leonardchan marked an inline comment as done. leonardchan added a comment. > Generally I think it's good! One final note; I assume we could technically > reuse/rename the EmitFixedPointAdd function and use it to emit other binops > when those are added?
Yes, but I imagine if we choose to keep the call to `EmitFixedPointConversion` to cast both operands to a common type, this wouldn't be reused for division or multiplication since I believe those do not require for the operands to be converted to a common type. ================ Comment at: clang/test/Frontend/fixed_point_add.c:269 + // UNSIGNED-NEXT: [[SUM:%[0-9]+]] = call i15 @llvm.uadd.sat.i15(i15 [[USA_TRUNC]], i15 [[USA_SAT_TRUNC]]) + // UNSIGNED-NEXT: [[SUM_EXT:%[a-z0-9]+]] = zext i15 [[SUM]] to i16 + // UNSIGNED-NEXT: store i16 [[SUM_EXT]], i16* %usa_sat, align 2 ---------------- ebevhan wrote: > leonardchan wrote: > > ebevhan wrote: > > > This is probably a candidate for an isel optimization. This operation > > > also works as an `i16 ssat.add` with a negative-clamp-to-zero afterwards, > > > and if the target supports `i16 ssat.add` natively then it will likely be > > > a lot more efficient than whatever an `i15 uadd.sat` produces. > > Do you think it would be more efficient for now then if instead we did SHL > > by 1, saturate, then [AL]SHR by 1? This way we could use `i16 ssat.add` > > instead of `i15 ssat.add`? > We should probably just do it in isel or instcombine instead. We don't know > at this point which intrinsic is a better choice (though, I think > power-of-two-types are generally better). Ok. Are you suggesting something should be changed here though? I imagine that during legalization, `i15 ssat.add` would be legalized into `i16 ssat.add` if that is what's natively supported. Repository: rC Clang CHANGES SINCE LAST ACTION https://reviews.llvm.org/D53738/new/ https://reviews.llvm.org/D53738 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
