[PATCH] D157273: [GlobalISel] Add dead flags to implicit defs in ISel

[Matt Arsenault via Phabricator via llvm-commits]

arsenm accepted this revision.
arsenm added inline comments.
This revision is now accepted and ready to land.


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Comment at: llvm/include/llvm/CodeGen/GlobalISel/GIMatchTableExecutor.h:335
   /// - RegNum - The register to add
+  /// - Dead - Whether this is a dead def.
   GIR_AddImplicitDef,
----------------
Pierre-vh wrote:
> arsenm wrote:
> > arsenm wrote:
> > > Can just make the flag value?
> > actually you can compact the two into one field, register is 32-bits and the flags are 16 I think
> I think compacting it is more trouble than it's worth, and it'd make this opcode an outlier - e.g. `AddTempRegister` doesn't compact, `AddTempSubRegister` doesn't, etc.
> 
> We should just look into making this a variable-length encoded array at some point, but it's quite a bit of work. Probably not worth it until we get actual performance numbers.
> 
> I wonder if we ever make use of the upper 32 bits though, maybe the table should always be 32 bits, with an option to variable-length-encode bigger values.
could change all these easy cases at once


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Comment at: llvm/include/llvm/CodeGen/GlobalISel/GIMatchTableExecutorImpl.h:950
       assert(OutMIs[InsnID] && "Attempted to add to undefined instruction");
-      OutMIs[InsnID].addDef(RegNum, RegState::Implicit);
+      Flags |= RegState::Implicit;
+      OutMIs[InsnID].addDef(RegNum, Flags);
----------------
This could have just been in the table


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D157273/new/

https://reviews.llvm.org/D157273