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Rollup merge of #69158 - ecstatic-morse:graphviz-diff, r=matthewjasper

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Don't print block exit state in dataflow graphviz if unchanged

A small quality-of-life improvement I was using while working on #68528. It's pretty common to have a lot of zero-statement basic blocks, especially before a `SimplifyCfg` pass is run. When the dataflow state was dense, these blocks could take up a lot of vertical space since the full flow state was printed on both entry and exit. After this PR, we only print a block's exit state if it differs from that block's entry state. Take a look at the two basic blocks on the left.

Before:

![image](https://user-images.githubusercontent.com/29463364/74505395-e2d1dd00-4eab-11ea-8006-ec8f0dc9d1b6.png)

After:
![image](https://user-images.githubusercontent.com/29463364/74505277-98506080-4eab-11ea-8d95-5190bc378331.png)
This commit is contained in:
Yuki Okushi 2020-02-17 13:46:54 +09:00 • committed by GitHub
commit 50ddda6949
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1 changed files with 34 additions and 19 deletions
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53
src/librustc_mir/dataflow/generic/graphviz.rs
View file

@ -195,6 +195,8 @@ where
// C: Entry state
self.bg = Background::Light;
self.results.seek_to_block_start(block);
let block_entry_state = self.results.get().clone();
self.write_row_with_full_state(w, "", "(on entry)")?;
// D: Statement transfer functions
@ -213,29 +215,42 @@ where
self.write_row_for_location(w, "T", &terminator_str, terminator_loc)?;
// F: Exit state
// Write the full dataflow state immediately after the terminator if it differs from the
// state at block entry.
self.results.seek_after(terminator_loc);
if let mir::TerminatorKind::Call { destination: Some(_), .. } = &terminator.kind {
self.write_row_with_full_state(w, "", "(on unwind)")?;
if self.results.get() != &block_entry_state {
let after_terminator_name = match terminator.kind {
mir::TerminatorKind::Call { destination: Some(_), .. } => "(on unwind)",
_ => "(on exit)",
};
let num_state_columns = self.num_state_columns();
self.write_row(w, "", "(on successful return)", |this, w, fmt| {
write!(
w,
r#"<td balign="left" colspan="{colspan}" {fmt} align="left">"#,
colspan = num_state_columns,
fmt = fmt,
)?;
let state_on_unwind = this.results.get().clone();
this.results.seek_after_assume_call_returns(terminator_loc);
write_diff(w, this.results.analysis(), &state_on_unwind, this.results.get())?;
write!(w, "</td>")
})?;
} else {
self.write_row_with_full_state(w, "", "(on exit)")?;
self.write_row_with_full_state(w, "", after_terminator_name)?;
}
// Write any changes caused by terminator-specific effects
match terminator.kind {
mir::TerminatorKind::Call { destination: Some(_), .. } => {
let num_state_columns = self.num_state_columns();
self.write_row(w, "", "(on successful return)", |this, w, fmt| {
write!(
w,
r#"<td balign="left" colspan="{colspan}" {fmt} align="left">"#,
colspan = num_state_columns,
fmt = fmt,
)?;
let state_on_unwind = this.results.get().clone();
this.results.seek_after_assume_call_returns(terminator_loc);
write_diff(w, this.results.analysis(), &state_on_unwind, this.results.get())?;
write!(w, "</td>")
})?;
}
_ => {}
};
write!(w, "</table>")
}