[llvm] [InstCombine] Canonicalise SextADD + GEP (PR #69581)

[via llvm-commits]

LiqinWeng wrote:

> Also, why did you drop the limitation to having one constant operand again?

I have a question. Why is there no nuw flag when executing the following code on a 64-bit platform?

code：
`void test1(unsigned int array1[50], unsigned int a, unsigned int b) {
    unsigned int loc;
    loc = a + 5;
    array1[loc] = b;
    array1[loc + 1] = array1[loc];
    array1[loc + 30] = loc;
}`

https://github.com/llvm/llvm-project/pull/69581