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>

1 files changed, 3 insertions, 5 deletions

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;";
                 }
             }
         }