Map HLSL `lerp` to GLSL `mix`

- Also fix a bug in `emit.cpp` where I wasn't detecting `__intrinsic` remaps that don't include `$` (this is a byproduct of changing the string index type to be unsigned; other bugs like this may be lurking)

2 files changed, 15 insertions, 4 deletions

diff --git a/source/slang/emit.cpp b/source/slang/emit.cpp
index 5d85b4d57..df74d19e4 100644
--- a/source/slang/emit.cpp
+++ b/source/slang/emit.cpp
@@ -1466,7 +1466,7 @@ struct EmitVisitor
                 {
                     auto name = getStringOrIdentifierTokenValue(targetIntrinsicModifier->definitionToken);
 
-                    if(name.IndexOf('$') < 0)
+                    if(name.IndexOf('$') == -1)
                     {
                         // Simple case: it is just an ordinary name, so we call it like a builtin.
                         //
diff --git a/source/slang/slang-stdlib.cpp b/source/slang/slang-stdlib.cpp
index 87c2c2e8a..e1bba8885 100644
--- a/source/slang/slang-stdlib.cpp
+++ b/source/slang/slang-stdlib.cpp
@@ -592,9 +592,20 @@ __generic<T : __BuiltinFloatingPointType, let N : int, let M : int> __intrinsic
 __generic<T : __BuiltinFloatingPointType, let N : int> __intrinsic T length(vector<T,N> x);
 
 // Linear interpolation
-__generic<T : __BuiltinFloatingPointType> __intrinsic T lerp(T x, T y, T s);
-__generic<T : __BuiltinFloatingPointType, let N : int> __intrinsic vector<T,N> lerp(vector<T,N> x, vector<T,N> y, vector<T,N> s);
-__generic<T : __BuiltinFloatingPointType, let N : int, let M : int> __intrinsic matrix<T,N,M> lerp(matrix<T,N,M> x, matrix<T,N,M> y, matrix<T,N,M> s);
+__generic<T : __BuiltinFloatingPointType>
+__intrinsic(glsl, mix)
+__intrinsic
+T lerp(T x, T y, T s);
+
+__generic<T : __BuiltinFloatingPointType, let N : int>
+__intrinsic(glsl, mix)
+__intrinsic
+vector<T,N> lerp(vector<T,N> x, vector<T,N> y, vector<T,N> s);
+
+__generic<T : __BuiltinFloatingPointType, let N : int, let M : int>
+__intrinsic(glsl, mix)
+__intrinsic
+matrix<T,N,M> lerp(matrix<T,N,M> x, matrix<T,N,M> y, matrix<T,N,M> s);
 
 // Legacy lighting function (obsolete)
 __intrinsic float4 lit(float n_dot_l, float n_dot_h, float m);