Stack optimization missing on create some stack variables

When I using retdec to reverse md5 algorithm. I found a kind of conditon that stack pass will fail to create stack variables. such as
```
store i32 %506, i32* %512
-----------------------------------------------
>| %511 = add i64 %510, %509
>| %510 = add i64 %507, -128
>| %507 = load i64, i64* @rbp
>| i64 -8
>| i64 -128
>| %509 = mul i64 %508, 4
>| %508 = load i64, i64* @rdx
>| %504 = load i64, i64* @rcx
>| %502 = load i32, i32* %stack_var_-156
>| %stack_var_-156 = alloca i32
>| i64 4
-----------------------------------------------
after simplifyNode
-----------------------------------------------
>| %511 = add i64 %510, %509
>| %509 = mul i64 %508, 4
>| %stack_var_-156 = alloca i32
>| i64 4
>| i64 -136
-----------------------------------------------
```
Obviously, %510 should be stack_var_-136. But stack pass will fail to recognize it, and will not create related stack variable.

Here is my binary. And this instruction is at address 0x400858
[md5.zip](https://github.com/avast/retdec/files/4392142/md5.zip)

Reproduce the failure with the attached md5.zip binary at instruction address 0x400858 and inspect the stack pass output before and after simplifyNode. Trace why %510 is not recognized as stack_var_-136 and verify that the related stack variable is created and the shown expression is simplified correctly.

Written by the indexing model from the issue text.