[PATCH] D128192: [GlobalISel][DebugInfo] Propagate debug location for localized constants

Mon Jul 25 15:27:52 PDT 2022

dblaikie added a comment.

In D128192#3677707 <https://reviews.llvm.org/D128192#3677707>, @dzhidzhoev wrote:

> In D128192#3659407 <https://reviews.llvm.org/D128192#3659407>, @dzhidzhoev wrote:
>
>> In D128192#3658500 <https://reviews.llvm.org/D128192#3658500>, @dblaikie wrote:
>>
>>> @aprantl @probinson I'm really not sure, but should we consider backpropagating the first non-zero location to cover zero-location instructions at the start of a basic block more generally than this patch is proposing?
>>
>> BTW discussion about backpropagation for zero-location-instructions at the start of a basic block took in place here https://lists.llvm.org/pipermail/lldb-dev/2018-October/014263.html . There was a point against backpropagation of location for arbitrary instructions.
>
> The objection was that it is incorrect to backpropagate debug locations of the nearest instruction below on arbitrary instructions, since there is no knowledge about their semantics on AsmPrinter stage. In contrast to that, in this commit we know that instructions being marked are generated from constants and are used by the nearest following instruction.

We forward propagate such locations, though, right? So I'm not sure back propagating is especially worse/more problematic.

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https://reviews.llvm.org/D128192