Add the `WANT_FORCE_OPTIMIZATION_DOWNGRADE' knob. If set to an integer

value, it forces GCC to not optimize above this level.  For intance, GCC
made with "WANT_FORCE_OPTIMIZATION_DOWNGRADE=1" is a good setting for the
Alpha platform when building ports.

5 files changed, 36 insertions, 8 deletions

diff --git a/contrib/gcc/toplev.c b/contrib/gcc/toplev.c
index 95835bb..e9d8886 100644
--- a/contrib/gcc/toplev.c
+++ b/contrib/gcc/toplev.c
@@ -4851,17 +4851,22 @@ main (argc, argv)
 	      if (optimize_val != -1)
 		{
 		  optimize = optimize_val;
-#ifdef __alpha__
+#ifdef FORCE_OPTIMIZATION_DOWNGRADE
+#warning FORCE_OPTIMIZATION_DOWNGRADE
+		  if (optimize > FORCE_OPTIMIZATION_DOWNGRADE)
+		    {
+		      optimize = FORCE_OPTIMIZATION_DOWNGRADE;
+		      warning ("\n***\n***\t-O%d converted to \"-O%d\" due to optimizer bugs on this platform\n***\n",
+			      optimize_val,
+			      FORCE_OPTIMIZATION_DOWNGRADE);
+
+		    }
+#endif /*FORCE_OPTIMIZATION_DOWNGRADE*/
+#if defined(__alpha__)
 		  if (optimize > 1)
 		    {
-		      #ifdef FORCE_OPTIMIZATION_DOWNGRADE
-		      optimize = 1;
-		      warning ("\n***\n***\t-O%d converted to \"-O1\" due to optimizer bugs on this platform\n***\n",
-			      optimize_val);
-		      #else
 		      warning ("\n***\n***\tThe -O%d flag TRIGGERS KNOWN OPTIMIZER BUGS ON THIS PLATFORM\n***\n",
 			      optimize_val);
-		      #endif
 		    }
 #endif /*__alpha__*/
 		  optimize_size = 0;
diff --git a/etc/defaults/make.conf b/etc/defaults/make.conf
index ca68587..683f286 100644
--- a/etc/defaults/make.conf
+++ b/etc/defaults/make.conf
@@ -65,6 +65,12 @@ BDECFLAGS=	-W -Wall -ansi -pedantic -Wbad-function-cast -Wcast-align \
 #
 #COPTFLAGS= -O -pipe
 #
+# To build the system compiler such that it forces high optimization levels to
+# a lower one.  GCC -O2+ is known to trigger known optimizer bugs at various
+# times -- this is worse on the Alpha platform.  The value assigned here will
+# be the highest optimization value used.
+#WANT_FORCE_OPTIMIZATION_DOWNGRADE=1
+#
 # Compare before install
 #INSTALL=install -C
 #
diff --git a/gnu/usr.bin/cc/Makefile.inc b/gnu/usr.bin/cc/Makefile.inc
index 4fe0547..7b6a2ec 100644
--- a/gnu/usr.bin/cc/Makefile.inc
+++ b/gnu/usr.bin/cc/Makefile.inc
@@ -39,6 +39,10 @@ CFLAGS+=	-DHAIFA
 CFLAGS+=	-DCROSS_COMPILE
 .endif
 
+.if defined(WANT_FORCE_OPTIMIZATION_DOWNGRADE)
+CFLAGS+= -DFORCE_OPTIMIZATION_DOWNGRADE=${WANT_FORCE_OPTIMIZATION_DOWNGRADE}
+.endif
+
 .if exists(${.OBJDIR}/../cc_tools)
 CFLAGS+=	-I${.OBJDIR}/../cc_tools
 .endif
diff --git a/share/examples/etc/make.conf b/share/examples/etc/make.conf
index ca68587..683f286 100644
--- a/share/examples/etc/make.conf
+++ b/share/examples/etc/make.conf
@@ -65,6 +65,12 @@ BDECFLAGS=	-W -Wall -ansi -pedantic -Wbad-function-cast -Wcast-align \
 #
 #COPTFLAGS= -O -pipe
 #
+# To build the system compiler such that it forces high optimization levels to
+# a lower one.  GCC -O2+ is known to trigger known optimizer bugs at various
+# times -- this is worse on the Alpha platform.  The value assigned here will
+# be the highest optimization value used.
+#WANT_FORCE_OPTIMIZATION_DOWNGRADE=1
+#
 # Compare before install
 #INSTALL=install -C
 #
diff --git a/share/man/man5/make.conf.5 b/share/man/man5/make.conf.5
index f21660e..538493a 100644
--- a/share/man/man5/make.conf.5
+++ b/share/man/man5/make.conf.5
@@ -249,7 +249,7 @@ Controls the compiler settings when building the
 kernel.
 Optimization levels above
 .Oo Fl O ( O2 , No ...\& ) Oc
-are not supported.
+are not guaranteed to work.
 .It Va KERNEL
 .Pq Vt str
 Controls which kernel configurations will be
@@ -538,6 +538,13 @@ command when building
 .It Va SENDMAIL_DPADD
 .Pq Vt str
 This variable is undocumented.
+.It Va WANT_FORCE_OPTIMIZATION_DOWNGRADE
+.Pq Vt int
+Causes the system compiler to be built such that it forces high optimization
+levels to a lower one.
+GCC -O2 and above is known to trigger known optimizer bugs at various
+times -- this is worse on the Alpha platform.
+The value assigned is the highest optimization value used.
 .El
 .Pp
 The following list provides a name and short description for variables