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Improve unwinding through interpreter frames.
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Instead of throwing a c++ exception from mono_handle_exception ()
when an exception is caught in AOTed code, set context->has_resume_state,
so the intepreter will normally unwind until exiting interpreted code.
Then throw the c++ exception after the call to interp_exec_method ()
to unwind through the runtime code and the AOTed frames
which can't handle the exception.
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@vargaz
vargaz committed Feb 28, 2022
1 parent eaf6fc8 commit ea36376
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Showing 3 changed files with 20 additions and 24 deletions.
3 changes: 1 addition & 2 deletions src/mono/mono/mini/interp/interp-internals.h
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Original file line number Diff line number Diff line change
Expand Up @@ -210,6 +210,7 @@ typedef struct {
/* Lets interpreter know it has to resume execution after EH */
gboolean has_resume_state;
/* Frame to resume execution at */
/* Can be NULL if the exception is caught in an AOTed frame */
InterpFrame *handler_frame;
/* IP to resume execution at */
const guint16 *handler_ip;
Expand All @@ -231,8 +232,6 @@ typedef struct {
guchar *stack_pointer;
/* Used for allocation of localloc regions */
FrameDataAllocator data_stack;
/* Whenever to unwind from interpreter code back to the caller */
gboolean pending_unwind;
} ThreadContext;

typedef struct {
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37 changes: 16 additions & 21 deletions src/mono/mono/mini/interp/interp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -427,13 +427,12 @@ interp_free_context (gpointer ctx)
g_free (context);
}

/* Continue unwinding if there is an exception that needs to be handled in an AOTed frame above us */
static void
check_pending_unwind (ThreadContext *context)
{
if (context->pending_unwind) {
context->pending_unwind = FALSE;
if (context->has_resume_state && !context->handler_frame)
mono_llvm_cpp_throw_exception ();
}
}

void
Expand Down Expand Up @@ -2657,11 +2656,10 @@ do_jit_call (ThreadContext *context, stackval *ret_sp, stackval *sp, InterpFrame
/*
* This c++ exception is going to be caught by an AOTed frame above us.
* We can't rethrow here, since that will skip the cleanup of the
* interpreter stack space etc. So set a flag and the caller
* will rethrow the exception.
* interpreter stack space etc. So instruct the interpreter to unwind.
*/
//mono_llvm_cpp_throw_exception ();
context->pending_unwind = TRUE;
context->has_resume_state = TRUE;
context->handler_frame = NULL;
return;
}
MonoObject *obj = mini_llvmonly_load_exception ();
Expand Down Expand Up @@ -3518,8 +3516,6 @@ static long total_executed_opcodes;
* The ERROR argument is used to avoid declaring an error object for every interp frame, its not used
* to return error information.
* FRAME is only valid until the next call to alloc_frame ().
* After the call, if context->pending_unwind is set, the caller should clean up then
* call mono_llvm_cpp_throw_exception () to continue unwinding.
*/
static MONO_NEVER_INLINE void
interp_exec_method (InterpFrame *frame, ThreadContext *context, FrameClauseArgs *clause_args)
Expand Down Expand Up @@ -3937,8 +3933,6 @@ interp_exec_method (InterpFrame *frame, ThreadContext *context, FrameClauseArgs
frame->state.ip = ip;
error_init_reuse (error);
do_jit_call (context, (stackval*)(locals + return_offset), (stackval*)(locals + call_args_offset), frame, cmethod, error);
if (context->pending_unwind)
return;
if (!is_ok (error)) {
MonoException *ex = interp_error_convert_to_exception (frame, error, ip);
THROW_EX (ex, ip);
Expand Down Expand Up @@ -4040,8 +4034,6 @@ interp_exec_method (InterpFrame *frame, ThreadContext *context, FrameClauseArgs
/* for calls, have ip pointing at the start of next instruction */
frame->state.ip = ip + 4;
do_jit_call (context, (stackval*)(locals + ip [1]), (stackval*)(locals + ip [2]), frame, rmethod, error);
if (context->pending_unwind)
return;
if (!is_ok (error)) {
MonoException *ex = interp_error_convert_to_exception (frame, error, ip);
THROW_EX (ex, ip);
Expand All @@ -4060,8 +4052,6 @@ interp_exec_method (InterpFrame *frame, ThreadContext *context, FrameClauseArgs

