When using a new enough CMake (3.15+) prefer to use the
`MSVC_RUNTIME_LIBRARY` property on targets to select the runtime library
variant. This property is automatically set to the value specified by
`CMAKE_MSVC_RUNTIME_LIBRARY`. This property requires that the CMake
Policy 91 is set to new (see CMP0091).
The primary motivation for this change is to avoid referring to the
`upb_msglayout` object when we are trying to fetch the `upb_msglayout`
object for a sub-message. This will help pave the way for parsing
extensions. We also implement several optimizations so that we can
make this change without regressing performance.
Normally we compute the layout for a sub-message field like so:
```
const upb_msglayout *get_submsg_layout(
const upb_msglayout *layout,
const upb_msglayout_field *field) {
return layout->submsgs[field->submsg_index]
}
```
The reason for this indirection is to avoid storing a pointer directly
in `upb_msglayout_field`, as this would double its size (from 12 to 24
bytes on 64-bit architectures) which is wasteful as this pointer is
only needed for message typed fields.
However `get_submsg_layout` as written above does not work for
extensions, as they will not have entries in the message's
`layout->submsgs` array by nature, and we want to avoid creating
an entire fake `upb_msglayout` for each such extension since that
would also be wasteful.
This change removes the dependency on `upb_msglayout` by passing down
the `submsgs` array instead:
```
const upb_msglayout *get_submsg_layout(
const upb_msglayout *const *submsgs,
const upb_msglayout_field *field) {
return submsgs[field->submsg_index]
}
```
This will pave the way for parsing extensions, as we can more easily
create an alternative `submsgs` array for extension fields without
extra overhead or waste.
Along the way several optimizations presented themselves that allow
a nice increase in performance:
1. Passing the parsed `wireval` by address instead of by value ended
up avoiding an expensive and useless stack copy (this is on Clang,
which was used for all measurements).
2. When field numbers are densely packed, we can find a field by number
with a single indexed lookup instead of linear search. At codegen
time we can compute the maximum field number that will allow such
an indexed lookup.
3. For fields that do require linear search, we can start the linear
search at the location where we found the previous field, taking
advantage of the fact that field numbers are generally increasing.
4. When the hasbit index is less than 32 (the common case) we can use
a less expensive code sequence to set it.
5. We check for the hasbit case before the oneof case, as optional
fields are more common than oneof fields.
Benchmark results indicate a 20% improvement in parse speed with a
small code size increase:
```
name old time/op new time/op delta
ArenaOneAlloc 21.3ns ± 0% 21.5ns ± 0% +0.96% (p=0.000 n=12+12)
ArenaInitialBlockOneAlloc 6.32ns ± 0% 6.32ns ± 0% +0.03% (p=0.000 n=12+10)
LoadDescriptor_Upb 53.5µs ± 1% 51.5µs ± 2% -3.70% (p=0.000 n=12+12)
LoadAdsDescriptor_Upb 2.78ms ± 2% 2.68ms ± 0% -3.57% (p=0.000 n=12+12)
LoadDescriptor_Proto2 240µs ± 0% 240µs ± 0% +0.12% (p=0.001 n=12+12)
LoadAdsDescriptor_Proto2 12.8ms ± 0% 12.7ms ± 0% -1.15% (p=0.000 n=12+10)
Parse_Upb_FileDesc<UseArena,Copy> 13.2µs ± 2% 10.7µs ± 0% -18.49% (p=0.000 n=10+12)
Parse_Upb_FileDesc<UseArena,Alias> 11.3µs ± 0% 9.6µs ± 0% -15.11% (p=0.000 n=12+11)
Parse_Upb_FileDesc<InitBlock,Copy> 12.7µs ± 0% 10.3µs ± 0% -19.00% (p=0.000 n=10+12)
Parse_Upb_FileDesc<InitBlock,Alias> 10.9µs ± 0% 9.2µs ± 0% -15.82% (p=0.000 n=12+12)
Parse_Proto2<FileDesc,NoArena,Copy> 29.4µs ± 0% 29.5µs ± 0% +0.61% (p=0.000 n=12+12)
Parse_Proto2<FileDesc,UseArena,Copy> 20.7µs ± 2% 20.6µs ± 2% ~ (p=0.260 n=12+11)
Parse_Proto2<FileDesc,InitBlock,Copy> 16.7µs ± 1% 16.7µs ± 0% -0.25% (p=0.036 n=12+10)
Parse_Proto2<FileDescSV,InitBlock,Alias> 16.5µs ± 0% 16.5µs ± 0% +0.20% (p=0.016 n=12+11)
SerializeDescriptor_Proto2 5.30µs ± 1% 5.36µs ± 1% +1.09% (p=0.000 n=12+11)
SerializeDescriptor_Upb 12.9µs ± 0% 13.0µs ± 0% +0.90% (p=0.000 n=12+11)
FILE SIZE VM SIZE
-------------- --------------
+1.5% +176 +1.6% +176 upb/decode.c
+1.8% +176 +1.9% +176 decode_msg
+0.4% +64 +0.4% +64 upb/def.c
+1.4% +64 +1.4% +64 _upb_symtab_addfile
+1.2% +48 +1.4% +48 upb/reflection.c
+15% +32 +18% +32 upb_msg_set
+2.9% +16 +3.1% +16 upb_msg_mutable
-9.3% -288 [ = ] 0 [Unmapped]
[ = ] 0 +0.2% +288 TOTAL
```
This change refactors util::Status to have a similar shape as the
recently open-sourced absl::Status. This will allow Protobuf to
eventually use absl::Status and reduce the codesize.
Note that there is more work required before absl::Status can be used.
This is useful for Conan recipes that build Protobuf, in which
whatever we want to enable has to be enabled in the initial command line.
Without this, the people maintaining the recipe have to patch the CMake
setup of Protobuf before building the binaries.
Closes#5541
This is useful for Conan recipes that build Protobuf, in which
whatever we want to enable has to be enabled in the initial command line.
Without this, the people maintaining the recipe have to patch the CMake
setup of Protobuf before building the binaries.
Closes#5541
Unfortunately a few of the Clang warnings did not have easy fixes:
../../../../ext/google/protobuf_c/ruby-upb.c: In function ‘fastdecode_err’:
../../../../ext/google/protobuf_c/ruby-upb.c:353:13: warning: function might be candidate for attribute ‘noreturn’ [-Wsuggest-attribute=noreturn]
353 | const char *fastdecode_err(upb_decstate *d) {
| ^~~~~~~~~~~~~~
../../../../ext/google/protobuf_c/ruby-upb.c: In function ‘_upb_decode’:
../../../../ext/google/protobuf_c/ruby-upb.c:867:30: warning: argument ‘buf’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Wclobbered]
867 | bool _upb_decode(const char *buf, size_t size, void *msg,
I even tried to suppress the first error, but it still shows up.
Bo Yang
Joshua Haberman
Adam Cozzette
Saleem Abdulrasool
Jorge López Fueyo
Deanna Garcia
Yannic Bonenberger
Florian Simon
Igor Sirotin
Anton Danielsson
deannagarcia
Rosen Penev
Biswapriyo Nath
Tongliang Liao