GXRuntime: inline the hot paths of the FP gate and paired-single access

[dougchansan]

Profiling a recompiled Mario Kart: Double Dash on Apple Silicon (sample, race scene) put two runtime helpers near the top of self time inside StaticRecompCore::Run:

symbol	self samples	share
ppc_fp_available	869	~7.1%
psq_load_value + psq_store_value	1101	~9.0%

Generated code calls them once per instruction site — 121,874 FP sites and 19,642 paired-single sites on this title.

What changed

ppc_fp_available_inline() puts the MSR[FP] test in the header, leaving only the exception raise out of line. A running game always has MSR[FP] set, so the cost was the call, not the test.

ppc_psq_load_inline() / ppc_psq_store_inline() handle GQR type 0 — plain IEEE singles, no quantisation, no scale, which is what games leave GQR0 at — as two 32-bit accesses and a conversion. Quantised types (4..7), invalid types, and the LSQE illegal-instruction check all fall through to the existing out-of-line functions, so behaviour is unchanged.

Nothing new had to be exposed: f64_value, convert_to_double, convert_to_single_ftz and f64_bits were already static inline in core/types.h, and the memory accessors and PPC_HID2_LSQE were already header-visible.

ppc_fp_available(), ppc_psq_load() and ppc_psq_store() all remain real symbols — the LLVM backend emits calls to them by name.

Measured

Idle Apple M5, alternating A/B with a reversed-order block, largest competing process under 70%:

change	delta	ranges
inline FP gate	+11.8%	do not overlap
inline paired-single	+4.0%	do not overlap

Both beat their profiled share. An out-of-line call is also an optimisation barrier: at every generated site w, gqr_index, indexed and cia are literals, so inlining lets the compiler fold the LSQE test and the w branch away per site. The paired-single module came out slightly smaller despite 19,642 inlined sites, which is that folding showing up.

With PGO on top (+7.5%), MKDD under static recompilation on Metal went 51.1 → 62.5 fps single-player and 40.6 → 50.8 fps split-screen.

Ordering

Pairs with a DolRecomp change that emits the _inline forms. This one should land first — with the emitter updated and these absent, a port fails to compile.