tmatheson added a comment. In D146242#4427707 <https://reviews.llvm.org/D146242#4427707>, @chill wrote:
> I was just thinking to LGTM it :) > > IMHO, the alignment adjustment happens because of C.4 (B.3 indeed leave the > HFA/HVA unmodified). > >> C.4 If the argument is an HFA, an HVA, a Quad-precision Floating-point or >> short vector type then the NSAA is rounded up to the next multiple of 8 if >> its natural alignment is ≤ 8 or the next multiple of 16 if its natural >> alignment is ≥ 16. I think that C2 would be hit first, suggesting it should be allocated a SIMD register and alignment should be irrelevant, assuming sufficient registers: > C.2 If the argument is an HFA or an HVA and there are sufficient unallocated > SIMD and Floating-point registers (NSRN + number of members ≤ 8), then the > argument is allocated to SIMD and Floating-point registers (with one register > per member of the HFA or HVA). The NSRN is incremented by the number of > registers used. The argument has now been allocated. If not enough registers, the size also needs rounded up: > C.3 If the argument is an HFA or an HVA then the NSRN is set to 8 and the > size of the argument is rounded up to the nearest multiple of 8 bytes. After that C4 would indeed be hit. However C4 differs from B6 <https://reviews.llvm.org/B6>, in that C4 rounds up to the nearest multiple of 8 or 16 (which is not what the patch currently does) whereas B6 <https://reviews.llvm.org/B6> restricts it to either 6 or 16 (which this what this patch does, but shouldn't apply to HVAs). The final rule that actually does the allocation is C6: > C.6 If the argument is an HFA, an HVA, a Half-, Single-, Double- or Quad- > precision Floating-point or short vector type, then the argument is copied to > memory at the adjusted NSAA. The NSAA is incremented by the size of the > argument. The argument has now been allocated. (This is all in reference to HVA types like `struct { uint8x16_t m; };`) Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D146242/new/ https://reviews.llvm.org/D146242 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
