Unnecessary sign-extension for (nuint)span.Length #84564
Description
@EgorBo In theory, the length in
(nuint)span.Lengthshould be recognized as never negative, and the sign-extension elided, but doesn't appear to be the case (at least in R2R), see https://csharp.godbolt.org/z/14oW68fqz.
Originally posted by @xtqqczze in #84524 (comment)
static nuint Span0(ReadOnlySpan<byte> span) => (nuint)span.Length;
static nuint Span1(ReadOnlySpan<byte> span) => (uint)span.Length;// crossgen2 8.0.0-preview.4.23208.99+07f00dc2f624946c54dbf85fea79c600a690f634
C:Span0(System.ReadOnlySpan`1[ubyte]):ulong:
; Emitting BLENDED_CODE for X64 CPU with AVX - Windows
;; size=0 bbWeight=1 PerfScore 0.00
movsxd rax, dword ptr [rcx+08H]
;; size=4 bbWeight=1 PerfScore 4.00
ret
;; size=1 bbWeight=1 PerfScore 1.00
C:Span1(System.ReadOnlySpan`1[ubyte]):ulong:
; Emitting BLENDED_CODE for X64 CPU with AVX - Windows
;; size=0 bbWeight=1 PerfScore 0.00
mov eax, dword ptr [rcx+08H]
;; size=3 bbWeight=1 PerfScore 2.00
ret
;; size=1 bbWeight=1 PerfScore 1.00