/** Applies the optimization. */
private void run() {
int regSz = ssaMeth.getRegCount();
ArrayList<TypedConstant> constantList = getConstsSortedByCountUse();
int toCollect = Math.min(constantList.size(), MAX_COLLECTED_CONSTANTS);
SsaBasicBlock start = ssaMeth.getEntryBlock();
// Constant to new register containing the constant
HashMap<TypedConstant, RegisterSpec> newRegs =
new HashMap<TypedConstant, RegisterSpec>(toCollect);
for (int i = 0; i < toCollect; i++) {
TypedConstant cst = constantList.get(i);
RegisterSpec result = RegisterSpec.make(ssaMeth.makeNewSsaReg(), cst);
Rop constRop = Rops.opConst(cst);
if (constRop.getBranchingness() == Rop.BRANCH_NONE) {
start.addInsnToHead(
new PlainCstInsn(
Rops.opConst(cst), SourcePosition.NO_INFO, result, RegisterSpecList.EMPTY, cst));
} else {
// We need two new basic blocks along with the new insn
SsaBasicBlock entryBlock = ssaMeth.getEntryBlock();
SsaBasicBlock successorBlock = entryBlock.getPrimarySuccessor();
// Insert a block containing the const insn.
SsaBasicBlock constBlock = entryBlock.insertNewSuccessor(successorBlock);
constBlock.replaceLastInsn(
new ThrowingCstInsn(
constRop, SourcePosition.NO_INFO, RegisterSpecList.EMPTY, StdTypeList.EMPTY, cst));
// Insert a block containing the move-result-pseudo insn.
SsaBasicBlock resultBlock = constBlock.insertNewSuccessor(successorBlock);
PlainInsn insn =
new PlainInsn(
Rops.opMoveResultPseudo(result.getTypeBearer()),
SourcePosition.NO_INFO,
result,
RegisterSpecList.EMPTY);
resultBlock.addInsnToHead(insn);
}
newRegs.put(cst, result);
}
updateConstUses(newRegs, regSz);
}
/**
* Tries to replace an instruction with a const instruction. The given instruction must have a
* constant result for it to be replaced.
*
* @param insn {@code non-null;} instruction to try to replace
* @return true if the instruction was replaced
*/
private boolean tryReplacingWithConstant(NormalSsaInsn insn) {
Insn originalRopInsn = insn.getOriginalRopInsn();
Rop opcode = originalRopInsn.getOpcode();
RegisterSpec result = insn.getResult();
if (result != null && !ssaMeth.isRegALocal(result) && opcode.getOpcode() != RegOps.CONST) {
TypeBearer type = insn.getResult().getTypeBearer();
if (type.isConstant() && type.getBasicType() == Type.BT_INT) {
// Replace the instruction with a constant
replacePlainInsn(insn, RegisterSpecList.EMPTY, RegOps.CONST, (Constant) type);
// Remove the source as well if this is a move-result-pseudo
if (opcode.getOpcode() == RegOps.MOVE_RESULT_PSEUDO) {
int pred = insn.getBlock().getPredecessors().nextSetBit(0);
ArrayList<SsaInsn> predInsns = ssaMeth.getBlocks().get(pred).getInsns();
NormalSsaInsn sourceInsn = (NormalSsaInsn) predInsns.get(predInsns.size() - 1);
replacePlainInsn(sourceInsn, RegisterSpecList.EMPTY, RegOps.GOTO, null);
}
return true;
}
}
return false;
}