[NativeAOT-LLVM]: Question: Data()/gtOp2 for GT_OBJ ?

[yowl]

When converting GT_LCL_VAR to GT_OBJ for GC tracked objects, currently the gtOp2/Data() field for the GT_OBJ is not set.

https://github.com/yowl/runtimelab/blob/f8f9280b7e655d48fde4c437d8ad82d8ff5d3507/src/coreclr/jit/llvm.cpp#L1456-L1468

This causes a problem when dumping the tree at

https://github.com/yowl/runtimelab/blob/f8f9280b7e655d48fde4c437d8ad82d8ff5d3507/src/coreclr/jit/gentree.h#L7213

with stack

 	clrjit_browser_wasm32_x64.dll!GenTree::gtSkipReloadOrCopy() Line 7560	C++
>	clrjit_browser_wasm32_x64.dll!GenTree::OperIsInitBlkOp() Line 7213	C++
 	clrjit_browser_wasm32_x64.dll!GenTree::OperIsCopyBlkOp() Line 7220	C++
 	clrjit_browser_wasm32_x64.dll!Compiler::gtDispTree(GenTree * tree, IndentStack * indentStack, const char * msg, bool topOnly, bool isLIR) Line 12242	C++
 	clrjit_browser_wasm32_x64.dll!Compiler::gtDispLIRNode(GenTree * node, const char * prefixMsg) Line 13154	C++
 	clrjit_browser_wasm32_x64.dll!Compiler::gtDispRange(const LIR::ReadOnlyRange & range) Line 12984	C++
 	clrjit_browser_wasm32_x64.dll!Compiler::fgDumpBlock(BasicBlock * block) Line 2242	C++
 	clrjit_browser_wasm32_x64.dll!Compiler::fgDumpTrees(BasicBlock * firstBlock, BasicBlock * lastBlock) Line 2259	C++
 	clrjit_browser_wasm32_x64.dll!Compiler::fgDispBasicBlocks(BasicBlock * firstBlock, BasicBlock * lastBlock, bool dumpTrees) Line 2198	C++
 	clrjit_browser_wasm32_x64.dll!Compiler::fgDispBasicBlocks(bool dumpTrees) Line 2205	C++
 	clrjit_browser_wasm32_x64.dll!Phase::PostPhase(PhaseStatus status) Line 211	C++

What should GT_OBJ be storing in the second operand, gtOp2 ?

[SingleAccretion]

Technically it should be set to nullptr. But SetOper already does this for debug builds, so it is a bit mysterious to me how this path is hit when dumping. What is the value of gtOp2 that you're seeing?

Edit: actually, nevermind, I see the issue, the check in SetOper is for an exact kind, but GT_OBJ is a GTF_EXOP as well.

I think the proper fix is to make OperIsBlkOp not rely on this Data() != nullptr fragile invariant and instead make it check explicitly for the interesting opers (i. e. GT_STORE_DYN_BLK, GT_STORE_BLK, GT_STORE_OBJ).

[yowl]

Thanks