llvm dev - Sep 2017 - Clang/LLVM 5.0 optnone attribute with -O0

Hi,

We have a research LLVM-based domain-specific code generator that we 
want to upgrade form LLVM 4.0 to 5.0. The code generator is written as 
an out-of-tree loadable module for opt.

Till Clang 4.0 we were compiling the front-end code (annotated C++) 
using -O0. The generated bitcode was further processed using opt with 
our module loaded. In Clang 5.0 we see that using -O0 adds the optnone 
attribute to all functions, making it impossible to use any existing 
LLVM passes in our code generator.

We also tried using -
"clang -Xclang -load -Xclang <module>.so -mllvm <custom
options>"

, but this caused a segfault at 
llvm::legacy::FunctionPassManagerImpl::doInitialization(llvm::Module&).

What is the right way to get around this issue?

Dipto

To prevent optnone from being added you can replace -O0 with "-O1 -Xclang
-disable-llvm-passes". The -O1 will prevent the optnone, and the rest will
stop clang from performing any optimizations.

~Craig

On Sun, Sep 17, 2017 at 10:12 PM, Diptorup Deb via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi,
>
> We have a research LLVM-based domain-specific code generator that we want
> to upgrade form LLVM 4.0 to 5.0. The code generator is written as an
> out-of-tree loadable module for opt.
>
> Till Clang 4.0 we were compiling the front-end code (annotated C++) using
> -O0. The generated bitcode was further processed using opt with our module
> loaded. In Clang 5.0 we see that using -O0 adds the optnone attribute to
> all functions, making it impossible to use any existing LLVM passes in our
> code generator.
>
> We also tried using -
> "clang -Xclang -load -Xclang <module>.so -mllvm <custom
options>"
>
> , but this caused a segfault at llvm::legacy::FunctionPassMana
> gerImpl::doInitialization(llvm::Module&).
>
> What is the right way to get around this issue?
>
> Dipto
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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You can also add the -Xclang -disable-O0-optnone flag to your command line. This
will disable the implicit optnone when compiling with O0.

Cheers,
Michael



On Mon, Sep 18, 2017 at 7:27 AM +0200, "Craig Topper via llvm-dev"
<llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>>
wrote:

To prevent optnone from being added you can replace -O0 with "-O1 -Xclang
-disable-llvm-passes". The -O1 will prevent the optnone, and the rest will
stop clang from performing any optimizations.

~Craig

On Sun, Sep 17, 2017 at 10:12 PM, Diptorup Deb via llvm-dev <llvm-dev at
lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
Hi,

We have a research LLVM-based domain-specific code generator that we want to
upgrade form LLVM 4.0 to 5.0. The code generator is written as an out-of-tree
loadable module for opt.

Till Clang 4.0 we were compiling the front-end code (annotated C++) using -O0.
The generated bitcode was further processed using opt with our module loaded. In
Clang 5.0 we see that using -O0 adds the optnone attribute to all functions,
making it impossible to use any existing LLVM passes in our code generator.

We also tried using -
"clang -Xclang -load -Xclang <module>.so -mllvm <custom
options>"

, but this caused a segfault at
llvm::legacy::FunctionPassManagerImpl::doInitialization(llvm::Module&).

What is the right way to get around this issue?

Dipto

_______________________________________________
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llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

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