Support Array Sizes using Generic arguments to be initialized via {} (#6720)

* Add support for Array Sizes using Generic arguments to be initialized via {}

Fixes one subissue of #6138

This change adds support for initializing Arrays with Generic size arguments via {}
and adds a test to verify it.

The change checks for an array whose size parameter is a GenericParamIntVal
and since the size of such an array will be known at link time, is not considered
as a case of the size not being known statically.

* Add support for Array Sizes using Generic arguments to be initialized via {}

Fixes one subissue of #6138.
Fixes the issue #6958.

This change adds support for initializing Arrays with Generic size arguments via {}
and adds a test to verify it.

Support is added by means of adding a new AST Expr node that lowers down to the IR MakeArrayFromElement
and the emission of a diagnostic is replaced with the creation of this new AST Expr node.

* format code

---------

Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>
Co-authored-by: Ellie Hermaszewska <ellieh@nvidia.com>

6 files changed, 57 insertions, 12 deletions

diff --git a/source/slang/slang-ast-expr.h b/source/slang/slang-ast-expr.h
index 5d8caefa9..346ed56f1 100644
--- a/source/slang/slang-ast-expr.h
+++ b/source/slang/slang-ast-expr.h
@@ -139,6 +139,12 @@ class StringLiteralExpr : public LiteralExpr
     FIDDLE() String value;
 };
 
+FIDDLE()
+class MakeArrayFromElementExpr : public Expr
+{
+    FIDDLE(...)
+};
+
 // An initializer list, e.g. `{ 1, 2, 3 }`
 FIDDLE()
 class InitializerListExpr : public Expr
diff --git a/source/slang/slang-check-conversion.cpp b/source/slang/slang-check-conversion.cpp
index 1c8846e66..a2cb0f91b 100644
--- a/source/slang/slang-check-conversion.cpp
+++ b/source/slang/slang-check-conversion.cpp
@@ -613,19 +613,13 @@ bool SemanticsVisitor::_readAggregateValueFromInitializerList(
             }
             else
             {
-                // We don't know the element count statically,
-                // so what are we supposed to be doing?
-                //
-                if (outToExpr)
-                {
-                    getSink()->diagnose(
-                        fromInitializerListExpr,
-                        Diagnostics::cannotUseInitializerListForArrayOfUnknownSize,
-                        toElementCount);
-                }
-                return false;
-            }
+                auto toMakeArrayFromElementExpr = m_astBuilder->create<MakeArrayFromElementExpr>();
+                toMakeArrayFromElementExpr->loc = fromInitializerListExpr->loc;
+                toMakeArrayFromElementExpr->type = QualType(toType);
 
+                *outToExpr = toMakeArrayFromElementExpr;
+                return true;
+            }
             for (UInt ee = 0; ee < elementCount; ++ee)
             {
                 Expr* coercedArg = nullptr;
diff --git a/source/slang/slang-check-expr.cpp b/source/slang/slang-check-expr.cpp
index 87f29d367..48f32952b 100644
--- a/source/slang/slang-check-expr.cpp
+++ b/source/slang/slang-check-expr.cpp
@@ -5181,6 +5181,11 @@ Expr* SemanticsExprVisitor::visitMemberExpr(MemberExpr* expr)
     }
 }
 
+Expr* SemanticsExprVisitor::visitMakeArrayFromElementExpr(MakeArrayFromElementExpr* expr)
+{
+    return expr;
+}
+
 Expr* SemanticsExprVisitor::visitInitializerListExpr(InitializerListExpr* expr)
 {
     // If we are assigned a type, expr has already been legalized
diff --git a/source/slang/slang-check-impl.h b/source/slang/slang-check-impl.h
index 1e93d8381..a910a3722 100644
--- a/source/slang/slang-check-impl.h
+++ b/source/slang/slang-check-impl.h
@@ -2954,6 +2954,7 @@ public:
     Expr* visitMemberExpr(MemberExpr* expr);
 
     Expr* visitInitializerListExpr(InitializerListExpr* expr);
+    Expr* visitMakeArrayFromElementExpr(MakeArrayFromElementExpr* expr);
 
     Expr* visitThisExpr(ThisExpr* expr);
     Expr* visitThisTypeExpr(ThisTypeExpr* expr);
diff --git a/source/slang/slang-lower-to-ir.cpp b/source/slang/slang-lower-to-ir.cpp
index 90780882d..1006a3489 100644
--- a/source/slang/slang-lower-to-ir.cpp
+++ b/source/slang/slang-lower-to-ir.cpp
@@ -4825,6 +4825,17 @@ struct ExprLoweringVisitorBase : public ExprVisitor<Derived, LoweredValInfo>
         }
     }
 
+    LoweredValInfo visitMakeArrayFromElementExpr(MakeArrayFromElementExpr* expr)
+    {
+        auto irType = lowerType(context, expr->type);
+        auto irDefaultElement = getSimpleVal(
+            context,
+            getDefaultVal(as<ArrayExpressionType>(expr->type)->getElementType()));
+
+        return LoweredValInfo::simple(
+            getBuilder()->emitMakeArrayFromElement(irType, irDefaultElement));
+    }
+
     LoweredValInfo visitInitializerListExpr(InitializerListExpr* expr)
     {
         // Allocate a temporary of the given type
diff --git a/tests/initializer-list/generic-array-init.slang b/tests/initializer-list/generic-array-init.slang
new file mode 100644
index 000000000..4257e2972
--- /dev/null
+++ b/tests/initializer-list/generic-array-init.slang
@@ -0,0 +1,28 @@
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=BUFFER):-shaderobj -vk
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=BUFFER):-shaderobj -mtl
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=BUFFER):-cpu -compute -entry computeMain
+
+//TEST_INPUT:ubuffer(data=[9 9 9 9], stride=4):out,name=outputBuffer
+RWStructuredBuffer<int> outputBuffer;
+
+void test<let TSize : uint>()
+{
+    // Test array initialization with generic size
+    int array[TSize] = {};
+
+    // BUFFER: 0
+    outputBuffer[0] = array[0];
+    // BUFFER-NEXT: 0
+    outputBuffer[1] = array[1];
+    // BUFFER-NEXT: 0
+    outputBuffer[2] = array[2];
+    // BUFFER-NEXT: 3
+    outputBuffer[3] = array.getCount();
+}
+
+[shader("compute")]
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    test<3>();
+}