[PATCH] D99048: [RFC][DebugInfo] Do not use the DBG_VALUE to calculate debug info of spill location

Thu Apr 1 17:45:33 PDT 2021

probinson added inline comments.

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Comment at: llvm/lib/CodeGen/InlineSpiller.cpp:979
+      if (CopyReg.isValid())
+        TryKillReg();
       HSpiller.addToMergeableSpills(*FoldMI, StackSlot, Original);
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jmorse wrote:
> dongAxis1944 wrote:
> > @jmorse In addition, when regalloc tries to spill vreg to stack. llvm forget to mark kill flags for copy instruction. I think it might be useful for dwarf construction. What's your opinions?
> Interesting -- I'm not very familiar with the kill flags, I've always relied on analysis passes to determine liveness information. If it's legitimate to place a a kill flag here, and it improves variable location tracking like you suggested in D41226, then it's probably a worthwhile improvement.
> 
> However, you should first check whether this causes LLVM to ever generate different code. I think most of the community doesn't want to change the code generated simply to improve debug-info (unless it's a trivial alteration).
What we don't like is when adding -g changes codegen at all. Making slightly different choices (at -O0) that gives better debug experience without particularly affecting performance is okay, as long as that choice doesn't depend on the presence of debug info.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D99048/new/

https://reviews.llvm.org/D99048