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[mono][aot] Enable direct call transformation for MONO_PATCH_INFO_METHOD #82711

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[mono][aot] Enable direct call transformation for MONO_PATCH_INFO_METHOD #82711

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9c91a8e
Enable direct call transformation where caller requires no initializa…
kotlarmilos Feb 27, 2023
8f995a1
Callee can specialize
kotlarmilos Feb 27, 2023
882353e
Use m_class_has_cctor method to check if class requires no initializa…
kotlarmilos Feb 28, 2023
1a182a1
Move the condition into is_direct_callable
kotlarmilos Mar 1, 2023
282fb7e
Revert last commit
kotlarmilos Mar 2, 2023
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7 changes: 2 additions & 5 deletions src/mono/mono/mini/aot-compiler.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6588,12 +6588,10 @@ emit_and_reloc_code (MonoAotCompile *acfg, MonoMethod *method, guint8 *code, gui
direct_call_target = symbol;
patch_info->type = MONO_PATCH_INFO_NONE;
} else if ((m_class_get_image (patch_info->data.method->klass) == acfg->image) && !got_only && is_direct_callable (acfg, method, patch_info)) {
#if 0
// FIXME: Currently not used. It fails as some callees require initialization.
MonoCompile *callee_cfg = (MonoCompile *)g_hash_table_lookup (acfg->method_to_cfg, cmethod);

// Don't compile inflated methods if we're doing dedup
if (acfg->aot_opts.dedup && !mono_aot_can_dedup (cmethod)) {
// Enable direct call transformation where caller's class requires no initialization and callee can specialize
if (!m_class_has_static_refs (method->klass) && mono_aot_can_specialize (cmethod)) {
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@vargaz vargaz Feb 27, 2023

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has_static_refs () means the class has static reference fields, not that it has an initializer.

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@kotlarmilos kotlarmilos Feb 28, 2023

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The assumption is that if a caller method has static reference fields it requires initialization. Is there a better way to check if the caller method has to be initialized?

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@vargaz vargaz Feb 28, 2023

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m_class_has_cctor (method->klass) will return whenever the class has a static ctor.

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@vargaz vargaz Feb 28, 2023

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Why is this condition required ?

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@kotlarmilos kotlarmilos Feb 28, 2023

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This PR enables direct call transformation for MONO_PATCH_INFO_METHOD. If a caller requires initialization but got transformed, it fails with SIGSEGV as static fields are null. If a called method is invoked by reflection or can be invoked externally, it can't be transformed. m_class_has_cctor checks if the caller requires no initialization, while mono_aot_can_specialize checks if the called method isn't called externally or by using reflection.

Does that make sense?

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@kotlarmilos kotlarmilos Mar 1, 2023 •
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Actually it might be good to add it to is_direct_callable.

char *name = mono_aot_get_mangled_method_name (cmethod);
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@vargaz vargaz Mar 2, 2023

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Looked into why this was not enabled before, and i don't think this is going to work. The callee method might use GOT slots etc. which are not initialized if the method is directly called. So before this can be enabled, the AOTed code needs to be changed to init itself, the same way the llvm compiled code does.

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@kotlarmilos kotlarmilos Mar 3, 2023

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Good point! Let's first try to enable method initialization during the invocation before proceeding with this and other direct call transformations.

mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_AOT, "DIRECT CALL: %s by %s", name, method ? mono_method_full_name (method, TRUE) : "");
g_free (name);
Expand All @@ -6603,7 +6601,6 @@ emit_and_reloc_code (MonoAotCompile *acfg, MonoMethod *method, guint8 *code, gui
patch_info->type = MONO_PATCH_INFO_NONE;
acfg->stats.direct_calls ++;
}
#endif
}

acfg->stats.all_calls ++;
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