Remove WEXPERIMENTAL for "if with unsupported statements"

Author: mandolaerik

RELEASENOTES.md

@@ -204,3 +204,11 @@
   (fixes SIMICS-22848).
 - `release 6 6349`
 - `release 7 7054`
+- `note 6` DMLC no longer emits warnings saying
+  `top-level 'if' body with unsupported statements`. These warnings were
+  often triggered in common code, causing excessive polution in build logs.
+  The same rules as before apply to `#if` statements: Statements such as
+  `param` and `template` are forbidden inside `#if`, but a special exception
+  allows forbidden statements to appear specifically inside an `#if (dml_1_2)`
+  block. The warning message was meant to highlight this irregularity, but
+  caused more harm than good; error messages surrounding the special case have been improved instead.

doc/1.4/language.md

@@ -2318,8 +2318,8 @@ The *object declarations* are any number of declarations of objects, session
 variables, saved variables, methods, or other `#if` statements, but not
 parameters, `is` statements, or `in each` statements . When the conditional is
 `true` (or if it's the else branch of a false conditional), the object
-declarations are treated as if they had appeared without any surrounding *#if*.
-So the two following declarations are equivalent:
+declarations are treated as if they had appeared without any surrounding `#if`.
+Thus, the two following snippets are equivalent:
 
 ```
 #if (true) {
@@ -2329,12 +2329,34 @@ So the two following declarations are equivalent:
 }
 ```
 
-is equivalent to
-
 ```
 register R size 4;
 ```
 
+As a special exception, an `#if` statement that appears on top level is allowed
+to contain any type of statement, as long as the condition doesn't reference
+any identifiers other than `dml_1_2`, `true` and `false`. This is often useful
+while migrating the devices of a system from DML 1.2 to DML 1.4,
+as it allows conditional definitions of templates in common code used from both DML 1.2 and DML 1.4. For example, let's say an existing template `reset_to_seven`
+is used in DML 1.2 code to set the reset value of a field to 7 in DML 1.2.
+The parameters that control reset values have changed from DML 1.2 to DML 1.4,
+and one way to handle this is to provide separate template definitions
+depending on whether the device uses DML 1.2 or DML 1.4:
+```
+#if (dml_1_2) {
+    template seven is field {
+        param hard_reset_value = 7;
+        param soft_reset_value = 7;
+    }
+} #else {
+    template seven is field {
+        param init_val = 7;
+    }
+}
+```
+Later, when all related devices have been ported to DML 1.4,
+the `dml_1_2` clause can be removed.
+
 ## In Each Declarations
 
 In Each declarations are a convenient mechanism to apply a

py/dml/dmlparse.py

@@ -270,12 +270,12 @@ def toplevel_param(t):
 def toplevel_if(t):
     '''toplevel_if : hashif LPAREN expression RPAREN \
                    LBRACE device_statements RBRACE toplevel_else'''
-    if all(stmt.kind in allowed_in_hashif for stmt in t[6] + t[8]):
-        t[0] = ast.hashif(site(t), t[3], t[6], t[8])
+    bad_stmts = [stmt for stmt in t[6] + t[8]
+                 if stmt.kind not in allowed_in_hashif]
+    if bad_stmts:
+        t[0] = ast.toplevel_if(site(t), t[3], t[6], t[8], bad_stmts)
     else:
-        report(WEXPERIMENTAL(site(t), ("top-level 'if' body with unsupported "
-                                       + "statements")))
-        t[0] = ast.toplevel_if(site(t), t[3], t[6], t[8])
+        t[0] = ast.hashif(site(t), t[3], t[6], t[8])
 
 @prod_dml14
 def toplevel_else_no(t):

py/dml/messages.py

@@ -829,6 +829,18 @@ class ECONDINEACH(DMLError):
     version = "1.4"
     fmt = "conditional 'in each' is not allowed"
 
+class EBADCONDSTMT(DMLError):
+    """
+    `#if` statements in object scope are only allowed to contain
+    certain kinds of declarations: objects, `method`, `session`,
+    `saved`, `#if`, or `error`.
+
+    A special exception is that a `#if` on top scope may contain any
+    kind of statement as long as the `#if` condition doesn't reference
+    any identifiers other than `dml_1_2`, `true`, and `false`.
+    """
+    fmt = "object of type %s not allowed inside `#if`"
+
 # TODO: Consider re-wording the semantics of this error, allocate_type is only
 # relevant in 1.4 when imported from 1.2, and as per SIMICS-9393 this
 # error might not even be necessary

