Add ability for intrinsics to require GLSL extensions

When cross-compiling, we need to detect when an intrinsic is used that required non-default GLSL capabilities and emit an appropriate `#extension ... : require` line.

I'm handling this by attaching a custom modifier to declarations that require an extension in order to be callable.

4 files changed, 59 insertions, 0 deletions

diff --git a/source/slang/emit.cpp b/source/slang/emit.cpp
index f5b4a8b56..6905a8a76 100644
--- a/source/slang/emit.cpp
+++ b/source/slang/emit.cpp
@@ -52,6 +52,10 @@ struct SharedEmitContext
     ProgramSyntaxNode*  program;
 
     bool                needHackSamplerForTexelFetch = false;
+
+    // Record the GLSL extnsions we have already emitted a `#extension` for
+    HashSet<String> glslExtensionsRequired;
+    StringBuilder glslExtensionRequireLines;
 };
 
 struct EmitContext
@@ -1594,6 +1598,19 @@ struct EmitVisitor
         }
     }
 
+    void requireGLSLExtension(String const& name)
+    {
+        if (context->shared->glslExtensionsRequired.Contains(name))
+            return;
+
+        StringBuilder& sb = context->shared->glslExtensionRequireLines;
+
+        sb.append("#extension ");
+        sb.append(name);
+        sb.append(" : require\n");
+
+        context->shared->glslExtensionsRequired.Add(name);
+    }
 
     void visitInvokeExpressionSyntaxNode(
         RefPtr<InvokeExpressionSyntaxNode>  callExpr,
@@ -1708,6 +1725,17 @@ struct EmitVisitor
             }
             else if(auto targetIntrinsicModifier = findTargetIntrinsicModifier(funcDecl))
             {
+                if (context->shared->target == CodeGenTarget::GLSL)
+                {
+                    // Does this intrinsic requie a particular GLSL extension that wouldn't be available by default?
+                    if (auto requiredGLSLExtensionModifier = funcDecl->FindModifier<RequiredGLSLExtensionModifier>())
+                    {
+                        // If so, we had better request the extension.
+                        requireGLSLExtension(requiredGLSLExtensionModifier->extensionNameToken.Content);
+                    }
+                }
+
+
                 if(targetIntrinsicModifier->definitionToken.Type != TokenType::Unknown)
                 {
                     auto name = getStringOrIdentifierTokenValue(targetIntrinsicModifier->definitionToken);
@@ -3550,6 +3578,8 @@ String emitEntryPoint(
     StringBuilder finalResultBuilder;
     finalResultBuilder << prefix;
 
+    finalResultBuilder << sharedContext.glslExtensionRequireLines.ProduceString();
+
     if (sharedContext.needHackSamplerForTexelFetch)
     {
         finalResultBuilder << "layout(set = 0, binding = 0) uniform sampler SLANG_hack_samplerForTexelFetch;\n";
diff --git a/source/slang/modifier-defs.h b/source/slang/modifier-defs.h
index 2b5c77d86..9806a12a5 100644
--- a/source/slang/modifier-defs.h
+++ b/source/slang/modifier-defs.h
@@ -53,6 +53,12 @@ SYNTAX_CLASS(TargetIntrinsicModifier, IntrinsicModifierBase)
     FIELD(Token, definitionToken)
 END_SYNTAX_CLASS()
 
+// A modifier to tag something as an intrinsic that requires
+// a certain GLSL extension to be enabled when used
+SYNTAX_CLASS(RequiredGLSLExtensionModifier, Modifier)
+    FIELD(Token, extensionNameToken)
+END_SYNTAX_CLASS()
+
 SIMPLE_SYNTAX_CLASS(InOutModifier, OutModifier)
 
 // This is a special sentinel modifier that gets added
diff --git a/source/slang/parser.cpp b/source/slang/parser.cpp
index de63793b1..8314b0930 100644
--- a/source/slang/parser.cpp
+++ b/source/slang/parser.cpp
@@ -717,6 +717,17 @@ namespace Slang
                 AddModifier(&modifierLink, modifier);
             }
 
