From b91f061797d746c40ebe7cf0b702079dfb1fa142 Mon Sep 17 00:00:00 2001
From: Quaternions <krakow20@gmail.com>
Date: Wed, 25 Sep 2024 09:46:44 -0700
Subject: [PATCH] implement same-size wide mul more efficiently

---
 fixed_wide/src/fixed.rs | 56 +++++++++++++++++++++++++++++++++++------
 1 file changed, 48 insertions(+), 8 deletions(-)

diff --git a/fixed_wide/src/fixed.rs b/fixed_wide/src/fixed.rs
index 7d592d5..446d957 100644
--- a/fixed_wide/src/fixed.rs
+++ b/fixed_wide/src/fixed.rs
@@ -510,18 +510,54 @@ macro_rules! impl_wide_not_const_generic{
 		impl_wide_operators!($lhs,$rhs);
 	};
 }
+macro_rules! impl_wide_same_size_not_const_generic{
+	(
+		(),
+		$width:expr
+	)=>{
+		impl Fixed<$width,{$width*32}>
+		{
+			paste::item!{
+				#[inline]
+				pub fn [<wide_mul_ $width _ $width>](self,rhs:Fixed<$width,{$width*32}>)->Fixed<{$width*2},{$width*2*32}>{
+					let (low,high)=self.bits.unsigned_abs().widening_mul(rhs.bits.unsigned_abs());
+					let out:BInt::<{$width*2}>=unsafe{core::mem::transmute([low,high])};
+					if self.is_negative()==rhs.is_negative(){
+						Fixed::from_bits(out)
+					}else{
+						// Wrapping is the cheapest negation operation
+						// And the inputs cannot reach the point where it matters
+						Fixed::from_bits(out.wrapping_neg())
+					}
+				}
+				/// This operation cannot represent the fraction exactly,
+				/// but it shapes the output to have precision for the
+				/// largest and smallest possible fractions.
+				#[inline]
+				pub fn [<wide_div_ $width _ $width>](self,rhs:Fixed<$width,{$width*32}>)->Fixed<{$width*2},{$width*2*32}>{
+					// (lhs/2^LHS_FRAC)/(rhs/2^RHS_FRAC)
+					let lhs=self.bits.as_::<BInt<{$width*2}>>().shl($width*64);
+					let rhs=rhs.bits.as_::<BInt<{$width*2}>>();
+					Fixed::from_bits(lhs/rhs)
+				}
+			}
+		}
+		#[cfg(feature="wide-mul")]
+		impl_wide_operators!($width,$width);
+	};
+}
 
 //const generics sidestepped wahoo
 macro_repeated!(
 	impl_wide_not_const_generic,(),
-	(1,1),(2,1),(3,1),(4,1),(5,1),(6,1),(7,1),(8,1),(9,1),(10,1),(11,1),(12,1),(13,1),(14,1),(15,1),
-	(1,2),(2,2),(3,2),(4,2),(5,2),(6,2),(7,2),(8,2),(9,2),(10,2),(11,2),(12,2),(13,2),(14,2),
-	(1,3),(2,3),(3,3),(4,3),(5,3),(6,3),(7,3),(8,3),(9,3),(10,3),(11,3),(12,3),(13,3),
-	(1,4),(2,4),(3,4),(4,4),(5,4),(6,4),(7,4),(8,4),(9,4),(10,4),(11,4),(12,4),
-	(1,5),(2,5),(3,5),(4,5),(5,5),(6,5),(7,5),(8,5),(9,5),(10,5),(11,5),
-	(1,6),(2,6),(3,6),(4,6),(5,6),(6,6),(7,6),(8,6),(9,6),(10,6),
-	(1,7),(2,7),(3,7),(4,7),(5,7),(6,7),(7,7),(8,7),(9,7),
-	(1,8),(2,8),(3,8),(4,8),(5,8),(6,8),(7,8),(8,8),(9,8),
+	      (2,1),(3,1),(4,1),(5,1),(6,1),(7,1),(8,1),(9,1),(10,1),(11,1),(12,1),(13,1),(14,1),(15,1),
+	(1,2),      (3,2),(4,2),(5,2),(6,2),(7,2),(8,2),(9,2),(10,2),(11,2),(12,2),(13,2),(14,2),
+	(1,3),(2,3),      (4,3),(5,3),(6,3),(7,3),(8,3),(9,3),(10,3),(11,3),(12,3),(13,3),
+	(1,4),(2,4),(3,4),      (5,4),(6,4),(7,4),(8,4),(9,4),(10,4),(11,4),(12,4),
+	(1,5),(2,5),(3,5),(4,5),      (6,5),(7,5),(8,5),(9,5),(10,5),(11,5),
+	(1,6),(2,6),(3,6),(4,6),(5,6),      (7,6),(8,6),(9,6),(10,6),
+	(1,7),(2,7),(3,7),(4,7),(5,7),(6,7),      (8,7),(9,7),
+	(1,8),(2,8),(3,8),(4,8),(5,8),(6,8),(7,8),      (9,8),
 	(1,9),(2,9),(3,9),(4,9),(5,9),(6,9),(7,9),
 	(1,10),(2,10),(3,10),(4,10),(5,10),(6,10),
 	(1,11),(2,11),(3,11),(4,11),(5,11),
@@ -530,6 +566,10 @@ macro_repeated!(
 	(1,14),(2,14),
 	(1,15)
 );
+macro_repeated!(
+	impl_wide_same_size_not_const_generic,(),
+	1,2,3,4,5,6,7,8
+);
 
 pub trait Fix<Out>{
 	fn fix(self)->Out;