On some architectures, being too optimistic in preserve_subexpressions_p(),

for example when -fexpensive-optimizations is used, sometimes causes incorrect
code sequences to be generated.

As -fexpensive-optimizations is implied by -O2, this means we are potentially
affected by this in numerous places... so add a specific workaround to nullify
expensizve-optimizations in preserve_subexpressions_p() on a
known-to-be-affected basis.

So far, only alpha, powerpc, m88k, sparc and sparc64 are affected.

Problem tracked down by henning@ - analysis by etoh@ and I - ugly workaround
by me - ok deraadt@

6 files changed, 13 insertions, 1 deletions

diff --git a/gnu/egcs/gcc/config/alpha/openbsd.h b/gnu/egcs/gcc/config/alpha/openbsd.h
index d9b7696209b..36e1a020693 100644
--- a/gnu/egcs/gcc/config/alpha/openbsd.h
+++ b/gnu/egcs/gcc/config/alpha/openbsd.h
@@ -90,3 +90,5 @@ Boston, MA 02111-1307, USA.  */
   assemble_name (FILE, LO);                                             \
  } while (0)
 
+/* problems occur if we're too liberal in preserve_subexpressions_p */
+#define	BROKEN_PRESERVE_SUBEXPRESSIONS_P
diff --git a/gnu/egcs/gcc/config/m88k/openbsd.h b/gnu/egcs/gcc/config/m88k/openbsd.h
index 9c195b18f6a..87e6e9ca6ce 100644
--- a/gnu/egcs/gcc/config/m88k/openbsd.h
+++ b/gnu/egcs/gcc/config/m88k/openbsd.h
@@ -67,3 +67,6 @@ Boston, MA 02111-1307, USA.  */
 /* Every structure or union's size must be a multiple of 2 bytes.  */
 #undef STRUCTURE_SIZE_BOUNDARY
 #define STRUCTURE_SIZE_BOUNDARY 16 
+
+/* problems occur if we're too liberal in preserve_subexpressions_p */
+#define	BROKEN_PRESERVE_SUBEXPRESSIONS_P
diff --git a/gnu/egcs/gcc/config/rs6000/openbsd.h b/gnu/egcs/gcc/config/rs6000/openbsd.h
index ec34255ab8e..6f47b793190 100644
--- a/gnu/egcs/gcc/config/rs6000/openbsd.h
+++ b/gnu/egcs/gcc/config/rs6000/openbsd.h
@@ -88,4 +88,5 @@ Boston, MA 02111-1307, USA.  */
    default to using nm. */
 #undef OBJECT_FORMAT_COFF
 
-
+/* problems occur if we're too liberal in preserve_subexpressions_p */
+#define	BROKEN_PRESERVE_SUBEXPRESSIONS_P
diff --git a/gnu/egcs/gcc/config/sparc/openbsd.h b/gnu/egcs/gcc/config/sparc/openbsd.h
index 5cb2ab90018..a13f03d54d0 100644
--- a/gnu/egcs/gcc/config/sparc/openbsd.h
+++ b/gnu/egcs/gcc/config/sparc/openbsd.h
@@ -65,3 +65,5 @@ Boston, MA 02111-1307, USA.  */
 #undef DEFAULT_PCC_STRUCT_RETURN
 #define DEFAULT_PCC_STRUCT_RETURN 0
 
+/* problems occur if we're too liberal in preserve_subexpressions_p */
+#define	BROKEN_PRESERVE_SUBEXPRESSIONS_P
diff --git a/gnu/egcs/gcc/config/sparc/openbsd64.h b/gnu/egcs/gcc/config/sparc/openbsd64.h
index cba0919547f..4a4d9a77f59 100644
--- a/gnu/egcs/gcc/config/sparc/openbsd64.h
+++ b/gnu/egcs/gcc/config/sparc/openbsd64.h
@@ -115,3 +115,5 @@ Boston, MA 02111-1307, USA.  */
     fprintf ((FILE), "\n");						\
   } while (0)
 
+/* problems occur if we're too liberal in preserve_subexpressions_p */
+#define	BROKEN_PRESERVE_SUBEXPRESSIONS_P
diff --git a/gnu/egcs/gcc/stmt.c b/gnu/egcs/gcc/stmt.c
index 6ca6197bc58..7f8a571c4d1 100644
--- a/gnu/egcs/gcc/stmt.c
+++ b/gnu/egcs/gcc/stmt.c
@@ -2437,8 +2437,10 @@ preserve_subexpressions_p ()
 {
   rtx insn;
 
+#ifndef	BROKEN_PRESERVE_SUBEXPRESSIONS_P
   if (flag_expensive_optimizations)
     return 1;
+#endif
 
   if (optimize == 0 || loop_stack == 0)
     return 0;