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[Flang] no debug line table after D136543 #58634

Closed vzakhari closed 1 year ago

vzakhari commented 1 year ago

After https://reviews.llvm.org/D136543 Flang is not producing debug line table for compiled Fortran programs. Even though the new code can translate MLIR Locaction's into debug line entries, it bails out for functions (llvm.func) that do not provide FusedLoc with the metadata holding DIScopeAttr.

I suppose the expectation is that the MLIR producer (e.g. Flang front-end) establishes proper FusedLoc for the generated func.func's, which are then propagated to llvm.func during conversion to LLVM dialect.

FYI, @River707

llvmbot commented 1 year ago

@llvm/issue-subscribers-flang-ir

vzakhari commented 1 year ago

OR, should func.func to llvm.func converter automatically create FusedLoc with DI metadata, if there is none attached?

River707 commented 1 year ago

I wouldn't expect the converter to implicitly add metadata if it wasn't there. Part of this effort to actually setup debug info to work the way it's expected, i.e. we should no longer be implicitly adding metadata (at least in the general infra, specific projects can of course do what works best for them).

River707 commented 1 year ago

I suppose the expectation is that the MLIR producer (e.g. Flang front-end) establishes proper FusedLoc for the generated func.func's, which are then propagated to llvm.func during conversion to LLVM dialect.

Yeah, that's the intention of this effort; to enable frontends to specify debug information and have it correctly propagated/exported to LLVM. It means losing the implicity, but you gain the ability to specify real debug info (instead of the fake stuff we generated before).

vzakhari commented 1 year ago

Thank you for clarification, River!

kiranchandramohan commented 1 year ago

I have a WIP patch for this https://reviews.llvm.org/D137956.

This patch adds a pass that provides some foundation work with which
basic line table debug info can be generated. A walk is performed on
all the func ops in the module and they are decorated with a fusedLoc
op that contains the debug metadata for the subroutine along with
location information.

Alternatives ways include populating this info during lowering or during FIR
to LLVM Dialect conversion.