Support derivative functions in compute & capabilities adjustments (#4014)

* Support derivative functions in compute & capabilities adjustments

fixes #4000

PR implements derivative functions in compute shaders properly so we have the functionality for SPIR-V & GLSL. Tests reflect fragment and compute paths.

PR also adjusts capabilities to correct wrong SPRI-V target capabilities for when using textures.

Remarks:
1. __requireComputeDerivative(); is a intrinsic_op and not modifier since inlining will destroy the modifier.
2. Derivative mode is tied to an entry point decoration `[DerivativeGroupQuad]`/`[DerivativeGroupLinear]` or GLSL syntax ``derivative_group_linearNV`. Default is to set the mode to `[DerivativeGroupQuad]`

* remove -emit-spirv-directly

* fixes

1. fix minor issue fwidth change where I returned the wrong type
2. fix issue where glslang{glsl->spirv} is wrong, so we don't run that test and just run the glsl test & direct spir-v test for intrinsic-texture.slang

* adjust as per review and refine code

1. add test to ensure multi-diverging-in-logic entry points work -- 2 functions which may cause computeDerivatives + 1 that uses, 1 that does not.
2. naming
3. use entry point ref graph for c-like-targets
4. reordered some code to util's and removed `static linline` since that was just for ease of coding on my end (should not have been pushed).

* Grammer

* split up source file + issolate GLSL emit path change.

---------

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

1 files changed, 12 insertions, 1 deletions

diff --git a/source/slang/slang-emit-c-like.cpp b/source/slang/slang-emit-c-like.cpp
index bd3337769..fa380e061 100644
--- a/source/slang/slang-emit-c-like.cpp
+++ b/source/slang/slang-emit-c-like.cpp
@@ -129,6 +129,11 @@ void CLikeSourceEmitter::emitPreModuleImpl()
         m_writer->emit(prelude->getStringSlice());
         m_writer->emit("\n");
     }
+    for (auto prelude : m_requiredPreludesRaw)
+    {
+        m_writer->emit(prelude);
+        m_writer->emit("\n");
+    }
 }
 
 //
@@ -2747,6 +2752,10 @@ void CLikeSourceEmitter::defaultEmitInstExpr(IRInst* inst, const EmitOpInfo& inO
     {
         break; //should already have set requirement; case covered for empty intrinsic block
     }
+    case kIROp_RequireComputeDerivative:
+    {
+        break; //should already have been parsed and used.
+    }
     default:
         diagnoseUnhandledInst(inst);
         break;
@@ -3358,7 +3367,8 @@ void CLikeSourceEmitter::emitSimpleFuncImpl(IRFunc* func)
 
     // Deal with decorations that need
     // to be emitted as attributes
-    if ( IREntryPointDecoration* entryPointDecor = func->findDecoration<IREntryPointDecoration>())
+    IREntryPointDecoration* entryPointDecor = func->findDecoration<IREntryPointDecoration>();
+    if (entryPointDecor)
     {
         emitEntryPointAttributes(func, entryPointDecor);
     }
@@ -4446,6 +4456,7 @@ void CLikeSourceEmitter::emitModuleImpl(IRModule* module, DiagnosticSink* sink)
 
     List<EmitAction> actions;
 
+    beforeComputeEmitActions(module);
     computeEmitActions(module, actions);
     executeEmitActions(actions);
 }