[LLVMdev] What does LLVM ERROR: Cannot select.. mean?

Krzysztof Parzyszek kparzysz at codeaurora.org
Mon Dec 3 15:40:43 PST 2012

On 12/3/2012 5:07 PM, Roman Kennke wrote:
> Hello,
> I am currently working on Shark, a backend for the Hotspot VM of
> OpenJDK, which uses LLVM to generate target machine code.
> I am currently running into an LLVM error message, and I don't know
> exactly what it means or what I am doing wrong:

The instruction selection cannot find a way to convert this into machine 
instructions.  Most likely there is no pattern to match this part of the 
graph in your .td file.

You can see what's going on during selection with -mllvm 
-debug-only=isel.  The dumps are somewhat cumbersome to read, but not 
hard overall.


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