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[mono][aot] Type load checks do not fail at compile time but produce a runtime exception #91261

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merged 21 commits into from
Sep 27, 2023
Merged

[mono][aot] Type load checks do not fail at compile time but produce a runtime exception #91261

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78ce32e
Enable tests.
jandupej Aug 28, 2023
3c32b67
When AOTing, type checks do not fail compilation but create a runtime…
jandupej Aug 29, 2023
7676e00
Cleaned up type load error cleaning. TypeLoadException icall now has …
jandupej Aug 30, 2023
611888b
Removed another instance of indiscriminate exception clearing.
jandupej Aug 30, 2023
15b7aa5
Fixed build warning.
jandupej Aug 30, 2023
90aa674
Using class const instead of string const. Reverted some compile to r…
jandupej Aug 31, 2023
d4b6c9f
White space.
jandupej Aug 31, 2023
bda12b3
Fixed build warning.
jandupej Aug 31, 2023
fbd3614
Trying to fix weird AOT errors, fixed type load throw function.
jandupej Aug 31, 2023
805d6c4
Fixed build error.
jandupej Aug 31, 2023
0b50974
Special handling for classes that are NULL.
jandupej Sep 1, 2023
19c5155
Providing for a null klass when generating exception.
jandupej Sep 6, 2023
83bcc30
Removed flow control directive from macro.
jandupej Sep 6, 2023
c6fe63b
Fixed stack corruption.
jandupej Sep 6, 2023
9cb3d1a
Attempt to push the correct type onto the stack.
jandupej Sep 8, 2023
025ed7a
Fixing uninitialized ins.
jandupej Sep 8, 2023
4633336
Fixing ro_type.
jandupej Sep 8, 2023
55db3c6
Initializing ins.
jandupej Sep 8, 2023
4b35af0
Complex cases with type load failures replace method body with a throw.
jandupej Sep 20, 2023
ca7530d
Cleaning up superfluous code changes.
jandupej Sep 21, 2023
9709a89
Restored sizeof cosntant on failed types.
jandupej Sep 21, 2023
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62 changes: 48 additions & 14 deletions src/mono/mono/mini/method-to-ir.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6193,6 +6193,49 @@ emit_llvmonly_interp_entry (MonoCompile *cfg, MonoMethodHeader *header)
link_bblock (cfg, cfg->cbb, cfg->bb_exit);
}

static void
method_make_alwaysthrow_typeloadfailure (MonoCompile* cfg, MonoClass* klass)
{
// Get rid of all out-BBs from the entry BB. (all but init BB)
for (gint16 i = cfg->bb_entry->out_count - 1; i >= 0; i--) {
if (cfg->bb_entry->out_bb [i] != cfg->bb_init) {
mono_unlink_bblock (cfg, cfg->bb_entry, cfg->bb_entry->out_bb [i]);
mono_remove_bblock (cfg, cfg->bb_entry->out_bb [i]);
}
}

// Discard all out-BBs from the init BB.
for (gint16 i = cfg->bb_init->out_count - 1; i >= 0; i--) {
if (cfg->bb_init->out_bb [i] != cfg->bb_exit) {
mono_unlink_bblock (cfg, cfg->bb_init, cfg->bb_init->out_bb [i]);
mono_remove_bblock (cfg, cfg->bb_init->out_bb [i]);
}
}

// Maintain linked list consistency. This BB should have been added as the last,
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Is it necessary to remove dead blocks between the bb_init and bb_exit which may not have a direct link to them?

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@jandupej jandupej Sep 20, 2023 •
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Possibly not; it seems that unreachable blocks are detected (and removed) without my explicitly doing it. This is the first iteration that seems to work locally, waiting for CI. I may be able to simplify it if CI turns out favorable.

EDIT: Are you aware of any unlinked blocks that should be kept?

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This change looks good to me. I was just curious whether the unreachable blocks are detected and removed.

Is it possible to skip the bb_init and link the bb_entry with the throw block?

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I had control flow issues when generating LLVM IR without the init block (which was empty no less). I'll see if it can be done.

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An alternative is to restart the compilation, there is already a mechanism to do that if llvm fails, etc. and emit the exception without compiling the rest of the IL.

// ignoring the ones that held actual method code.
cfg->cbb = cfg->bb_init;

// Create a new BB that only throws, link it after the entry.
MonoBasicBlock* bb;
NEW_BBLOCK (cfg, bb);
bb->cil_code = NULL;
bb->cil_length = 0;
cfg->cbb->next_bb = bb;
cfg->cbb = bb;

emit_type_load_failure (cfg, klass);
MonoInst* ins;
MONO_INST_NEW (cfg, ins, OP_NOT_REACHED);
MONO_ADD_INS (cfg->cbb, ins);

ADD_BBLOCK (cfg, bb);
mono_link_bblock (cfg, cfg->bb_init, bb);
mono_link_bblock (cfg, bb, cfg->bb_exit);

cfg->disable_inline = TRUE;
}

typedef union _MonoOpcodeParameter {
gint32 i32;
gint64 i64;
Expand Down Expand Up @@ -9939,19 +9982,10 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
EMIT_NEW_PCONST (cfg, *sp, NULL);
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sp++;
} else if (il_op == MONO_CEE_LDFLD || il_op == MONO_CEE_LDSFLD) {
// An object is expected. Make best effort to find its type and push that. If that
// attempt fails, push a pointer to balance the stack.
mono_class_init_internal (klass);
field = mono_class_get_field (klass, token);

if (field == NULL) {
// FIXME: this may be incorrect. Either find the correct type to push or skip the rest of BB.
EMIT_NEW_PCONST (cfg, *sp, NULL);
sp++;
} else {
ftype = mono_field_get_type_internal (field);
goto fld_emit_stage;
}
// An object is expected here. It may be impossible to correctly infer its type,
// we turn this entire method into a throw.
method_make_alwaysthrow_typeloadfailure (cfg, klass);
goto all_bbs_done;
}

break;
Expand Down Expand Up @@ -10349,7 +10383,6 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
if (!addr)
addr = mono_static_field_get_addr (vtable, field);

fld_emit_stage:
ro_type = ftype->type;
if (ro_type == MONO_TYPE_VALUETYPE && m_class_is_enumtype (ftype->data.klass)) {
ro_type = mono_class_enum_basetype_internal (ftype->data.klass)->type;
Expand Down Expand Up @@ -12079,6 +12112,7 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
}
if (start_new_bblock != 1)
UNVERIFIED;
all_bbs_done:

cfg->cbb->cil_length = GPTRDIFF_TO_INT32 (ip - cfg->cbb->cil_code);
if (cfg->cbb->next_bb) {
Expand Down