diff options
| author |  Abseil Team <absl-team@google.com> | 2024-01-04 13:14:50 -0800 |
|---|---|---|
| committer |  Copybara-Service <copybara-worker@google.com> | 2024-01-04 13:15:44 -0800 |
| commit | d5a2cec006d14c6801ddeb768bf2574a1cf4fa7f (patch) | |
| tree | 3dc1ffb00d164ddda4c22b8abfc42594db1fa2da /absl/base | |
| parent | ccf0c7730db976d2b7814e74f6f01d044ae6f853 (diff) | |
Optimize integer-to-string conversions
The updated code is designed to:
- Be branch-predictor-friendly
- Be cache-friendly
- Minimize the lengths of critical paths
- Minimize slow operations (particularly multiplications)
- Minimize binary/codegen bloat
The most notable performance trick here is perhaps the precomputation & caching of the number of digits, so that we can reuse/exploit it when writing the output.
This precomputation of the exact length enables 2 further performance benefits:
- It makes `StrCat` and `StrAppend` zero-copy when only integers are passed, by avoiding intermediate `AlphaNum` entirely in those cases. If needed in the future, we can probably also make many other mixtures of non-integer types zero-copy as well.
- It avoids over-reservation of the string buffer, allowing for more strings to fit inside SSO, which will likely have further performance benefits.
There is also a side benefit of preventing `FastIntToBuffer` from writing beyond the end of the buffer, which has caused buffer overflows in the past.
The new code continues to use & extend some of the existing core tricks (such as the division-by-100 trick), as those are already efficient.
PiperOrigin-RevId: 595785531
Change-Id: Id6920e7e038fec10b2c45f213de75dc7e2cbddd1
Diffstat (limited to 'absl/base')
| -rw-r--r-- | absl/base/macros.h | 12 |
1 files changed, 0 insertions, 12 deletions
diff --git a/absl/base/macros.h b/absl/base/macros.h index cd7cf498..f33cd192 100644 --- a/absl/base/macros.h +++ b/absl/base/macros.h @@ -138,16 +138,4 @@ ABSL_NAMESPACE_END #define ABSL_INTERNAL_RETHROW do {} while (false) #endif // ABSL_HAVE_EXCEPTIONS -// Requires the compiler to prove that the size of the given object is at least -// the expected amount. -#if ABSL_HAVE_ATTRIBUTE(diagnose_if) && ABSL_HAVE_BUILTIN(__builtin_object_size) -#define ABSL_INTERNAL_NEED_MIN_SIZE(Obj, N) \ - __attribute__((diagnose_if(__builtin_object_size(Obj, 0) < N, \ - "object size provably too small " \ - "(this would corrupt memory)", \ - "error"))) -#else -#define ABSL_INTERNAL_NEED_MIN_SIZE(Obj, N) -#endif - #endif // ABSL_BASE_MACROS_H_ |