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compiler optimization options for ARMv8 GCC compiler on ARM cortex a53 (bare metal application)

khan777 over 5 years ago

I am using ARMv8 GCC compiler(aarch64-none-elf-gcc) for my bare metal application on ARM cortex a53. I am using neon intrinsics with plain C in my code so I would like to ensure to use all optimization option available for this compiler.

I tried -mfpu = neon but compiler is not recognizing it. So, what are the possible optimization option available for my application setting. I am using Xilinx SDK IDE for my application.

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0 42Bastian Schick over 5 years ago in reply to khan777

If you look at the assembly, you will see: It is on by default.

int res(float a, float b)
{
  return (int)(a+b);
}

Compile with -O

       .arch armv8-a
        .file   "calling.c"
        .text
        .align  2
        .global res
        .type   res, %function
res:
        fadd    s0, s0, s1
        fcvtzs  w0, s0
        ret
        .size   res, .-res

Reply

0 42Bastian Schick over 5 years ago in reply to khan777

If you look at the assembly, you will see: It is on by default.

int res(float a, float b)
{
  return (int)(a+b);
}

Compile with -O

       .arch armv8-a
        .file   "calling.c"
        .text
        .align  2
        .global res
        .type   res, %function
res:
        fadd    s0, s0, s1
        fcvtzs  w0, s0
        ret
        .size   res, .-res

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