Optimize performance of GetHashCode for ContentType comparers, remove allocs

[h3xds1nz]

Description

Removes allocations for ContentType's WeakComparer and StrongComparer (which are used in the related dictionaries).

• We will use StringComparer.OrdinalIgnoreCase.GetHashCode(src) instead of src.ToUpperInvariant.GetHashCode() as that creates a new string everytime just so we can retrieve HashCode out of it.
• This will reduce allocations to zero and also save about 40ns (depending on length, it scales up) per invocation while preserving functionality.

Benchmarks

Method	Mean [ns]	Error [ns]	StdDev [ns]	Gen0	Code Size [B]	Allocated [B]
Original	34.736 ns	0.2199 ns	0.2057 ns	0.0038	392 B	64 B
PR_EDIT	8.620 ns	0.0279 ns	0.0247 ns	-	330 B	-

Method	Mean [ns]	Error [ns]	StdDev [ns]	Gen0	Code Size [B]	Allocated [B]
Original	70.84 ns	1.404 ns	1.379 ns	0.0110	394 B	184 B
PR_EDIT	41.27 ns	0.127 ns	0.113 ns	-	316 B	-

Method	Mean [ns]	Error [ns]	StdDev [ns]	Gen0	Code Size [B]	Allocated [B]
Original	183.5 ns	2.76 ns	2.58 ns	0.0310	394 B	520 B
PR_EDIT	132.4 ns	0.40 ns	0.35 ns	-	333 B	-

Benchmark code

//First invocation
return "aBCD".ToUpperInvariant().GetHashCode() ^ "xDDAH".ToUpperInvariant().GetHashCode();
return StringComparer.OrdinalIgnoreCase.GetHashCode("aBCD") ^ StringComparer.OrdinalIgnoreCase.GetHashCode("xDDAH");

//Second invocation
return "aBCDnowimagineifthisisLongstring".ToUpperInvariant().GetHashCode() ^ "xDDAHaBCDnowimagineifthisisLongstring".ToUpperInvariant().GetHashCode();
return StringComparer.OrdinalIgnoreCase.GetHashCode("aBCDnowimagineifthisisLongstring") ^ StringComparer.OrdinalIgnoreCase.GetHashCode("xDDAHaBCDnowimagineifthisisLongstring");

//Third invocation
return "aBCDnowimagineifthisisLongstringWeNeedthistobewaylongeeeeeeerrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr".ToUpperInvariant().GetHashCode() ^
"xDDAHaBCDnowimagineifthisisLongstringaBCDnowimagineifthisisLongstringWeNeedthistobewaylongeeeeeeerrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr".ToUpperInvariant().GetHashCode();
return StringComparer.OrdinalIgnoreCase.GetHashCode("aBCDnowimagineifthisisLongstringWeNeedthistobewaylongeeeeeeerrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr") ^ 
StringComparer.OrdinalIgnoreCase.GetHashCode("xDDAHaBCDnowimagineifthisisLongstringaBCDnowimagineifthisisLongstringWeNeedthistobewaylongeeeeeeerrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr");

Customer Impact

Increased performance, including start-up performance, decreased allocations.

Regression

No.

Testing

Local build, assert test:

int hashCode1 = "áBCD".ToUpperInvariant().GetHashCode() ^ "xDDAH".ToUpperInvariant().GetHashCode();
int hashCode2 = StringComparer.OrdinalIgnoreCase.GetHashCode("ÁBCD") ^ StringComparer.OrdinalIgnoreCase.GetHashCode("xDDAH");
Assert.AreEqual(hashCode1, hashCode2);

Risk

Low.

Microsoft Reviewers: Open in CodeFlow

[h3xds1nz]

CI failure caused by #9632 requesting System.Drawing.Common from .NET 8 (v8.0.8).

[harshit7962]

/azp run

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