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Diffstat (limited to 'lib/README.md')
| -rw-r--r-- | lib/README.md | 20 |
1 files changed, 14 insertions, 6 deletions
diff --git a/lib/README.md b/lib/README.md index 707d777..3653c81 100644 --- a/lib/README.md +++ b/lib/README.md @@ -46,11 +46,11 @@ and `LZ4F_PUBLISH_STATIC_FUNCTIONS`. #### Build macros -The following build macro can be selected at compilation time : +The following build macro can be selected to adjust source code behavior at compilation time : -- `LZ4_FAST_DEC_LOOP` : this triggers the optimized decompression loop. - This loops works great on x86/x64 cpus, and is automatically enabled on this platform. - It's possible to enable or disable it manually, by passing `LZ4_FAST_DEC_LOOP=1` or `0` to the preprocessor. +- `LZ4_FAST_DEC_LOOP` : this triggers a speed optimized decompression loop, more powerful on modern cpus. + This loop works great on x86, x64 and aarch64 cpus, and is automatically enabled for them. + It's also possible to enable or disable it manually, by passing `LZ4_FAST_DEC_LOOP=1` or `0` to the preprocessor. For example, with `gcc` : `-DLZ4_FAST_DEC_LOOP=1`, and with `make` : `CPPFLAGS+=-DLZ4_FAST_DEC_LOOP=1 make lz4`. @@ -66,9 +66,17 @@ The following build macro can be selected at compilation time : Should this be a problem, it's generally possible to make the compiler ignore these warnings, for example with `-Wno-deprecated-declarations` on `gcc`, or `_CRT_SECURE_NO_WARNINGS` for Visual Studio. - Another method is to define `LZ4_DISABLE_DEPRECATE_WARNINGS` + Another project-specific method is to define `LZ4_DISABLE_DEPRECATE_WARNINGS` before including the LZ4 header files. +- `LZ4_FORCE_SW_BITCOUNT` : by default, the compression algorithm tries to determine lengths + by using bitcount instructions, generally implemented as fast single instructions in many cpus. + In case the target cpus doesn't support it, or compiler intrinsic doesn't work, or feature bad performance, + it's possible to use an optimized software path instead. + This is achieved by setting this build macros . + In most cases, it's not expected to be necessary, + but it can be legitimately considered for less common platforms. + #### Amalgamation @@ -103,7 +111,7 @@ The compiled executable will require LZ4 DLL which is available at `dll\liblz4.d #### Miscellaneous -Other files present in the directory are not source code. There are : +Other files present in the directory are not source code. They are : - `LICENSE` : contains the BSD license text - `Makefile` : `make` script to compile and install lz4 library (static and dynamic) |