* doc/tm.texi (HARD_REGNO_NREGS): Note that this macro must not

return zero.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@131703 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 2786579..873cdd4 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2008-01-21  DJ Delorie  <dj@redhat.com>
+
+       * doc/tm.texi (HARD_REGNO_NREGS): Note that this macro must not
+       return zero.
+
 2008-01-21  Richard Guenther  <rguenther@suse.de>
 
        PR middle-end/34856

diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 00dde97..89d4302 100644 (file)
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -2079,7 +2079,9 @@ consecutive registers are needed for a given mode.
 @defmac HARD_REGNO_NREGS (@var{regno}, @var{mode})
 A C expression for the number of consecutive hard registers, starting
 at register number @var{regno}, required to hold a value of mode
-@var{mode}.
+@var{mode}.  This macro must never return zero, even if a register
+cannot hold the requested mode - indicate that with HARD_REGNO_MODE_OK
+and/or CANNOT_CHANGE_MODE_CLASS instead.
 
 On a machine where all registers are exactly one word, a suitable
 definition of this macro is