// Create a conflict resolution stub for the set of interface method signatures l.
//
public static ArchitectureSpecific.VM_CodeArray createStub(int[] sigIds, VM_Method[] targets) {
// (1) Create an assembler.
int numEntries = sigIds.length;
VM_Assembler asm =
new ArchitectureSpecific.VM_Assembler(numEntries); // pretend each entry is a bytecode
// (2) signatures must be in ascending order (to build binary search tree).
if (VM.VerifyAssertions) {
for (int i = 1; i < sigIds.length; i++) {
VM._assert(sigIds[i - 1] < sigIds[i]);
}
}
// (3) Assign synthetic bytecode numbers to each switch such that we'll generate them
// in ascending order. This lets us use the general forward branching mechanisms
// of the VM_Assembler.
int[] bcIndices = new int[numEntries];
assignBytecodeIndices(0, bcIndices, 0, numEntries - 1);
// (4) Generate the stub.
insertStubPrologue(asm);
insertStubCase(asm, sigIds, targets, bcIndices, 0, numEntries - 1);
ArchitectureSpecific.VM_CodeArray stub = asm.makeMachineCode().getInstructions();
// (5) synchronize icache with generated machine code that was written through dcache
if (VM.runningVM)
VM_Memory.sync(VM_Magic.objectAsAddress(stub), stub.length() << LG_INSTRUCTION_WIDTH);
return stub;
}
// Generate a subtree covering from low to high inclusive.
private static void insertStubCase(
VM_Assembler asm, int[] sigIds, VM_Method[] targets, int[] bcIndices, int low, int high) {
int middle = (high + low) / 2;
asm.resolveForwardReferences(bcIndices[middle]);
if (low == middle && middle == high) {
// a leaf case; can simply invoke the method directly.
VM_Method target = targets[middle];
if (target.isStatic()) {
// an error case.
asm.emitLAddrToc(S0, target.getOffset());
} else {
asm.emitLAddrOffset(S0, S0, target.getOffset());
}
asm.emitMTCTR(S0);
asm.emitBCCTR();
} else {
asm.emitCMPI(S1, sigIds[middle]);
if (low < middle) {
asm.emitShortBC(LT, 0, bcIndices[(low + middle - 1) / 2]);
}
if (middle < high) {
asm.emitShortBC(GT, 0, bcIndices[(middle + 1 + high) / 2]);
}
// invoke the method for middle.
VM_Method target = targets[middle];
if (target.isStatic()) {
// an error case.
asm.emitLAddrToc(S0, target.getOffset());
} else {
asm.emitLAddrOffset(S0, S0, target.getOffset());
}
asm.emitMTCTR(S0);
asm.emitBCCTR();
// Recurse.
if (low < middle) {
insertStubCase(asm, sigIds, targets, bcIndices, low, middle - 1);
}
if (middle < high) {
insertStubCase(asm, sigIds, targets, bcIndices, middle + 1, high);
}
}
}