[PATCH] D141189: [Mips] Set setMaxAtomicSizeInBitsSupported

[Brad Smith via Phabricator via llvm-commits]

brad added inline comments.


================
Comment at: llvm/lib/Target/Mips/MipsISelLowering.cpp:500-501
+    setMaxAtomicSizeInBitsSupported(32);
+  else
+    setMaxAtomicSizeInBitsSupported(0);
+
----------------
wzssyqa wrote:
> brad wrote:
> > arsenm wrote:
> > > Else case doesn't make sense to me but I know nothing about mips 
> > > Else case doesn't make sense to me but I know nothing about mips 
> > 
> > To deal with MIPS-I not having support for atomics.
> Sorry for me. I am no idea about what's the mean of the value of `setMaxAtomicSizeInBitsSupported`.
> 
> Maybe:
> 1) load/store instructions no quirky behavior: an instruction can be split to in result.
>     If so, MIPS has never this problem since MIPS I.
> 2) normal load/store instructions can make sure that the data sync in a multicore system.
>     If so, MIPS never archives this.
> 3) architecture has some instructions to help atomic ops.
>     If so, MIPS has LL/SC since MIPS II.
setMaxAtomicSizeInBitsSupported() indicates the maximum size of supported atomic operations that are *all* lock-free. 32-bit MIPS does not have hardware support for lock-free 64-bit atomics.


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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D141189/new/

https://reviews.llvm.org/D141189