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Rollup merge of #142934 - nnethercote:tweak-macro-stats, r=petrochenkov

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Tweak `-Zmacro-stats` measurement.

It currently reports net size, i.e. size(output) - size(input). After some use I think this is sub-optimal, and it's better to just report size(output). Because for derive macros the input size is always 1, and for attribute macros it's almost always 1.

r? ```@petrochenkov```
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Jubilee 2025-06-24 19:45:33 -07:00 committed by GitHub
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4 changed files with 34 additions and 42 deletions
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26
compiler/rustc_expand/src/stats.rs
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@ -15,15 +15,11 @@ pub struct MacroStat {
/// Number of uses of the macro.
pub uses: usize,
/// Net increase in number of lines of code (when pretty-printed), i.e.
/// `lines(output) - lines(invocation)`. Can be negative because a macro
/// output may be smaller than the invocation.
pub lines: isize,
/// Number of lines of code (when pretty-printed).
pub lines: usize,
/// Net increase in number of lines of code (when pretty-printed), i.e.
/// `bytes(output) - bytes(invocation)`. Can be negative because a macro
/// output may be smaller than the invocation.
pub bytes: isize,
/// Number of bytes of code (when pretty-printed).
pub bytes: usize,
}
pub(crate) fn elems_to_string<T>(elems: &SmallVec<[T; 1]>, f: impl Fn(&T) -> String) -> String {
@ -131,16 +127,12 @@ pub(crate) fn update_macro_stats(
input: &str,
fragment: &AstFragment,
) {
fn lines_and_bytes(s: &str) -> (usize, usize) {
(s.trim_end().split('\n').count(), s.len())
}
// Measure the size of the output by pretty-printing it and counting
// the lines and bytes.
let name = Symbol::intern(&pprust::path_to_string(path));
let output = fragment.to_string();
let (in_l, in_b) = lines_and_bytes(input);
let (out_l, out_b) = lines_and_bytes(&output);
let num_lines = output.trim_end().split('\n').count();
let num_bytes = output.len();
// This code is useful for debugging `-Zmacro-stats`. For every
// invocation it prints the full input and output.
@ -157,7 +149,7 @@ pub(crate) fn update_macro_stats(
{name}: [{crate_name}] ({fragment_kind:?}) {span}\n\
-------------------------------\n\
{input}\n\
-- ({in_l} lines, {in_b} bytes) --> ({out_l} lines, {out_b} bytes) --\n\
-- {num_lines} lines, {num_bytes} bytes --\n\
{output}\n\
"
);
@ -166,6 +158,6 @@ pub(crate) fn update_macro_stats(
// The recorded size is the difference between the input and the output.
let entry = ecx.macro_stats.entry((name, macro_kind)).or_insert(MacroStat::default());
entry.uses += 1;
entry.lines += out_l as isize - in_l as isize;
entry.bytes += out_b as isize - in_b as isize;
entry.lines += num_lines;
entry.bytes += num_bytes;
}

4
compiler/rustc_interface/src/passes.rs
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@ -355,9 +355,9 @@ fn print_macro_stats(ecx: &ExtCtxt<'_>) {
"{prefix} {:<name_w$}{:>uses_w$}{:>lines_w$}{:>avg_lines_w$}{:>bytes_w$}{:>avg_bytes_w$}",
name,
thousands::usize_with_underscores(uses),
thousands::isize_with_underscores(lines),
thousands::usize_with_underscores(lines),
thousands::f64p1_with_underscores(avg_lines),
thousands::isize_with_underscores(bytes),
thousands::usize_with_underscores(bytes),
thousands::f64p1_with_underscores(avg_bytes),
);
}

6
src/doc/unstable-book/src/compiler-flags/macro-stats.md
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@ -10,12 +10,12 @@ generated code is normally invisible to the programmer.
This flag helps identify such cases. When enabled, the compiler measures the
effect on code size of all used macros and prints a table summarizing that
effect. For each distinct macro, it counts how many times it is used, and the
net effect on code size (in terms of lines of code, and bytes of code). The
effect. For each distinct macro, it counts how many times it is used, and how
much code it produces when expanded (in lines of code, and bytes of code). The
code size evaluation uses the compiler's internal pretty-printing, and so will
be independent of the formatting in the original code.
Note that the net effect of a macro may be negative. E.g. the `cfg!` and
Note that the output size of a macro may be zero. E.g. the `cfg!` and
`#[test]` macros often strip out code.
If a macro is identified as causing a large increase in code size, it is worth

40
tests/ui/stats/macro-stats.stderr
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@ -2,25 +2,25 @@ macro-stats ====================================================================
macro-stats MACRO EXPANSION STATS: macro_stats
macro-stats Macro Name Uses Lines Avg Lines Bytes Avg Bytes
macro-stats -----------------------------------------------------------------------------------
macro-stats #[derive(Clone)] 8 56 7.0 1_660 207.5
macro-stats #[derive(PartialOrd)] 1 16 16.0 654 654.0
macro-stats #[derive(Hash)] 2 15 7.5 547 273.5
macro-stats #[derive(Ord)] 1 14 14.0 489 489.0
macro-stats q! 1 24 24.0 435 435.0
macro-stats #[derive(Default)] 2 14 7.0 367 183.5
macro-stats #[derive(Eq)] 1 10 10.0 312 312.0
macro-stats #[derive(Debug)] 1 7 7.0 261 261.0
macro-stats #[derive(PartialEq)] 1 8 8.0 247 247.0
macro-stats #[derive(Copy)] 1 1 1.0 46 46.0
macro-stats p! 1 2 2.0 28 28.0
macro-stats trait_impl_tys! 1 1 1.0 11 11.0
macro-stats foreign_item! 1 0 0.0 6 6.0
macro-stats impl_const! 1 0 0.0 4 4.0
macro-stats trait_tys! 1 1 1.0 3 3.0
macro-stats u32! 1 0 0.0 -3 -3.0
macro-stats none! 1 0 0.0 -3 -3.0
macro-stats n99! 2 0 0.0 -8 -4.0
macro-stats #[derive(Clone)] 8 64 8.0 1_788 223.5
macro-stats #[derive(PartialOrd)] 1 17 17.0 675 675.0
macro-stats #[derive(Hash)] 2 17 8.5 577 288.5
macro-stats q! 1 26 26.0 519 519.0
macro-stats #[derive(Ord)] 1 15 15.0 503 503.0
macro-stats #[derive(Default)] 2 16 8.0 403 201.5
macro-stats #[derive(Eq)] 1 11 11.0 325 325.0
macro-stats #[derive(Debug)] 1 8 8.0 277 277.0
macro-stats #[derive(PartialEq)] 1 9 9.0 267 267.0
macro-stats #[derive(Copy)] 1 2 2.0 61 61.0
macro-stats p! 1 3 3.0 32 32.0
macro-stats trait_impl_tys! 1 2 2.0 28 28.0
macro-stats foreign_item! 1 1 1.0 21 21.0
macro-stats this_is_a_really_really_long_macro_name!
macro-stats 1 0 0.0 -30 -30.0
macro-stats #[test] 1 -6 -6.0 -158 -158.0
macro-stats 1 1 1.0 18 18.0
macro-stats impl_const! 1 1 1.0 17 17.0
macro-stats trait_tys! 1 2 2.0 15 15.0
macro-stats n99! 2 2 1.0 4 2.0
macro-stats none! 1 1 1.0 4 4.0
macro-stats u32! 1 1 1.0 3 3.0
macro-stats #[test] 1 1 1.0 0 0.0
macro-stats ===================================================================================