Introduce CDataLayout & -fvk-use-c-layout (#8136)

Closes #8112. ~~The issue asks for a "C layout", but in this PR I use
the term "CPU layout" because this naming was pre-existing in the
codebase as `kCPULayoutRulesImpl_`. The primary purpose of this layout
is to match CPU-side struct definitions with the shader side. I'm open
to better naming suggestions, though.~~

Edit: switched back to using `CDataLayout` & `-fvk-use-c-layout`, as the
CPU target depends on the object layout rules of existing CPU layout
rules, but they're incompatible with actual shaders. So a new
`kCLayoutRulesImpl_` was needed anyway.

---------

Co-authored-by: Ellie Hermaszewska <ellieh@nvidia.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/source/slang/slang-options.cpp b/source/slang/slang-options.cpp
index b0eb1748d..2115a096f 100644
--- a/source/slang/slang-options.cpp
+++ b/source/slang/slang-options.cpp
@@ -663,6 +663,12 @@ void initCommandOptions(CommandOptions& options)
          "-fvk-use-dx-layout",
          nullptr,
          "Pack members using FXCs member packing rules when targeting GLSL or SPIRV."},
+        {OptionKind::ForceCLayout,
+         "-fvk-use-c-layout",
+         nullptr,
+         "Make data accessed through ConstantBuffer, ParameterBlock, StructuredBuffer, "
+         "ByteAddressBuffer and general pointers follow the C/C++ structure layout rules "
+         "when targeting SPIRV."},
         {OptionKind::VulkanBindShift,
          vkShiftNames.getBuffer(),
          "-fvk-<vulkan-shift>-shift <N> <space>",
@@ -2670,6 +2676,11 @@ SlangResult OptionsParser::_parse(int argc, char const* const* argv)
                 getCurrentTarget()->optionSet.add(CompilerOptionName::ForceDXLayout, true);
                 break;
             }
+        case OptionKind::ForceCLayout:
+            {
+                getCurrentTarget()->optionSet.add(CompilerOptionName::ForceCLayout, true);
+                break;
+            }
         case OptionKind::EnableEffectAnnotations:
             {
                 m_compileRequest->setEnableEffectAnnotations(true);
@@ -3707,6 +3718,11 @@ SlangResult OptionsParser::_parse(int argc, char const* const* argv)
                 m_compileRequest->setTargetForceDXLayout(targetID, true);
             }
 
+            if (rawTarget.optionSet.shouldUseCLayout())
+            {
+                m_compileRequest->setTargetForceCLayout(targetID, true);
+            }
+
             if (rawTarget.optionSet.getBoolOption(CompilerOptionName::GenerateWholeProgram))
             {
                 m_compileRequest->setTargetGenerateWholeProgram(targetID, true);