[llvm-dev] Performace regression in llvm::ExecutionEngine::finalizeObject

[gaurav phatnani via llvm-dev]

Hello,

I am working on upgrading an app from using llvm 8.0.1 to llvm 10.0.

I create a JIT llvm::ExecutionEngine(i386 CPU, NONE codegenopt) which
contains a single module.

Below are some numbers for call to llvm::ExecutionEngine::finalizeObject:
llvm 8.0.1 - less than 0.5 seconds
llvm 10.0 - greater than 170 seconds

Using Vtune, was able to trace the regression to
llvm::SDNode::hasNUsesOfValue(which is called by
llvm::X86TargetLowering::PerformDAGCombine)

I want to check if anyone has faced a similar problem or has any ideas what
the root cause/fix might be?

Thanks,
Gaurav
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