## Motivation As we have replaced `truncdiv`/`truncmod` by `floordiv`/`floormod` in most places, there's a large demand for simplification to know the sign of the expression. For example, knowing the tensor shape bound can help reduce the if/else conditions significantly.
Here's an example of generated cuda code for the tvm program posted in this [troubleshooting](https://discuss.tvm.ai/t/significant-increase-in-the-amount-of-cuda-code-gen-after-migrating-indexdiv-mod-to-floordiv-mod/) * without knowing `tindex >= 0`: https://gist.github.com/yzhliu/f1aa7c1f25cfd8788cda75a350c4b274 * knowing that `tindex >= 0`: https://gist.github.com/yzhliu/217e997157efcfc2a34e5c27b357fcaa ## Approach * Following [the disucss](https://discuss.tvm.ai/t/discuss-embed-more-bound-information-into-var-or-expr/), we would like to introduce `AssertLowerBound`, `tvm.placeholder` and `tvm.compute` inserts `assert_lower_bound(i, 0)` automatically. ```cpp class AssertLowerBound : public ExprNode { public: Expr value; Expr bound; void VisitAttrs(AttrVisitor* v) { v->Visit("value", &value); v->Visit("bound", &bound); } TVM_DLL static Expr make(Expr value, Expr bound); static constexpr const char* _type_key = "AssertLowerBound"; TVM_DECLARE_NODE_TYPE_INFO(AssertLowerBound, ExprNode); }; ``` * `ConstIntBoundAnalyzer` will recognize `AssertLowerBound` and generate the Bound accordingly for the variables. * Modify `CodeGenC` and `CodeGenLLVM` to support `AssertLowerBound` - simply replace with its value. (Should we insert extra assertion instructions?) Here is a draft of the implement: https://github.com/apache/incubator-tvm/pull/4486 @tqchen @icemelon9 @reminisce -- You are receiving this because you are subscribed to this thread. Reply to this email directly or view it on GitHub: https://github.com/apache/incubator-tvm/issues/4487
