Implement specialization constant support in numthreads / local_size (#5963)

* Allow using specialization constants in numthreads attribute

* Add support for GLSL local_size_x_id syntax

* Fix overeager specialization constant parsing

* Add diagnostics for specialization constant numthreads

* Remove unused variable

* Fix local_size_x_id not finding existing specialization constant

* Allow materializeGetWorkGroupSize to reference specialization constants

* Use SpvOpExecutionModeId for modes that require it

* Cleanup specialization constant numthreads code

* Add tests for specialization constant work group sizes

* Fix implicit Slang::Int -> int32_t cast

* Fix querying thread group size in reflection API

---------

Co-authored-by: Yong He <yonghe@outlook.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/source/slang/slang-parser.cpp b/source/slang/slang-parser.cpp
index c275a868b..6ae41a2eb 100644
--- a/source/slang/slang-parser.cpp
+++ b/source/slang/slang-parser.cpp
@@ -8437,7 +8437,9 @@ static NodeBase* parseLayoutModifier(Parser* parser, void* /*userData*/)
 
         int localSizeIndex = -1;
         if (nameText.startsWith(localSizePrefix) &&
-            nameText.getLength() == SLANG_COUNT_OF(localSizePrefix) - 1 + 1)
+            (nameText.getLength() == SLANG_COUNT_OF(localSizePrefix) - 1 + 1 ||
+             (nameText.endsWith("_id") &&
+              (nameText.getLength() == SLANG_COUNT_OF(localSizePrefix) - 1 + 4))))
         {
             char lastChar = nameText[SLANG_COUNT_OF(localSizePrefix) - 1];
             localSizeIndex = (lastChar >= 'x' && lastChar <= 'z') ? (lastChar - 'x') : -1;
@@ -8451,6 +8453,8 @@ static NodeBase* parseLayoutModifier(Parser* parser, void* /*userData*/)
                 numThreadsAttrib->args.setCount(3);
                 for (auto& i : numThreadsAttrib->args)
                     i = nullptr;
+                for (auto& b : numThreadsAttrib->axisIsSpecConstId)
+                    b = false;
 
                 // Just mark the loc and name from the first in the list
                 numThreadsAttrib->keywordName = getName(parser, "numthreads");
@@ -8467,6 +8471,11 @@ static NodeBase* parseLayoutModifier(Parser* parser, void* /*userData*/)
                 }
 
                 numThreadsAttrib->args[localSizeIndex] = expr;
+
+                // We can't resolve the specialization constant declaration
+                // here, because it may not even exist. IDs pointing to unnamed
+                // specialization constants are allowed in GLSL.
+                numThreadsAttrib->axisIsSpecConstId[localSizeIndex] = nameText.endsWith("_id");
             }
         }
         else if (nameText == "derivative_group_quadsNV")