frame->state.ip = ip + 6;
do_jit_call (context, (stackval*)(locals + ip [1]), frame, rmethod, error);
if (context->pending_unwind)
return;
if (!is_ok (error)) {
MonoException *ex = interp_error_convert_to_exception (frame, error);
THROW_EX (ex, ip);
Expand Down Expand Up @@ -7304,6 +7294,8 @@ interp_parse_options (const char *options)
* interp_set_resume_state:
*
* Set the state the interpeter will continue to execute from after execution returns to the interpreter.
* If INTERP_FRAME is NULL, that means the exception is caught in an AOTed frame and the interpreter needs to
* unwind back to AOT code.
*/
static void
interp_set_resume_state (MonoJitTlsData *jit_tls, MonoObject *ex, MonoJitExceptionInfo *ei, MonoInterpFrameHandle interp_frame, gpointer handler_ip)
Expand All @@ -7321,8 +7313,10 @@ interp_set_resume_state (MonoJitTlsData *jit_tls, MonoObject *ex, MonoJitExcepti
mono_gchandle_free_internal (context->exc_gchandle);
context->exc_gchandle = mono_gchandle_new_internal ((MonoObject*)ex, FALSE);
/* Ditto */
if (ei)
*(MonoObject**)(frame_locals (context->handler_frame) + ei->exvar_offset) = ex;
if (context->handler_frame) {
if (ei)
*(MonoObject**)(frame_locals (context->handler_frame) + ei->exvar_offset) = ex;
}
context->handler_ip = (const guint16*)handler_ip;
}

Expand Down Expand Up @@ -7433,6 +7427,7 @@ interp_run_filter (StackFrameInfo *frame, MonoException *ex, int clause_index, g
return retval.data.i ? TRUE : FALSE;
}

/* Returns TRUE if there is a pending exception */
static gboolean
interp_run_clause_with_il_state (gpointer il_state_ptr, int clause_index, gpointer handler_ip, gpointer handler_ip_end,
MonoObject *ex, gboolean *filtered, MonoExceptionEnum clause_type)
Expand Down Expand Up @@ -7516,6 +7511,9 @@ interp_run_clause_with_il_state (gpointer il_state_ptr, int clause_index, gpoint
// this informs MINT_ENDFINALLY to return to EH
*(guint16**)(frame_locals (&frame) + imethod->clause_data_offsets [clause_index]) = NULL;

/* Set in mono_handle_exception () */
context->has_resume_state = FALSE;

interp_exec_method (&frame, context, &clause_args);

/* Write back args */
Expand Down Expand Up @@ -7557,10 +7555,7 @@ interp_run_clause_with_il_state (gpointer il_state_ptr, int clause_index, gpoint

check_pending_unwind (context);

if (context->has_resume_state)
return TRUE;
else
return FALSE;
return context->has_resume_state;
}

typedef struct {
Expand Down
4 changes: 3 additions & 1 deletion src/mono/mono/mini/mini-exceptions.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2502,7 +2502,9 @@ mono_handle_exception_internal (MonoContext *ctx, MonoObject *obj, gboolean resu
jit_tls->resume_state.ji = ji;
jit_tls->resume_state.clause_index = i;
jit_tls->resume_state.il_state = frame.il_state;
mono_llvm_cpp_throw_exception ();

/* Instruct the intepreter to unwind back to AOTed code */
mini_get_interp_callbacks ()->set_resume_state (jit_tls, ex_obj, ei, NULL, NULL);
}

if (in_interp) {
Expand Down

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