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, 12 insertions, 0 deletions

diff --git a/source/slang/options.cpp b/source/slang/options.cpp
index 7eea3fecc..452e7c439 100644
--- a/source/slang/options.cpp
+++ b/source/slang/options.cpp
@@ -80,6 +80,7 @@ struct OptionsParser
     int profileOptionCount = 0;
 
     SlangCompileFlags flags = 0;
+    SlangTargetFlags targetFlags = 0;
 
     struct RawOutputPath
     {
@@ -279,6 +280,10 @@ struct OptionsParser
                 {
                     requestImpl->shouldSkipCodegen = true;
                 }
+                else if(argStr == "-parameter-blocks-use-register-spaces" )
+                {
+                    targetFlags |= SLANG_TARGET_FLAG_PARAMETER_BLOCKS_USE_REGISTER_SPACES;
+                }
                 else if (argStr == "-backend" || argStr == "-target")
                 {
                     String name = tryReadCommandLineArgument(arg, &argCursor, argEnd);
@@ -729,6 +734,13 @@ struct OptionsParser
             }
         }
 
+        // If the user specifed and per-compilation-target flags, make sure
+        // to apply them here.
+        if(targetFlags)
+        {
+            spSetTargetFlags(compileRequest, 0, targetFlags);
+        }
+
         // Next, we want to make sure that entry points get attached to the appropriate translation
         // unit that will provide them.
         {