Address glslang ordering requirments for 'derivative_group_*NV' (#4323)

* Address glslang ordering requirments for 'derivative_group_*NV'

fixes: #4305

The solution is to emit some `layout`s after a module source is emitted.

Added to slangs gfx backend code to enable the compute shader derivative extension for testing purposes.

* address review

* enable removed test

---------

Co-authored-by: Yong He <yonghe@outlook.com>

4 files changed, 18 insertions, 9 deletions

diff --git a/source/slang/slang-emit-c-like.cpp b/source/slang/slang-emit-c-like.cpp
index d85c72ae5..6412ff730 100644
--- a/source/slang/slang-emit-c-like.cpp
+++ b/source/slang/slang-emit-c-like.cpp
@@ -129,9 +129,12 @@ void CLikeSourceEmitter::emitPreModuleImpl()
         m_writer->emit(prelude->getStringSlice());
         m_writer->emit("\n");
     }
-    for (auto prelude : m_requiredPreludesRaw)
+}
+void CLikeSourceEmitter::emitPostModuleImpl()
+{   
+    if(m_requiredAfter.requireComputeDerivatives.getLength() > 0)
     {
-        m_writer->emit(prelude);
+        m_writer->emit(m_requiredAfter.requireComputeDerivatives);
         m_writer->emit("\n");
     }
 }
diff --git a/source/slang/slang-emit-c-like.h b/source/slang/slang-emit-c-like.h
index 9b39aa6f4..ecff57296 100644
--- a/source/slang/slang-emit-c-like.h
+++ b/source/slang/slang-emit-c-like.h
@@ -431,7 +431,7 @@ public:
     void emitFrontMatter(TargetRequest* targetReq) { emitFrontMatterImpl(targetReq); }
 
     void emitPreModule() { emitPreModuleImpl(); }
-
+    void emitPostModule() { emitPostModuleImpl(); }
     void emitModule(IRModule* module, DiagnosticSink* sink)
         { m_irModule = module; emitModuleImpl(module, sink); }
 
@@ -476,6 +476,7 @@ public:
         /// For example on targets that don't have built in vector/matrix support, this is where
         /// the appropriate generated declarations occur.
     virtual void emitPreModuleImpl();
+    virtual void emitPostModuleImpl();
 
     virtual void beforeComputeEmitActions(IRModule* module) { SLANG_UNUSED(module); };
 
@@ -590,8 +591,11 @@ public:
     // to use for it when emitting code.
     Dictionary<IRInst*, String> m_mapInstToName;
 
-    OrderedHashSet<String> m_requiredPreludesRaw;
     OrderedHashSet<IRStringLit*> m_requiredPreludes;
+    struct RequiredAfter
+    {
+        String requireComputeDerivatives;
+    }m_requiredAfter;
 };
 
 }
diff --git a/source/slang/slang-emit-glsl.cpp b/source/slang/slang-emit-glsl.cpp
index 8063fcc1d..d13bc96d1 100644
--- a/source/slang/slang-emit-glsl.cpp
+++ b/source/slang/slang-emit-glsl.cpp
@@ -2208,9 +2208,7 @@ void GLSLSourceEmitter::handleRequiredCapabilitiesImpl(IRInst* inst)
         {
             // only allowed 1 of derivative_group_quadsNV or derivative_group_linearNV
             if (m_entryPointStage != Stage::Compute
-                || m_requiredPreludesRaw.contains("layout(derivative_group_quadsNV) in;")
-                || m_requiredPreludesRaw.contains("layout(derivative_group_linearNV) in;")
-                )
+                || m_requiredAfter.requireComputeDerivatives.getLength() > 0)
                 return;
 
             _requireGLSLExtension(UnownedStringSlice("GL_NV_compute_shader_derivatives"));
@@ -2225,12 +2223,12 @@ void GLSLSourceEmitter::handleRequiredCapabilitiesImpl(IRInst* inst)
                 if (isQuad)
                 {
                     verifyComputeDerivativeGroupModifiers(getSink(), inst->sourceLoc, true, false, numThreadsDecor);
-                    m_requiredPreludesRaw.add("layout(derivative_group_quadsNV) in;");
+                    m_requiredAfter.requireComputeDerivatives = "layout(derivative_group_quadsNV) in;";
                 }
                 else
                 {
                     verifyComputeDerivativeGroupModifiers(getSink(), inst->sourceLoc, false, true, numThreadsDecor);
-                    m_requiredPreludesRaw.add("layout(derivative_group_linearNV) in;");
+                    m_requiredAfter.requireComputeDerivatives = "layout(derivative_group_linearNV) in;";
                 }
             }
         }
diff --git a/source/slang/slang-emit.cpp b/source/slang/slang-emit.cpp
index da348fa64..6d0ab1daa 100644
--- a/source/slang/slang-emit.cpp
+++ b/source/slang/slang-emit.cpp
@@ -1587,6 +1587,10 @@ SlangResult CodeGenContext::emitEntryPointsSourceFromIR(ComPtr<IArtifact>& outAr
     // Append the modules output code
     finalResult.append(code);
 
+    // Append all content that should be at the end of a module
+    sourceEmitter->emitPostModule();
+    finalResult.append(sourceWriter.getContentAndClear());
+
     // Write out the result
 
     auto artifact = ArtifactUtil::createArtifactForCompileTarget(asExternal(target));