shaderpipeline: front-end fixes, Cg improvements

panda/src/shaderpipeline/cg_preamble.hlsl

@@ -130,3 +130,16 @@ float4 f4texCUBE(samplerCUBE samp, float4 s, float3 dx, float3 dy) {
 #define f3texCUBE(x, y) (f4texCUBE((x), (y)).rgb)
 #define texCUBE f4texCUBE
 */
+
+uint bitfieldExtract(uint val, int off, int size) {
+  uint mask = uint((1 << size) - 1);
+  return uint(val >> off) & mask;
+}
+
+#define bitCount(x) (countbits(x))
+#define bitfieldReverse(x) (reversebits(x))
+#define findLSB(x) (firstbitlow(x))
+#define findMSB(x) (firstbithigh(x))
+#define floatToIntBits(x) (asint(x))
+#define floatToRawIntBits(x) (asint(x))
+#define intBitsToFloat(x) (asfloat(x))

panda/src/shaderpipeline/shaderCompilerGlslang.cxx

@@ -284,9 +284,8 @@ compile_now(ShaderModule::Stage stage, std::istream &in,
   bool add_include_directive = false;
   int glsl_version = 110;
 
-  // Is this a Cg shader or a GLSL shader?
-  if (code.size() >= 5 &&
-      strncmp((const char *)&code[0], "//Cg", 4) == 0 && isspace(code[4])) {
+  // Look for a special //Cg header.  Otherwise, it's a GLSL shader.
+  if (check_cg_header(code)) {
     is_cg = true;
   }
   else if (!preprocess_glsl(code, glsl_version, add_include_directive)) {
@@ -317,6 +316,9 @@ compile_now(ShaderModule::Stage stage, std::istream &in,
   case ShaderModule::Stage::fragment:
     language = EShLangFragment;
     break;
+  case ShaderModule::Stage::compute:
+    language = EShLangCompute;
+    break;
   default:
     shader_cat.error()
       << "glslang compiler does not support " << stage << " shaders.\n";
@@ -443,6 +445,22 @@ compile_now(ShaderModule::Stage stage, std::istream &in,
   return new ShaderModuleSpirV(stage, std::move(optimized));
 }
 
+/**
+ * Returns true if there is a special //Cg header at the beginning of the code.
+ */
+bool ShaderCompilerGlslang::
+check_cg_header(const vector_uchar &code) {
+  const char *p = (const char *)&code[0];
+  const char *end = p + code.size();
+  while (isspace(*p) && p < end) {
+    // Skip leading whitespace.
+    ++p;
+  }
+  return (end - p) >= 5
+      && strncmp(p, "//Cg", 4) == 0
+      && isspace(p[4]);
+}
+
 /**
  * Do some very basic preprocessing of the GLSL shader to extract the GLSL
  * version and fix the use of #pragma include (which glslang doesn't support,
@@ -506,7 +524,8 @@ preprocess_glsl(vector_uchar &code, int &glsl_version, bool &uses_pragma_include
           p[-1] = '0';
         }
       }
-      else if (directive_size == 6 && strncmp(directive, "pragma", directive_size) == 0) {
+      else if (directive_size == 6 && glsl_preprocess &&
+               strncmp(directive, "pragma", directive_size) == 0) {
         if (strncmp(p, "include", 7) == 0 && !isalnum(p[7]) && p[7] != '_') {
           // Turn this into a normal include directive (by replacing the word
           // "pragma" with spaces) and enable the GL_GOOGLE_include_directive

panda/src/shaderpipeline/shaderCompilerGlslang.h

@@ -34,6 +34,7 @@ public:
                                        BamCacheRecord *record = nullptr) const override;
 
 private:
+  static bool check_cg_header(const vector_uchar &code);
   static bool preprocess_glsl(vector_uchar &code, int &glsl_version, bool &uses_pragma_include);
   static bool postprocess_glsl150(ShaderModuleSpirV::InstructionStream &stream);