/**
* This method is called when a call stack edge needs to be sampled. Expect the sfp argument to
* point to the stack frame that contains the target of the edge to be sampled.
*
* <p>NOTE: This method is uninterruptible, therefore we don't need to disable thread switching
* during stackframe inspection.
*
* @param sfp a pointer to the stack frame that corresponds to the callee of the call graph edge
* that is to be sampled.
* @param whereFrom Was this a yieldpoint in a PROLOGUE, BACKEDGE, or EPILOGUE?
*/
@Override
public final void update(Address sfp, int whereFrom) {
if (DEBUG) {
VM.sysWrite("EdgeListener.update(", sfp, ",", whereFrom);
VM.sysWriteln("): enter ", samplesTaken);
}
Synchronization.fetchAndAdd(this, AosEntrypoints.edgeListenerUpdateCalledField.getOffset(), 1);
// don't take a sample for back edge yield points
if (whereFrom == RVMThread.BACKEDGE) return;
int calleeCMID = 0;
int callerCMID = 0;
Address returnAddress = Address.zero();
if (sfp.loadAddress().EQ(STACKFRAME_SENTINEL_FP)) {
if (DEBUG) VM.sysWrite(" Walking off end of stack!\n");
return;
}
calleeCMID = Magic.getCompiledMethodID(sfp);
if (calleeCMID == INVISIBLE_METHOD_ID) {
if (DEBUG) {
VM.sysWrite(" INVISIBLE_METHOD_ID (assembler code) ");
VM.sysWrite(calleeCMID);
VM.sysWrite("\n");
}
return;
}
returnAddress = Magic.getReturnAddress(sfp); // return address in caller
sfp = Magic.getCallerFramePointer(sfp); // caller's frame pointer
if (sfp.loadAddress().EQ(STACKFRAME_SENTINEL_FP)) {
if (DEBUG) VM.sysWrite(" Walking off end of stack\n");
return;
}
callerCMID = Magic.getCompiledMethodID(sfp);
if (callerCMID == INVISIBLE_METHOD_ID) {
if (DEBUG) {
VM.sysWrite(" INVISIBLE_METHOD_ID (assembler code) ");
VM.sysWrite(callerCMID);
VM.sysWrite("\n");
}
return;
}
// store the offset of the return address from the beginning of the
// instruction
CompiledMethod callerCM = CompiledMethods.getCompiledMethod(callerCMID);
if (callerCM.getCompilerType() == CompiledMethod.TRAP) {
if (DEBUG) {
VM.sysWriteln(" HARDWARE TRAP FRAME ");
}
return;
}
Offset callSite = callerCM.getInstructionOffset(returnAddress);
if (DEBUG) {
VM.sysWrite(" <");
VM.sysWrite(calleeCMID);
VM.sysWrite(",");
VM.sysWrite(callerCMID);
VM.sysWrite(",");
VM.sysWrite(returnAddress);
VM.sysWrite(">\n");
}
// Find out what sample we are.
int sampleNumber =
Synchronization.fetchAndAdd(
this, AosEntrypoints.edgeListenerSamplesTakenField.getOffset(), 1);
int idx = 3 * sampleNumber;
// If we got buffer slots that are beyond the end of the buffer, that means
// that we're actually not supposed to take the sample at all (the system
// is in the process of activating our organizer and processing the buffer).
if (idx < buffer.length) {
buffer[idx + 1] = callerCMID;
buffer[idx + 2] = callSite.toInt();
Magic.sync();
buffer[idx + 0] = calleeCMID;
// If we are the last sample, we need to activate the organizer.
if (sampleNumber + 1 == desiredSamples) {
activateOrganizer();
}
}
}
