vkd3d-shader/hlsl: Support log2() intrinsic.

Approved-by: Giovanni Mascellani (@giomasce)
Approved-by: Zebediah Figura (@zfigura)
Approved-by: Francisco Casas (@fcasas)
Approved-by: Henri Verbeet (@hverbeet)
Approved-by: Alexandre Julliard (@julliard)
Merge-Request: https://gitlab.winehq.org/wine/vkd3d/-/merge_requests/89

Makefile.am

@@ -122,6 +122,7 @@ vkd3d_shader_tests = \
 	tests/hlsl-vector-indexing.shader_test \
 	tests/hlsl-vector-indexing-uniform.shader_test \
 	tests/lit.shader_test \
+	tests/log.shader_test \
 	tests/logic-operations.shader_test \
 	tests/majority-syntax.shader_test \
 	tests/math.shader_test \

libs/vkd3d-shader/hlsl.y

@@ -2843,6 +2843,17 @@ static bool intrinsic_lit(struct hlsl_ctx *ctx,
     return true;
 }
 
+static bool intrinsic_log2(struct hlsl_ctx *ctx,
+        const struct parse_initializer *params, const struct vkd3d_shader_location *loc)
+{
+    struct hlsl_ir_node *arg;
+
+    if (!(arg = intrinsic_float_convert_arg(ctx, params, params->args[0], loc)))
+        return false;
+
+    return !!add_unary_arithmetic_expr(ctx, params->instrs, HLSL_OP1_LOG2, arg, loc);
+}
+
 static bool intrinsic_max(struct hlsl_ctx *ctx,
         const struct parse_initializer *params, const struct vkd3d_shader_location *loc)
 {
@@ -3300,6 +3311,7 @@ intrinsic_functions[] =
     {"length",                              1, true,  intrinsic_length},
     {"lerp",                                3, true,  intrinsic_lerp},
     {"lit",                                 3, true,  intrinsic_lit},
+    {"log2",                                1, true,  intrinsic_log2},
     {"max",                                 2, true,  intrinsic_max},
     {"min",                                 2, true,  intrinsic_min},
     {"mul",                                 2, true,  intrinsic_mul},

tests/log.shader_test

@@ -0,0 +1,12 @@
+[pixel shader]
+uniform float4 x;
+
+float4 main() : sv_target
+{
+    return log2(x);
+}
+
+[test]
+uniform 0 float4 2.0 4.0 5.0 0.4
+draw quad
+probe all rgba (1.0, 2.0, 2.32192802, -1.32192802) 1