llvm dev - Oct 2019 - Easy way to add common pass for optimization

Hi all,
I wrote a compiler front end which generates IR codes, but due to the
logic, the IR codes have a lot of  instructions like unnecessary br jump,
basic block creation, load instructions and expression which can be
simplified.
now I want to use built in passes to optimize the generated code, but after
I read the tutorial: https://llvm.org/docs/tutorial/MyFirstLanguageFrontend,
I found that I have to add passess one by one, on function level.

I know these passes for module level, but I don't know what passes I should
add, and I do not have special optimization requirements, so built-in
passes will meet my requirements, So this there any easy way to add most
common passes which all compilers will probable used?
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It depends on if you’re using the new or old pass managers, though if you’re
following that tutorial you’re probably using the old
one (looking at
https://llvm.org/docs/tutorial/MyFirstLanguageFrontend/LangImpl04.html#llvm-optimization-passes).

If so then you can use PassManagerBuilder
(http://llvm.org/doxygen/classllvm_1_1PassManagerBuilder.html). It may be also
worthwhile looking at what opt does (AddOptimizationLevel.cpp in opt.cpp) as it
uses PassManagerBuilder but does something
a bit more complex than just setting the optlevel then populating the pass
manager (but maybe just setting optlevel is all you
need for your purposes).

John

From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Yafei
Liu via llvm-dev
Sent: 15 October 2019 09:54
To: llvm-dev
Subject: [llvm-dev] Easy way to add common pass for optimization

Hi all,
I wrote a compiler front end which generates IR codes, but due to the logic, the
IR codes have a lot of  instructions like unnecessary br jump, basic block
creation, load instructions and expression which can be simplified.
now I want to use built in passes to optimize the generated code, but after I
read the tutorial: https://llvm.org/docs/tutorial/MyFirstLanguageFrontend, I
found that I have to add passess one by one, on function level.

I know these passes for module level, but I don't know what passes I should
add, and I do not have special optimization requirements, so built-in passes
will meet my requirements, So this there any easy way to add most common passes
which all compilers will probable used?
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Hi John, I didn't find any file named AddOptimizationLevel.cpp in my llvm
project, where is it?

On Tue, Oct 15, 2019 at 8:39 PM John Brawn <John.Brawn at arm.com> wrote:
> It depends on if you’re using the new or old pass managers, though if
> you’re following that tutorial you’re probably using the old
>
> one (looking at
>
https://llvm.org/docs/tutorial/MyFirstLanguageFrontend/LangImpl04.html#llvm-optimization-passes
> ).
>
>
>
> If so then you can use PassManagerBuilder (
> http://llvm.org/doxygen/classllvm_1_1PassManagerBuilder.html). It may be
> also
>
> worthwhile looking at what opt does (AddOptimizationLevel.cpp in opt.cpp)
> as it uses PassManagerBuilder but does something
>
> a bit more complex than just setting the optlevel then populating the pass
> manager (but maybe just setting optlevel is all you
>
> need for your purposes).
>
>
>
> John
>
>
>
> *From:* llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] *On Behalf Of
*Yafei
> Liu via llvm-dev
> *Sent:* 15 October 2019 09:54
> *To:* llvm-dev
> *Subject:* [llvm-dev] Easy way to add common pass for optimization
>
>
>
> Hi all,
>
> I wrote a compiler front end which generates IR codes, but due to the
> logic, the IR codes have a lot of  instructions like unnecessary br jump,
> basic block creation, load instructions and expression which can be
> simplified.
>
> now I want to use built in passes to optimize the generated code, but
> after I read the tutorial:
> https://llvm.org/docs/tutorial/MyFirstLanguageFrontend, I found that I
> have to add passess one by one, on function level.
>
>
>
> I know these passes for module level, but I don't know what passes I
> should add, and I do not have special optimization requirements, so
> built-in passes will meet my requirements, So this there any easy way to
> add most common passes which all compilers will probable used?
>
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