Parameter block work (#276)

* Don't auto-enable IR use for compute tests

The `COMPARE_COMPUTE` and `COMPARE_RENDER_COMPUTE` test fixtures were set up to always enable the `-use-ir` flag on Slang, which precludes having any tests that confirm functionality on the old non-IR path (which is still required by our main customer).

This change adds the `-xslang -use-ir` flags explicitly to any compute test cases that left them out, and makes the fixture no longer add it by default.

* Continue building out parameter block support

The initial front-end logic for parameter blocks was already added, but they are still missing a bunch of functionality. This change addresses some of the known issues:

- Bug fix: don't try to emit HLSL `register` bindings for variables that consume whole register spaces/sets

- Overhaul type layout logic so that it can make decisions based on a given code generation target (currently passed in as a `TargetRequest`), which allows us to decide whether or not a parameter block should get its own register set on a per-target basis.
  - Always use a register space/set for Vulkan
  - Never use a register space/set for HLSL SM 5.0 and lower
  - By default, don't use register spaces/sets for HLSL output
  - Add a command-line flag and some "target flags" to enable register-space usage for D3D targets

- Hackily add initial support for parameter blocks in the AST-to-AST path
  - This just blindly lowers `ParameterBlock<T>` to `T`, which shouldn't quite work
  - A more complete overhaul will probably need to wait until the AST-to-AST legalization is changed to use the `LegalType`s from the IR legalization pass.

- Add a compute-based test case to actually run code using parameter blocks
  - This file runs test cases both with and without the IR

1 files changed, 4 insertions, 12 deletions

diff --git a/source/slang/ir-legalize-types.cpp b/source/slang/ir-legalize-types.cpp
index 5b42407c2..5b08acee8 100644
--- a/source/slang/ir-legalize-types.cpp
+++ b/source/slang/ir-legalize-types.cpp
@@ -660,13 +660,13 @@ static LegalVal declareSimpleVar(
         // those to all the nested resource infos.
         for (auto vv = varChain; vv; vv = vv->next)
         {
-            auto parentSpaceInfo = vv->varLayout->findOrAddResourceInfo(LayoutResourceKind::ParameterBlock);
+            auto parentSpaceInfo = vv->varLayout->findOrAddResourceInfo(LayoutResourceKind::RegisterSpace);
             if (!parentSpaceInfo)
                 continue;
 
             for (auto& rr : varLayout->resourceInfos)
             {
-                if (rr.kind == LayoutResourceKind::ParameterBlock)
+                if (rr.kind == LayoutResourceKind::RegisterSpace)
                 {
                     rr.index += parentSpaceInfo->index;
                 }
@@ -827,21 +827,13 @@ static void legalizeGlobalVar(
     RefPtr<VarLayout> varLayout = findVarLayout(irGlobalVar);
     RefPtr<TypeLayout> typeLayout = varLayout ? varLayout->typeLayout : nullptr;
 
-    // If we've decided to do implicit deref on the type,
-    // then go ahead and declare a value of the pointed-to type.
-    LegalType maybeSimpleType = legalValueType;
-    while (maybeSimpleType.flavor == LegalType::Flavor::implicitDeref)
-    {
-        maybeSimpleType = maybeSimpleType.getImplicitDeref()->valueType;
-    }
-
-    switch (maybeSimpleType.flavor)
+    switch (legalValueType.flavor)
     {
     case LegalType::Flavor::simple:
         // Easy case: the type is usable as-is, and we
         // should just do that.
         irGlobalVar->type = context->session->getPtrType(
-            maybeSimpleType.getSimple());
+            legalValueType.getSimple());
         break;
 
     default: