Fix parameter block loads in GLSL emit. (#2946)

* Fix parameter block loads in GLSL emit.

* Revert `[NoSideEffect]` declarations in DXR1.1 API.

* fix.

---------

Co-authored-by: Yong He <yhe@nvidia.com>

4 files changed, 48 insertions, 5 deletions

diff --git a/source/slang/hlsl.meta.slang b/source/slang/hlsl.meta.slang
index b42e17fbe..89a34588c 100644
--- a/source/slang/hlsl.meta.slang
+++ b/source/slang/hlsl.meta.slang
@@ -5750,7 +5750,6 @@ struct RayQuery <let rayFlagsGeneric : RAY_FLAG = RAY_FLAG_NONE>
     // must obey any API-imposed restrictions.
     //
     __target_intrinsic(hlsl)
-    [__NoSideEffect]
     [mutating]
     void TraceRayInline(
         RaytracingAccelerationStructure accelerationStructure,
@@ -5773,7 +5772,6 @@ struct RayQuery <let rayFlagsGeneric : RAY_FLAG = RAY_FLAG_NONE>
 
     [__unsafeForceInlineEarly]
     __specialized_for_target(glsl)
-    [__NoSideEffect]
     [mutating]
     void TraceRayInline(
         RaytracingAccelerationStructure accelerationStructure,
@@ -5808,7 +5806,6 @@ struct RayQuery <let rayFlagsGeneric : RAY_FLAG = RAY_FLAG_NONE>
     __target_intrinsic(glsl, rayQueryProceedEXT)
     __glsl_extension(GL_EXT_ray_query)
     __glsl_version(460)
-    [__NoSideEffect]
     [mutating]
     bool Proceed();
 
@@ -5821,7 +5818,6 @@ struct RayQuery <let rayFlagsGeneric : RAY_FLAG = RAY_FLAG_NONE>
     __target_intrinsic(glsl, rayQueryTerminateEXT)
     __glsl_extension(GL_EXT_ray_query)
     __glsl_version(460)
-    [__NoSideEffect]
     [mutating]
     void Abort();
 
diff --git a/source/slang/slang-emit.cpp b/source/slang/slang-emit.cpp
index f1ec402dd..b34483cf2 100644
--- a/source/slang/slang-emit.cpp
+++ b/source/slang/slang-emit.cpp
@@ -783,12 +783,13 @@ Result linkAndOptimizeIR(
         break;
     }
 
-    // Legalize `ImageSubscript` for GLSL.
+    // Legalize `ImageSubscript` and constant buffer loads for GLSL.
     switch (target)
     {
     case CodeGenTarget::GLSL:
         {
             legalizeImageSubscriptForGLSL(irModule);
+            legalizeConstantBufferLoadForGLSL(irModule);
         }
         break;
     default:
diff --git a/source/slang/slang-ir-glsl-legalize.cpp b/source/slang/slang-ir-glsl-legalize.cpp
index f02360416..216471d65 100644
--- a/source/slang/slang-ir-glsl-legalize.cpp
+++ b/source/slang/slang-ir-glsl-legalize.cpp
@@ -2778,4 +2778,48 @@ void legalizeEntryPointsForGLSL(
     }
 }
 
+void legalizeConstantBufferLoadForGLSL(IRModule* module)
+{
+    // Constant buffers and parameter blocks are represented as `uniform` blocks
+    // in GLSL. These uniform blocks can't be used directly as a value of the underlying
+    // struct type. If we see a direct load of the constant buffer pointer,
+    // we need to replace it with a `MakeStruct` inst where each field is separately
+    // loaded.
+    IRBuilder builder(module);
+    for (auto globalInst : module->getGlobalInsts())
+    {
+        if (auto func = as<IRGlobalValueWithCode>(globalInst))
+        {
+            for (auto block : func->getBlocks())
+            {
+                for (auto inst = block->getFirstInst(); inst;)
+                {
+                    auto load = as<IRLoad>(inst);
+                    inst = inst->next;
+                    if (!load) continue;
+                    auto bufferType = load->getPtr()->getDataType();
+                    if (as<IRConstantBufferType>(bufferType) || as<IRParameterBlockType>(bufferType))
+                    {
+                        auto parameterGroupType = as<IRUniformParameterGroupType>(bufferType);
+                        auto elementType = as<IRStructType>(parameterGroupType->getElementType());
+                        if (!elementType) continue;
+                        List<IRInst*> elements;
+                        builder.setInsertBefore(load);
+                        for (auto field : elementType->getFields())
+                        {
+                            auto fieldAddr = builder.emitFieldAddress(field->getFieldType(), load->getPtr(), field->getKey());
+                            auto fieldValue = builder.emitLoad(field->getFieldType(), fieldAddr);
+                            elements.add(fieldValue);
+                        }
+                        auto makeStruct = builder.emitMakeStruct(elementType, elements.getCount(), elements.getBuffer());
+                        load->replaceUsesWith(makeStruct);
+                        load->removeAndDeallocate();
+                    }
+                }
+            }
+        }
+    }
+}
+
+
 } // namespace Slang
diff --git a/source/slang/slang-ir-glsl-legalize.h b/source/slang/slang-ir-glsl-legalize.h
index 8a49fb2ec..1816df1f2 100644
--- a/source/slang/slang-ir-glsl-legalize.h
+++ b/source/slang/slang-ir-glsl-legalize.h
@@ -23,4 +23,6 @@ void legalizeEntryPointsForGLSL(
 
 void legalizeImageSubscriptForGLSL(IRModule* module);
 
+void legalizeConstantBufferLoadForGLSL(IRModule* module);
+
 }