[Unity][Transform] Handle replacement at both var binding and usage #16367
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Resolve a bug that caused undefined relax variables in the output of `CanonicalizeBindings` for cases where `VisitVarDef(const Var&)` replaces a variable, and `VisitExpr_(const VarNode*)` returns a value with different struct info, both occurring within the same `VarBinding`. The ExprMutator is only allowed to update a variable's struct info if the value bound to it has new struct info. When CanonicalizeBindings replaces a trivial binding, this may provide better struct info as a result. Prior to this commit, `ExprMutator::ReEmitBinding` defined a remap for `binding->var->vid`, even if the derived class defined a replacement by overriding `VisitVarDef`. If the derived class defines a new variable binding by overriding `VisitVarDef`, and also causes a variable replacement by overriding `VisitExpr` and returning a type with different struct info, then `ExprMutator` must check for both `binding->var->vid` *AND* `new_var->vid`. The former may be present in the unmodified graph, and the latter may be produced by the derived class before delegating to the base class. This commit updates `ExprMutator::ReEmitBinding` to define entries for both replacements that may be required.
Hzfengsy
approved these changes
Jan 9, 2024
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Resolve a bug that caused undefined relax variables in the output of
CanonicalizeBindingsfor cases whereVisitVarDef(const Var&)replaces a variable, andVisitExpr_(const VarNode*)returns a value with different struct info, both occurring within the sameVarBinding.The ExprMutator is only allowed to update a variable's struct info if the value bound to it has new struct info. When CanonicalizeBindings replaces a trivial binding, this may provide better struct info as a result.
Prior to this commit,
ExprMutator::ReEmitBindingdefined a remap forbinding->var->vid, even if the derived class defined a replacement by overridingVisitVarDef. If the derived class defines a new variable binding by overridingVisitVarDef, and also causes a variable replacement by overridingVisitExprand returning a type with different struct info, thenExprMutatormust check for bothbinding->var->vidANDnew_var->vid. The former may be present in the unmodified graph, and the latter may be produced by the derived class before delegating to the base class.This commit updates
ExprMutator::ReEmitBindingto define entries for both replacements that may be required.