Updated fixed point negation function to avoid branching.

Ash Pook · Ash Pook · commit fe00f9d02775 · 2020-07-30T12:37:18.000+01:00
diff --git a/source/abacus/gen/main/Fixed.X.t4 b/source/abacus/gen/main/Fixed.X.t4
@@ -156,9 +156,10 @@
         }
 
         public static void Negate (ref <#= ftd.TypeName #> f, out <#= ftd.TypeName #> result) {
-            result.numerator = (f.numerator == <#= ftd.RawTypeName #>.MinValue)
-                ? <#= ftd.RawTypeName #>.MaxValue // overflow case
-                : -f.numerator;
+            <#= ftd.RawTypeName #> s = f.numerator >> (<#= ftd.BitCount #> - 1); // sign of argument
+            result.numerator = -f.numerator;
+            <#= ftd.RawTypeName #> sr = result.numerator >> (<#= ftd.BitCount #> - 1); // sign of result
+            result.numerator = (result.numerator & ~(sr & s)) | ((sr & s) & <#= ftd.RawTypeName #>.MaxValue);
         }
 
         public static void Sqrt (ref <#= ftd.TypeName #> f, out <#= ftd.TypeName #> result) {
diff --git a/source/abacus/src/main/Abacus.Fixed32.cs b/source/abacus/src/main/Abacus.Fixed32.cs
@@ -210,9 +210,10 @@ public static void Modulo (ref Fixed32 a, ref Fixed32 b, out Fixed32 result) {
         }
 
         public static void Negate (ref Fixed32 f, out Fixed32 result) {
-            result.numerator = (f.numerator == Int32.MinValue)
-                ? Int32.MaxValue // overflow case
-                : -f.numerator;
+            Int32 s = f.numerator >> (32 - 1); // sign of argument
+            result.numerator = -f.numerator;
+            Int32 sr = result.numerator >> (32 - 1); // sign of result
+            result.numerator = (result.numerator & ~(sr & s)) | ((sr & s) & Int32.MaxValue);
         }
 
         public static void Sqrt (ref Fixed32 f, out Fixed32 result) {
diff --git a/source/abacus/src/main/Abacus.Fixed64.cs b/source/abacus/src/main/Abacus.Fixed64.cs
@@ -211,9 +211,10 @@ public static void Modulo (ref Fixed64 a, ref Fixed64 b, out Fixed64 result) {
         }
 
         public static void Negate (ref Fixed64 f, out Fixed64 result) {
-            result.numerator = (f.numerator == Int64.MinValue)
-                ? Int64.MaxValue // overflow case
-                : -f.numerator;
+            Int64 s = f.numerator >> (64 - 1); // sign of argument
+            result.numerator = -f.numerator;
+            Int64 sr = result.numerator >> (64 - 1); // sign of result
+            result.numerator = (result.numerator & ~(sr & s)) | ((sr & s) & Int64.MaxValue);
         }
 
         public static void Sqrt (ref Fixed64 f, out Fixed64 result) {

Original file line number	Diff line number	Diff line change
`@@ -156,9 +156,10 @@`
`156`	`156`	`}`
`157`	`157`
`158`	`158`	`public static void Negate (ref <#= ftd.TypeName #> f, out <#= ftd.TypeName #> result) {`
`159`		`- result.numerator = (f.numerator == <#= ftd.RawTypeName #>.MinValue)`
`160`		`- ? <#= ftd.RawTypeName #>.MaxValue // overflow case`
`161`		`- : -f.numerator;`
	`159`	`+ <#= ftd.RawTypeName #> s = f.numerator >> (<#= ftd.BitCount #> - 1); // sign of argument`
	`160`	`+ result.numerator = -f.numerator;`
	`161`	`+ <#= ftd.RawTypeName #> sr = result.numerator >> (<#= ftd.BitCount #> - 1); // sign of result`
	`162`	`+ result.numerator = (result.numerator & ~(sr & s)) \| ((sr & s) & <#= ftd.RawTypeName #>.MaxValue);`
`162`	`163`	`}`
`163`	`164`
`164`	`165`	`public static void Sqrt (ref <#= ftd.TypeName #> f, out <#= ftd.TypeName #> result) {`
Original file line number	Diff line number	Diff line change
`@@ -210,9 +210,10 @@ public static void Modulo (ref Fixed32 a, ref Fixed32 b, out Fixed32 result) {`
`210`	`210`	`}`
`211`	`211`
`212`	`212`	`public static void Negate (ref Fixed32 f, out Fixed32 result) {`
`213`		`- result.numerator = (f.numerator == Int32.MinValue)`
`214`		`- ? Int32.MaxValue // overflow case`
`215`		`- : -f.numerator;`
	`213`	`+ Int32 s = f.numerator >> (32 - 1); // sign of argument`
	`214`	`+ result.numerator = -f.numerator;`
	`215`	`+ Int32 sr = result.numerator >> (32 - 1); // sign of result`
	`216`	`+ result.numerator = (result.numerator & ~(sr & s)) \| ((sr & s) & Int32.MaxValue);`
`216`	`217`	`}`
`217`	`218`
`218`	`219`	`public static void Sqrt (ref Fixed32 f, out Fixed32 result) {`
Original file line number	Diff line number	Diff line change
`@@ -211,9 +211,10 @@ public static void Modulo (ref Fixed64 a, ref Fixed64 b, out Fixed64 result) {`
`211`	`211`	`}`
`212`	`212`
`213`	`213`	`public static void Negate (ref Fixed64 f, out Fixed64 result) {`
`214`		`- result.numerator = (f.numerator == Int64.MinValue)`
`215`		`- ? Int64.MaxValue // overflow case`
`216`		`- : -f.numerator;`
	`214`	`+ Int64 s = f.numerator >> (64 - 1); // sign of argument`
	`215`	`+ result.numerator = -f.numerator;`
	`216`	`+ Int64 sr = result.numerator >> (64 - 1); // sign of result`
	`217`	`+ result.numerator = (result.numerator & ~(sr & s)) \| ((sr & s) & Int64.MaxValue);`
`217`	`218`	`}`
`218`	`219`
`219`	`220`	`public static void Sqrt (ref Fixed64 f, out Fixed64 result) {`