[JIT][arm64] double dmb

[EgorBo]

public class Program
{
    volatile int a;

    void Test2(Program p) => p.a = a;
}

currently emits:

; Method Program:Test2(Program):this
G_M27705_IG01:              ;; offset=0000H
        A9BF7BFD          stp     fp, lr, [sp,#-16]!
        910003FD          mov     fp, sp
						;; bbWeight=1    PerfScore 1.50

G_M27705_IG02:              ;; offset=0008H
        B9400800          ldr     w0, [x0,#8]
        D50339BF          dmb     ishld
        D5033BBF          dmb     ish
        B9000820          str     w0, [x1,#8]
						;; bbWeight=1    PerfScore 24.00

G_M27705_IG03:              ;; offset=0018H
        A8C17BFD          ldp     fp, lr, [sp],#16
        D65F03C0          ret     lr
						;; bbWeight=1    PerfScore 2.00
; Total bytes of code: 32

I guess the 2nd dmb is redundant here (not even mentioning that both of them actually redundant here?)

[ghost]

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Issue Details

---

public class Program
{
    volatile int a;

    void Test2(Program p) => p.a = a;
}

currently emits:

; Method Program:Test2(Program):this
G_M27705_IG01:              ;; offset=0000H
        A9BF7BFD          stp     fp, lr, [sp,#-16]!
        910003FD          mov     fp, sp
						;; bbWeight=1    PerfScore 1.50

G_M27705_IG02:              ;; offset=0008H
        B9400800          ldr     w0, [x0,#8]
        D50339BF          dmb     ishld
        D5033BBF          dmb     ish
        B9000820          str     w0, [x1,#8]
						;; bbWeight=1    PerfScore 24.00

G_M27705_IG03:              ;; offset=0018H
        A8C17BFD          ldp     fp, lr, [sp],#16
        D65F03C0          ret     lr
						;; bbWeight=1    PerfScore 2.00
; Total bytes of code: 32

I guess the 2nd dmb is redundant here (not even mentioning that both of them actually redundant here?)

Author:	EgorBo
Assignees:	-
Labels:	tenet-performance, area-CodeGen-coreclr, untriaged
Milestone:	-