the new contracts seems to make more sense :
updateRep() updates an array of repeat offsets _in place_,
while newRep() generates a new structure with the updated repeat-offset array.
Most callers are actually expecting the in-place variant,
and a limited sub-section, in `zstd_opt.c` mainly, prefer `newRep()`.
this meant to abstract the sumtype representation required
to transfert `offcode` to `ZSTD_storeSeq()`.
Unfortunately, the sumtype numeric representation is currently a leaky abstraction
that has permeated many other parts of the code,
especially within `zstd_lazy.c` and also within `zstd_opt.c` and `zstd_compress.c`.
While this PR makes a good job a transfering a large nb of call sites
to using the new macros, there are still a few sites where this transformation is more complex,
or where the numeric representation itself it used "as is".
One of the problematics area is the decision to use the numeric format of the sumtype
within the match finders of `zstd_lazy`.
This commit doesn't change the behavior, it only introduces and employes the macros,
but eventually the resulting code remains identical.
At target, if the numeric representation of the sumtype can be completely abstracted
and no other part of the code depends on it,
it will be possible to move it towards something slightly more efficient.
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.
* 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.
Previously, if an index was equal to `reducerValue + 1`, it would get remapped
during index reduction to 1 i.e. `ZSTD_DUBT_UNSORTED_MARK`. This can affect the
parsing of the input slightly, by causing tree nodes to be nullified when they
otherwise wouldn't be. This hardly matters from a correctness or efficiency
perspective, but it does impact determinism.
So this commit changes index reduction to avoid mapping indices to collide with
`ZSTD_DUBT_UNSORTED_MARK`.
that's clearer than finding the tables somewhere in the middle of `compress.c`.
Also, down the line, it may potentially allows zstd to feature adjusted tables depending on target cpu.
There is no minimum value check, so the parameter could be negative.
Switch to the standard pattern of using `BOUNDCHECK()`.
The bug was reported by Dan Carpenter and found by Smatch static
checker.
https://lore.kernel.org/all/20211008063704.GA5370@kili/
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.
This new setup is slighly better on `silesia.tar` :
Ratio : 3.649 -> 3.655
Speed : 11.9 MB/s -> 12.2 MB/s
At the cost of more memory : 24 MB -> 32 MB
The new memory budget is a reasonable interpolation between neighboring levels 12 and 14:
level 12 : 24 MB
level 13 : 32 MB (increased from 24 MB)
level 14 : 48 MB
Window size remains unaffected (4 MB)
* The block splitter missed a bounds check, so when the buffer is too small it
passes an erroneously large size to `ZSTD_entropyCompressSeqStore()`, which
can then write the compressed data past the end of the buffer. This is a new
regression in v1.5.0 when the block splitter is enabled. It is either enabled
explicitly, or implicitly when using the optimal parser and `ZSTD_compress2()`
or `ZSTD_compressStream*()`.
* `HUF_writeCTable_wksp()` omits a bounds check when calling
`HUF_compressWeights()`. If it is called with `dstCapacity == 0` it will pass
an erroneously large size to `HUF_compressWeights()`, which can then write
past the end of the buffer. This bug has been present for ages. However, I
believe that zstd cannot trigger the bug, because it never calls
`HUF_compress*()` with `dstCapacity == 0` because of [this check][1].
Credit to: Oss-Fuzz
[1]: https://github.com/facebook/zstd/blob/89127e5ee2f3c1e141668fa6d4ee91245f05d132/lib/compress/zstd_compress_literals.c#L100
* Flatten ZSTD_row_getMatchMask
* Remove the SIMD abstraction layer.
* Add big endian support.
* Align `hashTags` within `tagRow` to a 16-byte boundary.
* Switch SSE2 to use aligned reads.
* Optimize scalar path using SWAR.
* Optimize neon path for `n == 32`
* Work around minor clang issue for NEON (https://bugs.llvm.org/show_bug.cgi?id=49577)
* replace memcpy with MEM_readST
* silence alignment warnings
* fix neon casts
* Update zstd_lazy.c
* unify simd preprocessor detection (#3)
* remove duplicate asserts
* tweak rotates
* improve endian detection
* add cast
there is a fun little catch-22 with gcc: result from pmovmskb has to be cast to uint32_t to avoid a zero-extension
but must be uint16_t to get gcc to generate a rotate instruction..
* more casts
* fix casts
better work-around for the (bogus) warning: unary minus on unsigned
Even with -fvisibility=hidden added to CFLAGS, any symbol which is
given a default visibility attribute ends up exported in the dynamic
library. This happens through zstd_internal.h which defines
..._STATIC_LINKING_ONLY before including various header files, and is
included for example in lib/common/pool.c.
To avoid this, this patch distinguishes static and non-static APIs, by
using ZSTDLIB_API only for the latter, and introducing
ZSTDLIB_STATIC_API for the former. For now, both are exported, but
non-static APIs can be hidden by overriding the definition
ZSTDLIB_STATIC_API. lib/Makefile is modified to allow this using
make CPPFLAGS_DYNLIB=-DZSTDLIB_STATIC_API=ZSTDLIB_HIDDEN
In addition, API declarations are dropped from zstd_compress.c (they
aren't needed there).
Signed-off-by: Stephen Kitt <steve@sk2.org>
Call `ZSTD_enforceMaxDist()` before each block with the beginning of the
block. This ensures that `lowLimit` is updated to `dictLimit` whenever
the ext-dict is out of range, so we can use prefix mode for speed.
This can cause non-determinism because prefix mode and ext-dict mode
match finders can return different results. It can also hurt speed
because ext-dict match finders are slower.
The scenario is:
1. Compress large data with a dictionary.
2. The dictionary goes out of bounds, so we invalidate it.
3. However, we still have `lowLimit < dictLimit`, since it is
never updated.
4. We will call the ext-dict match finder instead of the prefix one.
This flag forces zstd to always load the prefix in ext-dict mode, even
if it happens to be contiguous, to force determinism. It also applies to
dictionaries that are re-processed.
A determinism test case is also added, which fails without
`ZSTD_c_deterministicRefPrefix` and passes with it set.
Question: Should this be the default behavior? It isn't in this PR.
Yann Collet