Northwestern UniversityEECS 213 HOMEWORK 2 SOLUTION FALL 2020

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EECS­213, Fall 2015 HOMEWORK 2 SOLUTION Problem 1 (20 points) For each IA32 assembly code sequence below on the left, fill in the missing portion of corresponding C line on the right. Simplify th... e C code as much as possible. foo: pushl %ebp movl %esp,%ebp movl 8(%ebp),%eax sall $5,%eax subl 8(%ebp),%eax movl %ebp,%esp popl %ebp ret int foo(int x) { return 31*x; // (x<<5) ­ x } foo: pushl %ebp movl %esp,%ebp movl 8(%ebp),%eax testl %eax,%eax jge .L4 addl $3,%eax .L4: sarl $2,%eax movl %ebp,%esp popl %ebp ret int foo(int x) { return x/4; // (x>=0 ? x:(x+3)) >> 2; } foo: pushl %ebp movl %esp,%ebp movl 8(%ebp),%eax shrl $16,%eax movl %ebp,%esp popl %ebp ret int foo(int x) { return (int) ((unsigned int)x >> 16); } foo: pushl %ebp movl %esp,%ebp movl 8(%ebp),%eax sall $4,%eax addl 8(%ebp),%eax addl %eax,%eax movl %ebp,%esp popl %ebp ret int foo(int x) { return 34*x; // 2*(x<<4 + x); } foo: pushl %ebp movl %esp,%ebp movl 8(%ebp),%edx movl 12(%ebp),%eax movl %ebp,%esp movl (%edx),%edx addl %edx,(%eax) movl %edx,%eax popl %ebp ret int foo(int *xp, int *yp) { int x = *xp; *yp += *xp; // or *yp += x; return x; } This study source was downloaded by 100000784424693 from CourseHero.com on 04-28-2021 01:53:06 GMT -05:00 https://www.coursehero.com/file/14225010/HW2sol/ his stu ed via y re | ourse urce wa Hero.co sha Problem 2 (20 points) Consider the following assembly representation of a function forloop containing a loop: forloop: pushl %ebp movl %esp, %ebp subl $16, %esp movl $1, ­4(%ebp) movl $0, ­8(%ebp) jmp .L2 .L3: movl ­8(%ebp), %eax addl %eax, %eax addl $5, %eax addl %eax, ­4(%ebp) addl $1, ­8(%ebp) .L2: movl ­8(%ebp), %eax cmpl 8(%ebp), %eax jl .L3 movl ­4(%ebp), %eax leave ret Fill in the blanks to provide the functionality of the loop. Note that 8(%ebp) stores the argument a. int​forloop​ (​ int​a) { ​ int​i; ​ int​result ​ =​1; ​ for​ (​i ​ =​​ 0​ ;​i ​ <​a​ ;​i​ ++​​ )​{ result ​ +=​​ (​ 2​ *​ i ​ +​​ 5​ ); }​re turn​result; } W hat is the size of stack frame in bytes (including %ebp and %esp)? 20 ... a ret address forloop %ebp result [Show More]

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