CODEWITHSUNDEEP
coptimizationarmarmcc
Mark Luko
Mark Luko

Reputation: 31

ARMCC remove unused variables

I'm trying to remove unused code with Keil ARM tools that use ARMCC compiler. I've previously used GCC based compilers for ARM and I could easily remove the unused code with:

-fdata-sections -ffunction-sections

For ARMCC i found similar flag

--split_sections

but it works only with functions and not with variables.

Is there any way to remove unused variables with ARMCC?

Edit:

For example giving the following library code:

lib.c :

static int veryBigArray[1000000UL];

int func1() { ... }

int func2() { memset(veryBigArray, 0, sizeof(veryBigArray); }

and my project code:

project.c:

int main(void)
{
   func1();
}

I want to remove func2() and veryBigArray using compiler/linker optimizations.

Upvotes: 2

Views: 2330

Answers (2)

user6596283
user6596283

Reputation: 11

In most cases, unused data can be removed with --remove as a linker option, when the data is in its own section. To place data in its own section, you may create another file or use the section attribute: http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0375g/chr1359124982450.html

For example, if global data is used in only one function, and the function is defined but never used, then the data is automatically removed in armcc, without --remove.

I say "in most cases" because there are situations where the user tells the compiler to specifically not optimize it out.

Arm Compiler version 6, (armclang), does have -fdata-sections.

Upvotes: 1

Mark Luko
Mark Luko

Reputation: 31

The official answer that we received from ARM support is that currently (ARMCC v5.03 [Build 24]) there is no such option available in ARMCC compiler - They just never thought about such scenario.

Hopefully it will be added to future ARMCC versions.

Upvotes: 1

Related Questions