+            else if (AdvanceIf(parser, "__glsl_extension"))
+            {
+                auto modifier = new RequiredGLSLExtensionModifier();
+                modifier->Position = loc;
+
+                parser->ReadToken(TokenType::LParent);
+                modifier->extensionNameToken = parser->ReadToken(TokenType::Identifier);
+                parser->ReadToken(TokenType::RParent);
+
+                AddModifier(&modifierLink, modifier);
+            }
 
             else if (AdvanceIf(parser, "layout"))
             {
diff --git a/source/slang/slang-stdlib.cpp b/source/slang/slang-stdlib.cpp
index bcc87b201..563f5a015 100644
--- a/source/slang/slang-stdlib.cpp
+++ b/source/slang/slang-stdlib.cpp
@@ -413,27 +413,33 @@ __intrinsic
 matrix<T,N,M> ddx(matrix<T,N,M> x);
 
 __generic<T : __BuiltinFloatingPointType>
+__glsl_extension(GL_ARB_derivative_control)
 __intrinsic(glsl, dFdxCoarse)
 __intrinsic
 T ddx_coarse(T x);
 __generic<T : __BuiltinFloatingPointType, let N : int>
+__glsl_extension(GL_ARB_derivative_control)
 __intrinsic(glsl, dFdxCoarse)
 __intrinsic
 vector<T,N> ddx_coarse(vector<T,N> x);
 __generic<T : __BuiltinFloatingPointType, let N : int, let M : int>
+__glsl_extension(GL_ARB_derivative_control)
 __intrinsic(glsl, dFdxCoarse)
 __intrinsic
 matrix<T,N,M> ddx_coarse(matrix<T,N,M> x);
 
 __generic<T : __BuiltinFloatingPointType>
+__glsl_extension(GL_ARB_derivative_control)
 __intrinsic(glsl, dFdxFine)
 __intrinsic
 T ddx_fine(T x);
 __generic<T : __BuiltinFloatingPointType, let N : int>
+__glsl_extension(GL_ARB_derivative_control)
 __intrinsic(glsl, dFdxFine)
 __intrinsic
 vector<T,N> ddx_fine(vector<T,N> x);
 __generic<T : __BuiltinFloatingPointType, let N : int, let M : int>
+__glsl_extension(GL_ARB_derivative_control)
 __intrinsic(glsl, dFdxFine)
 __intrinsic
 matrix<T,N,M> ddx_fine(matrix<T,N,M> x);
@@ -452,27 +458,33 @@ __intrinsic
  matrix<T,N,M> ddy(matrix<T,N,M> x);
 
 __generic<T : __BuiltinFloatingPointType>
+__glsl_extension(GL_ARB_derivative_control)
 __intrinsic(glsl, dFdyCoarse)
 __intrinsic
 T ddy_coarse(T x);
 __generic<T : __BuiltinFloatingPointType, let N : int>
+__glsl_extension(GL_ARB_derivative_control)
 __intrinsic(glsl, dFdyCoarse)
 __intrinsic
 vector<T,N> ddy_coarse(vector<T,N> x);
 __generic<T : __BuiltinFloatingPointType, let N : int, let M : int>
+__glsl_extension(GL_ARB_derivative_control)
 __intrinsic(glsl, dFdyCoarse)
 __intrinsic
 matrix<T,N,M> ddy_coarse(matrix<T,N,M> x);
 
 __generic<T : __BuiltinFloatingPointType>
+__glsl_extension(GL_ARB_derivative_control)
 __intrinsic(glsl, dFdyFine)
 __intrinsic
 T ddy_fine(T x);
 __generic<T : __BuiltinFloatingPointType, let N : int>
+__glsl_extension(GL_ARB_derivative_control)
 __intrinsic(glsl, dFdyFine)
 __intrinsic
 vector<T,N> ddy_fine(vector<T,N> x);
 __generic<T : __BuiltinFloatingPointType, let N : int, let M : int>
+__glsl_extension(GL_ARB_derivative_control)
 __intrinsic(glsl, dFdyFine)
 __intrinsic
 matrix<T,N,M> ddy_fine(matrix<T,N,M> x);