Use a switch statement to select the search function instead of an
indirect function call. This results in a sizable performance win.
This PR is a modification of the approach taken in PR #2828.
When I measured performance for that commit, it was neutral.
However, I now see a performance regression on gcc, but still
neutral on clang. I'm measuring on the same platform, but with
newer compilers. The new approach beats both the current dev
branch and the baseline before PR #2828 was merged.
This PR is necessary for Issue #3275, to update zstd in the kernel.
Without this PR there is a large regression in greedy - btlazy2
compression speed. With this PR it is about neutral.
gcc version: 12.2.0
clang version: 14.0.6
dataset: silesia.tar
| Compiler | Level | Dev Speed (MB/s) | PR Speed (MB/s) | Delta |
|----------|-------|------------------|-----------------|--------|
| gcc | 5 | 102.6 | 113.7 | +10.8% |
| gcc | 7 | 66.6 | 74.8 | +12.3% |
| gcc | 9 | 51.5 | 58.9 | +14.3% |
| gcc | 13 | 14.3 | 14.3 | +0.0% |
| clang | 5 | 108.1 | 114.8 | +6.2% |
| clang | 7 | 68.5 | 72.3 | +5.5% |
| clang | 9 | 53.2 | 56.2 | +5.6% |
| clang | 13 | 14.3 | 14.7 | +2.8% |
The binary size stays just about the same for clang and gcc, measured
using the `size` command:
| Compiler | Branch | Text | Data | BSS | Total |
|----------|--------|---------|------|-----|---------|
| gcc | dev | 1127950 | 3312 | 280 | 1131542 |
| gcc | PR | 1123422 | 2512 | 280 | 1126214 |
| clang | dev | 1046254 | 3256 | 216 | 1049726 |
| clang | PR | 1048198 | 2296 | 216 | 1050710 |
since this is effectively what is stored in this field (== matchLength - MINMATCH).
This makes it clearer what needs to be done when reading from / writing to this field.
This saves some 1.7Kb in rodata section (x86_64, zstd tool),
while assembler code stays the same except
the type of a few load/extend instructions.
Should not have negative performance implications.
no idea why visual + clang-cl + appveyor don't like them,
I've not been able to reproduce the issue locally,
but these static assert are very unlikely to deliver a useful signal,
I can't imagine a situation where they will be wrong,
and if they are, then a ton of other things will be broken way before reaching that point.
Move portability macros to `lib/common/portability_macros.h`. This file
only contains platform/feature detection (e.g. 0/1 macros). This file is
shared between C and ASM code, so it cannot include any C code.
Rename `HUF_` ASM macros to be `ZSTD_` prefixed, and move to the new
header.
Restrict `ZSTD_ASM_SUPPORTED` to `__GNUC__`, because we need the GAS
assembler.
Finally, only include the ASM code if we are actually going to use it.
This disables it on all Windows platforms, which should resolve the
problem brought up in Issue #2789.
because mem.h is dropped in the Linux kernel.
Changed macro definition order (gcc/clang/msvc before c11)
due to a limitation in the kernel source builder.
Changed the backup to sizeof(),
reverting to previous behavior when no support of alignof() is detected.
short-tests-0 were silently failing. I think because of the && make clean construction. Switch to ; instead.
Also fix all the test failures that were exposed.
`make all` is failing on CircleCI because it is missing Docker. Move that test
to GitHub actions, and switch the pedantic CircleCI test to `make allmost`.
* When dynamic dispatching to bmi2 add lzcnt and bmi to the
TARGET_ATTRIBUTE.
* Centralize the bmi2 TARGET_ATTRIBUTE definition to
BMI2_TARGET_ATTRIBUTE so we can change it in the future.
* Only enable bmi2 when both bmi1 & bmi2 are supported. There shouldn't
be any cases where bmi2 is supported but bmi1 isn't. But, since we are
using the instruction we should check bmi1 as well.
Switch to a macro `ZSTD_FALLTHROUGH;` instead of a comment. On supported
compilers this uses an attribute, otherwise it becomes a comment.
This is necessary to be compatible with clang's `-Wfall-through`, and
gcc's `-Wfall-through=2` which don't support comments. Without this the
linux build emits a bunch of warnings.
Also add a test to CI to ensure that we don't regress.
* Add a Huffman round trip fuzzer
* Fix two minor bugs in Huffman that aren't exposed in zstd
- Incorrect weight comparison (weights are allowed to be equal to
table log).
- HUF_compress1X_usingCTable_internal() can return compressed
size >= source size, so the assert that `cSize <= 65535` isn't
correct, and it needs to be checked instead.
Nick Terrell