* doc/tm.texi.in: Spell out that a lack of register class unions

	can lead to ICEs.
	* doc/tm.texi: Regenerate.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@168998 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b799162..9af2456 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2011-01-19  Joern Rennecke  <amylaar@spamcop.net>
+
+       * doc/tm.texi.in: Spell out that a lack of register class unions
+       can lead to ICEs.
+       * doc/tm.texi: Regenerate.
+
 2011-01-19  Jakub Jelinek  <jakub@redhat.com>
 
        PR rtl-optimization/47337

diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 010e77b..e3325b0 100644 (file)
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -2341,7 +2341,9 @@ You should define a class for the union of two classes whenever some
 instruction allows both classes.  For example, if an instruction allows
 either a floating point (coprocessor) register or a general register for a
 certain operand, you should define a class @code{FLOAT_OR_GENERAL_REGS}
-which includes both of them.  Otherwise you will get suboptimal code.
+which includes both of them.  Otherwise you will get suboptimal code,
+or even internal compiler errors when reload cannot find a register in the
+the class computed via @code{reg_class_subunion}.
 
 You must also specify certain redundant information about the register
 classes: for each class, which classes contain it and which ones are

diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 3298c3d..1a5f040 100644 (file)
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -2331,7 +2331,9 @@ You should define a class for the union of two classes whenever some
 instruction allows both classes.  For example, if an instruction allows
 either a floating point (coprocessor) register or a general register for a
 certain operand, you should define a class @code{FLOAT_OR_GENERAL_REGS}
-which includes both of them.  Otherwise you will get suboptimal code.
+which includes both of them.  Otherwise you will get suboptimal code,
+or even internal compiler errors when reload cannot find a register in the
+the class computed via @code{reg_class_subunion}.
 
 You must also specify certain redundant information about the register
 classes: for each class, which classes contain it and which ones are