Method infer_function

crates/rustc_codegen_spirv/src/linker/specializer.rs:652–694

Perform inference across the entire definition of `func`, including all the instructions in its body, and either store the resulting `Replacements` in its `Generic` (if `func` is "generic"), or return them otherwise.

(&mut self, func: &Function)

    /// the instructions in its body, and either store the resulting `Replacements`
    /// in its `Generic` (if `func` is "generic"), or return them otherwise.
    fn infer_function(&mut self, func: &Function) -> Option<Replacements> {
        let func_id = func.def_id().unwrap();

        let param_count = self
            .generics
            .get(&func_id)
            .map_or(0, |generic| generic.param_count);

        let (param_values, replacements) = {
            let mut infer_cx = InferCx::new(self);
            infer_cx.instantiate_function(func);

            // FIXME(eddyb) dedup this with `collect_generics`.
            let param_values = infer_cx.infer_var_values[..param_count as usize]
                .iter()
                .map(|v| v.map_var(|InferVar(i)| Param(i)));
            // Only allocate `param_values` if they constrain parameters.
            let param_values = if param_values.clone().any(|v| v != Value::Unknown) {
                Some(param_values.collect())
            } else {
                None
            };

            (
                param_values,
                infer_cx.into_replacements(..Param(param_count)),
            )
        };

        if let Some(generic) = self.generics.get_mut(&func_id) {
            // All constraints `func` could have from `collect_generics`
            // would have to come from its `OpTypeFunction`, but types don't have
            // internal constraints like e.g. `OpConstant*` and `OpVariable` do.
            assert!(generic.param_values.is_none());

            generic.param_values = param_values;
            generic.replacements = replacements;

            None
        } else {
            Some(replacements)
        }
    }
}

/// Newtype'd inference variable index.