[PATCH] D56636: [CodeGen][X86] Expand vector USUBSAT to UMAX+SUB

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


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Comment at: lib/Target/X86/X86ISelLowering.cpp:1224
+    if (!HasInt256)
+      setOperationAction(ISD::USUBSAT, MVT::v8i32, Custom);
 
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nikic wrote:
> RKSimon wrote:
> > LowerADDSAT_SUBSAT supports AVX1 splitting, so why not:
> > ```
> > setOperationAction(ISD::USUBSAT, MVT::v8i32, HasInt256 ? Legal : Custom);
> > ```
> > 
> > Also, v4i64  should be ok as well.
> I've added this to get the splitting, but I don't think v8i32 would be legal, as we need it to expand. Maybe `hasInt256 ? Expand : Custom` would make it more obvious what the intention here is?
Better for the existing x86 lowering code to handle it IMO - that's what we do for nearly all 256-bit integer code on AVX1 targets.


Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D56636/new/

https://reviews.llvm.org/D56636