Use user-arg accessors when expanding runtime lookups#130949
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Use user-arg accessors when expanding runtime lookups#130949tannergooding wants to merge 2 commits into
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fgExpandRuntimeLookupsForCall indexed the helper call's arguments with the raw CountArgs/GetArgByIndex accessors, assuming the runtime-lookup helper has exactly its two user args (genericCtx, signatureCns). On wasm, AddFinalArgsAndDetermineABIInfo prepends a non-user WasmShadowStackPointer arg to every managed call during global morph, which runs before the runtime-lookup expansion phase. That leading arg shifted the raw indices, tripping assert(CountArgs() == 2) and, with asserts off, reading the context and signature from the wrong nodes. Switch to CountUserArgs/GetUserArgByIndex, which skip non-user args (r2r cell, wasm sp) the same way the rest of the JIT already reads helper-call args. This is identical on targets that don't prepend such args. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch |
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CC. @dotnet/jit-contrib, @adamperlin, @lewing this fixes around 10k helperexpansion asserts from SPMI, is product code impacting |
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Pull request overview
This PR updates fgExpandRuntimeLookupsForCall to read runtime-lookup helper-call arguments via the “user arg” APIs (CountUserArgs / GetUserArgByIndex) instead of raw indices, so non-user arguments prepended during morphing (e.g., on TARGET_WASM) don’t shift the expected (genericCtx, signatureCns) positions.
Changes:
- Switch runtime-lookup helper-call arity assertion from
CountArgs()toCountUserArgs(). - Switch argument reads from
GetArgByIndex(0/1)toGetUserArgByIndex(0/1)when extractinggenericCtxandsignatureCns.
Show a summary per file
| File | Description |
|---|---|
| src/coreclr/jit/helperexpansion.cpp | Uses user-arg accessors for runtime lookup helper-call argument indexing to avoid non-user arg prepends shifting indices (notably on wasm). |
Copilot's findings
- Files reviewed: 1/1 changed files
- Comments generated: 1
Both fgExpandThreadLocalAccessForCall and fgExpandStackArrayAllocation indexed the IL args by raw position, which the wasm shadow-stack arg prepended during morph shifts. Switch them to the user-arg accessors used elsewhere in the file so they skip the non-user leading arg. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
This was referenced Jul 17, 2026
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CC. @dotnet/wasm-contrib |
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fgExpandRuntimeLookupsForCallindexed the runtime-lookup helper call's arguments with the rawCountArgs/GetArgByIndexaccessors, assuming exactly its two user args(genericCtx, signatureCns).On wasm,
AddFinalArgsAndDetermineABIInfoprepends a non-userWasmShadowStackPointerarg to the front of every managed call during global morph, which runs beforefgExpandRuntimeLookups. That leading arg shifts the raw indices, so:assert(call->gtArgs.CountArgs() == 2)fires (there are three args), andGetArgByIndex(0)/GetArgByIndex(1)read the shadow-stack pointer and the context instead of the context and the signature.Switch to
CountUserArgs/GetUserArgByIndex, which skip non-user args (r2r cell,wasm sp) the same way the rest of the JIT already reads helper-call args. This is behavior-identical on targets that don't prepend such args, and fixes shared-generic runtime lookups on wasm.This shows up across shared-generic (
[System.__Canon]) methods; it accounts for ~10k of the assert-failing methods in a wasm SuperPMI altjit replay over the libraries/coreclr test collections.Note
This PR was authored with GitHub Copilot.