[Mlir-commits] [mlir] EmitC: Add emitc.global and emitc.get_global (#145) (PR #88701)

[Marius Brehler]

================
@@ -1016,6 +1016,75 @@ def EmitC_VariableOp : EmitC_Op<"variable", []> {
   let hasVerifier = 1;
 }
 
+def EmitC_GlobalOp : EmitC_Op<"global", [Symbol]> {
+  let summary = "A global variable";
+  let description = [{
+    The `emitc.global` operation declares or defines a named global variable.
+    The backing memory for the variable is allocated statically and is
+    described by the type of the variable.
+    Optionally, and `initial_value` can be provided.
+    Internal linkage can be specified using the `staticSpecifier` unit attribute
+    and external linkage can be specified using the `externSpecifier` unit attribute.
+    Note that the default linkage without those two keywords depends on whether
+    the target is C or C++ and whether the global variable is `const`.
+    The global variable can also be marked constant using the `constSpecifier`
+    unit attribute. Writing to such constant global variables is
+    undefined.
+
+    The global variable can be accessed by using the `emitc.get_global` to
+    retrieve the value for the global variable.
+
+    Example:
+
+    ```mlir
+    // Global variable with an initial value.
+    emitc.global @x : emitc.array<2xf32> = dense<0.0, 2.0>
+    // External global variable
+    emitc.global extern @x : emitc.array<2xf32>
+    // Constant global variable with internal linkage
+    emitc.global static const @x : i32 = 0
+    ```
+  }];
+
+  let arguments = (ins SymbolNameAttr:$sym_name,
+                       TypeAttr:$type,
+                       OptionalAttr<EmitC_OpaqueOrTypedAttr>:$initial_value,
+                       UnitAttr:$externSpecifier,
+                       UnitAttr:$staticSpecifier,
+                       UnitAttr:$constSpecifier);
----------------
marbre wrote:

For consistency this could be changed to
```suggestion
                       UnitAttr:$extern_specifier,
                       UnitAttr:$static_specifier,
                       UnitAttr:$const_specifier);
```

https://github.com/llvm/llvm-project/pull/88701