/**
* Replace a Load instruction s with a load from a scalar register r TODO: factor this
* functionality out elsewhere
*/
static void replaceLoadWithMove(Register r, Instruction load) {
RegisterOperand dest = ResultCarrier.getResult(load);
RegisterOperand rop = new RegisterOperand(r, dest.getType());
load.replace(Move.create(IRTools.getMoveOp(dest.getType()), dest, rop));
}
/**
* Perform scalar replacement actions for a Def of a heap variable. NOTE: Even loads can def a
* heap variable.
*
* @param UseRepSet stores the uses(loads) that have been eliminated
* @param registers mapping from valueNumber -> temporary register
*/
static void replaceDefs(IR ir, UseRecordSet UseRepSet, HashMap<UseRecord, Register> registers) {
SSADictionary ssa = ir.HIRInfo.dictionary;
for (Enumeration<Instruction> e = ir.forwardInstrEnumerator(); e.hasMoreElements(); ) {
Instruction s = e.nextElement();
if (!GetField.conforms(s)
&& !GetStatic.conforms(s)
&& !PutField.conforms(s)
&& !PutStatic.conforms(s)
&& !ALoad.conforms(s)
&& !AStore.conforms(s)) {
continue;
}
if (!ssa.defsHeapVariable(s)) {
continue;
}
// this instruction is a DEF of heap variable H.
// Check if UseRepSet needs the scalar assigned by this def
HeapOperand<?>[] H = ssa.getHeapDefs(s);
if (H.length != 1) {
throw new OptimizingCompilerException(
"LoadElimination: encountered a store with more than one def? " + s);
}
int valueNumber = -1;
Object index = null;
if (AStore.conforms(s)) {
Object address = AStore.getArray(s);
index = AStore.getIndex(s);
valueNumber = ir.HIRInfo.valueNumbers.getValueNumber(address);
} else if (GetField.conforms(s)) {
Object address = GetField.getRef(s);
valueNumber = ir.HIRInfo.valueNumbers.getValueNumber(address);
} else if (PutField.conforms(s)) {
Object address = PutField.getRef(s);
valueNumber = ir.HIRInfo.valueNumbers.getValueNumber(address);
} else if (GetStatic.conforms(s)) {
valueNumber = 0;
} else if (PutStatic.conforms(s)) {
valueNumber = 0;
} else if (ALoad.conforms(s)) {
Object address = ALoad.getArray(s);
valueNumber = ir.HIRInfo.valueNumbers.getValueNumber(address);
index = ALoad.getIndex(s);
}
if (index == null) {
// Load/Store
if (UseRepSet.containsMatchingUse(H[0].getHeapVariable(), valueNumber)) {
Operand value = null;
if (PutField.conforms(s)) {
value = PutField.getValue(s);
} else if (PutStatic.conforms(s)) {
value = PutStatic.getValue(s);
} else if (GetField.conforms(s) || GetStatic.conforms(s)) {
value = ResultCarrier.getResult(s);
}
TypeReference type = value.getType();
Register r =
findOrCreateRegister(H[0].getHeapType(), valueNumber, registers, ir.regpool, type);
appendMove(r, value, s);
}
} else {
// ALoad / AStore
int v1 = valueNumber;
int v2 = ir.HIRInfo.valueNumbers.getValueNumber(index);
if (UseRepSet.containsMatchingUse(H[0].getHeapVariable(), v1, v2)) {
Operand value = null;
if (AStore.conforms(s)) {
value = AStore.getValue(s);
} else if (ALoad.conforms(s)) {
value = ALoad.getResult(s);
}
TypeReference type = value.getType();
Register r =
findOrCreateRegister(H[0].getHeapType(), v1, v2, registers, ir.regpool, type);
appendMove(r, value, s);
}
}
}
}
/**
* Walk over each instruction. If its a USE (load) of a heap variable and the value is available,
* then replace the load with a move from a register.
*
* <p>POSTCONDITION: sets up the mapping 'registers' from value number to temporary register
*
* @param ir the IR
* @param available information on which values are available
* @param registers a place to store information about temp registers
*/
static UseRecordSet replaceLoads(
IR ir, DF_Solution available, HashMap<UseRecord, Register> registers) {
UseRecordSet result = new UseRecordSet();
SSADictionary ssa = ir.HIRInfo.dictionary;
GlobalValueNumberState valueNumbers = ir.HIRInfo.valueNumbers;
for (Enumeration<Instruction> e = ir.forwardInstrEnumerator(); e.hasMoreElements(); ) {
Instruction s = e.nextElement();
if (!GetField.conforms(s) && !GetStatic.conforms(s) && !ALoad.conforms(s)) {
continue;
}
// this instruction is a USE of heap variable H.
// get the lattice cell that holds the available indices
// for this heap variable
HeapOperand<?>[] H = ssa.getHeapUses(s);
if (H == null) {
// this case can happen due to certain magics that insert
// INT_LOAD instructions in HIR
// TODO: clean up HIR representation of these magics
continue;
}
if (H.length != 1) {
throw new OptimizingCompilerException(
"LoadElimination: load with wrong number of heap uses");
}
if (GetField.conforms(s) || GetStatic.conforms(s)) {
int valueNumber = -1;
if (GetField.conforms(s)) {
Object address = GetField.getRef(s);
valueNumber = valueNumbers.getValueNumber(address);
} else {
// for getStatic, always use the value number 0
valueNumber = 0;
}
ObjectCell cell = (ObjectCell) available.lookup(H[0].getHeapVariable());
if (cell == null) {
continue; // nothing available
}
// .. if H{valueNumber} is available ...
if (cell.contains(valueNumber)) {
result.add(H[0].getHeapVariable(), valueNumber);
TypeReference type = ResultCarrier.getResult(s).getType();
Register r =
findOrCreateRegister(H[0].getHeapType(), valueNumber, registers, ir.regpool, type);
if (DEBUG) {
System.out.println("ELIMINATING LOAD " + s);
}
replaceLoadWithMove(r, s);
}
} else { // ALoad.conforms(s)
Object array = ALoad.getArray(s);
Object index = ALoad.getIndex(s);
ArrayCell cell = (ArrayCell) available.lookup(H[0].getHeapVariable());
if (cell == null) {
continue; // nothing available
}
int v1 = valueNumbers.getValueNumber(array);
int v2 = valueNumbers.getValueNumber(index);
// .. if H{<v1,v2>} is available ...
if (cell.contains(v1, v2)) {
result.add(H[0].getHeapVariable(), v1, v2);
TypeReference type = ALoad.getResult(s).getType();
Register r =
findOrCreateRegister(
H[0].getHeapVariable().getHeapType(), v1, v2, registers, ir.regpool, type);
if (DEBUG) {
System.out.println("ELIMINATING LOAD " + s);
}
replaceLoadWithMove(r, s);
}
}
}
return result;
}
