similar(value)) {
// eliminate useless move
p.remove();
} else {
int i = PhysicalRegisterSet.getFPRIndex(result.asRegister().getRegister());
int j = PhysicalRegisterSet.getFPRIndex(value.asRegister().getRegister());
if (i == 0) {
MIR_XChng.mutate(p, IA32_FXCH, result, value);
} else if (j == 0) {
MIR_XChng.mutate(p, IA32_FXCH, value, result);
} else {
expandFmov(p, phys);
}
}
} else {
expandFmov(p, phys);
}
break;
}
case DUMMY_DEF_opcode:
case DUMMY_USE_opcode:
case REQUIRE_ESP_opcode:
case ADVISE_ESP_opcode:
p.remove();
break;
case IA32_FMOV_opcode:
expandFmov(p, phys);
break;
case IA32_MOV_opcode:
// Replace result = IA32_MOV 0 with result = IA32_XOR result, result
if (MIR_Move.getResult(p).isRegister()
&& MIR_Move.getValue(p).isIntConstant()
&& MIR_Move.getValue(p).asIntConstant().value == 0) {
// Calculate what flags are defined in coming instructions before a use of a flag or
// BBend
Instruction x = next;
int futureDefs = 0;
while (!BBend.conforms(x) && !PhysicalDefUse.usesEFLAGS(x.operator())) {
futureDefs |= x.operator().implicitDefs;
x = x.nextInstructionInCodeOrder();
}
// If the flags will be destroyed prior to use or we reached the end of the basic block
if (BBend.conforms(x)
|| (futureDefs & PhysicalDefUse.maskAF_CF_OF_PF_SF_ZF)
== PhysicalDefUse.maskAF_CF_OF_PF_SF_ZF) {
Operand result = MIR_Move.getClearResult(p);
MIR_BinaryAcc.mutate(p, IA32_XOR, result, result.copy());
}
}
break;
case IA32_SET__B_opcode:
// Replace <cmp>, set__b, movzx__b with xor, <cmp>, set__b
if (MIR_Set.getResult(p).isRegister()
&& MIR_Unary.conforms(next)
&& (next.operator() == IA32_MOVZX__B)
&& MIR_Unary.getResult(next).isRegister()
&& MIR_Unary.getVal(next).similar(MIR_Unary.getResult(next))
&& MIR_Unary.getVal(next).similar(MIR_Set.getResult(p))) {
// Find instruction in this basic block that defines flags
Instruction x = p.prevInstructionInCodeOrder();
Operand result = MIR_Unary.getResult(next);
boolean foundCmp = false;
outer:
while (!Label.conforms(x)) {
Enumeration<Operand> e = x.getUses();
while (e.hasMoreElements()) {
// We can't use an xor to clear the register if that register is
// used by the <cmp> or intervening instruction
if (e.nextElement().similar(result)) {
break outer;
}
}
if (PhysicalDefUse.definesEFLAGS(x.operator())
&& !PhysicalDefUse.usesEFLAGS(x.operator())) {
// we found a <cmp> that doesn't use the result or the flags
// that would be clobbered by the xor
foundCmp = true;
break outer;
}
x = x.prevInstructionInCodeOrder();
}
if (foundCmp) {
// We found the <cmp>, mutate the movzx__b into an xor and insert it before the <cmp>
next.remove();
MIR_BinaryAcc.mutate(next, IA32_XOR, result, MIR_Unary.getVal(next));
x.insertBefore(next);
// get ready for the next instruction
next = p.nextInstructionInCodeOrder();
}
}
break;
case IA32_LEA_opcode:
{
// Sometimes we're over eager in BURS in using LEAs and after register
// allocation we can simplify to the accumulate form
// replace reg1 = LEA [reg1 + reg2] with reg1 = reg1 + reg2
// replace reg1 = LEA [reg1 + c1] with reg1 = reg1 + c1
// replace reg1 = LEA [reg1 << c1] with reg1 = reg1 << c1
MemoryOperand value = MIR_Lea.getValue(p);
RegisterOperand result = MIR_Lea.getResult(p);
if ((value.base != null && value.base.getRegister() == result.getRegister())
|| (value.index != null && value.index.getRegister() == result.getRegister())) {
// Calculate what flags are defined in coming instructions before a use of a flag or
// BBend
Instruction x = next;
