stor-layout.c (byte_from_pos): Amend comment.

2012-05-10  Richard Guenther  <rguenther@suse.de>

	* stor-layout.c (byte_from_pos): Amend comment.

From-SVN: r187367

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 7a8814afe10296d1c2830eed78f509c99acfe4ed..8da7a7f88e9e0d07a747d3f04bc2e53856f5b50c 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2012-05-10  Richard Guenther  <rguenther@suse.de>
+
+       * stor-layout.c (byte_from_pos): Amend comment.
+
 2012-05-10  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
 
        * doc/extend.texi (X86 Built-in Functions, __builtin_cpu_init):

diff --git a/gcc/stor-layout.c b/gcc/stor-layout.c
index 842b506ab25180c7c2beeec8f8a3a8b2010931ae..cb47a52b715cf10a67af6ebd4d14b52399e7c2c3 100644 (file)
--- a/gcc/stor-layout.c
+++ b/gcc/stor-layout.c
@@ -798,7 +798,13 @@ bit_from_pos (tree offset, tree bitpos)
 }
 
 /* Return the combined truncated byte position for the byte offset OFFSET and
-   the bit position BITPOS.  */
+   the bit position BITPOS.
+
+   These functions operate on byte and bit positions as present in FIELD_DECLs
+   and assume that these expressions result in no (intermediate) overflow.
+   This assumption is necessary to fold the expressions as much as possible,
+   so as to avoid creating artificially variable-sized types in languages
+   supporting variable-sized types like Ada.  */
 
 tree
 byte_from_pos (tree offset, tree bitpos)