From 9ae9b85c758a0995be948c217a07f53be61c0b98 Mon Sep 17 00:00:00 2001
From: Kermalis <29823718+Kermalis@users.noreply.github.com>
Date: Tue, 5 Nov 2024 07:02:02 -0500
Subject: [PATCH] register match sub_800A4E4

---
 asm/math.s | 106 -----------------------------------------------------
 src/math.c |  72 +++++++++++++++++++++++++++++++++++-
 2 files changed, 71 insertions(+), 107 deletions(-)

diff --git a/asm/math.s b/asm/math.s
index b74ecdb9..75220355 100644
--- a/asm/math.s
+++ b/asm/math.s
@@ -5,112 +5,6 @@
 
 	.text
 
-	thumb_func_start sub_800A4E4
-sub_800A4E4:
-	push {r4-r7,lr}
-	mov r7, r10
-	mov r6, r9
-	mov r5, r8
-	push {r5-r7}
-	mov r8, r0
-	adds r5, r1, 0
-	adds r6, r2, 0
-	adds r0, r5, 0
-	bl sub_800A2A0
-	lsls r0, 24
-	lsrs r4, r0, 24
-	cmp r4, 0
-	beq _0800A50C
-	movs r0, 0
-	mov r1, r8
-	str r0, [r1]
-	str r0, [r1, 0x4]
-	b _0800A596
-_0800A50C:
-	adds r0, r6, 0
-	bl sub_800A2A0
-	lsls r0, 24
-	cmp r0, 0
-	beq _0800A520
-	mov r7, r8
-	str r4, [r7]
-	str r4, [r7, 0x4]
-	b _0800A596
-_0800A520:
-	ldr r1, [r5]
-	ldr r4, [r5, 0x4]
-	ldr r0, [r6]
-	mov r10, r0
-	ldr r2, [r6, 0x4]
-	movs r6, 0
-	movs r5, 0
-	movs r7, 0x80
-	lsls r7, 24
-	mov r9, r7
-	movs r0, 0x3F
-	mov r12, r0
-_0800A538:
-	adds r3, r5, 0
-	movs r0, 0x1
-	ands r0, r2
-	cmp r0, 0
-	beq _0800A54C
-	adds r5, r4
-	adds r6, r1
-	cmp r3, r5
-	bls _0800A54C
-	adds r6, 0x1
-_0800A54C:
-	lsrs r2, 1
-	movs r3, 0x1
-	mov r0, r10
-	ands r0, r3
-	cmp r0, 0
-	beq _0800A55C
-	mov r7, r9
-	orrs r2, r7
-_0800A55C:
-	mov r0, r10
-	lsrs r0, 1
-	mov r10, r0
-	lsls r1, 1
-	adds r0, r4, 0
-	mov r7, r9
-	ands r0, r7
-	cmp r0, 0
-	beq _0800A570
-	orrs r1, r3
-_0800A570:
-	lsls r4, 1
-	movs r0, 0x1
-	negs r0, r0
-	add r12, r0
-	mov r7, r12
-	cmp r7, 0
-	bge _0800A538
-	lsrs r1, r5, 15
-	ands r1, r3
-	lsrs r5, 16
-	lsls r0, r6, 16
-	orrs r5, r0
-	lsrs r6, 16
-	cmp r1, 0
-	beq _0800A590
-	adds r5, 0x1
-_0800A590:
-	mov r0, r8
-	str r6, [r0]
-	str r5, [r0, 0x4]
-_0800A596:
-	pop {r3-r5}
-	mov r8, r3
-	mov r9, r4
-	mov r10, r5
-	pop {r4-r7}
-	pop {r0}
-	bx r0
-	thumb_func_end sub_800A4E4
-
 	thumb_func_start sub_800A5A4
 sub_800A5A4:
 	push {r4-r7,lr}
diff --git a/src/math.c b/src/math.c
index 701db666..b1cb1b21 100644
--- a/src/math.c
+++ b/src/math.c
@@ -9,7 +9,7 @@ u24_8 u24_8_mul(u24_8, u24_8);
 bool8 u32_pair_less_than(u32, u32, u32, u32);
 
 void sub_800A5A4(unkStruct_80943A8 *, unkStruct_80943A8 *, unkStruct_80943A8 *);
-void sub_800A4E4(unkStruct_80943A8 *, unkStruct_80943A8 *, unkStruct_80943A8 *);
+static void sub_800A4E4(unkStruct_80943A8 *, unkStruct_80943A8 *, unkStruct_80943A8 *);
 
 /**
  * This function computes a value modulo 3, using a lookup table for values less
@@ -677,4 +677,74 @@ void sub_800A4A0(unkStruct_80943A8 *a)
         a->s0 = res.s0;
         a->s4 = res.s4;
     }
+}
+
+// Regswap https://decomp.me/scratch/HNmlz
+static void sub_800A4E4(unkStruct_80943A8 *dst, unkStruct_80943A8 *a, unkStruct_80943A8 *b)
+{
+    u32 sl;
+    u32 r1;
+    u32 r2;
+    u32 r3;
+    u32 r4;
+    #ifdef NONMATCHING
+    u32 r5;
+    #else
+    register u32 r5 asm("r5");
+    #endif
+    u32 r6;
+    s32 i;
+    
+    if (sub_800A2A0(a)) {
+        dst->s0 = 0;
+        dst->s4 = 0;
+    }
+    else if (sub_800A2A0(b)) {
+        dst->s0 = 0;
+        dst->s4 = 0;
+    }
+    else {
+        r1 = a->s0;
+        r4 = a->s4;
+        sl = b->s0;
+        r2 = b->s4;
+        r6 = 0;
+        r5 = 0;
+
+        for (i = 0; i < 64; i++) {
+            r3 = r5;
+
+            if (r2 & 1) {
+                r5 += r4;
+                r6 += r1;
+
+                if (r3 > r5)
+                    r6++;
+            }
+
+            r2 >>= 1;
+
+            if (sl & 1)
+                r2 |= 0x80000000;
+
+            sl >>= 1;
+            r1 <<= 1;
+
+            if (r4 & 0x80000000)
+                r1 |= 1;
+
+            r4 <<= 1;
+        }
+
+        r1 = (r5 >> 15) & 1;
+        r5 >>= 16;
+        r5 |= (r6 << 16);
+        r6 >>= 16;
+
+        if (r1 != 0)
+            r5++;
+
+        dst->s0 = r6;
+        dst->s4 = r5;
+    }
 }
\ No newline at end of file