[GitHub] [tvm] AndrewZhaoLuo commented on a diff in pull request #10922: [FIX][FQ2I] Add abs to FQ2I, fix abs implementation for int

[GitBox <gi...@apache.org>]

AndrewZhaoLuo commented on code in PR #10922:
URL: https://github.com/apache/tvm/pull/10922#discussion_r845307339


##########
src/tir/op/op.cc:
##########
@@ -653,7 +653,27 @@ PrimExpr abs(PrimExpr x, Span span) {
     if (px) {
       return IntImm(x.dtype(), std::abs(px->value), px->span);
     }
-    return tir::Select(x >= make_zero(x.dtype()), x, -x, span);
+

Review Comment:
   Hmm honestly I'm not sure if I like this change since it actually is a change in the semantics of abs. 
   
   E.g. abs(-128) = 128 which should overflow to -128 with only 8 bits. 
   
   IMO two solutions:
   1. For integers, make it return uint version so it never overflows.
   2. Just handle the edge case manually in fq2i 
   
   If I understand this is only important to handle the -128 --> 127 case in quantized models so I say just put it in 2.



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