ARM64: issue with frame pointer offsets out of range

[BruceForstall]

There are a couple cases where the expression generated by arm64 codegen might not be encodable.

In CodeGen::genReportGenericContextArg(regNumber initReg, bool* pInitRegZeroed)
...
    getEmitter()->emitIns_R_R_I(ins_Store(TYP_I_IMPL), EA_PTRSIZE, reg, genFramePointerReg(),
                                compiler->lvaCachedGenericContextArgOffset());

With a huge frame (>32760 bytes), generating [fp + lvaCachedGenericContextArgOffset()] won't be encodable, if it is placed on the frame far from fp.

In genFnProlog():

    if (compiler->info.compPublishStubParam)
    {
#if CPU_LOAD_STORE_ARCH
        getEmitter()->emitIns_R_R_I(ins_Store(TYP_I_IMPL), EA_PTRSIZE, REG_SECRET_STUB_PARAM, genFramePointerReg(),
                                    compiler->lvaTable[compiler->lvaStubArgumentVar].lvStkOffs);

If the sub argument is far from fp, the expression won't be encodable.

[BruceForstall]

Fixed by dotnet/coreclr#21997