There are three types:

Basic assembly

https://gcc.gnu.org/onlinedocs/gcc/Basic-Asm.html

This can be used at top-level or within functions, and essentially just inserts the string in the output. This is probably easily supported by QBE.

Extended assembly

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

This can only be used within functions, and allows you to access C variables.

Assembler names (implemented)

https://gcc.gnu.org/onlinedocs/gcc/Asm-Labels.html

These appear after a declaration, and allow you to specify the assembly label name. This probably doesn't need any QBE support.