[PATCH] D68633: fix debug info affects output when opt inline

Wed Oct 9 00:20:23 PDT 2019

bjope added a comment.

In D68633#1699421 <https://reviews.llvm.org/D68633#1699421>, @bjope wrote:

> I do not understand how this helps. The code is written in a way that it skips any instruction, but moves contigous blocks of allocas in one splice (not sure exactly why, is that really faster?). Maybe the difference is that the check for AI->useEmpty() only is done for the first alloca in a sequence of alloca instructions? Or can't we just remove the loop at line 1847 (only moving one alloca at a time).

The patch description really needs to be updated. Afaict the old code has been doing "Skip dbg instr while allocas scanning.", but with this patch you in some sense start to scan for both alloca instructions _and_ dbg intrinsics. And then some dbg intrinsics will be part of the splice.
As Johannes mentioned this is incomplete (since not all dbg intrinsics are considered, only those appearing after the first alloca in for each lap in the outer for loop).
Besides, inlining decisions should not be impacted by if we move the dbg intrinsics or not, right? That is why I think this fix isn't solving the problem seen in the bugzilla ticket. It only hides the actual problem (given the reduced reproducer).

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  https://reviews.llvm.org/D68633/new/

https://reviews.llvm.org/D68633