[Unity][Bugfix] Check for trivial re-bindings in MatchCast nodes #15854
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The `KillAfterLastUse` pass that was implemented in apache#15810 checked for trivial re-bindings in `VarBinding` nodes, but not in `MatchCast` nodes. As a result, `CodeGenVM`'s de-duplication of registers resulted in the object being killed prematurely. ```python y = R.match_cast(x, R.Tensor(...)) # Trivial rebinding here. # CodeGenVM has these share a register. R.memory.kill_tensor(x) # Kill x after last usage. # Register is set to None. _ = R.ExternFunc("set_item")(y) # Use of the cleared register through y. ```
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@junrushao This change should resolve the MLC-LLM error you found in #15852. It works in my local setup, and it would be good to validate that it works on your side as well. |
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Oct 2, 2023
Lunderberg
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Oct 2, 2023
Prior to this commit, if a relax variable were assigned to itself, through either `VarBinding` or `MatchCast` nodes, the two relax variables would share the same register in the VM. As a result, any upstream transform that deletes an object with `R.memory.kill_tensor` or `R.memory.kill_storage` must be aware of this VM behavior, and to only output one such instruction for each set of aliased registers. This commit updates the VM to produce one register for each aliased relax variable. The trivial bindings can be removed applying `relax.transform.CanonicalizeBindings`, instead of being implicitly de-duplicated at the codegen level. This PR is a follow-up to apache#15854, with a better long-term solution, but which may have knock-on effects that must also be resolved. In addition, this adds a usage example for the bug reported in apache#15852, to avoid re-occurrence of similar issues.
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Just hit the issue of |
Lunderberg
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Oct 3, 2023
Prior to this commit, if a relax variable were assigned to itself, through either `VarBinding` or `MatchCast` nodes, the two relax variables would share the same register in the VM. As a result, any upstream transform that deletes an object with `R.memory.kill_tensor` or `R.memory.kill_storage` must be aware of this VM behavior, and to only output one such instruction for each set of aliased registers. This commit updates the VM to produce one register for each aliased relax variable. The trivial bindings can be removed applying `relax.transform.CanonicalizeBindings`, instead of being implicitly de-duplicated at the codegen level. This PR is a follow-up to apache#15854, with a better long-term solution, but which may have knock-on effects that must also be resolved. In addition, this adds a usage example for the bug reported in apache#15852, to avoid re-occurrence of similar issues.
Lunderberg
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Oct 24, 2023
Prior to this commit, if a relax variable were assigned to itself, through either `VarBinding` or `MatchCast` nodes, the two relax variables would share the same register in the VM. As a result, any upstream transform that deletes an object with `R.memory.kill_tensor` or `R.memory.kill_storage` must be aware of this VM behavior, and to only output one such instruction for each set of aliased registers. This commit updates the VM to produce one register for each aliased relax variable. The trivial bindings can be removed applying `relax.transform.CanonicalizeBindings`, instead of being implicitly de-duplicated at the codegen level. This PR is a follow-up to apache#15854, with a better long-term solution, but which may have knock-on effects that must also be resolved. In addition, this adds a usage example for the bug reported in apache#15852, to avoid re-occurrence of similar issues.
Lunderberg
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Oct 25, 2023
Prior to this commit, if a relax variable were assigned to itself, through either `VarBinding` or `MatchCast` nodes, the two relax variables would share the same register in the VM. As a result, any upstream transform that deletes an object with `R.memory.kill_tensor` or `R.memory.kill_storage` must be aware of this VM behavior, and to only output one such instruction for each set of aliased registers. This commit updates the VM to produce one register for each aliased relax variable. The trivial bindings can be removed applying `relax.transform.CanonicalizeBindings`, instead of being implicitly de-duplicated at the codegen level. This PR is a follow-up to apache#15854, with a better long-term solution, but which may have knock-on effects that must also be resolved. In addition, this adds a usage example for the bug reported in apache#15852, to avoid re-occurrence of similar issues.
Lunderberg
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Oct 31, 2023
* [Unity] Ensure one VM register for each relax binding Prior to this commit, if a relax variable were assigned to itself, through either `VarBinding` or `MatchCast` nodes, the two relax variables would share the same register in the VM. As a result, any upstream transform that deletes an object with `R.memory.kill_tensor` or `R.memory.kill_storage` must be aware of this VM behavior, and to only output one such instruction for each set of aliased registers. This commit updates the VM to produce one register for each aliased relax variable. The trivial bindings can be removed applying `relax.transform.CanonicalizeBindings`, instead of being implicitly de-duplicated at the codegen level. This PR is a follow-up to #15854, with a better long-term solution, but which may have knock-on effects that must also be resolved. In addition, this adds a usage example for the bug reported in #15852, to avoid re-occurrence of similar issues. * Add unit test to validate that the alias is preserved * Use the new GetBoundValue utility function * Update VMTIRCodeGen to also avoid de-duplication of bindings * Move the callback definition to tvm.relax.testing.vm namespace
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The
KillAfterLastUsepass that was implemented in #15810 checked for trivial re-bindings inVarBindingnodes, but not inMatchCastnodes. As a result,CodeGenVM's de-duplication of registers resulted in the object being killed prematurely.