324_Book

1 int mat1mn 148 2 3 4 5 6 7 chapter 3 machine level

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Unformatted text preview: m %eax to a different register. Practice Problem 3.16: Given the following C function: 1 2 3 4 5 6 int proc(void) { int x,y; scanf(&quot;%x %x&quot;, &amp;y, &amp;x); return x-y; } generates the following assembly code proc: pushl %ebp movl %esp,%ebp subl \$24,%esp addl \$-4,%esp leal -4(%ebp),%eax pushl %eax leal -8(%ebp),%eax pushl %eax pushl \$.LC0 Pointer to string &quot;%x %x&quot; call scanf Diagram stack frame at this point GCC 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 movl movl subl movl movl popl ret -8(%ebp),%eax -4(%ebp),%edx %eax,%edx %edx,%eax %ebp,%esp %ebp Assume that procedure proc starts executing with the following register values: Register %esp %ebp Value 0x800040 0x800060 140 CHAPTER 3. MACHINE-LEVEL REPRESENTATION OF C PROGRAMS code/asm/ﬁb.c 1 2 3 4 5 6 7 8 9 10 int fib_rec(int n) { int prev_val, val; if (n &lt;= 2) return 1; prev_val = fib_rec(n-2); val = fib_rec(n-1); return prev_val + val; } code/asm/ﬁb.c Figure 3.19: C Code for Recursive Fibonacci Program. Suppose proc calls scanf...
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