# How remove this optimization of hexrays?

**URL:** <https://community.hex-rays.com/t/how-remove-this-optimization-of-hexrays/132>\
**Category:** IDA General\
**Created:** [February 5, 2025, 5:37pm UTC](https://community.hex-rays.com/t/how-remove-this-optimization-of-hexrays/132 "2025-02-05T17:37:36Z")\
**Posts on this page:** 11\
**Page:** 1

<div class="post-metadata">

**Author:** ![revs](https://avatars.discourse-cdn.com/v4/letter/r/dc4da7/32.png) [@revs](https://community.hex-rays.com/u/revs)\
**Post date:** [February 5, 2025, 5:37pm UTC](https://community.hex-rays.com/t/how-remove-this-optimization-of-hexrays/132/1 "2025-02-05T17:37:36Z")

</div>

I think hexrays forgot what it is not  
and it is not a compiler  
and it should not optimize the code that the compiler left

so how to disable/drop/remove such optimization?

1. hexrays looks for similar patterns in the microcode and replaces them with one,  
adding or redirecting via GOTO to them

if (a()) { return b(); return; }  
if (c()) { return b(); return; }  
if (d()) { return b(); return; }  
if (e()) { return b(); return; }

is replaced by

if (a()) { A: return b(); return; }  
if (c()) { goto A; }  
if (d()) { goto A; }  
if (e()) { goto A; }

or even worse  
is replaced by

if (a() || c() || d() || e()) { return b(); return; }

why is it bad?

firstly, the original instructions are deleted  
if the compiler left them, it means he considered it correct  
or he did not optimize it and you can see the original idea of ​​the developer himself  
and hexrays has no right to put itself above the compiler and optimize something

secondly, with the advent of eh34, this will interfere with creating correct places for installing try/catch blocks

1. replaces all comparisons with zero with regular uint a; if(a\>0) → if(a)  
you will say yes, this comparison does not make sense  
I will say, and what right do you have to decide for the compiler?  
again, if the compiler left it - then I want to see it

moreover, in some platforms, these can be different types, signed or unsigned  
and this code was compiled in the unsigned version

that’s why I really want to see the comparison with zero

1. replaces if (a == 0 || a == 1) → if (a \< 2)  
which subsequently creates problems with using enum  
instead of enum { A = 0, B, C }; if (a == A || a == B) → if (a \< C)

there are actually a lot of such optimizations  
I can’t remember absolutely all of them now  
but I can add them to this topic as I come across or remember them

if you don’t want to remove these optimizations, then is it possible to add something to the API so that you can remove these optimizations by writing your own plugin

---

<div class="post-metadata">

**Author:** ![igor](https://sea2.discourse-cdn.com/flex002/user_avatar/community.hex-rays.com/igor/32/35_2.png) [@igor](https://community.hex-rays.com/u/igor)\
**Post date:** [February 14, 2025, 3:18pm UTC](https://community.hex-rays.com/t/how-remove-this-optimization-of-hexrays/132/2 "2025-02-14T15:18:59Z")

</div>

If the decompiler didn’t perform optimizations because “the compiler knows better”, you’d be looking at unreadable mess with all individual operations, gotos and dead code left as-is. We have tried to pick optimizations and transformations which produce compact but (usually) correct representation of the underlying binary code. Some of them can be changed in decompiler options or config file, others currently not.

Additionally, It’s a little difficult to discuss abstract code snippets without the underlying code. If you are certain that the decompiler made a wrong decision in a specific situation, we’d encourage you to submit reports _with binaries_ (e.g. via the [support portal](https://support.hex-rays.com/), [Help \> Send Database](https://docs.hex-rays.com/user-guide/decompiler/interactive#help-send-database), or [by email](mailto:support@hex-rays.com)) so that they can be investigated in detail.

