[llvm-dev] GVN pass limitation.

[xiuli pan via llvm-dev]

Hello,

 

We are now facing a bug caused by the GVN pass, only part of the code was
optimized. I have found that the problem is cause by an Limit in
lib/Analysis/MemoryDependenceAnalysis.cpp

 

00055 static cl::opt<unsigned> BlockScanLimit(

00056     "memdep-block-scan-limit", cl::Hidden, cl::init(100),

00057     cl::desc("The number of instructions to scan in a block in memory
"

00058              "dependency analysis (default = 100)"));

The args can be changed using opt, but we are using libclang and libllvm and
running pass with llvm passmangers. I know that -mllvm can pass llvm args,
but the llvm::cl::ParseCommandLineOptions has some issues with mutlethread
and I have reported a bug in https://llvm.org/bugs/show_bug.cgi?id=25735,
and we could not use this for now.

 

So if there is another way to pass this memdep-block-scan-limit into the
pass manager or context? Or how could I set this memdep-block-scan-limit
right with libclang and libllvm?

 

Thanks

Xiuli

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