[LLVMdev] Question about NoWrap flag for SCEVAddRecExpr

[Tong Chen]

I am testing vectorization on the following test case:

float x[1024], y[1024];

void myloop1() {
        for (long int k = 0; k < 512; k++) {
           x[2*k] = x[2*k]+y[k];
        }
}

Vectorization failed due to "unsafe dependent memory operation". I traced 
the LoopAccessAnalysis.cpp and found the reason is the NoWrapFlag for 
SCEVAddRecExpr is not set and consequently the dependence distant became 
unknown. 

Can anyone familiar with ScalarRevolution tell me whether this is an 
expected behavior or a bug? 

Tong
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