Because enabling ThinLTO makes some constructor functions not called
in arm64 executables.
Bug: 295944813
Test: build
Change-Id: Ic0cab5fd80aa86d0d9ca1131564b747a445c6e46
Reduce the import instr limit from the LLVM default (100) to 40. This
helps reduce the binary size as well as improving performance slightly.
Size:
Default(100) 40 30
libhwui.so 11059040 11058912 11060872
libart.so 10697576 10697160 10696568
Performance:
40 vs. default: 0.37% improvement
http://go/art-benchmark?p=BootImageProfileId:36054
30 vs. default: 0.36% improvement
http://go/art-benchmark?p=BootImageProfileId:36058
Test: presubmit
Change-Id: Id800ff7818cde908daab784bac0a312c6a71272d
Build C/C++ targets with ThinLTO with "--lto-O0" by default. This takes
advantage of better dead code elimination and CFG simplification due to
ThinLTO's global view of the program, but do not enable the costly LTO
optimizations. This also makes builds faster because we can avoid doing
codegen for the dead code.
Code size for panther-userdebug:
/system/bin /system/lib /system/lib64
Original 57648 86264 181700
Global ThinLTO 55764 84916 175728
-3.27% -1.56% -3.29%
Build time for aosp_arm64-userdebug:
clang time linker time
Original 56993.87s 1712.36s
Global ThinLTO 52839.18s 3114.93s
saving 4.68% build time in total.
Bug: 169004486
Test: presubmit
Change-Id: Idb0f4675ca4750b8b12b24f4679579419d3448c8
This option is unsupported on the MacOS ld used in Android, leading to
compilation errors when LTO is enabled for binaries.
In particular the error includes:
```
ld64.lld: error: unknown argument '-plugin-opt'
ld64.lld: error: unknown argument '-import-instr-limit=5'
```
Test: m libc++ on a Mac OS machine
Bug: 288983988
Change-Id: I1873e0a77777832f833f211beb42633d462f04d5
We removed Full LTO support, now LTO is a binary choice. This allows us
to greatly simplify the LTO propagation logic.
Test: m
Test: GLBOAL_THINLTO=true m
Bug: 169004486
Change-Id: Ie4e453d7518c7069a7c755734dab1e776c16e656
We do not have any more projects directly depending on Full LTO (except
CFI which manages their own LTO flags), remove full LTO support from the
build system.
Test: presubmit
Bug: 169004486
Change-Id: I8d6b7999d716158b5d8fe34b2f197653d7bae8dd
Building for riscv64 fails with link errors on __thread variables.
Set -fno-emulated-tls to fix it.
Bug: 254713216
Test: lunch aosp_riscv64-userdebug && m ALLOW_MISSING_DEPENDENCIES=true ndk_sysroot
Change-Id: I3dca81dfd277d681b6c868a5e8385e3a37335a5f
Building with LTO and CFI enabled for riscv64 causes link failures:
ld.lld: error: lto.tmp: cannot link object files with different floating-point ABI
ld.lld: error: undefined symbol: guard variable for android::hardware::BufferedTextOutput::getBuffer() const::ts
Disable them for now.
Test: lunch aosp_riscv64-userdebug && m ALLOW_MISSING_DEPENDENCIES=true ndk_sysroot
Change-Id: I3489952abebeeb3f4de664fd3e436232aac298d7
Tests are not shipped, no need to spend extra CPU cycles optimising them
during build.
Test: GLOBAL_THINLTO=true m
Bug: 169004486
Change-Id: I66ede9c01d43b574a7fe9f74f0bc6ba97f51be06
This reverts commit b90ff82772.
All the breakages are now fixed or mitigated.
Bug: 169004486
Change-Id: Ibec4b1f0a50c5ef6769bc6916a81721a4ce03c60
Test: presubmit
Apply ThinLTO without optimization (--lto-O0) globally. This saves us
2.24% in binary size for system/lib64, as well as more than 4.68% build
time improvement.
Test: presubmit
Bug: 169004486
Change-Id: I1ed90c2058f9ff1fa8a2d3fd7ac1191c5d98dac1
Due to the lack of engineering efforts into LP32 targets, do not enable
global ThinLTO for them by default.
Test: presubmit
Bug: 169004486
Change-Id: I79b77baecf16fda95ff5dccc5a401596a0557d5d
On second thought, this is actually counter-productive rather than an
optimisation. LTOing test code is usually quite cheap, however since
tests can pull in additional static libraries (e.g. to set up test
environment), we will have to create non-LTO variants for these
dependent libraries, which can be much more expensive.
This reverts commit 85d7297318.
Bug: 195134194
Bug: 203737712
Change-Id: I1a105136075133a5b5895d00847d8796c419964c
Test: m GLOBAL_THINLTO=true dist device-tests platform_tests
There's not a great return on investment for spending additional
compilation/link time on tests that may only be run once or very few
times (as compared to actual library code that ships and is run orders
of magnitude more times).
Bug: 195134194
Bug: 203737712
Test: m GLOBAL_THINLTO=true dist device-tests platform_tests
Change-Id: I7149c4140f7c52b22bedbe322f1bf2c81f7ad66b
Instead of making everything into ThinLTO variant by default (it works
but many Soong tests don't like this, and got bit rot due to lack of
active builder for this configuration), let the default option be
ThinLTO and no LTO be a special variant.
