From 957f89ce4abb6ad2228b882cf4dde40325ee1ce0 Mon Sep 17 00:00:00 2001
From: Timon Kruiper <timonkruiper@gmail.com>
Date: Thu, 13 Apr 2023 19:17:34 +0200
Subject: [PATCH] AK: Add very naive implementation of {sin,cos,tan} for
 aarch64

The {sin,cos,tan} functions in AK are used as the implementation of the
same function in libm. We cannot use the __builtin_foo functions as
these would just call the libc functions. This was causing an infinite
loop. Fix this by adding a very naive implementation of
AK::{sin, cos,tan}, that is only valid for small inputs. For the other
functions in this file, I added a TODO() such that we'll crash, instead
of infinite looping.
---
 AK/Math.h | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/AK/Math.h b/AK/Math.h
index 982ae5c89a5..f67c86c6e15 100644
--- a/AK/Math.h
+++ b/AK/Math.h
@@ -90,6 +90,8 @@ constexpr T fmod(T x, T y)
     } while (fpu_status & 0x400);
     return x;
 #else
+    // TODO: Add implementation for this function.
+    TODO();
     return __builtin_fmod(x, y);
 #endif
 }
@@ -109,6 +111,8 @@ constexpr T remainder(T x, T y)
     } while (fpu_status & 0x400);
     return x;
 #else
+    // TODO: Add implementation for this function.
+    TODO();
     return __builtin_fmod(x, y);
 #endif
 }
@@ -244,7 +248,9 @@ constexpr T sin(T angle)
         : "0"(angle));
     return ret;
 #else
-    return __builtin_sin(angle);
+    // FIXME: This is a very naive implementation, and is only valid for small x.
+    //        Probably a good idea to use a better algorithm in the future, such as a taylor approximation.
+    return angle;
 #endif
 }
 
@@ -261,7 +267,9 @@ constexpr T cos(T angle)
         : "0"(angle));
     return ret;
 #else
-    return __builtin_cos(angle);
+    // FIXME: This is a very naive implementation, and is only valid for small x.
+    //        Probably a good idea to use a better algorithm in the future, such as a taylor approximation.
+    return 1 - ((angle * angle) / 2);
 #endif
 }
 
@@ -298,7 +306,9 @@ constexpr T tan(T angle)
 
     return ret;
 #else
-    return __builtin_tan(angle);
+    // FIXME: This is a very naive implementation, and is only valid for small x.
+    //        Probably a good idea to use a better algorithm in the future, such as a taylor approximation.
+    return angle;
 #endif
 }
 
@@ -316,6 +326,8 @@ constexpr T atan(T value)
         : "0"(value));
     return ret;
 #else
+    // TODO: Add implementation for this function.
+    TODO();
     return __builtin_atan(value);
 #endif
 }
@@ -371,6 +383,8 @@ constexpr T atan2(T y, T x)
         : "st(1)");
     return ret;
 #else
+    // TODO: Add implementation for this function.
+    TODO();
     return __builtin_atan2(y, x);
 #endif
 }
@@ -404,6 +418,8 @@ constexpr T log(T x)
         : "0"(x));
     return ret;
 #else
+    // TODO: Add implementation for this function.
+    TODO();
     return __builtin_log(x);
 #endif
 }
@@ -423,6 +439,8 @@ constexpr T log2(T x)
         : "0"(x));
     return ret;
 #else
+    // TODO: Add implementation for this function.
+    TODO();
     return __builtin_log2(x);
 #endif
 }
@@ -442,6 +460,8 @@ constexpr T log10(T x)
         : "0"(x));
     return ret;
 #else
+    // TODO: Add implementation for this function.
+    TODO();
     return __builtin_log10(x);
 #endif
 }
@@ -466,6 +486,8 @@ constexpr T exp(T exponent)
         : "0"(exponent));
     return res;
 #else
+    // TODO: Add implementation for this function.
+    TODO();
     return __builtin_exp(exponent);
 #endif
 }
@@ -488,6 +510,8 @@ constexpr T exp2(T exponent)
         : "0"(exponent));
     return res;
 #else
+    // TODO: Add implementation for this function.
+    TODO();
     return __builtin_exp2(exponent);
 #endif
 }