Refactor prelude emit (#2236)

* #include an absolute path didn't work - because paths were taken to always be relative.

* Refactor how prelude output works in emit.

* Small improvement to emit output.

* Move around comment on target specific language directives based on review.

Co-authored-by: Theresa Foley <10618364+tangent-vector@users.noreply.github.com>

1 files changed, 62 insertions, 42 deletions

diff --git a/source/slang/slang-emit-glsl.cpp b/source/slang/slang-emit-glsl.cpp
index 7578a2dd5..d9c81f14b 100644
--- a/source/slang/slang-emit-glsl.cpp
+++ b/source/slang/slang-emit-glsl.cpp
@@ -12,6 +12,10 @@
 
 namespace Slang {
 
+void trackGLSLTargetCaps(
+    GLSLExtensionTracker* extensionTracker,
+    CapabilitySet const& caps);
+
 GLSLSourceEmitter::GLSLSourceEmitter(const Desc& desc) :
     Super(desc)
 {
@@ -1740,7 +1744,33 @@ void GLSLSourceEmitter::handleRequiredCapabilitiesImpl(IRInst* inst)
     }
 }
 
-void GLSLSourceEmitter::emitPreprocessorDirectivesImpl()
+static Index _getGLSLVersion(ProfileVersion profile)
+{
+    switch (profile)
+    {
+#define CASE(TAG, VALUE) case ProfileVersion::TAG: return VALUE; 
+        CASE(GLSL_110, 110);
+        CASE(GLSL_120, 120);
+        CASE(GLSL_130, 130);
+        CASE(GLSL_140, 140);
+        CASE(GLSL_150, 150);
+        CASE(GLSL_330, 330);
+        CASE(GLSL_400, 400);
+        CASE(GLSL_410, 410);
+        CASE(GLSL_420, 420);
+        CASE(GLSL_430, 430);
+        CASE(GLSL_440, 440);
+        CASE(GLSL_450, 450);
+        CASE(GLSL_460, 460);
+#undef CASE
+
+    default:
+        break;
+    }
+    return -1;
+}
+
+void GLSLSourceEmitter::emitFrontMatterImpl(TargetRequest* targetReq)
 {
     auto effectiveProfile = m_effectiveProfile;
     if (effectiveProfile.getFamily() == ProfileFamily::GLSL)
@@ -1759,44 +1789,34 @@ void GLSLSourceEmitter::emitPreprocessorDirectivesImpl()
     // the user to specify a version as part of the target.
     m_glslExtensionTracker->requireVersion(ProfileVersion::GLSL_450);
 
-    auto requiredProfileVersion = m_glslExtensionTracker->getRequiredProfileVersion();
-    switch (requiredProfileVersion)
+    Index glslVersion = _getGLSLVersion(m_glslExtensionTracker->getRequiredProfileVersion());
+    if (glslVersion < 0)
     {
-#define CASE(TAG, VALUE)    \
-case ProfileVersion::TAG: m_writer->emit("#version " #VALUE "\n"); return
-
-        CASE(GLSL_110, 110);
-        CASE(GLSL_120, 120);
-        CASE(GLSL_130, 130);
-        CASE(GLSL_140, 140);
-        CASE(GLSL_150, 150);
-        CASE(GLSL_330, 330);
-        CASE(GLSL_400, 400);
-        CASE(GLSL_410, 410);
-        CASE(GLSL_420, 420);
-        CASE(GLSL_430, 430);
-        CASE(GLSL_440, 440);
-        CASE(GLSL_450, 450);
-        CASE(GLSL_460, 460);
-#undef CASE
+        // No information is available for us to guess a profile,
+        // so it seems like we need to pick one out of thin air.
+        //
+        // Ideally we should infer a minimum required version based
+        // on the constructs we have seen used in the user's code
+        //
+        // For now we just fall back to a reasonably recent version.
 
-        default:
-            break;
+        glslVersion = 420;
     }
 
-    // No information is available for us to guess a profile,
-    // so it seems like we need to pick one out of thin air.
-    //
-    // Ideally we should infer a minimum required version based
-    // on the constructs we have seen used in the user's code
-    //
-    // For now we just fall back to a reasonably recent version.
+    m_writer->emit("#version ");
+    m_writer->emit(glslVersion);
+    m_writer->emit("\n");
 
-    m_writer->emit("#version 420\n");
-}
+    // Output the extensions
+    if (m_glslExtensionTracker)
+    {
+        trackGLSLTargetCaps(m_glslExtensionTracker, targetReq->getTargetCaps());
+
+        StringBuilder builder;
+        m_glslExtensionTracker->appendExtensionRequireLines(builder);
+        m_writer->emit(builder.getUnownedSlice());
+    }
 
-void GLSLSourceEmitter::emitLayoutDirectivesImpl(TargetRequest* targetReq)
-{
     // Reminder: the meaning of row/column major layout
     // in our semantics is the *opposite* of what GLSL
     // calls them, because what they call "columns"
@@ -1804,16 +1824,16 @@ void GLSLSourceEmitter::emitLayoutDirectivesImpl(TargetRequest* targetReq)
     //
     switch (targetReq->getDefaultMatrixLayoutMode())
     {
-        case kMatrixLayoutMode_RowMajor:
-        default:
-            m_writer->emit("layout(column_major) uniform;\n");
-            m_writer->emit("layout(column_major) buffer;\n");
-            break;
+    case kMatrixLayoutMode_RowMajor:
+    default:
+        m_writer->emit("layout(column_major) uniform;\n");
+        m_writer->emit("layout(column_major) buffer;\n");
+        break;
 
-        case kMatrixLayoutMode_ColumnMajor:
-            m_writer->emit("layout(row_major) uniform;\n");
-            m_writer->emit("layout(row_major) buffer;\n");
-            break;
+    case kMatrixLayoutMode_ColumnMajor:
+        m_writer->emit("layout(row_major) uniform;\n");
+        m_writer->emit("layout(row_major) buffer;\n");
+        break;
     }
 }