si_ftol: 9-byte naked asm using FISTTP (SSE3 truncate-from-x87) replaces
the 39-byte FSTCW/FLDCW/FISTP rounding mode dance. 4 vs 7 cycles (1.7x).
13.2M calls/7.5s in-game -- ~13ms savings per period.
Benchmark: patch-in-place at mapped 0x40A2B0, test parity across 19 values,
best-of-5 timing with varying inputs. Framework for all silicon functions.
Also disabled h67 (ConvertPixelsToScreenAlt) probe -- game passes ECX=0
as valid input, thiscall probe crashes on null this.
callFtol: use f32 multiply instead of f64 intermediate. Parity holds --
the delta*scale product is well within f32 precision range.
fastMod: replace integer modulo (idiv, ~25 cycles) with conditional
subtract (~2 cycles) for looping animation frame computation. Falls
back to real modulo for large time skips (alt-tab, etc).
3609 cycles (-14% vs 4176 baseline), parity PASS.
findInterpIdx now returns {idx0, idx1, t} as a struct instead of writing
all three to the output buffer. Only output[0] is written for next-frame
cache persistence. All 29 call sites updated to use returned values.
3574 cycles (-14% vs 4176 baseline), was 3841 (-8%). Parity PASS.
Replaced all remaining game function calls:
- findInterpIdx (0x713D50): full temporal-coherence search reimplementation
- interpAnimKF in boneKeyframeLoop: reuses existing pure Zig version
- applyTranslation/rotateByQuaternion/scaleMatrix3x3 in boneKeyframeLoop
- getInterpolatedFloat (0x71AF20): replaced with interpFloatTrack (identical)
- extractByte (0x71AE90): findInterpIdx + direct byte read
- Child recursion: direct call to transformImpl_SSE instead of 0x714260 hook
Only 2 game calls remain (cannot be replaced):
- 0x409AEF: one-time atexit registration in boneKeyframeLoop
- 0x7B5F60: IsParticleBufferEmpty (reads game particle state)
Root cause of billboard visual artifacts: callVec3SqMag used inline asm
to call game's x87 vec3SqMag (0x4549F0) with fstps to capture ST0.
With SSE2 codegen, the x87/SSE state interaction caused corrupted float
values in billboard bone matrices (mat[0][2] wildly wrong).
Replaced with pure Zig: x*x + y*y + z*z — no x87, no inline asm.
Also replaced:
- matMul (0x74A7C0): pure Zig f64 scalar matmul, no alignment needs
- callFtol (0x40A2B0): f64 intermediate + @intFromFloat (cvttsd2si)
Architecture: bone_sse.zig is REF code compiled with SSE2, called as
cdecl from thiscall wrapper in transform44.zig (cross-object to prevent
LLVM inlining AND ESP alignment into thiscall frame).
A/B: other hooks gated behind AB_OTHER_HOOKS=false for isolated testing.
Assembly-verified fixes from t44_helpers_asm.txt:
findInterpIdx (0x713D50):
- Range format is [start, last] not [start, count] (DEC EDI pattern)
- Backward scan entry: delta >= 0xFFFFFE0C not > (JC = unsigned below)
- 500-tick threshold (0x1F4) for forward/backward vs binary search
- GS check is CMP AX,0xFFFF (word compare), not >= 0
- t computation: FILD qword (i64 numer) / FIDIV dword (i32 denom)
interpAnimKF (0x713EA0):
- Keyframe stride is 16 bytes (SHL EAX,0x4), NOT 8 (CompQuat)
- Values are raw floats, no short-to-float conversion needed
Runtime constants — all now read from game memory:
- 0x80297C (3.0) and 0x802990 (6.0) for Hermite/Bezier basis
- 0x80C5C8 for billboard squared magnitude threshold
- 0x811610 and 0x8029D4 already read at runtime
Wrapper pattern: thiscall export delegates to normal fn for AVX alignment.
Full 5317-instruction walkthrough of t44_full_asm.txt vs bone_sse_reference.zig.
Crash fix (Issues 1-2): When anim_start >= anim_end in the looping animation
path, assembly always writes prim_time/sec_time = anim_start as fallback.
REF skipped the write, leaving garbage in bone_rt timing fields. On newly
loaded world SceneObjects this propagated through findInterpIdx → extractByte
→ ACCESS_VIOLATION at 0x71AEBC with ECX=0x7FFFFFFF (self-reinforcing bad
cached index).
Time clamp fix (Issues 3-4): Clamped-not-passed animation path now clamps
cur_time to sec_start when sec_start > cur_time, matching assembly at
0x7145EB/0x71474B.
Crossfade fix (Issues 5-6): interpVec3Track36 and interpFloatTrack12 had
'else return' for unknown interp modes. Assembly's JNZ skips primary interp
but falls through to crossfade check. Changed to 'else {}' fallthrough.
Also includes prior uncommitted fixes: particle crossfade blend_weight
restoration, bw>0→bw!=0, attach_count==0 early-return removal.
- Particle interpVec3Track/interpFloatTrack: pass 0.0 blend_weight to
disable crossfade, matching original which has no crossfade in particle
sections (only bone loop and boneKeyframeLoop have crossfade).
- interpFloatTrack: add explicit blend_weight parameter instead of
reading from bone_rt internally, allowing callers to control crossfade.
- Revert extractByte guard (was added then removed during investigation).
Known crash: extractByte (0x71AE90) crashes at 0x71AEBC with idx=0x7FFFFFFF
on world entry. findInterpIdx reads output[0] as cached search position;
if hierarchy buffer contains stale 0x7FFFFFFF, search overflows and
self-reinforces. Investigation ongoing — REF's attachment section matches
original assembly instruction-for-instruction.
MarcelineVQ