build(mingw): Use the portable memcchr when SSE2 is not enabled

[bobtista]

• Follow up for chore(string): Implement memcchr utility function #3430

stringex.h picks the SSE2 memcchr when _M_IX86 is defined. MinGW-w64 headers define _M_IX86 too, but i686 GCC does not enable SSE2 by default, so the intrinsics fail to inline and the MinGW build breaks.

Now the SSE2 version is used for MSVC x86 and x64, or when the compiler defines __SSE2__. Other builds use the portable version.

Todo:

• Build MinGW-w64 i686
• Build vc6 and win32

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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• Run ID: 0b91c7d8-bf38-43b4-b9c6-c3ec61d1e7f1

📥 Commits

Reviewing files that changed from the base of the PR and between 2d6761c and 239a38e.

📒 Files selected for processing (1)

• Dependencies/Utility/Utility/stringex.h

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Walkthrough

The SSE2 include condition in stringex.h now requires _MSC_VER with _M_IX86 or _M_X64, unless __SSE2__ is defined. Other builds use the portable implementation.

Changes

SSE2 selection

Layer / File(s)	Summary
SSE2 compiler guard Dependencies/Utility/Utility/stringex.h	The SSE2 include condition now requires _MSC_VER with _M_IX86 or _M_X64, unless __SSE2__ is defined. Other builds use the portable implementation.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~4 minutes

Change: Bug fix

Suggested reviewers: stephanmeesters

Merge Risk: ⚪ Minimal · up to 239a3

The compiler guard addresses the reported MinGW build failure, with no remaining issue established that should block merging.

Pre-merge checks · 4

Passed checks (4 passed)

Check name	Status	Explanation
Title check		The title clearly identifies the MinGW build fix and the use of the portable memcchr implementation when SSE2 is unavailable.
Description check		The description accurately explains the _M_IX86 and SSE2 issue, the implementation change, and the reported build validation.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

• Autofix · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

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[greptile-apps]

Confidence Score: 4/5

[Medium impact] Changes a preprocessor condition for string search optimization.

The production change appears safe to merge, with a non-blocking suggestion to align the SSE2 test check.

Findings

1.  Tests keep the old check ▶

Summary

Changes memcchr selection so non-MSVC builds need __SSE2__ to use SSE2.

• The byte scan uses SSE2 only when the compiler supports it.

_{Reviews (1) · Last reviewed commit: "build(mingw): Use the portable memcchr w..." · Reviewed by Greptile}

[greptile-apps]

Tests keep the old check

MemcchrSse2 still accepts _M_IX86 without _MSC_VER or __SSE2__. If MinGW headers define _M_IX86 before that test's check and SSE2 is disabled, the test still includes the unsupported SSE2 implementation, even though this header now selects portable code. Enabling tests could therefore bring back the build error. Apply the same check to stringex_memcchr_sse2_test.cpp.

[Mauller]

Reverse the original ordering and it will fix the problem.

#if defined(__SSE2__) || defined(_M_X64) || ( defined(_MSC_VER) && defined(_M_IX86) )

The OR check will short circuit and return a true before checking any others.

[stephanmeesters]

Perhaps this can be simplified further by doing this somewhere (could be a bad idea):

#if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
    #ifndef __SSE2__
        #define __SSE2__ 1
    #endif
#endif