Prologue/epilogue optimization

[mskvortsov]

Input: int foo() { return 1; }
Clang -O2/-Os output:

foo:
       0:	04 12 	push	r4
       2:	04 41 	mov	r1, r4
       4:	1c 43 	mov	#1, r12
       6:	34 41 	pop	r4
       8:	30 41 	ret

GCC:

foo:
       0:	5c 43 	mov.b	#1, r12
       2:	30 41 	ret

[asl]

Interesting. Looks like we default to frame pointer? What does clang -fomit-frame-pointer do?

[mskvortsov]

Yep, -fomit-frame-pointer does exactly what GCC does by default.