From 366a947cdf2e3c6958b7a9e17d561ce76ab0f594 Mon Sep 17 00:00:00 2001
From: ArielG-NV <159081215+ArielG-NV@users.noreply.github.com>
Date: Thu, 25 Apr 2024 09:18:32 -0400
Subject: 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>
---
 source/slang/slang-emit-spirv.cpp | 44 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

(limited to 'source/slang/slang-emit-spirv.cpp')

diff --git a/source/slang/slang-emit-spirv.cpp b/source/slang/slang-emit-spirv.cpp
index 06e5f0766..106248ef8 100644
--- a/source/slang/slang-emit-spirv.cpp
+++ b/source/slang/slang-emit-spirv.cpp
@@ -4,6 +4,7 @@
 #include "slang-emit-base.h"
 
 #include "slang-ir-util.h"
+#include "slang-ir-call-graph.h"
 #include "slang-ir.h"
 #include "slang-ir-insts.h"
 #include "slang-ir-layout.h"
@@ -437,6 +438,7 @@ constexpr bool isPlural<IRUse*> = true;
 template<typename T>
 constexpr bool isSingular = !isPlural<T>;
 
+
 // Now that we've defined the intermediate data structures we will
 // use to represent SPIR-V code during emission, we will move on
 // to defining the main context type that will drive SPIR-V
@@ -1278,6 +1280,11 @@ struct SPIRVEmitContext
         return result;
     }
 
+    bool hasExtensionDeclaration(const UnownedStringSlice& name)
+    {
+        return m_extensionInsts.containsKey(name);
+    }
+
     struct SpvTypeInstKey
     {
         List<SpvWord> words;
@@ -2730,6 +2737,43 @@ struct SPIRVEmitContext
                 auto inner = ensureInst(location);
                 registerInst(inst, inner);
                 result = inner;
+                break;
+            }
+        case kIROp_RequireComputeDerivative:
+            {
+                auto parentFunc = getParentFunc(inst);
+
+                HashSet<IRFunc*>* entryPointsUsingInst = getReferencingEntryPoints(m_referencingEntryPoints, parentFunc);
+                for (IRFunc* entryPoint : *entryPointsUsingInst)
+                {
+                    bool isQuad = true;
+                    IREntryPointDecoration* entryPointDecor = nullptr;
+                    for(auto dec : entryPoint->getDecorations())
+                    {
+                        if(auto maybeEntryPointDecor = as<IREntryPointDecoration>(dec))
+                            entryPointDecor = maybeEntryPointDecor;
+                        if(as<IRDerivativeGroupLinearDecoration>(dec))
+                            isQuad = false;
+                    }
+                    if (!entryPointDecor || entryPointDecor->getProfile().getStage() != Stage::Compute)
+                        continue;
+
+                    ensureExtensionDeclaration(UnownedStringSlice("SPV_NV_compute_shader_derivatives"));
+                    auto numThreadsDecor =  entryPointDecor->findDecoration<IRNumThreadsDecoration>();
+                    if (isQuad)
+                    {
+                        verifyComputeDerivativeGroupModifiers(this->m_sink, inst->sourceLoc, true, false, numThreadsDecor);
+                        emitOpExecutionMode(getSection(SpvLogicalSectionID::ExecutionModes), nullptr, entryPoint, SpvExecutionModeDerivativeGroupQuadsNV);
+                        emitOpCapability(getSection(SpvLogicalSectionID::Capabilities), nullptr, SpvCapabilityComputeDerivativeGroupQuadsNV);
+                    }
+                    else
+                    {
+                        verifyComputeDerivativeGroupModifiers(this->m_sink, inst->sourceLoc, false, true, numThreadsDecor);
+                        emitOpExecutionMode(getSection(SpvLogicalSectionID::ExecutionModes), nullptr, entryPoint, SpvExecutionModeDerivativeGroupLinearNV);
+                        emitOpCapability(getSection(SpvLogicalSectionID::Capabilities), nullptr, SpvCapabilityComputeDerivativeGroupLinearNV);
+                    }
+                }
+
                 break;
             }
         case kIROp_Return:
-- 
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