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, 25 insertions, 3 deletions

diff --git a/slang.h b/slang.h
index 67d364898..c4c2f54b7 100644
--- a/slang.h
+++ b/slang.h
@@ -136,6 +136,16 @@ extern "C"
     };
 
     /*!
+    @brief Flags to control code generation behavior of a compilation target */
+    typedef unsigned int SlangTargetFlags;
+    enum
+    {
+        /* When compiling for a D3D Shader Model 5.1 or higher target, allocate
+           distinct register spaces for parameter blocks. */
+        SLANG_TARGET_FLAG_PARAMETER_BLOCKS_USE_REGISTER_SPACES = 1 << 4,
+    };
+
+    /*!
     @brief Options to control emission of `#line` directives
     */
     typedef unsigned int SlangLineDirectiveMode;
@@ -249,10 +259,20 @@ extern "C"
     /*!
     @brief Add a code-generation target to be used.
     */
-    SLANG_API void spAddCodeGenTarget(
+    SLANG_API int spAddCodeGenTarget(
         SlangCompileRequest*    request,
         SlangCompileTarget      target);
 
+    SLANG_API void spSetTargetProfile(
+        SlangCompileRequest*    request,
+        int                     targetIndex,
+        SlangProfileID          profile);
+
+    SLANG_API void spSetTargetFlags(
+        SlangCompileRequest*    request,
+        int                     targetIndex,
+        SlangTargetFlags        flags);
+
     /*!
     @brief Set the container format to be used for binary output.
     */
@@ -564,7 +584,9 @@ extern "C"
         SLANG_PARAMETER_CATEGORY_DESCRIPTOR_TABLE_SLOT,
         SLANG_PARAMETER_CATEGORY_SPECIALIZATION_CONSTANT,
         SLANG_PARAMETER_CATEGORY_PUSH_CONSTANT_BUFFER,
-        SLANG_PAREMTER_CATEGORY_PARAMETER_BLOCK,
+
+        // HLSL register `space`, Vulkan GLSL `set`
+        SLANG_PARAMETER_CATEGORY_REGISTER_SPACE,
 
         //
         SLANG_PARAMETER_CATEGORY_COUNT,
@@ -825,7 +847,7 @@ namespace slang
         DescriptorTableSlot = SLANG_PARAMETER_CATEGORY_DESCRIPTOR_TABLE_SLOT,
         SpecializationConstant = SLANG_PARAMETER_CATEGORY_SPECIALIZATION_CONSTANT,
         PushConstantBuffer = SLANG_PARAMETER_CATEGORY_PUSH_CONSTANT_BUFFER,
-        ParameterBlock = SLANG_PAREMTER_CATEGORY_PARAMETER_BLOCK,
+        RegisterSpace = SLANG_PARAMETER_CATEGORY_REGISTER_SPACE,
     };
 
     struct TypeLayoutReflection