(DECL_MODE, DECL_RTL): Update comments.

From-SVN: r2172

diff --git a/gcc/tree.h b/gcc/tree.h
index 06ef89764b2992c732e6aeba70a86682c5a1adf4..4c70438eb4c0b8cc28b8b57896d9a6e23de95050 100644 (file)
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -728,9 +728,15 @@ struct tree_type
 #define DECL_SIZE(NODE) ((NODE)->decl.size)
 /* Holds the alignment required for the datum.  */
 #define DECL_ALIGN(NODE) ((NODE)->decl.frame_size)
-/* Holds the machine mode of a variable or field.  */
+/* Holds the machine mode corresponding to the declaration of a variable or
+   field.  Always equal to TYPE_MODE (TREE_TYPE (decl)) except for a
+   FIELD_DECL.  */
 #define DECL_MODE(NODE) ((NODE)->decl.mode)
-/* Holds the RTL expression for the value of a variable or function.  */
+/* Holds the RTL expression for the value of a variable or function.  If
+   PROMOTED_MODE is defined, the mode of this expression may not be same
+   as DECL_MODE.  In that case, DECL_MODE contains the mode corresponding
+   to the variable's data type, while the mode
+   of DECL_RTL is the mode actually used to contain the data.  */
 #define DECL_RTL(NODE) ((NODE)->decl.rtl)
 /* For PARM_DECL, holds an RTL for the stack slot or register
    where the data was actually passed.  */