JIT: Use faster unchecked write-barrier for boxed statics

[EgorBo]

And a small clean up.

Example:

struct MyStruct
{
    public object Obj;
}

static MyStruct boxedStatic;

[MethodImpl(MethodImplOptions.NoInlining)]
static void Test(string str1, string str2)
{
    // simple way to trigger CSE:
    boxedStatic.Obj = str1;
    boxedStatic.Obj = str2;
}

Codegen diff for Test:

; Method Prog:Test(System.String,System.String) (FullOpts)
G_M57713_IG01:  
       push     rdi
       push     rsi
       push     rbx
       sub      rsp, 32
       mov      rbx, rcx
       mov      rsi, rdx
G_M57713_IG02:  
       test     byte  ptr [(reloc 0x7ff8e243b942)], 1      ; global ptr
       je       SHORT G_M57713_IG05
G_M57713_IG03:  
       mov      rcx, 0x21A0D401E10      ; box for Prog:boxedStatic
       mov      rdi, gword ptr [rcx]
       add      rdi, 8
       mov      rcx, rdi
       mov      rdx, rbx
-      call     CORINFO_HELP_CHECKED_ASSIGN_REF
+      call     CORINFO_HELP_ASSIGN_REF
       mov      rcx, rdi
       mov      rdx, rsi
-      call     CORINFO_HELP_CHECKED_ASSIGN_REF
+      call     CORINFO_HELP_ASSIGN_REF
       nop      
G_M57713_IG04:  
       add      rsp, 32
       pop      rbx
       pop      rsi
       pop      rdi
       ret      
G_M57713_IG05:  
       mov      rcx, 0x7FF8E243B910
       mov      edx, 2
       call     CORINFO_HELP_GETSHARED_NONGCSTATIC_BASE
       jmp      SHORT G_M57713_IG03
; Total bytes of code: 92

[ghost]

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
See info in area-owners.md if you want to be subscribed.

Issue Details

---

• small clean up.

Example:

struct MyStruct
{
    public object Obj;
}

static MyStruct boxedStatic;

[MethodImpl(MethodImplOptions.NoInlining)]
static void Test(string str1, string str2)
{
    boxedStatic.Obj = str1;
    boxedStatic.Obj = str2;
}

Codegen diff for Test:

; Method Prog:Test(System.String,System.String) (FullOpts)
G_M57713_IG01:  
       push     rdi
       push     rsi
       push     rbx
       sub      rsp, 32
       mov      rbx, rcx
       mov      rsi, rdx
G_M57713_IG02:  
       test     byte  ptr [(reloc 0x7ff8e243b942)], 1      ; global ptr
       je       SHORT G_M57713_IG05
G_M57713_IG03:  
       mov      rcx, 0x21A0D401E10      ; box for Prog:boxedStatic
       mov      rdi, gword ptr [rcx]
       add      rdi, 8
       mov      rcx, rdi
       mov      rdx, rbx
-      call     CORINFO_HELP_CHECKED_ASSIGN_REF
+      call     CORINFO_HELP_ASSIGN_REF
       mov      rcx, rdi
       mov      rdx, rsi
-      call     CORINFO_HELP_CHECKED_ASSIGN_REF
+      call     CORINFO_HELP_ASSIGN_REF
       nop      
G_M57713_IG04:  
       add      rsp, 32
       pop      rbx
       pop      rsi
       pop      rdi
       ret      
G_M57713_IG05:  
       mov      rcx, 0x7FF8E243B910
       mov      edx, 2
       call     CORINFO_HELP_GETSHARED_NONGCSTATIC_BASE
       jmp      SHORT G_M57713_IG03
; Total bytes of code: 92

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

[EgorBo]

@MihuBot

[EgorBo]

@AndyAyersMS @kunalspathak (cc @dotnet/jit-contrib) a quick follow up to my previous PR There are only a few text diffs after marking boxed static address as unchecked barrier + a small clean up.

[AndyAyersMS]

LGTM