Fix the gc layout algorithm to not double count byref #814
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This pull request is intended to fix the crossgen2 compilation crash of SlowTailCallArgs.csproj.
The compilation failure was found by @janvorli by running all the CoreCLR Pri 1 test on Linux under crossgen2 using SuperIlc.
This bug repro consistently on both debug and release compilation using
crossgen2on Linux only.The symptom is that when we generate code that put an instance of TestByRefStruct on the stack, we hit an assertion in the code generator here:
runtime/src/coreclr/src/jit/codegenxarch.cpp
Line 8312 in d8f744d
With some digging, I figured there is a bug in the GC layout algorithm. If a struct happens to contain two instances of
ByReferenceOfTorTypedReferenceplaced in the same location using ExplicitLayout, the existing code would have double-counted it.The obvious fix is to avoid double-counting, and that is what the code change does.
@dotnet/crossgen-contrib