On 2015/09/08 09:41:59, rmcilroy wrote:
> I am not an owner of anything in this CL, but I am happy to
> offer my thoughts
> ...
Sure, but Orion is not a committer yet and I need a committer stamp :).
Your
thoughts are much appreciated!
https://codereview.chromium.org/1308693014/diff/1/src/interpreter/bytecode-generator.cc
File src/interpreter/bytecode-generator.cc (right):
https://codereview.chromium.org/1308693014/diff/1/src/interpreter/bytecode-generator.cc#newcode50
src/interpreter/bytecode-generator.cc:50: if
(!builder_.HasExplicitReturn()) {
On 2015/09/08 08:25:10, Michael Starzinger wrote:
> This looks dangerous. Depending on how control flow is modeled there
could
very
> well be a case where the last instruction in the byte-code stream is a
return
> statement, but it is not guaranteed post-dominate all executions paths.
Consider
> the following ...
>
> function f(a) {
> if (a) { return 23; }
> }
Good point, we need to take this into account, but we would need to take
this
into account once we start adding control flow in any case since the if
block
will need to jump to an actual bytecode, and the bytecode array builder
will
need to back-patch the jump instruction with the target of the jump.
The last thing the bytecode-generator would do in the graph above would
be to
try and back-patch the if jump to target the next bytecode which is to be
emitted. Since that bytecode doesn't exist yet we could easily spot in the
bytecode-array-builder that there is a jump instruction which is patched
to a
non-existent bytecode (e.g., just having a field tracking the greatest
bytecode
indice which was patched into a jump instruction and check if that is
greater-than/equal than bytecodes_.size()), and add that to the
HasExplicitReturn conditions? WDYT?
An alternative would be to append "Ldar undefined; return" in
ToBytecodeArray
and add a comment that this needs to be addressed in the soon to start flow
control activity.
As long as we have a clear comment either way, in the near term, then lgtm.
https://codereview.chromium.org/1308693014/
--
--
v8-dev mailing list
[email protected]
http://groups.google.com/group/v8-dev
---
You received this message because you are subscribed to the Google Groups "v8-dev" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/d/optout.
