From 29e0494e56b88edf8abe71c07f8df8f7b7979e20 Mon Sep 17 00:00:00 2001
From: Hediadyoin1 <leon2002.la@gmail.com>
Date: Tue, 16 May 2023 15:07:17 +0200
Subject: [PATCH] AK: Use builtins in fabs implementation and move it to the
 top

Both GCC and Clang inline this function to use bit-wise logic and/or
appropriate instructions even on -O0 and allow their use in a constexpr
context, see
https://godbolt.org/z/de1393vha
---
 AK/Math.h | 29 ++++++++++++-----------------
 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/AK/Math.h b/AK/Math.h
index ef3b3a702f3..cd544da4a9b 100644
--- a/AK/Math.h
+++ b/AK/Math.h
@@ -81,6 +81,18 @@ constexpr size_t product_odd() { return value * product_odd<value - 2>(); }
         return res;                           \
     }
 
+template<FloatingPoint T>
+constexpr T fabs(T x)
+{
+    // Both GCC and Clang inline fabs by default, so this is just a cmath like wrapper
+    if constexpr (IsSame<T, long double>)
+        return __builtin_fabsl(x);
+    if constexpr (IsSame<T, double>)
+        return __builtin_fabs(x);
+    if constexpr (IsSame<T, float>)
+        return __builtin_fabsf(x);
+}
+
 namespace Rounding {
 template<FloatingPoint T>
 constexpr T ceil(T num)
@@ -494,23 +506,6 @@ constexpr T cbrt(T x)
     return r;
 }
 
-template<FloatingPoint T>
-constexpr T fabs(T x)
-{
-    if (is_constant_evaluated())
-        return x < 0 ? -x : x;
-#if ARCH(X86_64)
-    asm(
-        "fabs"
-        : "+t"(x));
-    return x;
-#elif ARCH(AARCH64)
-    AARCH64_INSTRUCTION(fabs, x);
-#else
-    return __builtin_fabs(x);
-#endif
-}
-
 namespace Trigonometry {
 
 template<FloatingPoint T>