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Fix timing of expression evaluation in blocks #337

Merged
merged 5 commits into from
Oct 26, 2016
Merged

Fix timing of expression evaluation in blocks #337

merged 5 commits into from
Oct 26, 2016

Commits on Oct 25, 2016

  1. Fix timing of expression evaluation in blocks 

    This commit fixes a compiler bug where certain built-in syntaxes would
re-evaluate its arguments when the block's assertion causes a re-entry
into the append VM, instead of reusing the argument references that were
created the first time.

In practice, this is observable when a "stateful helper" is used as an
argument to a syntax with an assertion (currently `#if`, `#unless`,
`#with`, `#each`, `partial`, `InElementSyntax` and dynamic components).

Because the argument references are created every time, any state stored
on the original instance of the helper will be observably wiped away
when used as an argument to an asserting block helper. Of course, it is
also observable by comparing the JavaScript identity of the helper in
question over time.

This commit fixes the compiler bug by moving the evaluation of the
expressions passed as arguments to the block syntaxes in question above
the `Try` block, and capturing the relevant registers (args and operand,
which store the results of evaluating the arguments) so they can be
restored when the append VM is re-entered for the same block.
    @chancancode
    Godhuda authored and chancancode committed Oct 25, 2016
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  2. Move test opcode out of stored blocks 

    The `condition` register is now saved and restored, like the operand
and args registers.
    @chancancode
    Godhuda authored and chancancode committed Oct 25, 2016
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  3. Improve {{partial}} implementation 

    This commit:

Switched partials to use the new opcode building style.

Moved the evaluation of the test opcode, and the production of the
condition register, outside of the block that could be re-entered. This
means that when the expression passed to a {{partial expr}} becomes
invalidated, we no longer generate a brand new reference for the
to-boolean operation on the operand (which produces the condition).
    @chancancode
    Godhuda authored and chancancode committed Oct 25, 2016
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  4. Improve encapsulation of captured VM state 

    Previously, the code that captured and restored VM state manually
captured a few registers and manually restored them.

This commit puts the Frame in charge of capturing and restoring, which
means that if we want to capture more registers in the future, it will
be easy to remember to update the restoring code at the same time.
    @chancancode
    Godhuda authored and chancancode committed Oct 25, 2016
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  5. Fix lazy deopt to have the right captured state 

    Now that we capture the conditional register, we have to also simulate
that effect when we lazily deopt (since we are essentially doing an OSR)
    @chancancode
    Godhuda authored and chancancode committed Oct 25, 2016
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