Feature: Precalculate constant 'sqrt(...)' expressions.

E.g. sqrt(4.0) => 2.0

Author: DeanEdisGG

ShaderShrinker/Shrinker.Parser/Optimizations/PerformArithmeticExtension.cs

@@ -152,6 +152,21 @@ public static bool PerformArithmetic(this SyntaxNode rootNode)
                     }
                 }
 
+                // sqrt(-1.1) => <the result>
+                foreach (var sqrtNode in rootNode.TheTree
+                    .OfType<GlslFunctionCallSyntaxNode>()
+                    .Where(o => o.Name == "sqrt" && o.Params.IsSimpleCsv())
+                    .ToList())
+                {
+                    var x = sqrtNode.Params.Children.Where(o => o.Token is FloatToken).Select(o => ((FloatToken)o.Token).Number).ToList();
+                    if (x.Count == 1)
+                    {
+                        sqrtNode.Params.Remove();
+                        sqrtNode.ReplaceWith(new GenericSyntaxNode(FloatToken.From(Math.Sqrt(Math.Abs(x[0])), MaxDp)));
+                        didChange = true;
+                    }
+                }
+
                 // vecN(...) + <float>
                 foreach (var vectorNode in rootNode.TheTree
                     .OfType<GenericSyntaxNode>()

ShaderShrinker/UnitTests/ShrinkerTests.cs

@@ -1545,6 +1545,27 @@ public void CheckArithmeticWithAbsFunction(
             Assert.That(rootNode.ToCode().ToSimple(), Is.EqualTo(expected));
         }
 
+        [Test, Sequential]
+        public void CheckArithmeticWitSqrtFunction(
+            [Values("float f = sqrt(4.0);",
+                    "float f = sqrt(-8.0);",
+                    "float f; f = sqrt(sqrt(4.));")] string code,
+            [Values("float f = 2.;",
+                    "float f = 2.82843;",
+                    "float f; f = 1.41421;")] string expected)
+        {
+            var lexer = new Lexer();
+            lexer.Load(code);
+
+            var options = CustomOptions.None();
+            options.PerformArithmetic = true;
+            var rootNode = new Parser(lexer)
+                .Parse()
+                .Simplify(options);
+
+            Assert.That(rootNode.ToCode().ToSimple(), Is.EqualTo(expected));
+        }
+
         [Test, Sequential]
         public void CheckArithmeticWithVectorAndScalar(
             [Values("vec2 f = vec2(1.1, 2.2) + 3.3;",