CODEWITHSUNDEEP
assemblyinline
MCG
MCG

Reputation: 1031

Understanding assembler instruction

I was looking into below answer at

LPC1768 / ARM Cortex-M3 microsecond delay

#define CAL_FACTOR ( 100 )

void delay (uint32_t interval)
{
  uint32_t iterations = interval / CAL_FACTOR;

  for(int i=0; i<iterations; ++i)
  {
    __asm__ volatile // gcc-ish syntax, don't know what compiler is used
    (
      "nop\n\t"
      "nop\n\t"
      :::
    );
  }
}

What is \n\t after nop? I looked into GCC Assembler guide but could not find answer.

Upvotes: 0

Views: 110

Answers (2)

MCG
MCG

Reputation: 1031

I found answer at http://asm.sourceforge.net/articles/rmiyagi-inline-asm.txt

'\n\t' at the end of each line except the last, and that each line is enclosed in quotes. This is because gcc sends each as instruction to as as a string. The newline/tab combination is required so that the lines are fed to as according to the correct format (recall that each line in assembler is indented one tab stop, generally 8 characters).

Upvotes: 1

Carlos Cortez
Carlos Cortez

Reputation: 170

The assembly block seems to be read as plain text and instructions are separated with line breaks, if you write

"nop\n\tnop\n\t"

it should work as well.

Upvotes: 0

Related Questions