compiler: better handling for mutated locals in funargs.

Instead of the conservative strategy in compiler comp-var of
loading variables into t-registers, and relying on optimization
to remove them, let's just go back to the old way: variables
are just registers. For function calls, we can detect mutated
variables and generate the conservative code.

* stdlib/compiler.tl (frag): New slots vbin and alt-oreg.
When a variable access is compiled, the binding is recorded
in vbin, and the desired output register in alt-oreg.
(simplify-var-spy): New struct type, used for detecting
mutated lexical variables when we compile a function argument
list.
(compiler comp-var): Revert to the old compilation strategy
for lexicals: the code fragment is empty, and the output
register is just the v-reg. However, we record the variable
binding and remember the caller's desired register in the
new frag fields.
(compiler comp-setq): Also revert the strategy here.
Here we get our frag from a recursive compilation, so
we just annotate it.
(compiler comp-call-impl): Use the simplify-var-spy to
obtain a list of the lexical variables that were mutated.
This is used for rewriting the frags, if necessary.
(handle-mutated-var-args): New function. If the mutated-vars
list is non-empty, it rewrites the frag list. Every element
in the frag which is a compiled reference to a lexical
variable which is mutated over the evaluation of the arg list
is substituted with a conservative frag which loads the
variable into a temporary register. That register thus
samples the value of the variable at the correct point in the
left-to-right evaluation, so the function is called with
the correct values.

0 files changed, 0 insertions, 0 deletions