Add `-fvk-use-dx-position-w` and fix ExecutionMode ordering for geometry shaders. (#3731)

* Add `-fvk-use-dx-position-w`.

* Fix ordering of OutputVertices and output primitive type decoration in spirv.

* Fix.

* fix

* Fix.

* Move test around.

1 files changed, 39 insertions, 19 deletions

diff --git a/source/slang/slang-emit-spirv.cpp b/source/slang/slang-emit-spirv.cpp
index 2f318c464..8063975e2 100644
--- a/source/slang/slang-emit-spirv.cpp
+++ b/source/slang/slang-emit-spirv.cpp
@@ -3074,16 +3074,9 @@ struct SPIRVEmitContext
             }
             break;
         case kIROp_MaxVertexCountDecoration:
-            {
-                auto section = getSection(SpvLogicalSectionID::ExecutionModes);
-                auto maxVertexCount = cast<IRMaxVertexCountDecoration>(decoration);
-                emitOpExecutionModeOutputVertices(
-                    section,
-                    decoration,
-                    dstID,
-                    SpvLiteralInteger::from32(int32_t(getIntVal(maxVertexCount->getCount())))
-                );
-            }
+            // Don't do anything here, instead wait until we see OutputTopologyDecoration
+            // and emit them together to ensure MaxVertexCount always appears before OutputTopology,
+            // which seemed to be required by SPIRV.
             break;
         case kIROp_InstanceDecoration:
             {
@@ -3094,22 +3087,49 @@ struct SPIRVEmitContext
             }
             break;
         case kIROp_TriangleInputPrimitiveTypeDecoration:
-            emitOpExecutionMode(getSection(SpvLogicalSectionID::ExecutionModes), decoration, dstID, SpvExecutionModeTriangles);
-            break;
         case kIROp_LineInputPrimitiveTypeDecoration:
-            emitOpExecutionMode(getSection(SpvLogicalSectionID::ExecutionModes), decoration, dstID, SpvExecutionModeInputLines);
-            break;
         case kIROp_LineAdjInputPrimitiveTypeDecoration:
-            emitOpExecutionMode(getSection(SpvLogicalSectionID::ExecutionModes), decoration, dstID, SpvExecutionModeInputLinesAdjacency);
-            break;
         case kIROp_PointInputPrimitiveTypeDecoration:
-            emitOpExecutionMode(getSection(SpvLogicalSectionID::ExecutionModes), decoration, dstID, SpvExecutionModeInputPoints);
-            break;
         case kIROp_TriangleAdjInputPrimitiveTypeDecoration:
-            emitOpExecutionMode(getSection(SpvLogicalSectionID::ExecutionModes), decoration, dstID, SpvExecutionModeInputTrianglesAdjacency);
+            // Defer this until we see kIROp_StreamOutputTypeDecoration because the driver wants to see
+            // them before the output.
             break;
         case kIROp_StreamOutputTypeDecoration:
             {
+                for (auto inputDecor : decoration->getParent()->getDecorations())
+                {
+                    switch (inputDecor->getOp())
+                    {
+                    case kIROp_TriangleInputPrimitiveTypeDecoration:
+                        emitOpExecutionMode(getSection(SpvLogicalSectionID::ExecutionModes), inputDecor, dstID, SpvExecutionModeTriangles);
+                        break;
+                    case kIROp_LineInputPrimitiveTypeDecoration:
+                        emitOpExecutionMode(getSection(SpvLogicalSectionID::ExecutionModes), inputDecor, dstID, SpvExecutionModeInputLines);
+                        break;
+                    case kIROp_LineAdjInputPrimitiveTypeDecoration:
+                        emitOpExecutionMode(getSection(SpvLogicalSectionID::ExecutionModes), inputDecor, dstID, SpvExecutionModeInputLinesAdjacency);
+                        break;
+                    case kIROp_PointInputPrimitiveTypeDecoration:
+                        emitOpExecutionMode(getSection(SpvLogicalSectionID::ExecutionModes), inputDecor, dstID, SpvExecutionModeInputPoints);
+                        break;
+                    case kIROp_TriangleAdjInputPrimitiveTypeDecoration:
+                        emitOpExecutionMode(getSection(SpvLogicalSectionID::ExecutionModes), inputDecor, dstID, SpvExecutionModeInputTrianglesAdjacency);
+                        break;
+                    }
+                }
+                // SPIRV requires MaxVertexCount decoration to appear before OutputTopologyDecoration,
+                // so we emit them here.
+                if (auto maxVertexCount = decoration->getParent()->findDecoration<IRMaxVertexCountDecoration>())
+                {
+                    auto section = getSection(SpvLogicalSectionID::ExecutionModes);
+                    emitOpExecutionModeOutputVertices(
+                        section,
+                        maxVertexCount,
+                        dstID,
+                        SpvLiteralInteger::from32(int32_t(getIntVal(maxVertexCount->getCount())))
+                    );
+                }
+
                 auto decor = as<IRStreamOutputTypeDecoration>(decoration);
                 IRType* type = decor->getStreamType();