DebugLLVM

LLVM is provided with a debug infrastructure. If you want to debug the compiler, you only need to build LLVM and Clang in debug mode.

Typical errors

Cannot select

fatal error: error in backend: Cannot select: 
	...
	...
	...
In function: function name
clang-3.9: error: clang frontend command failed with exit code 70 (use -v to see invocation)

This error occurs when the backend lacks a rule to perform the instruction selection of a certain SelectionDAG node. In such a case, you have a look at the NuPlusInstrFormats.td, NuPlusInstrInfo.td and NuPlusISelLowering.cpp files to understand why this node cannot be lowered.