[AMDGPU] Cope with SelectionDAG::UpdateNodeOperands returning a different SDNode #65765
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…rent SDNode SITargetLowering::adjustWritemask calls SelectionDAG::UpdateNodeOperands to update an EXTRACT_SUBREG node in-place to refer to a new IMAGE_LOAD instruction, before we delete the old IMAGE_LOAD instruction. But in UpdateNodeOperands can do CSE on the fly and return a different EXTRACT_SUBREG node, so the original EXTRACT_SUBREG node would still exist and would refer to the old deleted IMAGE_LOAD instruction. This caused errors like: t31: v3i32,ch = <<Deleted Node!>> # D:1 This target-independent node should have been selected! UNREACHABLE executed at lib/CodeGen/SelectionDAG/InstrEmitter.cpp:1209! Fix it by detecting the CSE case and replacing all uses of the original EXTRACT_SUBREG node with the CSE'd one. Recommit with a fix for a use-after-free bug in the first version of this patch (#65340) which was caught by asan.
jayfoad
commented
Sep 8, 2023
| SDNode *NewUser = DAG.UpdateNodeOperands(User, SDValue(NewNode, 0), Op); | ||
| if (NewUser != User) { | ||
| DAG.ReplaceAllUsesWith(SDValue(User, 0), SDValue(NewUser, 0)); | ||
| DAG.RemoveDeadNode(User); |
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This line is the fix for the asan error.
arsenm
approved these changes
Sep 8, 2023
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SITargetLowering::adjustWritemask calls SelectionDAG::UpdateNodeOperands
to update an EXTRACT_SUBREG node in-place to refer to a new IMAGE_LOAD
instruction, before we delete the old IMAGE_LOAD instruction. But in
UpdateNodeOperands can do CSE on the fly and return a different
EXTRACT_SUBREG node, so the original EXTRACT_SUBREG node would still
exist and would refer to the old deleted IMAGE_LOAD instruction. This
caused errors like:
t31: v3i32,ch = <<Deleted Node!>> # D:1
This target-independent node should have been selected!
UNREACHABLE executed at lib/CodeGen/SelectionDAG/InstrEmitter.cpp:1209!
Fix it by detecting the CSE case and replacing all uses of the original
EXTRACT_SUBREG node with the CSE'd one.
Recommit with a fix for a use-after-free bug in the first version of
this patch (#65340) which was caught by asan.