add some practice problems from 4HEADmaster

1 files changed, 25 insertions, 0 deletions

diff --git a/4/practice_problem_4_5.c b/4/practice_problem_4_5.c
new file mode 100644
index 0000000..604de44
--- /dev/null
+++ b/4/practice_problem_4_5.c
@@ -0,0 +1,25 @@
+#include <stdio.h>
+
+/*
+long sum(long *start, long count)
+start in %rdi, count in %rsi
+sum:
+	irmovq $8,%r8 		Constant 8
+	irmovq $1,%r9 		Constant 1
+	xorq %rax,%rax		sum = 0
+	andq %rsi,%rsi		Set cc
+	jmp test		Goto test
+loop:
+	mrmovq (%rdi), %r10 	Get *start
+	xorq %r11, %r11		Constant 0
+	subq %r10, %r11		-x
+	jle add			if x was positive, skip
+	rrmovq %r11, %r10	x = -x
+add:
+	addq %r10,%rax		Add to sum
+	addq %r8,%rdi 		start++
+	subq %r9,%rsi 		count--. Set CC
+test:
+	jne loop		Stop when 0
+	ret
+*/