---

<div class="post-metadata">

**Author:** ![revs](https://avatars.discourse-cdn.com/v4/letter/r/dc4da7/32.png) [@revs](https://community.hex-rays.com/u/revs)\
**Post date:** [February 16, 2025, 11:04am UTC](https://community.hex-rays.com/t/how-remove-this-optimization-of-hexrays/132/3 "2025-02-16T11:04:32Z")

</div>

```auto
#include <stdio.h>

#ifdef _WIN32
typedef unsigned long MYTIME;
#else
typedef long MYTIME;
#endif
#ifdef _WIN32
#define __PRETTY_FUNCTION__  __FUNCSIG__
#endif

MYTIME get_my_time()
{
	printf("%s %d\n", __PRETTY_FUNCTION__ , __LINE__ );
	return 10;
}

void check_time()
{
	MYTIME last_time = get_my_time();
	while (1)
	{
		MYTIME cur_time = get_my_time();
		MYTIME interval = cur_time - last_time;
		if (interval < 0 || interval > 10)
		{
			printf("%s %d\n", __PRETTY_FUNCTION__ , __LINE__ );
			return;
		}
		printf("%s %d\n", __PRETTY_FUNCTION__ , __LINE__ );
	}
}

unsigned int get_num()
{
	printf("%s %d\n", __PRETTY_FUNCTION__ , __LINE__ );
	return 10;
}

void check_zero()
{
	if (get_num() > 0)
	{
		printf("%s %d\n", __PRETTY_FUNCTION__ , __LINE__ );
	} else
	{
		printf("%s %d\n", __PRETTY_FUNCTION__ , __LINE__ );
	}
}

enum TEST
{
	TEST_0 = 0,
	TEST_1 = 1,
	TEST_2 = 2,
	TEST_3 = 3,
};

struct NESTED_RETURN
{
	int test = 0;
	TEST t = TEST_0;

	void check_enum1()
	{
		if (t == TEST_0 || t == TEST_1)
		{
			printf("%s %d\n", __PRETTY_FUNCTION__ , __LINE__ );
		} else
		{
			printf("%s %d\n", __PRETTY_FUNCTION__ , __LINE__ );
		}
	}

	void check_enum2()
	{
		if (t == TEST_0 || t == TEST_1 || t == TEST_2 || t == TEST_3)
		{
			printf("%s %d\n", __PRETTY_FUNCTION__ , __LINE__ );
		} else
		{
			printf("%s %d\n", __PRETTY_FUNCTION__ , __LINE__ );
		}
	}
};

void check_return()
{
	NESTED_RETURN nr;
	nr.check_enum1();
	nr.check_enum2();
}

int main()
{
	check_time();
	check_zero();
	check_return();
	return 0;
}

```

compile under windows without optimization  
i hope there is no need the binary file  
hexrays output

```auto
void check_time(void)
{
  unsigned int last_time; // [rsp+24h] [rbp-14h]

  last_time = get_my_time();
  while ( get_my_time() - last_time <= 10 )
    printf_0("%s %d\n", "void __cdecl check_time(void)", 29);
  printf_0("%s %d\n", "void __cdecl check_time(void)", 26);
}

```

```auto
void check_zero(void)
{
  if ( get_num() )
    printf_0("%s %d\n", "void __cdecl check_zero(void)", 43);
  else
    printf_0("%s %d\n", "void __cdecl check_zero(void)", 46);
}

```

```auto
void __fastcall NESTED_RETURN::check_enum1(NESTED_RETURN *this)
{
  if ( this->t > (unsigned int)TEST_1 )
    printf_0("%s %d\n", "void __cdecl NESTED_RETURN::check_enum1(void)", 71);
  else
    printf_0("%s %d\n", "void __cdecl NESTED_RETURN::check_enum1(void)", 68);
}

```

```auto
void __fastcall NESTED_RETURN::check_enum2(NESTED_RETURN *this)
{
  if ( this->t >= 4u )
    printf_0("%s %d\n", "void __cdecl NESTED_RETURN::check_enum2(void)", 82);
  else
    printf_0("%s %d\n", "void __cdecl NESTED_RETURN::check_enum2(void)", 79);
}

```

in assembler all instruction are present  
hexrays just remove it

may be your add into hexrays some optimization level option like compiler O0 O2 O3  
to disable some optimization by hexrays

---

<div class="post-metadata">

**Author:** ![ilfak](https://sea2.discourse-cdn.com/flex002/user_avatar/community.hex-rays.com/ilfak/32/49_2.png) [@ilfak](https://community.hex-rays.com/u/ilfak)\
**Post date:** [February 17, 2025, 9:22am UTC](https://community.hex-rays.com/t/how-remove-this-optimization-of-hexrays/132/4 "2025-02-17T09:22:56Z")

</div>

Adding optimization levels is not in our plans.

Your example is quite long, could you tell me what instructions were omitted to change the code semantics?

