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| author | thepudds <thepudds1460@gmail.com> | 2025-04-02 17:23:24 -0400 |
|---|---|---|
| committer | Gopher Robot <gobot@golang.org> | 2025-04-03 12:24:34 -0700 |
| commit | ab2926291ba7003dcec7f46824d5f58c344ca849 (patch) | |
| tree | 03d52928f31cf2789f8a75b4332a94eebf8b9d3f /src/testing | |
| parent | ce94e916fe262a51c398153b03dd9a657418bbe8 (diff) | |
| download | go-ab2926291ba7003dcec7f46824d5f58c344ca849.tar.xz | |
testing: clarify how B.Loop avoids optimizing away all the useful work
As discussed in #73137, we want to clarify the description of how
B.Loop avoids surprising optimizations, while also hinting that
the exact approach might change in the future.
Updates #73137
Change-Id: I8536540cd5d79804a47fba8cd6eec3821864309d
Reviewed-on: https://go-review.googlesource.com/c/go/+/662356
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Auto-Submit: Alan Donovan <adonovan@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
Diffstat (limited to 'src/testing')
| -rw-r--r-- | src/testing/benchmark.go | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/src/testing/benchmark.go b/src/testing/benchmark.go index 3c898f1453..43c7dc18f4 100644 --- a/src/testing/benchmark.go +++ b/src/testing/benchmark.go @@ -477,12 +477,13 @@ func (b *B) loopSlowPath() bool { // toward the benchmark measurement. Likewise, when it returns false, it stops // the timer so cleanup code is not measured. // -// The compiler never optimizes away calls to functions within the body of a -// "for b.Loop() { ... }" loop. This prevents surprises that can otherwise occur -// if the compiler determines that the result of a benchmarked function is -// unused. The loop condition must be written in exactly as "b.Loop()", and this -// only applies to calls syntactically between the curly braces of the loop. -// Optimizations are performed as usual in any functions called by the loop. +// Within the body of a "for b.Loop() { ... }" loop, arguments to and +// results from function calls within the loop are kept alive, preventing +// the compiler from fully optimizing away the loop body. Currently, this is +// implemented by disabling inlining of functions called in a b.Loop loop. +// This applies only to calls syntactically between the curly braces of the loop, +// and the loop condition must be written exactly as "b.Loop()". Optimizations +// are performed as usual in any functions called by the loop. // // After Loop returns false, b.N contains the total number of iterations that // ran, so the benchmark may use b.N to compute other average metrics. |