vm: charge samples collected in prolog to parent

Fixes #379

vm/errors.cpp

@@ -115,10 +115,10 @@ void factor_vm::verify_memory_protection_error(cell addr)
 		fatal_error("Memory protection fault during gc", addr);
 }
 
-void factor_vm::memory_protection_error(cell addr)
+void factor_vm::memory_protection_error(cell pc, cell addr)
 {
 	if(code->safepoint_p(addr))
-		safepoint.handle_safepoint(this);
+		safepoint.handle_safepoint(this, pc);
 	else if(ctx->datastack_seg->underflow_p(addr))
 		general_error(ERROR_DATASTACK_UNDERFLOW,false_object,false_object);
 	else if(ctx->datastack_seg->overflow_p(addr))
@@ -158,7 +158,7 @@ void factor_vm::primitive_unimplemented()
 
 void factor_vm::memory_signal_handler_impl()
 {
-	memory_protection_error(signal_fault_addr);
+	memory_protection_error(signal_fault_pc, signal_fault_addr);
 	if (!signal_resumable)
 	{
 		/* In theory we should only get here if the callstack overflowed during a

vm/mach_signal.cpp

@@ -40,6 +40,7 @@ void factor_vm::call_fault_handler(
 	if(exception == EXC_BAD_ACCESS)
 	{
 		signal_fault_addr = MACH_EXC_STATE_FAULT(exc_state);
+		signal_fault_pc = (cell)MACH_PROGRAM_COUNTER(thread_state);
 		verify_memory_protection_error(signal_fault_addr);
 		handler = (cell)factor::memory_signal_handler_impl;
 	}

vm/os-unix.cpp

@@ -167,6 +167,7 @@ void memory_signal_handler(int signal, siginfo_t *siginfo, void *uap)
 	factor_vm *vm = current_vm();
 	vm->verify_memory_protection_error((cell)siginfo->si_addr);
 	vm->signal_fault_addr = (cell)siginfo->si_addr;
+	vm->signal_fault_pc = (cell)UAP_PROGRAM_COUNTER(uap);
 	vm->dispatch_signal(uap,factor::memory_signal_handler_impl);
 }
 

vm/safepoints.cpp

@@ -35,7 +35,7 @@ void safepoint_state::enqueue_samples(factor_vm *parent, cell samples, cell pc,
 	}
 }
 
-void safepoint_state::handle_safepoint(factor_vm *parent) volatile
+void safepoint_state::handle_safepoint(factor_vm *parent, cell pc) volatile
 {
 	parent->code->unguard_safepoint();
 	parent->faulting_p = false;
@@ -49,7 +49,13 @@ void safepoint_state::handle_safepoint(factor_vm *parent) volatile
 		atomic::store(&fep_p, false);
 	}
 	else if (atomic::load(&parent->sampling_profiler_p))
-		parent->record_sample();
+	{
+		assert(parent->code->seg->in_segment_p(pc));
+		code_block *block = parent->code->code_block_for_address(pc);
+		bool prolog_p = (cell)block->entry_point() == pc;
+
+		parent->record_sample(prolog_p);
+	}
 }
 
 }

vm/safepoints.hpp

@@ -12,7 +12,7 @@ struct safepoint_state
 	{
 	}
 
-	void handle_safepoint(factor_vm *parent) volatile;
+	void handle_safepoint(factor_vm *parent, cell pc) volatile;
 
 	void enqueue_safepoint(factor_vm *parent) volatile;
 	void enqueue_samples(factor_vm *parent, cell samples, cell pc, bool foreign_thread_p) volatile;

vm/sampling_profiler.cpp

@@ -31,31 +31,46 @@ void profiling_sample_count::clear() volatile
 }
 
 profiling_sample::profiling_sample(factor_vm *vm,
+	bool prolog_p,
 	profiling_sample_count const &counts,
 	cell thread)
 	:
 	counts(counts),
 	thread(thread)
 {
-	vm->record_callstack_sample(&callstack_begin, &callstack_end);
+	vm->record_callstack_sample(&callstack_begin, &callstack_end, prolog_p);
 }
 
-void factor_vm::record_sample()
+void factor_vm::record_sample(bool prolog_p)
 {
 	profiling_sample_count counts = safepoint.sample_counts.record_counts();
 	if (!counts.empty())
-		samples.push_back(profiling_sample(this,
+		samples.push_back(profiling_sample(this, prolog_p,
 			counts, special_objects[OBJ_CURRENT_THREAD]));
 }
 
-void factor_vm::record_callstack_sample(cell *begin, cell *end)
+void factor_vm::record_callstack_sample(cell *begin, cell *end, bool prolog_p)
 {
 	*begin = sample_callstacks.size();
 	stack_frame *frame = ctx->bottom_frame();
-
-	while (frame >= ctx->callstack_top) {
-		sample_callstacks.push_back(frame_code(frame)->owner);
-		frame = frame_successor(frame);
+	if (prolog_p)
+	{
+		assert(frame >= ctx->callstack_top);
+		stack_frame *next_frame = frame_successor(frame);
+		while (next_frame >= ctx->callstack_top)
+		{
+			sample_callstacks.push_back(frame_code(frame)->owner);
+			frame = next_frame;
+			next_frame = frame_successor(next_frame);
+		}
+	}
+	else
+	{
+		while (frame >= ctx->callstack_top)
+		{
+			sample_callstacks.push_back(frame_code(frame)->owner);
+			frame = frame_successor(frame);
+		}
 	}
 
 	*end = sample_callstacks.size();
@@ -98,7 +113,7 @@ void factor_vm::end_sampling_profiler()
 {
 	atomic::store(&sampling_profiler_p, false);
 	end_sampling_profiler_timer();
-	record_sample();
+	record_sample(false);
 }
 
 void factor_vm::primitive_sampling_profiler()

vm/sampling_profiler.hpp

@@ -56,6 +56,7 @@ struct profiling_sample
 	cell callstack_begin, callstack_end;
 
 	profiling_sample(factor_vm *vm,
+		bool prolog_p,
 		profiling_sample_count const &counts,
 		cell thread);
 };

vm/vm.hpp

@@ -75,6 +75,7 @@ struct factor_vm
 	bool signal_resumable;
 	cell signal_number;
 	cell signal_fault_addr;
+	cell signal_fault_pc;
 	unsigned int signal_fpu_status;
 
 	/* Pipe used to notify Factor multiplexer of signals */
@@ -204,8 +205,8 @@ struct factor_vm
 
 	// sampling_profiler
 	void clear_samples();
-	void record_sample();
-	void record_callstack_sample(cell *begin, cell *end);
+	void record_sample(bool prolog_p);
+	void record_callstack_sample(cell *begin, cell *end, bool prolog_p);
 	void start_sampling_profiler(fixnum rate);
 	void end_sampling_profiler();
 	void set_sampling_profiler(fixnum rate);
@@ -218,7 +219,7 @@ struct factor_vm
 	void type_error(cell type, cell tagged);
 	void not_implemented_error();
 	void verify_memory_protection_error(cell addr);
-	void memory_protection_error(cell addr);
+	void memory_protection_error(cell pc, cell addr);
 	void signal_error(cell signal);
 	void divide_by_zero_error();
 	void fp_trap_error(unsigned int fpu_status);