[fpc-devel] Wrong debug info when using clang backend

[Jonas Maebe]

On 06/12/2023 22:17, Martin Frb via fpc-devel wrote:
> If I have enough code, so clang does not optimize the entire function 
> away in -O1, then clang writes info for some of the lines.
> Actually the variable is in a (or several?) registers.
> And clang misses some lines too.
> But it covers some lines in the procedure.

https://releases.llvm.org/11.0.0/docs/SourceLevelDebugging.html#format-common-intrinsics 
states that llvm.dbg.declare is identical to llvm.dbg.addr, except that 
it works badly in the context of optimisations, and that as a result it 
is deprecated and will be removed.

Because of this reason, FPC only uses llvm.dbg.addr. But clang still 
uses llvm.dbg.declare, and when I change FPC to use that one, the debug 
info for the variables in your test program is correct. So I'll change 
FPC to also use llvm.dbg.declare.


Jonas