It was switched from a function pointer to std::function in
TableGen: Make 2nd arg MainFn of TableGenMain(argv0, MainFn) optional.
f675ec6165ab6add5e57cd43a2e9fa1a9bc21d81
but there's no mention of any particular reason for that.
Reduces memory usage compiling backend sources, most notably for
AMDGPU by ~98 MB per source on average.
AMDGPUGenRegisterInfo.inc is tens of megabytes in size now, and
is even larger downstream. At the same time, it is included in
nearly all backend sources, typically just for a small portion of
its content, resulting in compilation being unnecessarily
memory-hungry, which in turn stresses buildbots and wastes their
resources.
Splitting .inc files also helps avoiding extra ccache misses
where changes in .td files don't cause changes in all parts of
what previously was a single .inc file.
It is thought that rather than building on top of the current
single-output-file design of TableGen, e.g., using `split-file`,
it would be more preferable to recognise the need for multi-file
outputs and give it a proper first-class support directly in
TableGen.
This mainly transitions the LLVM intrinsic string table from character
emission to string literal emission, which I confirmed happens for me
locally.
I moved the guts of StringToOffsetTable to a cpp file so I could move
the `EmitLongStrLiterals` cl::opt global to a non-vague linkage home in
the `TableGen` library. I had to add missing FormatVariadic.h includes
to account for moving other includes to a cpp file.
All the sources of `llvm-min-tblgen` are also used for `llvm-tblgen`,
with identical compilation flags. Reuse the object files of
`llvm-min-tblgen` for `llvm-tblgen` by applying the usual source
structure of an executable: One file per executable which named after
the executable name containing the (in this case trivial) main function,
which just calls the tblgen_main in TableGen.cpp. This should also clear
up any confusion (including mine) of where each executable's main
function is.
While this slightly reduces build time, the main motivation is ccache.
Using the hard_link
option, building the object files for `llvm-tblgen` will result in a
hard link to the same object file already used for `llvm-min-tblgen`. To
signal the build system that the file is new, ccache will update the
file's time stamp. Unfortunately, time stamps are shared between all
hard-linked files s.t. this will indirectly also update the time stamps
for the object files used for `llvm-tblgen`. At the next run, Ninja will
recognize this time stamp discrepancy to the expected stamp recorded in
`.ninja_log` and rebuild those object files for `llvm-min-tblgen`, which
again will also update the stamp for the `llvm-tblgen`... . This is
especially annoying for tablegen because it means Ninja will re-run all
tablegenning in every build.
I am using the hard_link option because it reduces the cost of having
multiple build-trees of the LLVM sources and reduces the wear to the SSD
they are stored on.
This reverts commit f6cb56902c6dcafede21eb6662910b6ff661fc0f.
Buildbot failures such as https://lab.llvm.org/buildbot/#/builders/89/builds/13541:
```
/usr/bin/ld: utils/TableGen/Basic/CMakeFiles/obj.LLVMTableGenBasic.dir/ARMTargetDefEmitter.cpp.o: undefined reference to symbol '_ZN4llvm23EnableABIBreakingChecksE'
/usr/bin/ld: /home/tcwg-buildbot/worker/flang-aarch64-libcxx/build/./lib/libLLVMSupport.so.20.0git: error adding symbols: DSO missing from command line
```
Going to investigate.
All the sources of `llvm-min-tblgen` are also used for `llvm-tblgen`,
with identical compilation flags. Reuse the object files of
`llvm-min-tblgen` for `llvm-tblgen` by applying the usual source
structure of an executable: One file per executable which named after
the executable name containing the (in this case trivial) main function,
which just calls the tblgen_main in TableGen.cpp. This should also clear
up any confusion (including mine) of where each executable's main
function is.
While this slightly reduces build time, the main motivation is ccache.
Using the hard_link
option, building the object files for `llvm-tblgen` will result in a
hard link to the same object file already used for `llvm-min-tblgen`. To
signal the build system that the file is new, ccache will update the
file's time stamp. Unfortunately, time stamps are shared between all
hard-linked files s.t. this will indirectly also update the time stamps
for the object files used for `llvm-tblgen`. At the next run, Ninja will
recognize this time stamp discrepancy to the expected stamp recorded in
`.ninja_log` and rebuild those object files for `llvm-min-tblgen`, which
again will also update the stamp for the `llvm-tblgen`... . This is
especially annoying for tablegen because it means Ninja will re-run all
tablegenning in every build.
I am using the hard_link option because it reduces the cost of having
multiple build-trees of the LLVM sources and reduces the wear to the SSD
they are stored on.
