Revert "Do not generate TYP_STRUCTLCL_FLD nodes (#66251)"

[SingleAccretion]

In #66251 I've enhanced IsLocalAddrExpr to look for zero-offset sequences on ADDRs.

This was a correctness fix.

Unfortunately, it also broke the structreturn test because we have the following tree there:

*****BB01, STMT00006(before)
N005 ( 10, 8) [000064] -A------R---*ASG long N004 ( 3, 2) [000062] D------N----+--*LCL_VAR long V04 tmp2 d:2N003 ( 6, 5) [000063] n-----------\--*IND long N002 ( 3, 3) [000043] ------------\--*ADDR byref ZeroFseq[a]
N001 ( 3, 2) [000044] -------N----\--*LCL_VAR struct<TestUnsafeCasts+largeStruct, 32> V00 loc0 u:6 (last use)

Where the field a does not belong to TestUnsafeCasts+largeStruct. This is the well-known VN problem with invalid field sequences, there is no expedient fix for it.

So I am reverting #66251, it seems TYP_STRUCTLCL_FLD is fully gated on fixing this problem (I knew it was gated at least partially, I did not anticipate it to break so quickly though).

Fixes#67346, #67355.

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Issue Details

---

In #66251 I've enhanced IsLocalAddrExpr to look for zero-offset sequences on ADDRs.

This was a correctness fix.

Unfortunately, it also broke the structreturn test because we have the following tree there:

*****BB01, STMT00006(before)
N005 ( 10, 8) [000064] -A------R---*ASG long N004 ( 3, 2) [000062] D------N----+--*LCL_VAR long V04 tmp2 d:2N003 ( 6, 5) [000063] n-----------\--*IND long N002 ( 3, 3) [000043] ------------\--*ADDR byref ZeroFseq[a]
N001 ( 3, 2) [000044] -------N----\--*LCL_VAR struct<TestUnsafeCasts+largeStruct, 32> V00 loc0 u:6 (last use)

Where the field a does not belong to TestUnsafeCasts+largeStruct. This is the well-known VN problem with invalid field sequences, there is no expedient fix for it.

So I am reverting #66251, it seems TYP_STRUCTLCL_FLD is fully gated on fixing this problem (I knew it was gated at least partially, I did not anticipate it to break so quickly though).

Fixes #67346, #67355.

Author:	SingleAccretion
Assignees:	-
Labels:	area-CodeGen-coreclr
Milestone:	-

[SingleAccretion]

@dotnet/jit-contrib