考虑以下 C 代码段。
for (i = 0, i以下哪一项是错误的?
(A)代码包含循环不变计算
(B)此代码中存在公共子表达式消除范围
(C)本规范存在强度降低的范围
(D)这段代码有死代码消除的范围答案： (D)
说明：问题询问虚假陈述
4*j is common subexpression elimination so B is true.
5*i can be moved out of inner loop so can be i%2.
Means, A is true as we have loop invariant computation.
Next, 4*j as well as 5*i can be replaced with a = - 4;
before j loop then a = a + 4; where 4*j is computed,
likewise for 5*i. C is true as there is scope of strength
reduction.
By choice elimination, we have D.这个问题的测验