Why use ‘call CORINFO_HELP_DBL2ULNG’ when double to ulong instead of vcvttsd2si

[minxuanz]

    [MethodImplAttribute(MethodImplOptions.NoInlining)]
    static public ulong D2UL(double d) => (ulong)d;

    [MethodImplAttribute(MethodImplOptions.NoInlining)]
    static public uint D2UINT(double d) => (uint)d;

    [MethodImplAttribute(MethodImplOptions.NoInlining)]
    static public long D2L(double d) => (long)d;

unlike double to uint,when double to ulong , it will call CORINFO_HELP_DBL2ULNG

Program:D2UL(double):ulong (FullOpts):
G_M33866_IG01:  ;; offset=0x0000
       push     rax
       vzeroupper 
G_M33866_IG02:  ;; offset=0x0004
       call     CORINFO_HELP_DBL2ULNG
       nop      
G_M33866_IG03:  ;; offset=0x000A
       add      rsp, 8
       ret   


Program:D2UINT(double):uint (FullOpts):
G_M22956_IG01:  ;; offset=0x0000
       vzeroupper 
G_M22956_IG02:  ;; offset=0x0003
       vcvttsd2si  rax, xmm0
G_M22956_IG03:  ;; offset=0x0008
       ret         

but c++ compiler codegen

D2UL(double):                               # @D2UL(double)
        vcvttsd2si      rcx, xmm0
        mov     rdx, rcx
        sar     rdx, 63
        vsubsd  xmm0, xmm0, qword ptr [rip + .LCPI0_0]
        vcvttsd2si      rax, xmm0
        and     rax, rdx
        or      rax, rcx
        ret
D2UINT(double):                             # @D2UINT(double)
        vcvttsd2si      rax, xmm0
        ret

[ghost]

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Issue Details

---

    [MethodImplAttribute(MethodImplOptions.NoInlining)]
    static public ulong D2UL(double d) => (ulong)d;

    [MethodImplAttribute(MethodImplOptions.NoInlining)]
    static public uint D2UINT(double d) => (uint)d;

    [MethodImplAttribute(MethodImplOptions.NoInlining)]
    static public long D2L(double d) => (long)d;

unlike double to uint,when double to ulong , it will call CORINFO_HELP_DBL2ULNG

Program:D2UL(double):ulong (FullOpts):
G_M33866_IG01:  ;; offset=0x0000
       push     rax
       vzeroupper 
G_M33866_IG02:  ;; offset=0x0004
       call     CORINFO_HELP_DBL2ULNG
       nop      
G_M33866_IG03:  ;; offset=0x000A
       add      rsp, 8
       ret   


Program:D2UINT(double):uint (FullOpts):
G_M22956_IG01:  ;; offset=0x0000
       vzeroupper 
G_M22956_IG02:  ;; offset=0x0003
       vcvttsd2si  rax, xmm0
G_M22956_IG03:  ;; offset=0x0008
       ret         

but c++ compiler codegen

D2UL(double):                               # @D2UL(double)
        vcvttsd2si      rcx, xmm0
        mov     rdx, rcx
        sar     rdx, 63
        vsubsd  xmm0, xmm0, qword ptr [rip + .LCPI0_0]
        vcvttsd2si      rax, xmm0
        and     rax, rdx
        or      rax, rcx
        ret
D2UINT(double):                             # @D2UINT(double)
        vcvttsd2si      rax, xmm0
        ret

Author:	monstercatss
Assignees:	-
Labels:	area-CodeGen-coreclr
Milestone:	-

[huoyaoyuan]

#89279