jameysharp opened PR #4764 from box-testname
to main
:
Following up on discussion in #4667, here's a way to avoid making sweeping changes while still using reasonable names in filetests. @afonso360, how does this look to you? @cfallin, do the numbers here sound okay to you?
In order to keep the
ExternalName
enum small, theTestcaseName
struct was limited to 17 bytes: a 1 byte length and a 16 byte buffer. Due to alignment, that madeExternalName
20 bytes.That fixed-size buffer means that the names of functions in Cranelift filetests are truncated to fit, which limits our ability to give tests meaningful names. And I think meaningful names are important in tests.
This patch replaces the inline
TestcaseName
buffer with a heap-allocated slice. We don't care about performance for test names, so an indirection out to the heap is fine in that case. But we do care somewhat about the size ofExternalName
when it's used during compiles.On 64-bit systems,
Box<[u8]>
is 16 bytes, soTestcaseName
gets one byte smaller. Unfortunately, its alignment is 8 bytes, soExternalName
grows from 20 to 24 bytes.According to
valgrind --tool=dhat
, this change has very little effect on compiler performance. Building wasmtime with--no-default-features --release
, and compiling the pulldown-cmark benchmark from Sightglass, I measured these differences betweenmain
and this patch:
- total number of allocations didn't change (
ExternalName::TestCase
is not used in normal compiles)- 592 more bytes allocated over the process lifetime, out of 171.5MiB
- 320 more bytes allocated at peak heap size, out of 12MiB
- 0.24% more instructions executed
- 16,987 more bytes written
- 12,120 _fewer_ bytes read
jameysharp requested cfallin for a review on PR #4764.
cfallin submitted PR review.
jameysharp merged PR #4764.
Last updated: Dec 23 2024 at 12:05 UTC