Test: m GLOBAL_THINLTO=true
Test: m
Bug: 195134194
Change-Id: I2fd98061ba55eba1fdfdd056fb2f8c2051fd2553
With global ThinLTO enabled, vndk version has different symbol ordering
from the platform version. Opt out any binaries that has vndk enabled as
a temporary workaround.
Test: GLOBAL_THINLTO=true m
Bug: 169217596
Change-Id: I75b060cbe6c74421d283c6dfbd669af20f466d1f
For global ThinLTO, don't implicitly turn on LTO for static libraries,
but instead rely on mutator to generate correct variants.
Bug: 169004486
Test: GLBOAL_THINLTO=true m
Change-Id: I9cdeea706ec6dd4ad31f55b9e12a96b42176aa89
Experimental global ThinLTO mode for compilation time evaluation.
Bug: 169004486
Test: GLBOAL_THINLTO=true m
Change-Id: I2ff06397be8b65c7972f1e5f09ab1496949567ee
We previously disabled inlining and unrolling completely during ThinLTO
in absense of PGO profile. For global ThinLTO, we want to better balance
binary size and performance.
We evaluated a number of combination of heuristics with global ThinLTO
configuration:
binary size change
no LTO baseline
no inline, no unroll -0.54%
no inline, unroll -0.50%
import-instr-limit=5, unroll +0.02%
import-instr-limit=10, unroll +0.13%
Loop unrolling does not contribute much to the binary size, therefore
it is re-enabled.
import-instr-limit=5 balances the binary size savings from ThinLTO and
size incrase due to additional optimisation.
Bug: 78485207
Bug: 169004486
Test: TreeHugger
Change-Id: I1c21153605e2ae42daa8857b06e27c081ee8ad85
-fwhole-program-vtables cflag requires LTO to be enabled. Some projects
add this flag unconditionally, breaking builds that turn off LTO.
Make this an LTO property so that build system will handle adding the
flag when LTO is on.
Test: build
Bug: 169004486
Change-Id: Ifce12c09e1d6b8c2807314c3bb982b076efcaaa4
The implementation before libraryDependencyTag was added failed to
treat the libgcc_unwind dependency as a static library when traversing
dependencies for LTO because it didn't handle staticUnwinderDepTag.
Bug: 162437057
Test: m checkbuild
Change-Id: Iccc96c0daa0379f51eb975c51fd5e8c507a0daba
dependencyTag uses a set of predefined tags to identify different types
of dependencies. There are already multiple bits of metadata stored
in the dependency tag (Library, Shared, ReexportFlags), and supporting
them all requires a combinatorial explosion of predefined tags and
causes issues when using equality comparisons if a new bit of metadata
is added.
Add a new libraryDependencyTag type that will contain the metadata
bits, and replace the quality comparisons with checks on the metadata
bits.
There are 5 TODOs where modifying the checks identified problems with
the existing checks. These were left in place to produce identical
build output and will be fixed separately.
Bug: 162437057
Test: no change to build.ninja or {Android,make_vars,late}-${TARGET_PRODUCT}.mk
Change-Id: I72d4207dcf381c07c92e00e5a03968ebb5ed8d30
Native compiler flags are currently applied in approximately:
global cflags
local cflags
local include dirs
global include dirs
global conlyflags
local conlyflags
global cppflags
local cppflags
This means that a flag that is enabled in the global cppflags
cannot be disabled in the local cflags, and an Android.bp author
must know to disable it in the local cppflags. A better order
would be:
global cflags
global conlyflags
global cppflags
local cflags
local conlyflags
local cppflags
local include dirs
global include dirs
We are mixing both the global and local cflags into a single
variable, and similar for conlyflags and cppflags, which
prevents reordering them. This CL prepares to reorder them
by splitting the global and local cflags into separate variables.
Bug: 143713277
Test: m native
Change-Id: Ic55a8c3516c331dc5f2af9d00e59ceca9d3e6c15
Adds an interface, CcLinkableInterface, for cc linkable dependencies
which come from other toolchains such as Rust.
Bug: 140726209
Test: Soong tests pass, rust modules still compile.
Change-Id: I7378a46fad94fd0b735746aaf4e265fd2c2c04d8
Bug: 131771163
LTO is currently broken when building with SANITIZE_TARGET=fuzzer. The
compiler bug is currently being addressed upstream (see linked bug), but
we have applied a local workaround in the build system to disable LTO
when building using the fuzzer config.
There is a bug here however. In the sanitizer mutator we explicitly
remove -flto and add -fno-lto. The sanitizer mutator runs after the LTO
mutator, so (in general) this works just fine. The problem exists when a
target specifies an explicit 'lto: { ... }' flag in their Android.bp. In
this case, the sanitizer mutator disables LTO, then the flags are parsed
from the Android.bp, re-enabling LTO.
This patch fixes this issue. If the sanitizer mutator has added the
-fsanitize=fuzzer-no-link flags, then the LTO mutator won't add the LTO
flags after this fact.
Test: Build a target with SANITIZE_TARGET=fuzzer (or a cc_fuzz target),
where there is an explitiy 'lto: { ... }' and watch it now succeed in
building.
Change-Id: I6643909417f666539c23469816926b806e204b06
