Generate simple code for "trivial" conversions

Generate simple code for "trivial" conversions

A trivial conversion is defined as one that cannot throw an exception,
and thus need no v8::TryCatch or ExceptionState, and no "did it succeed?"
check after the conversion.

For such conversions, generate the code

  Type variable = convertedValue()

instead of

  TONATIVE_VOID(Type, variable, convertedValue())

Also include all such conversions in the set of argument conversions that
don't require a v8::TryCatch, since they then no longer do.

BUG=413257
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=181897

[Jens Widell, 2014-09-12 10:28:57]

jl@opera.com changed reviewers:
+ haraken@chromium.org

[Jens Widell, 2014-09-12 10:28:57]

PTAL

Alternative approaches are possible. We could for instance introduce a
TONATIVE_TRIVIAL() macro. As long as that macro simply expands to the code this
patch generates, I think we might as well skip the macro, though.

One idea I've had is to add some exception handling assertions in the form of

  #define V8_ERROR_HANDLING_SCOPE() \
    v8::TryCatch block; \
    V8RethrowTryCatchScope rethrow(block)

and

  #define V8_ERROR_HANDLING_CHECK() \
    ASSERT(!block.HasCaught())

(both expanding to nothing if not ENABLE(ASSERT), of course.)

We would then have V8_ERROR_HANDLING_SCOPE() at the beginning of each function,
and V8_ERROR_HANDLING_CHECK() at every return point at which we don't knowingly
throw an exception.

If we then had a TONATIVE_TRIVIAL() macro, we could also add
V8_ERROR_HANDLING_CHECK() to it, thus making sure no supposedly trivial
conversion actually ended up throwing an exception.

[haraken, 2014-09-12 11:45:45]

On 2014/09/12 10:28:57, Jens Widell wrote:
> PTAL
> 
> Alternative approaches are possible. We could for instance introduce a
> TONATIVE_TRIVIAL() macro. As long as that macro simply expands to the code
this
> patch generates, I think we might as well skip the macro, though.
> 
> One idea I've had is to add some exception handling assertions in the form of
> 
>   #define V8_ERROR_HANDLING_SCOPE() \
>     v8::TryCatch block; \
>     V8RethrowTryCatchScope rethrow(block)
> 
> and
> 
>   #define V8_ERROR_HANDLING_CHECK() \
>     ASSERT(!block.HasCaught())
> 
> (both expanding to nothing if not ENABLE(ASSERT), of course.)
> 
> We would then have V8_ERROR_HANDLING_SCOPE() at the beginning of each
function,
> and V8_ERROR_HANDLING_CHECK() at every return point at which we don't
knowingly
> throw an exception.
> 
> If we then had a TONATIVE_TRIVIAL() macro, we could also add
> V8_ERROR_HANDLING_CHECK() to it, thus making sure no supposedly trivial
> conversion actually ended up throwing an exception.

Personally I'd prefer not using macros for readability.

LGTM for the patch set 1.

[Jens Widell, 2014-09-12 11:52:41]

The CQ bit was checked by jl@opera.com

[commit-bot: I haz the power, 2014-09-12 11:53:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/564063002/20001

[commit-bot: I haz the power, 2014-09-12 12:57:31]

Committed patchset #2 (id:20001) as 181897