[llvm-dev] Clang/LLVM 5.0 optnone attribute with -O0

Diptorup Deb via llvm-dev llvm-dev at lists.llvm.org
Sun Sep 17 22:12:46 PDT 2017


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 

What is the right way to get around this issue?


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