diff mbox series

Teach free_lang_data to simplify types of TYPE_VALUES in enumeral types

Message ID 20200522204249.GH59676@kam.mff.cuni.cz
State New
Headers show
Series Teach free_lang_data to simplify types of TYPE_VALUES in enumeral types | expand

Commit Message

Jan Hubicka May 22, 2020, 8:42 p.m. UTC 
Hi,
streaming code assumes that INTEGER_CST never appears in non-trivial component.
This is not true and we sometimes stream such components which sort of silently
works but breaks our IL invariant about tree sharing.  This patch fixes one
instance of this problem where ENUMERAL_TYPE lists all its valids in TYPE_VALUES
that with some FEs (like Ada and C++) are having the enumeral type as a type
while in other FEs (like C) are simple integer types.

I convert them all to integers which also increases chance that they will be
shared with other integer constants at stream time.

lto-bootstrapped/regtested x86_64-linux.  I plan to commit this shortly.

	* tree.c (free_lang_data_in_type): Simpify types of TYPE_VALUES in
	enumeral types.
diff mbox series

Patch

diff --git a/gcc/tree.c b/gcc/tree.c
index 54e471acc89..ea6692476e7 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -5556,6 +5556,7 @@  free_lang_data_in_type (tree type, class free_lang_data_d *fld)
     {
       if (TREE_CODE (type) == ENUMERAL_TYPE)
 	{
+	  tree it = NULL_TREE;
 	  ENUM_IS_OPAQUE (type) = 0;
 	  ENUM_IS_SCOPED (type) = 0;
 	  /* Type values are used only for C++ ODR checking.  Drop them
@@ -5568,8 +5569,27 @@  free_lang_data_in_type (tree type, class free_lang_data_d *fld)
 	  /* Simplify representation by recording only values rather
 	     than const decls.  */
 	    for (tree e = TYPE_VALUES (type); e; e = TREE_CHAIN (e))
-	      if (TREE_CODE (TREE_VALUE (e)) == CONST_DECL)
-		TREE_VALUE (e) = DECL_INITIAL (TREE_VALUE (e));
+	      {
+		if (TREE_CODE (TREE_VALUE (e)) == CONST_DECL)
+		  {
+		    TREE_VALUE (e) = DECL_INITIAL (TREE_VALUE (e));
+		    /* We can not stream values whose TREE_TYPE is type itself
+		       because that would create non-trivial CSS.  Canonicalize
+		       them to integer types.  */
+		  }
+		/* Some frontends use ENUMERAL_TYPE to represent the constants.
+		   This leads to nontrivial SCC components containing
+		   INTEGER_CST which is not good for streaming.  Convert them
+		   all to corresponding integer type.  */
+		if (TREE_CODE (TREE_TYPE (TREE_VALUE (e))) != INTEGER_TYPE)
+		  {
+		    if (!it)
+		      it = lang_hooks.types.type_for_size
+			       (TYPE_PRECISION (TREE_TYPE (TREE_VALUE (e))),
+				TYPE_UNSIGNED (TREE_TYPE (TREE_VALUE (e))));
+		    TREE_VALUE (e) = fold_convert (it, TREE_VALUE (e));
+		  }
+	       }
 	}
       free_lang_data_in_one_sizepos (&TYPE_MIN_VALUE (type));
       free_lang_data_in_one_sizepos (&TYPE_MAX_VALUE (type));