[llvm-dev] Understanding LLVM Optimization (Rpass=inline)
praveen via llvm-dev
llvm-dev at lists.llvm.org
Mon Sep 3 11:20:03 PDT 2018
Dear LLVM community :-)
I'm a novice in compiler principles and optimization, I'm currently
working with some example code to see what && how LLVM optimization is
doing to generate good machine code. While working I find some
functions are being inlined by llvm and some are not, but I don't know
the internals of optimization so I can't able to figure the reasons and
rationale behind them.
For example:
struct value{
int set(){} // Function does nothing!
};
void foo () {} // Function does nothing!
void func( ) {
value obj;
obj.set();
foo();
}
Compiling with command "clang++ -O2 -std=c++11
-stdlib=libc++/__//_*-Rpass=inline*_/ name.cpp prints
only obj.set() was inlined but not foo(). I don't understand the
rationale behind this (both are empty functions right ?). Why LLVM not
inlining the function "foo" ?
Could you please share some pointers (videos or blogs) which explains
the design of llvm optimizations :-). And also what is mean by _/cost
and threshold in inlining functions?/_/like (cost=always and
cost=never). /_/
/_
Next,
_//_
Clang documentation (here
<https://clang.llvm.org/docs/UsersManual.html#cmdoption-wambiguous-member-template>)
mentions that -_/Wambiguous-member-template/_ warning _is defaulted to
on_. But when I actually compile the same code as in documentation it
doesn't throw up any warnings. Is the documentation is out-dated for
clang 8.0.0 ?
Software details :
Clang 8.0.0 , Linux mint.
Hardware details:
X86-64 bit.
Could you please share your knowledge for the above questions ? it is a
great help to me
Thank you very much for your time,
PreeJackie
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20180903/1090e3c7/attachment.html>
More information about the llvm-dev
mailing list