Yes, I guess you are right. It is is probably very code-dependent, and
for raw C code LTO have a lot more sense than for complex C++ code with
crazy template magic.
Le 28/02/2020 à 12:16, Floh a écrit :
When I last tested I generally saw quite noticeable improvements for
inlined code (which LTO does across compilation units). Most of my
code is straight C without inline functions in headers. I guess this
scenario benefits more from LTO than typical C++ code where usually a
lot of implementation code sits in inline/template functions (at the
cost of increasing compile time for each compilation unit, versus
increasing link-time once for LTO).
I think it depends extremely on the code base at hand whether LTO is
useful or not :)
On Friday, 28 February 2020 11:32:09 UTC+1, Gabriel CV wrote:
Glad to!
By the way, I don't find that LTO brings any performance
improvements compared to a non-LTO builds (on latests Emscripten
backend). Maybe +1% at most (more probably benchmark noise to me),
but sometime more than 10% worse, and at the expense of a
*significant *link time increase and *significant *binary size
increase!
So I am not sure this is really an interesting option anymore...
Le 28/02/2020 à 11:14, Floh a écrit :
Whoops, thanks for making me aware of WASM_OBJECT_FILES being 1
by default... I've been building with LTO all the time (since the
asm.js days) and was expecting that the WASM backend would behave
identically there.
-Floh.
On Friday, 28 February 2020 10:07:11 UTC+1, Gabriel CV wrote:
Hi,
Try to remove --llvm-lto 3, as it might increase binary size
significantly when combined with -O2 or -O3 (and I am not
sure it is very usefull without using -DWASM_OBJECT_FILES=0)
Le 28/02/2020 à 08:12, Rohit Saini a écrit :
Hi All,
Previously we were using 1.38.28 emscripten version.
Recently we updated to latest llvm backend 1.39.7. But with
new backend there is drastic increase in wasm size. Size of
my side modules become almost double and size of my main
module also increased from 2.7mb to almost 4mb. Firstly we
are compiling to object files then we are linking them to
make wasm. Below are the flags I am passing while compiling
and linking. Is this size increase intentional or do I have
to change compiling or linking flags someway.
Compiling flags for main module:
-Oz -fPIC
-s DISABLE_EXCEPTION_CATCHING=0 -Wno-builtin-macro-redefined
-Wno-dollar-in-identifier-extension
Compiling flags for side module:
-std=c++14 -fPIC
Linking flags for main module:
-O3 -s EVAL_CTORS=0 --closure
0 -s ALIASING_FUNCTION_POINTERS=0 -s ELIMINATE_DUPLICATE_FUNCTIONS=1 -s
ELIMINATE_DUPLICATE_FUNCTIONS_PASSES=12 --llvm-lto 3 -s
FORCE_FILESYSTEM=1 -s ERROR_ON_UNDEFINED_SYMBOLS=0 -s
'EXTRA_EXPORTED_RUNTIME_METHODS=["getTempRet0","setTempRet0", "cwrap"]' -s
[email protected]
-s DISABLE_EXCEPTION_CATCHING=2 -s
[email protected]
Linking flags for side module:
-s SIDE_MODULE=1 -s WASM=1 -Oz -s EVAL_CTORS=0 --closure 0
-s ALIASING_FUNCTION_POINTERS=0 -s
ELIMINATE_DUPLICATE_FUNCTIONS=1 -s
ELIMINATE_DUPLICATE_FUNCTIONS_PASSES=12 --llvm-lto 3 -s
ERROR_ON_UNDEFINED_SYMBOLS=0
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