Remove GT_ADDEX and replace with more generalized containment handling

[tannergooding]

This makes more progress towards #68028

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Issue Details

---

This makes more progress towards #68028

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

[tannergooding]

/azp run runtime-coreclr jitstress, runtime-coreclr gcstress0x3-gcstress0xc, Fuzzlyn

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[EgorBo]

Any idea what causes size regressions? https://dev.azure.com/dnceng-public/public/_build/results?buildId=32858&view=ms.vss-build-web.run-extensions-tab

[tannergooding]

Any idea what causes size regressions? https://dev.azure.com/dnceng-public/public/_build/results?buildId=32858&view=ms.vss-build-web.run-extensions-tab

@EgorBo, looks like some places aren't getting contained anymore and they were on the previous path.

Looking again, this would be because the original path handles GT_CAST having a contained op itself by clearing the containment

Where-as the new path checked the containment the CastOp and exited early if it was contained.

[tannergooding]

/azp run runtime-coreclr jitstress, runtime-coreclr gcstress0x3-gcstress0xc, Fuzzlyn

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[TIHan]

Similar to what we did for msub and madd - let containment drive all of it rather than have a separate op.

[tannergooding]

Collection	Base size (bytes)	Diff size (bytes)
benchmarks.run.Linux.arm64.checked.mch	16,583,652	-988
coreclr_tests.run.Linux.arm64.checked.mch	164,421,868	-9,380
libraries.crossgen2.Linux.arm64.checked.mch	23,302,248	-244
libraries.pmi.Linux.arm64.checked.mch	64,553,072	-2,312
libraries_tests.pmi.Linux.arm64.checked.mch	143,626,968	-1,568

MinOpts is a size regression since it now only does this opt when optimizations are enabled, but that also gives a very minor throughput improvement (-0.01%).

If we were willing to take a regression to MinOpts instead (+0.01%) and do this containment even in minopts, then we'd save more than 24k size instead. Given that Arm64 has fixed-sized instructions, this might be beneficial overall.

[tannergooding]

Many diffs are cases like the following:

- add x0, x0, w26, UXTW- ldrb w0, [x0]+ ldrb w0, [x0, w26, UXTW #2]

These seem to mostly be due to ADDEX not being properly handled in many places while ADD always is.

---

There are a few small regressions such as:

+ lsl w0, w0, #8
ldr x1, [fp, #0xA8]	// [V192 tmp170]
ldrb w1, [x1, #0x01]
- add w1, w1, w0, LSL #8+ add w1, w0, w1

Notably we're checking if childNode->gtGetOp1() (the value to be shifted) is contained, the original doesn't (but it shouldn't be anyways since we need a register for it).

We're also checking IsSafeToContainMem(parentNode, childNode) where-as the original wasn't. I expect this is the "actual" reason for the "larger diff" since we always do "strict" checking and we don't allow reordering across anything with a "side effect". That being said, there is no actual interdependence between these two and so it is technically "safe" anyways.

[tannergooding]

/azp run Fuzzlyn

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[EgorBo]

Nice diffs from a clean up 🙂