main sources:

• GCC-Inline-Assembly-HowTo, Sandeep.S, https://www.ibiblio.org/gferg/ldp/GCC-Inline-Assembly-HOWTO.html
• 6.50.2 Extended Asm - Assembler Instructions with C Expression Operands, GNU, https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html

• syntax
  • AssemblerTemplate
  • OutputOperands
  • InputOperands
  • Clobbers
• Assembler Dialacts

§ syntax

asm asm-qualifiers ( AssemblerTemplate
                 : OutputOperands
                 [ : InputOperands
                 [ : Clobbers ] ])

asm asm-qualifiers ( AssemblerTemplate
                      : OutputOperands
                      : InputOperands
                      : Clobbers
                      : GotoLabels)

§§ AssemblerTemplate

format strings

%%

escaped % symbol

https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#AssemblerTemplate

§§ OutputOperands

§§ InputOperands

§§ Clobbers

the asm instructions may change regiters other than those listed in the output operands. Which would cause the compiler to generate wrong code. Clobers explicitly tell the compiler “here I’m writting to these registers”

§ Assembler Dialacts