1 files changed, 74 insertions, 8 deletions

diff --git a/source/slang/emit.cpp b/source/slang/emit.cpp
index af2fa68dc..e0f71aafe 100644
--- a/source/slang/emit.cpp
+++ b/source/slang/emit.cpp
@@ -979,7 +979,7 @@ struct EmitVisitor
         case CodeGenTarget::GLSL_Vulkan_OneDesc:
             {
                 // Need to special case if there is a single element in the vector
-                // as there is no such thing in glsl as vec1 
+                // as there is no such thing in glsl as vec1
                 IRInst* elementCountInst = vecType->getElementCount();
 
                 if (elementCountInst->op != kIROp_IntLit)
@@ -1914,6 +1914,68 @@ struct EmitVisitor
         // TODO: handle other cases...
     }
 
+    /// Emit directives to control overall layout computation for the emitted code.
+    void emitLayoutDirectives(TargetRequest* targetReq)
+    {
+        // We are going to emit the target-language-specific directives
+        // needed to get the default matrix layout to match what was requested
+        // for the given target.
+        //
+        // Note: we do not rely on the defaults for the target language,
+        // because a user could take the HLSL/GLSL generated by Slang and pass
+        // it to another compiler with non-default options specified on
+        // the command line, leading to all kinds of trouble.
+        //
+        // TODO: We need an approach to "global" layout directives that will work
+        // in the presence of multiple modules. If modules A and B were each
+        // compiled with different assumptions about how layout is performed,
+        // then types/variables defined in those modules should be emitted in
+        // a way that is consistent with that layout...
+
+        auto matrixLayoutMode = targetReq->defaultMatrixLayoutMode;
+
+        switch(context->shared->target)
+        {
+        default:
+            return;
+
+        case CodeGenTarget::GLSL:
+            // Reminder: the meaning of row/column major layout
+            // in our semantics is the *opposite* of what GLSL
+            // calls them, because what they call "columns"
+            // are what we call "rows."
+            //
+            switch(matrixLayoutMode)
+            {
+            case kMatrixLayoutMode_RowMajor:
+            default:
+                Emit("layout(column_major) uniform;\n");
+                Emit("layout(column_major) buffer;\n");
+                break;
+
+            case kMatrixLayoutMode_ColumnMajor:
+                Emit("layout(row_major) uniform;\n");
+                Emit("layout(row_major) buffer;\n");
+                break;
+            }
+            break;
+
+        case CodeGenTarget::HLSL:
+            switch(matrixLayoutMode)
+            {
+            case kMatrixLayoutMode_RowMajor:
+            default:
+                Emit("#pragma pack_matrix(row_major)\n");
+                break;
+
+            case kMatrixLayoutMode_ColumnMajor:
+                Emit("#pragma pack_matrix(column_major)\n");
+                break;
+            }
+            break;
+        }
+    }
+
     // Utility code for generating unique IDs as needed
     // during the emit process (e.g., for declarations
     // that didn't origianlly have names, but now need to).
@@ -4611,12 +4673,15 @@ struct EmitVisitor
         EmitContext*    ctx,
         VarLayout*      layout)
     {
-        // We need to handle the case where the variable has
-        // a matrix type, and has been given a non-standard
-        // layout attribute (for HLSL, `row_major` is the
-        // non-standard layout).
+        // When a variable has a matrix type, we want to emit an explicit
+        // layout qualifier based on what the layout has been computed to be.
         //
-        if (auto matrixTypeLayout = layout->typeLayout.As<MatrixTypeLayout>())
+
+        auto typeLayout = layout->typeLayout;
+        while(auto arrayTypeLayout = typeLayout.As<ArrayTypeLayout>())
+            typeLayout = arrayTypeLayout->elementTypeLayout;
+
+        if (auto matrixTypeLayout = typeLayout.As<MatrixTypeLayout>())
         {
             auto target = ctx->shared->target;
 
@@ -4626,7 +4691,6 @@ struct EmitVisitor
                 switch (matrixTypeLayout->mode)
                 {
                 case kMatrixLayoutMode_ColumnMajor:
-                    if(target == CodeGenTarget::GLSL)
                     emit("column_major ");
                     break;
 
@@ -4645,7 +4709,6 @@ struct EmitVisitor
                 switch (matrixTypeLayout->mode)
                 {
                 case kMatrixLayoutMode_ColumnMajor:
-                    if(target == CodeGenTarget::GLSL)
                     emit("layout(row_major)\n");
                     break;
 
@@ -5815,6 +5878,9 @@ String emitEntryPoint(
 
     // There may be global-scope modifiers that we should emit now
     visitor.emitGLSLPreprocessorDirectives(translationUnitSyntax);
+
+    visitor.emitLayoutDirectives(targetRequest);
+
     String prefix = sharedContext.sb.ProduceString();