Revert "Revert the Metal Experiment (#701)"

This reverts commit fe1617ffea.

src/Ryujinx.Graphics.Shader/CodeGen/Msl/HelperFunctions/FindLSB.metal

@@ -0,0 +1,5 @@
+template<typename T>
+inline T findLSB(T x)
+{
+    return select(ctz(x), T(-1), x == T(0));
+}

src/Ryujinx.Graphics.Shader/CodeGen/Msl/HelperFunctions/FindMSBS32.metal

@@ -0,0 +1,5 @@
+template<typename T>
+inline T findMSBS32(T x)
+{
+    return select(clz(T(0)) - (clz(x) + T(1)), T(-1), x == T(0));
+}

src/Ryujinx.Graphics.Shader/CodeGen/Msl/HelperFunctions/FindMSBU32.metal

@@ -0,0 +1,6 @@
+template<typename T>
+inline T findMSBU32(T x)
+{
+    T v = select(x, T(-1) - x, x < T(0));
+    return select(clz(T(0)) - (clz(v) + T(1)), T(-1), v == T(0));
+}

src/Ryujinx.Graphics.Shader/CodeGen/Msl/HelperFunctions/HelperFunctionNames.cs

@@ -0,0 +1,10 @@
+namespace Ryujinx.Graphics.Shader.CodeGen.Msl
+{
+    static class HelperFunctionNames
+    {
+        public static string FindLSB = "findLSB";
+        public static string FindMSBS32 = "findMSBS32";
+        public static string FindMSBU32 = "findMSBU32";
+        public static string SwizzleAdd = "swizzleAdd";
+    }
+}

src/Ryujinx.Graphics.Shader/CodeGen/Msl/HelperFunctions/Precise.metal

@@ -0,0 +1,14 @@
+template<typename T>
+[[clang::optnone]] T PreciseFAdd(T l, T r) {
+    return fma(T(1), l, r);
+}
+
+template<typename T>
+[[clang::optnone]] T PreciseFSub(T l, T r) {
+    return fma(T(-1), r, l);
+}
+
+template<typename T>
+[[clang::optnone]] T PreciseFMul(T l, T r) {
+    return fma(l, r, T(0));
+}

src/Ryujinx.Graphics.Shader/CodeGen/Msl/HelperFunctions/SwizzleAdd.metal

@@ -0,0 +1,7 @@
+float swizzleAdd(float x, float y, int mask, uint thread_index_in_simdgroup)
+{
+    float4 xLut = float4(1.0, -1.0, 1.0, 0.0);
+    float4 yLut = float4(1.0, 1.0, -1.0, 1.0);
+    int lutIdx = (mask >> (int(thread_index_in_simdgroup & 3u) * 2)) & 3;
+    return x * xLut[lutIdx] + y * yLut[lutIdx];
+}