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Move most of SequenceWriter::write_item to non-generic functions

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The size of LLVM IR for the `style` crate is reduced by ~1.5% (27k lines out of 1.8M)

CC https://github.com/servo/servo/issues/26713
This commit is contained in:
Simon Sapin 2020-06-02 19:51:28 +02:00
parent c4ea4b1d77
commit 4d0a9d8e91
1 changed files with 43 additions and 25 deletions
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68
components/style_traits/values.rs
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@ -197,33 +197,51 @@ where
where where
F: FnOnce(&mut CssWriter<'b, W>) -> fmt::Result, F: FnOnce(&mut CssWriter<'b, W>) -> fmt::Result,
{ {
let old_prefix = self.inner.prefix; // Separate non-generic functions so that this code is not repeated
if old_prefix.is_none() { // in every monomorphization with a different type `F` or `W`.
// If there is no prefix in the inner writer, a previous // https://github.com/servo/servo/issues/26713
// call to this method produced output, which means we need fn before(
// to write the separator next time we produce output again. prefix: &mut Option<&'static str>,
self.inner.prefix = Some(self.separator); separator: &'static str,
) -> Option<&'static str> {
let old_prefix = *prefix;
if old_prefix.is_none() {
// If there is no prefix in the inner writer, a previous
// call to this method produced output, which means we need
// to write the separator next time we produce output again.
*prefix = Some(separator);
}
old_prefix
} }
fn after(
old_prefix: Option<&'static str>,
prefix: &mut Option<&'static str>,
separator: &'static str,
) {
match (old_prefix, *prefix) {
(_, None) => {
// This call produced output and cleaned up after itself.
},
(None, Some(p)) => {
// Some previous call to `item` produced output,
// but this one did not, prefix should be the same as
// the one we set.
debug_assert_eq!(separator, p);
// We clean up here even though it's not necessary just
// to be able to do all these assertion checks.
*prefix = None;
},
(Some(old), Some(new)) => {
// No previous call to `item` produced output, and this one
// either.
debug_assert_eq!(old, new);
},
}
}
let old_prefix = before(&mut self.inner.prefix, self.separator);
f(self.inner)?; f(self.inner)?;
match (old_prefix, self.inner.prefix) { after(old_prefix, &mut self.inner.prefix, self.separator);
(_, None) => {
// This call produced output and cleaned up after itself.
},
(None, Some(p)) => {
// Some previous call to `item` produced output,
// but this one did not, prefix should be the same as
// the one we set.
debug_assert_eq!(self.separator, p);
// We clean up here even though it's not necessary just
// to be able to do all these assertion checks.
self.inner.prefix = None;
},
(Some(old), Some(new)) => {
// No previous call to `item` produced output, and this one
// either.
debug_assert_eq!(old, new);
},
}
Ok(()) Ok(())
} }