---

<div class="post-metadata">

**Author:** ![revs](https://avatars.discourse-cdn.com/v4/letter/r/dc4da7/32.png) [@revs](https://community.hex-rays.com/u/revs)\
**Post date:** [February 17, 2025, 11:02am UTC](https://community.hex-rays.com/t/how-remove-this-optimization-of-hexrays/132/5 "2025-02-17T11:02:17Z")

</div>

assembler

```auto
.text:0000000140006FB9 028 mov rax, [rsp+28h+this]
.text:0000000140006FBE 028 cmp dword ptr [rax+4], 0
.text:0000000140006FC2 028 jz short loc_140006FE5
.text:0000000140006FC4 028 mov rax, [rsp+28h+this]
.text:0000000140006FC9 028 cmp dword ptr [rax+4], 1
.text:0000000140006FCD 028 jz short loc_140006FE5
.text:0000000140006FCF 028 mov rax, [rsp+28h+this]
.text:0000000140006FD4 028 cmp dword ptr [rax+4], 2
.text:0000000140006FD8 028 jz short loc_140006FE5
.text:0000000140006FDA 028 mov rax, [rsp+28h+this]
.text:0000000140006FDF 028 cmp dword ptr [rax+4], 3
.text:0000000140006FE3 028 jnz short loc_140007000

```

decompiler

```auto
  if ( this->t >= 4u )

```

---

<div class="post-metadata">

**Author:** ![ilfak](https://sea2.discourse-cdn.com/flex002/user_avatar/community.hex-rays.com/ilfak/32/49_2.png) [@ilfak](https://community.hex-rays.com/u/ilfak)\
**Post date:** [February 17, 2025, 2:31pm UTC](https://community.hex-rays.com/t/how-remove-this-optimization-of-hexrays/132/6 "2025-02-17T14:31:10Z")

</div>

Aren’t they equivalent in this context?

---

<div class="post-metadata">

**Author:** ![revs](https://avatars.discourse-cdn.com/v4/letter/r/dc4da7/32.png) [@revs](https://community.hex-rays.com/u/revs)\
**Post date:** [February 17, 2025, 2:38pm UTC](https://community.hex-rays.com/t/how-remove-this-optimization-of-hexrays/132/7 "2025-02-17T14:38:46Z")

</div>

topic not about equivalent  
topic about remove/drop/disable some optimization  
let user decide about it  
not the hexrays

and again  
hexrays not a compiler to optimize this comparison

---

<div class="post-metadata">

**Author:** ![ilfak](https://sea2.discourse-cdn.com/flex002/user_avatar/community.hex-rays.com/ilfak/32/49_2.png) [@ilfak](https://community.hex-rays.com/u/ilfak)\
**Post date:** [February 17, 2025, 2:56pm UTC](https://community.hex-rays.com/t/how-remove-this-optimization-of-hexrays/132/8 "2025-02-17T14:56:05Z")

</div>

As I said, we do not plan to introduce these options.

---

<div class="post-metadata">

**Author:** ![Morgan](https://avatars.discourse-cdn.com/v4/letter/m/0ea827/32.png) [@Morgan](https://community.hex-rays.com/u/Morgan)\
**Post date:** [March 1, 2025, 5:23pm UTC](https://community.hex-rays.com/t/how-remove-this-optimization-of-hexrays/132/9 "2025-03-01T17:23:19Z")

</div>

Any reason why not? Because it seems like really nice thing to have…

---

<div class="post-metadata">

**Author:** ![revs](https://avatars.discourse-cdn.com/v4/letter/r/dc4da7/32.png) [@revs](https://community.hex-rays.com/u/revs)\
**Post date:** [March 3, 2025, 11:01am UTC](https://community.hex-rays.com/t/how-remove-this-optimization-of-hexrays/132/10 "2025-03-03T11:01:51Z")

</div>

such and similar optimizations  
it is better to split into another plugin product for hexray  
which will obviously be useful for all kinds of antivirus companies  
that do not deal with code recovery as such  
and such optimizations will not interfere with them

---

<div class="post-metadata">

**Author:** ![revs](https://avatars.discourse-cdn.com/v4/letter/r/dc4da7/32.png) [@revs](https://community.hex-rays.com/u/revs)\
**Post date:** [June 11, 2025, 11:52am UTC](https://community.hex-rays.com/t/how-remove-this-optimization-of-hexrays/132/11 "2025-06-11T11:52:14Z")

</div>

> [@revs](#):
>
> hexrays looks for similar patterns in the microcode and replaces them with one,  
> adding or redirecting via GOTO to them

such example sent as

Your reference is SUPPORT-4872