tcg optimization breaking memory access ordering
Description of problem:
The following code creates register dependency between 2 loads, which forces the first load to finish before the second:
```
movz	w0, #0x2
str	w0, [x1]
ldr	w2, [x1]
eor	w3, w2, w2
ldr	w4, [x5, w3, sxtw]
```

While translating it to tcg IR, it keeps this dependency correctly.
But after running tcg optimizations, it optimized the tcg sequence for `eor	w3, w2, w2` at `0000000000000144` to `mov_i64 x3,$0x0`. which then removes the dependency between the loads.

It results in incorrect behavior on the host on a multiple threaded program
Steps to reproduce:
1.
2.
3.
Additional information:
```
OP:
 ld_i32 loc0,env,$0xfffffffffffffff0
 brcond_i32 loc0,$0x0,lt,$L0
 st8_i32 $0x0,env,$0xfffffffffffffff4

 ---- 0000000000000134 0000000000000000 0000000000000000
 add_i64 x28,x28,$0x2

 ---- 0000000000000138 0000000000000000 0000000000000000
 mov_i64 x0,$0x2

 ---- 000000000000013c 0000000000000000 0000000000001c00
 mov_i64 loc3,x1
 mov_i64 loc4,loc3
 qemu_st_a64_i64 x0,loc4,w16+un+leul,2

 ---- 0000000000000140 0000000000000000 0000000000001c10
 mov_i64 loc5,x1
 mov_i64 loc6,loc5
 qemu_ld_a64_i64 x2,loc6,w16+un+leul,2

 ---- 0000000000000144 0000000000000000 0000000000000000
 and_i64 loc7,x2,$0xffffffff
 xor_i64 x3,x2,loc7
 and_i64 x3,x3,$0xffffffff

 ---- 0000000000000148 0000000000000000 0000000000001c20
 mov_i64 loc9,x5
 mov_i64 loc10,x3
 ext32s_i64 loc10,loc10
 add_i64 loc9,loc9,loc10
 mov_i64 loc11,loc9
 qemu_ld_a64_i64 x4,loc11,w16+un+leul,2
 st8_i32 $0x1,env,$0xfffffffffffffff4
```


```
OP after optimization and liveness analysis:
 ld_i32 tmp0,env,$0xfffffffffffffff0      pref=0xffffffff
 brcond_i32 tmp0,$0x0,lt,$L0              dead: 0
 st8_i32 $0x0,env,$0xfffffffffffffff4     dead: 0

 ---- 0000000000000134 0000000000000000 0000000000000000
 add_i64 x28,x28,$0x2                     sync: 0  dead: 0 1  pref=0xffffffff

 ---- 0000000000000138 0000000000000000 0000000000000000
 mov_i64 x0,$0x2                          sync: 0  dead: 0  pref=0xffffffff

 ---- 000000000000013c 0000000000000000 0000000000001c00
 qemu_st_a64_i64 $0x2,x1,w16+un+leul,2    dead: 0

 ---- 0000000000000140 0000000000000000 0000000000001c10
 qemu_ld_a64_i64 x2,x1,w16+un+leul,2      sync: 0  dead: 0 1  pref=0xffffffff

 ---- 0000000000000144 0000000000000000 0000000000000000
 mov_i64 x3,$0x0                          sync: 0  dead: 0 1  pref=0xffffffff

 ---- 0000000000000148 0000000000000000 0000000000001c20
 qemu_ld_a64_i64 x4,x5,w16+un+leul,2      sync: 0  dead: 0 1  pref=0xffffffff
 st8_i32 $0x1,env,$0xfffffffffffffff4     dead: 0
```