[Relax][Backend] Fix TVM crashes with default relax pipeline when opt_level=1: InternalError: Check failed: (slot->value_computed) is false #18491
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…vel=1: InternalError: Check failed: (slot->value_computed) is false
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| if (it != slot_map_.end() && !it->second->value_computed) { | ||
| // If it's a variable, mark it as ready for computation | ||
| if (expr.as<tir::VarNode>()) { | ||
| it->second->value_computed = true; |
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Marking arbitrary tir::VarNode instances as value_computed = true in VisitExpr_ is incorrect. In VMShapeLower, only Relax ShapeVars (from function parameters/match_cast) or IntImm constants can be safely marked as computed, because only these have runtime values accessible to the VM.
I think correct way is to fix this earlier in the pipeline (shape inference/canonicalization) by symbolizing composite PrimExpr (introduce Relax ShapeVars) or simplifying them before VMShapeLower.
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Hi Commiters,
This PR is trying to fix issues #17876. Any suggestions would be appreciated if you are available.
Root Cause
VMShapeLowercrashed when processingShapeExprcontaining compositePrimExprthat weren't computed yet.Solution
ModifiedVisitExpr_(const ShapeExprNode* op)invm_shape_lower.ccto:1. Mark uncomputed variables as ready for computation2. Trigger EmitOutstandingPrimExprCompute() to resolve the dependency chain3. Ensure all expressions are computed before callingMakeSymbolicShapeArgAdded test case:test_composite_shape_expression_fix()to prevent future occurrences.symbolizing the composite PrimExpr in the pipeline: canonicalization