From 11f9b29487b32c237159baaf48b2571231002b3d Mon Sep 17 00:00:00 2001
From: XProger <xproger@list.ru>
Date: Tue, 23 Nov 2021 10:07:52 +0300
Subject: [PATCH] #370 3DO save 14 ticks per vertex for projectVertices func

---
 src/platform/3do/projectVertices.s | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/src/platform/3do/projectVertices.s b/src/platform/3do/projectVertices.s
index 9c07304..f5e0f1c 100644
--- a/src/platform/3do/projectVertices.s
+++ b/src/platform/3do/projectVertices.s
@@ -8,20 +8,20 @@
     EXPORT projectVertices_asm
 
 vCount  RN r0
-mx      RN r0
+mx      RN vCount
 my      RN r1
 mz      RN r2
 x       RN r3
 y       RN r4
 z       RN r5
 dz      RN r6
-minX    RN dz
-minY    RN r7
-maxX    RN r8
+minX    RN r7
+minY    RN r8
+maxX    RN r9
 maxY    RN r12
-last    RN r9
-m       RN r10
-vp      RN m
+m       RN minX
+vp      RN minX
+last    RN r10
 vertex  RN r11
 divLUT  RN lr
 
@@ -36,7 +36,7 @@ CLIP_FAR        EQU (1 << 4)
 CLIP_NEAR       EQU (1 << 5)
 
 DIV_TABLE_END   EQU (1025 - 1)
-VIEW_DIST       EQU (1024 * 10)
+VIEW_DIST       EQU (1024 * 10)             ; max = DIV_TABLE_END << PROJ_SHIFT
 VIEW_MIN        EQU (256 << CLIP_SHIFT)
 VIEW_MAX        EQU (VIEW_DIST << CLIP_SHIFT)
 
@@ -58,9 +58,10 @@ projectVertices_asm
         swi MulManyVec3Mat33_F16
 
         add m, m, #36           ; skip 3x3 matrix part
-        ldmia m, {mx, my, mz}   ; get view space offset from matrix        
+        ldmia m, {mx, my, mz}   ; get view space offset from matrix
         ldr divLUT, =divTable
         ldr vp, =viewportRel
+        ldmia vp, {minX, minY, maxX, maxY}
 
 loop    ldmia vertex, {x, y, z}     ; read unpacked vertex
 
@@ -79,17 +80,14 @@ loop    ldmia vertex, {x, y, z}     ; read unpacked vertex
         orrgt z, z, #CLIP_FAR
 
     ; projection
-        mov dz, z, lsr #(PROJ_SHIFT + CLIP_SHIFT)
-        cmp dz, #DIV_TABLE_END
-        movge dz, #DIV_TABLE_END
+        mov dz, z, lsr #(PROJ_SHIFT + CLIP_SHIFT)   ; z is positive
         ldr dz, [divLUT, dz, lsl #2]
         mul x, dz, x
         mul y, dz, y
-        mov x, x, asr #12
-        mov y, y, asr #12
+        mov x, x, asr #(16 - PROJ_SHIFT)
+        mov y, y, asr #(16 - PROJ_SHIFT)
 
     ; check xy clipping
-        ldmia vp, {minX, minY, maxX, maxY}
         cmp x, minX
         orrlt z, z, #CLIP_LEFT
         cmp y, minY