[SPCA] Finish unorthodox control flow

semester3/spca/code-examples/01_asm/09_setjmp-longjmp.s

@@ -0,0 +1,27 @@
+# Copyright 2011-2012 Nicholas J. Kain, licensed under standard MIT license
+setjmp:
+	mov %rbx, (%rdi)
+	mov %rbp, 8(%rdi)
+	mov %r12, 16(%rdi)
+	mov %r13, 24(%rdi)
+	mov %r14, 32(%rdi)
+	mov %r15, 40(%rdi)
+	lea 8(%rsp), %rdx
+	mov %rdx, 48(%rdi)
+	mov (%rsp), %rdx
+	mov %rdx, 56(%rdi)
+	xor %eax, %eax
+	ret
+
+longjmp:
+	xor %eax, %eax
+	cmp $1, %esi       # CF = val ? 0 : 1
+	adc %esi, %eax     # eax = val + !val
+	mov (%rdi), %rbx   # rdi is the jmp_buf, restore regs from it
+	mov 8(%rdi), %rbp
+	mov 16(%rdi), %r12
+	mov 24(%rdi), %r13
+	mov 32(%rdi), %r14
+	mov 40(%rdi), %r15
+	mov 48(%rdi), %rsp
+	jmp *56(%rdi)      # goto saved address without altering rsp