ebevhan added inline comments.
================ Comment at: clang/test/Frontend/fixed_point_conversions.c:437 + // DEFAULT-NEXT: [[RES:%[a-z0-9]+]] = trunc i39 [[SATMIN]] to i16 + // DEFAULT-NEXT: store i16 [[RES]], i16* %sat_sa, align 2 + ---------------- leonardchan wrote: > ebevhan wrote: > > Conversions like this are a bit odd. There shouldn't be a need to > > upsize/upscale the container before the saturation, should there? > I see. You're saying that we can just check directly if the value exceeds 255 > (or goes under -256) since the range of target values can always fit in the > range of source values. Therefore we do not need to cast up since the only > reason we would need to is if converting to a type with a greater source > range. > > In this case, we could technically have a special case for integers where I > think we can perform the saturation checks without the initial sign > extension. I think it might be simpler though if in > `EmitFixedPointConversion`, we treat an integer as a 'zero-scale fixed point > number'. I think the reason the upsizing occurs in the first place is so that > we satisfy the first FX conversion rule of calculating the result with full > precision of both operands. > I see. You're saying that we can just check directly if the value exceeds 255 > (or goes under -256) since the range of target values can always fit in the > range of source values. Therefore we do not need to cast up since the only > reason we would need to is if converting to a type with a greater source > range. That's right. Though, for integer to fixed-point conversion, I don't think you ever need to upcast first; either the integer is larger than or equal to the integral part of the fixed-point type, in which case we can check the magnitude in the type as is, or it's smaller, and we don't have to do any saturation. > I think it might be simpler though if in `EmitFixedPointConversion`, we treat > an integer as a 'zero-scale fixed point number'. Isn't this already the case? The semantics for an integer type are fetched as a zero scale fixed-point type and used that way (except when the target is an integer due to the rounding requirement). Repository: rC Clang CHANGES SINCE LAST ACTION https://reviews.llvm.org/D56900/new/ https://reviews.llvm.org/D56900 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
