/**
* Rewrites a move instruction if it has 2 memory operands. One of the 2 memory operands must be a
* stack location operand. Move the SP to the appropriate location and use a push or pop
* instruction.
*
* @param s the instruction to rewrite
*/
private void rewriteMoveInstruction(Instruction s) {
// first attempt to mutate the move into a noop
if (mutateMoveToNop(s)) return;
Operand result = MIR_Move.getResult(s);
Operand val = MIR_Move.getValue(s);
if (result instanceof StackLocationOperand) {
if (val instanceof MemoryOperand || val instanceof StackLocationOperand) {
int offset = ((StackLocationOperand) result).getOffset();
byte size = ((StackLocationOperand) result).getSize();
offset = FPOffset2SPOffset(offset) + size;
moveESPBefore(s, offset);
MIR_UnaryNoRes.mutate(s, IA32_PUSH, val);
}
} else {
if (result instanceof MemoryOperand) {
if (val instanceof StackLocationOperand) {
int offset = ((StackLocationOperand) val).getOffset();
offset = FPOffset2SPOffset(offset);
moveESPBefore(s, offset);
MIR_Nullary.mutate(s, IA32_POP, result);
}
}
}
}
/**
* expand an FCLEAR pseudo-insruction using FFREEs.
*
* @param s the instruction to expand
* @param ir the containing IR
*/
private static void expandFClear(Instruction s, IR ir) {
int nSave = MIR_UnaryNoRes.getVal(s).asIntConstant().value;
int fpStackHeight = ir.MIRInfo.fpStackHeight;
PhysicalRegisterSet phys = ir.regpool.getPhysicalRegisterSet().asIA32();
for (int i = nSave; i < fpStackHeight; i++) {
Register f = phys.getFPR(i);
s.insertBefore(MIR_Nullary.create(IA32_FFREE, D(f)));
}
// Remove the FCLEAR.
s.remove();
}
/**
* Insert the epilogue before a particular return instruction.
*
* @param ret the return instruction.
*/
private void insertEpilogue(Instruction ret) {
// 1. Restore any saved registers
if (ir.compiledMethod.isSaveVolatile()) {
restoreVolatileRegisters(ret);
restoreFloatingPointState(ret);
}
restoreNonVolatiles(ret);
// 2. Restore caller's stackpointer and framepointer
int frameSize = getFrameFixedSize();
ret.insertBefore(MIR_UnaryNoRes.create(REQUIRE_ESP, IC(frameSize)));
MemoryOperand fpHome =
MemoryOperand.BD(
ir.regpool.makeTROp(),
ArchEntrypoints.framePointerField.getOffset(),
(byte) WORDSIZE,
null,
null);
ret.insertBefore(MIR_Nullary.create(IA32_POP, fpHome));
}