Combine writes in WidenAsciiToUtf16

[xtqqczze]

TODO: Check logic for big-endian.

Indicative codegen on ARM64 when widening ushort to uint.

;bc76418
            orr     w0, w3, w3,  LSL #8
            and     w0, w0, #0xD1FFAB1E
            ubfiz   x2, x2, #1, #32
            str     w0, [x1, x2]
						;; size=16 bbWeight=1 PerfScore 3.50

;base
            lsl     x0, x2, #1
            uxtb    w2, w3
            strh    w2, [x1, x0]
            uxth    w2, w3
            asr     w2, w2, #8
            add     x0, x1, x0
            strh    w2, [x0, #0x02]
						;; size=28 bbWeight=1 PerfScore 5.50

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Issue Details

---

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Author:	xtqqczze
Assignees:	-
Labels:	area-System.Text.Encoding, community-contribution
Milestone:	-

[xtqqczze]

/azp run runtime-community

[azure-pipelines]

Commenter does not have sufficient privileges for PR 88502 in repo dotnet/runtime

[xtqqczze]

@stephentoub Can we run checks on big-endian hardware?

[stephentoub]

/azp list

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[stephentoub]

/azp run runtime-community

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[xtqqczze]

/azp run runtime-community

@stephentoub

[azure-pipelines]

Commenter does not have sufficient privileges for PR 88502 in repo dotnet/runtime

[xtqqczze]

@stephentoub I think the runtime failures are unrelated. They appear to be linked to XUnitWrapperGenerator.

[xtqqczze]

@stephentoub Could you please run runtime-community again.

[ghost]

Draft Pull Request was automatically closed for 30 days of inactivity. Please let us know if you'd like to reopen it.