[PATCH] D54166: [AST] Store the string data in StringLiteral in a trailing array of chars

[John McCall via Phabricator via cfe-commits]

rjmccall added a comment.

In https://reviews.llvm.org/D54166#1299149, @riccibruno wrote:

> In https://reviews.llvm.org/D54166#1298889, @rjmccall wrote:
>
> > IIRC, abbreviations just silently don't take effect if the record doesn't conform; so things will appear to work, but the size on disk will be bigger.
>
>
> I looked at where the abbreviations are defined, and it seems that the only abbreviations for
>  statements/expressions are for `DeclRefExpr`, `IntegerLiteral`, `CharacterLiteral`
>  and `ImplicitCastExpr` (grep for `EmitAbbrev` in `Serialization/`,
>  for some reasons they are emitted in `WriteDeclAbbrev()`...).
>
> And indeed changing the serialization format of `CharacterLiteral` triggers various assertions
>  because of the abbreviation. Therefore unless I am missing something no other statement/expression
>  has currently an abbreviation. I suspect therefore that someone could go wild and cut the on-disk
>  size of the serialization format significantly here.
>
> I looked at the size of the generated pch for all of Boost, and I am only seeing an increase of
>  about 8k, which is entirely attributable to the fact that I am adding one field to the serialization
>  format. I can rework it to remove this additional field if needed.


If you're generally interested in improving build times, working on the serialization format would probably be really valuable.  We don't generally insist on a zero-regressions policy in other commits, though.


Repository:
  rC Clang

https://reviews.llvm.org/D54166