int futureDefs = 0;
while (!BBend.conforms(x) && !PhysicalDefUse.usesEFLAGS(x.operator())) {
futureDefs |= x.operator().implicitDefs;
x = x.nextInstructionInCodeOrder();
}
// If the flags will be destroyed prior to use or we reached the end of the basic
// block
if (BBend.conforms(x)
|| (futureDefs & PhysicalDefUse.maskAF_CF_OF_PF_SF_ZF)
== PhysicalDefUse.maskAF_CF_OF_PF_SF_ZF) {
if (value.base != null
&& value.index != null
&& value.index.getRegister() == result.getRegister()
&& value.disp.isZero()
&& value.scale == 0) {
// reg1 = lea [base + reg1] -> add reg1, base
MIR_BinaryAcc.mutate(p, IA32_ADD, result, value.base);
} else if (value.base != null
&& value.base.getRegister() == result.getRegister()
&& value.index != null
&& value.disp.isZero()
&& value.scale == 0) {
// reg1 = lea [reg1 + index] -> add reg1, index
MIR_BinaryAcc.mutate(p, IA32_ADD, result, value.index);
} else if (value.base != null
&& value.base.getRegister() == result.getRegister()
&& value.index == null) {
if (VM.VerifyAssertions) VM._assert(fits(value.disp, 32));
// reg1 = lea [reg1 + disp] -> add reg1, disp
MIR_BinaryAcc.mutate(p, IA32_ADD, result, IC(value.disp.toInt()));
} else if (value.base == null
&& value.index != null
&& value.index.getRegister() == result.getRegister()
&& value.scale == 0) {
if (VM.VerifyAssertions) VM._assert(fits(value.disp, 32));
// reg1 = lea [reg1 + disp] -> add reg1, disp
MIR_BinaryAcc.mutate(p, IA32_ADD, result, IC(value.disp.toInt()));
} else if (value.base == null
&& value.index != null
&& value.index.getRegister() == result.getRegister()
&& value.disp.isZero()) {
// reg1 = lea [reg1 << scale] -> shl reg1, scale
if (value.scale == 0) {
p.remove();
} else if (value.scale == 1) {
MIR_BinaryAcc.mutate(p, IA32_ADD, result, value.index);
} else {
MIR_BinaryAcc.mutate(p, IA32_SHL, result, IC(value.scale));
}
}
}
}
}
break;
case IA32_FCLEAR_opcode:
expandFClear(p, ir);
break;
case IA32_JCC2_opcode:
p.insertBefore(
MIR_CondBranch.create(
IA32_JCC,
MIR_CondBranch2.getCond1(p),
MIR_CondBranch2.getTarget1(p),
MIR_CondBranch2.getBranchProfile1(p)));
MIR_CondBranch.mutate(
p,
IA32_JCC,
MIR_CondBranch2.getCond2(p),
MIR_CondBranch2.getTarget2(p),
MIR_CondBranch2.getBranchProfile2(p));
break;
case CALL_SAVE_VOLATILE_opcode:
p.changeOperatorTo(IA32_CALL);
break;
case IA32_LOCK_CMPXCHG_opcode:
p.insertBefore(MIR_Empty.create(IA32_LOCK));
p.changeOperatorTo(IA32_CMPXCHG);
break;
case IA32_LOCK_CMPXCHG8B_opcode:
p.insertBefore(MIR_Empty.create(IA32_LOCK));
p.changeOperatorTo(IA32_CMPXCHG8B);
break;
case YIELDPOINT_PROLOGUE_opcode:
expandYieldpoint(
p, ir, Entrypoints.optThreadSwitchFromPrologueMethod, IA32ConditionOperand.NE());
break;
case YIELDPOINT_EPILOGUE_opcode:
expandYieldpoint(
p, ir, Entrypoints.optThreadSwitchFromEpilogueMethod, IA32ConditionOperand.NE());
break;
case YIELDPOINT_BACKEDGE_opcode:
expandYieldpoint(
p, ir, Entrypoints.optThreadSwitchFromBackedgeMethod, IA32ConditionOperand.GT());
break;
case YIELDPOINT_OSR_opcode:
// must yield, does not check threadSwitch request
expandUnconditionalYieldpoint(p, ir, Entrypoints.optThreadSwitchFromOsrOptMethod);
break;
}
}
return 0;
}
/** Return the basic block that s's block will goto if s is not taken. */
private BasicBlock getNotTakenBlock(Instruction s) {
s = s.nextInstructionInCodeOrder();
if (Goto.conforms(s)) return s.getBranchTarget();
if (VM.VerifyAssertions) VM._assert(s.operator() == BBEND);
return s.getBasicBlock().nextBasicBlockInCodeOrder();
}
