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[doc] add more switch docs

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teoxoy
2022-12-09 12:37:27 +01:00
committed by Jim Blandy
parent 63e85b4b15
commit 5a1f43d12d
2 changed files with 24 additions and 1 deletions
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24
src/back/hlsl/writer.rs
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@@ -1835,6 +1835,12 @@ impl<'a, W: fmt::Write> super::Writer<'a, W> {
}
}
// The new block is not only stylistic, it plays a role here:
// We might end up having to write the same case body
// multiple times due to FXC not supporting fallthrough.
// Therefore, some `Expression`s written by `Statement::Emit`
// will end up having the same name (`_expr<handle_index>`).
// So we need to put each case in its own scope.
let write_block_braces = !(case.fall_through && case.body.is_empty());
if write_block_braces {
writeln!(self.out, " {{")?;
@@ -1842,7 +1848,23 @@ impl<'a, W: fmt::Write> super::Writer<'a, W> {
writeln!(self.out)?;
}
// FXC doesn't support fallthrough so we duplicate the body of the following case blocks
// Although FXC does support a series of case clauses before
// a block[^yes], it does not support fallthrough from a
// non-empty case block to the next[^no]. If this case has a
// non-empty body with a fallthrough, emulate that by
// duplicating the bodies of all the cases it would fall
// into as extensions of this case's own body. This makes
// the HLSL output potentially quadratic in the size of the
// Naga IR.
//
// [^yes]: ```hlsl
// case 1:
// case 2: do_stuff()
// ```
// [^no]: ```hlsl
// case 1: do_this();
// case 2: do_that();
// ```
if case.fall_through && !case.body.is_empty() {
let curr_len = i + 1;
let end_case_idx = curr_len

1
src/back/spv/block.rs
View File

@@ -1687,6 +1687,7 @@ impl<'w> BlockContext<'w> {
let mut raw_cases = Vec::with_capacity(cases.len());
let mut case_ids = Vec::with_capacity(cases.len());
for case in cases.iter() {
// take id of previous empty fall-through case or generate a new one
let label_id = last_id.take().unwrap_or_else(|| self.gen_id());
if case.fall_through && case.body.is_empty() {