[Flamingo572]

What

Implement __powidf2 (double __powidf2(double base, int exponent)) in libc. Resolves dead stub libcCyberUnknown08 (NID H+8UBOwfScI), which was imported by Cyberpunk 2077.

Tested

Linux x86-64 (GCC 15.2 C++20), verified by running guest_math_tests covering positive/negative powers, quiet NaNs, zero powers, signed zeroes, INT_MIN/INT_MAX, and exponent underflow/overflow. Verified check_conventions.py and tool unit tests.

Checklist

• Based on current main; no other open PR implements the same functions
• One topic per PR; follow-ups go in a new PR
• No comments in code except technical debt
• Unimplemented paths throw (NotImplemented_nid_no_patch); silent stubs are listed in TechnicalDebt
• No notes, investigation .md files or images added to the repository (attach them to this PR)
• New third-party code is a submodule built from source
• Generic behaviour, not specific to one title
• Depends on: none
• AI-assisted: yes

[github-actions]

Other open pull requests touch the same code. Merging one will break the other, or both implement the same thing. If this one builds on them, list them in Depends on.

Pull request	Conflicting files (lines on main)	Same exports	Same new files
#2465		__powidf2_nid_postfix
#3690	core/libs/prx/libc/src/Math.cpp L148-160
#4378		__powidf2_nid_postfix

[Flamingo572]

Closing in favor of #4378 / #2465