py/dml/toplevel.py

@@ -148,25 +148,29 @@ def scan_statements(filename, site, stmts):
             [text] = s.args
             footers.append(ctree.mkCText(s.site, text))
         elif s.kind == 'toplevel_if':
-            [cond, tbranch, fbranch] = s.args
+            [cond, tbranch, fbranch, bad_stmts] = s.args
             scope = symtab.Symtab()
             bsite = SimpleSite('<builtin>',
                                dml_version=dml.globals.dml_version)
             # HACK Add constants to scope typically defined by dml-builtins,
             # which is not accessible here
-            def add_constant(name, expr):
+            constants = {
+                'dml_1_2': ctree.BoolConstant(
+                    bsite, dml.globals.dml_version == (1, 2)),
+                'true': ctree.BoolConstant(bsite, True),
+                'false': ctree.BoolConstant(bsite, False),
+            }
+            for (name, expr) in constants.items():
                 scope.add(ctree.ExpressionSymbol(name, expr, bsite))
 
-            add_constant(
-                'dml_1_2',
-                ctree.BoolConstant(bsite, dml.globals.dml_version == (1, 2)))
-            add_constant('true', ctree.BoolConstant(bsite, True))
-            add_constant('false', ctree.BoolConstant(bsite, False))
             try:
                 expr = ctree.as_bool(codegen.codegen_expression(
                     cond, None, scope))
                 if not expr.constant:
                     raise ENCONST(expr.site, expr)
+            except EIDENT:
+                for stmt in bad_stmts:
+                    report(EBADCONDSTMT(stmt.site, stmt.kind))
             except DMLError as e:
                 report(e)
             else:

test/1.2/misc/T_import_dml14.dml

@@ -12,7 +12,6 @@ constant x = 0;
 
 parameter is_dml_12 = true;
 
-/// WARNING WEXPERIMENTAL dml14.dml
 /// SCAN-FOR-TAGS dml14.dml
 import "dml14.dml";
 

test/1.2/misc/dml14.dml

@@ -401,7 +401,6 @@ bank testbank is (miss_pattern_bank, function_mapped_bank) {
 
 bank overridden_bank is (unified_hard_reset, unified_soft_reset);
 
-/// WARNING WEXPERIMENTAL
 #if (dml_1_2) {
     import "io-memory.dml";
 } #else {
@@ -475,10 +474,8 @@ attribute woa is (write_only_attr) {
 
 param global_sym = 14;
 
-/// WARNING WEXPERIMENTAL
 #if (!dml_1_2) {
     param cond = false;
-/// WARNING WEXPERIMENTAL
 } #else #if (!dml_1_2) {
     error;
 } #else {

test/1.4/errors/T_EBADCONDSTMT.dml

@@ -0,0 +1,28 @@
+/*
+  © 2024 Intel Corporation
+  SPDX-License-Identifier: MPL-2.0
+*/
+dml 1.4;
+
+device test;
+
+constant x = 1;
+
+#if (x == 1) {
+/// ERROR EBADCONDSTMT
+param p = 3;
+/// ERROR EBADCONDSTMT
+typedef int i_t;
+} #else {
+/// ERROR EBADCONDSTMT
+template t {
+}
+
+/// ERROR EBADCONDSTMT
+extern typedef int i_t;
+}
+
+#if (true) {
+// no error
+param p = 3;
+}

test/1.4/errors/T_ECONDINEACH.dml

@@ -22,7 +22,6 @@ port p {
     }
 }
 
-/// WARNING WEXPERIMENTAL
 #if (false && true && dml_1_2) {
     // Experimental support for complex top-level conditionals allows in-each
     // to be used

test/1.4/structure/T_top_hashif.dml

@@ -0,0 +1,51 @@
+/*
+  © 2024 Intel Corporation
+  SPDX-License-Identifier: MPL-2.0
+*/
+dml 1.4;
+
+device test;
+
+/// COMPILE-ONLY
+
+#if (true) {
+extern typedef int a_t;
+typedef int b_t;
+param p = 1;
+} #else {
+extern void *x;
+import "nonexisting.dml";
+param p = 2;
+error;
+}
+
+#if (p != 1) { error; }
+
+#if (false) {
+typedef void *a_t;
+extern typedef void *b_t;
+error;
+template t { error; }
+} #else {
+extern int x;
+import "imported.dml";
+template t { param from_t = true; }
+}
+
+#if (!imported) { error; }
+
+is t;
+#if (!from_t) { error; }
+
+#if (dml_1_2 || false) {
+error;
+} #else {
+  #if (true) {
+    #if (!false) {
+      // nested top-level #ifs are permitted
+      param foo = true;
+    }
+  }
+}
+
+#if (!foo) { error; }