* Start to implement optimization pipeline with new pass manager for LLVM15
* Set default to use legacy passmanager.
Co-authored-by: james <jamesragray@bitbucket.org>
* Newly require `-link-defaultlib-shared` for implicit dllimport.
E.g., this enables to compile druntime DLL with `-fvisibility=public`
for pure exports and no (local) imports (such as builtin TypeInfos).
* `-link-defaultlib-shared` alone now only implicitly imports symbols
from druntime/Phobos.
This simplifies building complex DLLs linked against a bunch of
static libs (dub only supports static lib dependencies!); the static
libs don't need to be compiled with `-fvisibility=public` anymore
(if the DLL itself isn't either), `-link-defaultlib-shared` is
sufficient.
This is mainly useful for existing DLLs with explicit exports, to make
them link against *shared* druntime/Phobos and so end up with a single
druntime/Phobos for the whole process.
* Add MSan compiler-rt library to LDC install and add it to linkerline for --fsanitize=memory
* MSan: Add support for `-fsanitize-memory-track-origins=`
References to dllimported globals in static data initializers lead to
undefined-symbol linker errors. We need to resolve the indirection
manually at runtime.
I went with an extra LLVM pass for Windows targets when using
`-fvisibility=public`, and scanning the initializers of all global
variables (well, only thread-global ones). The problematic pointers in
the initializers are nullified and initialized at runtime early via a
CRT constructor (working with -betterC as well).
People use `dflags "-enable-cross-module-inlining" platform="ldc"`
in their dub.sdl files; default and debug builds without -O thus
incur a superfluous compile-time cost for no benefit.
Which supports more cmdline options in the meantime than what we have
been supporting manually, and should be future-proof, similar to
InitTargetOptionsFromCodeGenFlags().
Attributes are only set if explicitly specified in the cmdline (and not
already present in the function's existing attributes).
This started out as a workaround for not being able to determine whether
the user has explicitly set -frame-pointer in the cmdline with LLVM 11,
and ended with having to touch more than I wanted. An *enabled*
-ffast-math flag (from us, not LLVM) overriding LLVM's
-enable-unsafe-fp-math, but e.g. -ffast-math=false NOT overriding was/is
one of the quirks.
By letting LLVM set up the inlining params (taking into account
`-inline-threshold`) instead of hardcoding them.
The old hardcoded thresholds were identical to the LLVM 3.9 defaults, but
they changed in LLVM 4.0:
* optLevel > 2: 275 => 250
* -Os: 75 => 50
* -Oz: 25 => 5
Apparently also fixes issue #2161.
Simplify LDMD quite a bit by translating the few different command-line
options directly in-place. This puts some more stress onto LDC's
command-line parsing, especially due to multiple occurrences of a single
Boolean option (e.g., '-o-') or mixtures of `-m64` and `-m32` etc. for
dmd-testsuite.
Also add new command-line option `-verrors-spec` showing gagged errors
(DMD's equivalent is `-verrors=<spec|limit>`) and sync the usage text with
DMD. LDMD now also recognizes `-h` (and `/?` on Windows).
Add the commandline options -fprofile-instr-generate[=filename] and -profile-instr-use=filename
-fprofile-instr-generate
-- Add instrumentation on branches, switches, and function entry; uses LLVM's InstrProf pass.
-- Link to profile runtime that writes instrumentation counters to a file.
-fprofile-instr-use
-- Read profile data from a file and apply branch weights to branches and switches, and annotate functions with entrycount in LLVM IR.
-- Functions with low or high entrycount are marked with 'cold' or 'inlinehint'.
The only statement type without PGO yet is "try-finally".
A new pragma, `pragma(LDC_profile_instr, [ true | false ])`, is added to selectively disable/enable instrumentation of functions (granularity = whole functions).
The runtime library ldc-profile-rt is a copy of LLVM compiler-rt lib/profile. It has to be exactly in-sync with the LLVM version, and thus we need a copy for each PGO-supported LLVM (>=3.7).
import ldc.profile for a D interface to ldc-profile-rt (for example to reset execution counts after a program startup phase).
The instrumentation data is mainly passed on to LLVM: function-entry counts and branch counts/probabilities. LDC marks functions as hot when "execution count is 30% of the maximum function execution count", and marks functions as cold if their count is 1% of maximum function execution count.
The source of LLVM's llvm-profdata tool is hereby included in LDCs repository (different source for each LLVM version), and the binary is included in the install bin folder.
The executable is named "ldc-profdata" to avoid clashing with llvm-profdata on the same machine. This is needed because profdata executable has to be in-sync with the LLVM version used to build LDC.
Maintenance burden: for trunk LLVM, we have to keep ldc-profile-rt and llvm-profdata in sync. There is no diff with upstream; but because of active development there are the occasional API changes.
