[PATCH] D124415: [PowerPC][NFC] Add a function to determine if a call needs to be NOTOC.

Tue Apr 26 06:49:15 PDT 2022

jsji added inline comments.

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Comment at: llvm/lib/Target/PowerPC/PPCInstrInfo.h:299
+  /// Check if Opcode corresponds to a call instruction that should be marked
+  /// with the NOTOC relocation.
+  bool isNoTOCCallInstr(unsigned Opcode) const {
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shchenz wrote:
> jsji wrote:
> > shchenz wrote:
> > > I am in favor of Jinsong's comment in https://reviews.llvm.org/D122012#3392673. Could we use a flag in the td file (with a default true/false value) instead of listing all call instructions in the cpp file?
> > Thanks Zheng, we had some offline discussion, and I agreed that this can be a tradeoff between cost and benefits.
> > So I am OK with this. 
> Oh, I don't realize this. Could you please explain why we choose the cpp function instead of a td flag? To me, when we add a new call instruction in td file in future, it should be easier to aware that there is a flag to tell whether this call instruction needs a nop or not. Thanks
We will need some big in `TSFlags` to check the td flag, and currently this only affects 3 opcode, and it is highly unlikely we will be adding more `NOTOC` call instructions. 
So this explicitly listed switch table is mostly as a tradeoff of saving bits in `TSFlags`

Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D124415/new/

https://reviews.llvm.org/D124415