[ARM64] CINC or CSINC is not emitted for conditional increment #96441
Description
Description
Creating a separate issue from #96380 to track CINC/CSINC not kicking in place of CSEL.
Analysis
Given method
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static int RuneLength(in byte value)
{
var lzcnt = (uint)BitOperations.LeadingZeroCount(~((uint)value << 24));
if (lzcnt is 0) lzcnt++;
return (int)lzcnt;
}Currently the following codegen is produced:
G_M000_IG01: ;; offset=0x0000
stp fp, lr, [sp, #-0x10]!
mov fp, sp
G_M000_IG02: ;; offset=0x0008
ldrb w0, [x0]
lsl w0, w0, #24
mvn w0, w0
clz w0, w0
mov w1, #1
cmp w0, #0
csel w0, w0, w1, ne ;; <-- Could have been just cinc with mov 1 elided - we're incrementing zero
G_M000_IG03: ;; offset=0x0024
ldp fp, lr, [sp], #0x10
ret lr
; Total bytes of code 44The mov, cmp, csel sequence can be produced in a more optimal way - cmp, cinc.
Configuration
.NET SDK:
Version: 8.0.100
Commit: 57efcf1350
Workload version: 8.0.100-manifests.71b9f198
Runtime Environment:
OS Name: Mac OS X
OS Version: 14.1
OS Platform: Darwin
RID: osx-arm64
Base Path: /usr/local/share/dotnet/sdk/8.0.100/
Regression?
No
