[LLVMdev] JumpThreading and @llvm.dbg.declare() (original) (raw)

Hans Wennborg hans at chromium.org
Thu Feb 5 11:21:08 PST 2015

On Thu, Feb 5, 2015 at 4:49 AM, Karl-Johan Karlsson <karl-johan.karlsson at ericsson.com> wrote:

I have a small issue with the JumpThreading pass (in opt). As described in the code (JumpThreading.cpp), the pass may if certain criteria are fulfilled duplicate the content of a block. If the duplicated block contain a call to @llvm.dbg.declare() you will end up with invalid code as the intrinsic @llvm.dbg.declare() only should occur once for each variable.

I think the JumpThreading pass should lower all llvm.dbg.declare() into llvm.dbg.value() the same way as the instcombine pass do (see InstructionCombining.cpp): // Lower dbg.declare intrinsics otherwise their value may be clobbered // by instcombiner. bool DbgDeclaresChanged = LowerDbgDeclare(F); Do you agree? Ok to commit?

Did you forget to attach a patch? A patch with a test case showing the problem you're describing would be great.

Also, patches should generally be sent to the llvm-commits list, not llvmdev.

Thanks, Hans

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