[PATCH] D58238: [DebugInfo] MachineSink: Insert undef DBG_VALUEs when sinking instructions, try to forward copies

[Wolfgang Pieb via Phabricator via llvm-commits]

wolfgangp added a comment.

So this basically prevents the debugger from displaying an inconsistent program state when some of the sideeffects from a line preceding its current stopping point have not been completed yet. Makes sense to me. One minor concern: If the sunk instruction does not get sunk past the next source line, we may create some unneeded location list entries, e.g.:

x = y; x = x + 3; z = z ? z + 3 : b;   // all on the same line

If the x + 3 is sunk past the assignment to z (but before any code attributed to the next line is executed) we generate an additional location list entry for x, where there is a small gap in the covered range for x, even though the user is not able to observe x until the next line.
Doesn't look like a big deal, though.


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  https://reviews.llvm.org/D58238/new/

https://reviews.llvm.org/D58238