From: Matthew Dillon <dillon@dragonflybsd.org>
Date: Fri, 6 Aug 2004 20:50:35 +0000 (+0000)
Subject: GCC3.4's (default) unit-at-a-time optimization is incompatible with -mrtd.
X-Git-Tag: v2.0.1~10568
X-Git-Url: https://gitweb.dragonflybsd.org/dragonfly.git/commitdiff_plain/3d310902fc8a687a85aec646f78b014082cc42c0

GCC3.4's (default) unit-at-a-time optimization is incompatible with -mrtd.
Bad code (missing stack pops) will be produced.  See the assembly generated
for 'xputc' with -mrtd and unit-at-a-time enabled for an example of this.

GCC3.4's unit-at-a-time seems to cause other problems as well, specifically
in boot2, as yet not tracked down, so disable unit-at-a-time optimizations
for the boot code if the compiler is not GCC2.
---

diff --git a/sys/boot/i386/boot2/Makefile b/sys/boot/i386/boot2/Makefile
index 12d6d4c38a..41492e33d6 100644
--- a/sys/boot/i386/boot2/Makefile
+++ b/sys/boot/i386/boot2/Makefile
@@ -1,5 +1,5 @@
 # $FreeBSD: src/sys/boot/i386/boot2/Makefile,v 1.47 2003/06/26 03:51:57 peter Exp $
-# $DragonFly: src/sys/boot/i386/boot2/Attic/Makefile,v 1.10 2004/07/27 19:37:17 dillon Exp $
+# $DragonFly: src/sys/boot/i386/boot2/Attic/Makefile,v 1.11 2004/08/06 20:50:35 dillon Exp $
 
 PROG=		boot2
 NOMAN=
@@ -51,10 +51,8 @@ BOOT2_UFS?=	UFS1_ONLY
 # gcc3.x
 #	-fno-guess-branch-probability
 #	-mno-align-long-strings
-
 CFLAGS=	-elf -ffreestanding -Os -fno-builtin -fno-stack-protector \
 	-fomit-frame-pointer \
-	-mrtd \
 	-D${BOOT2_UFS} \
 	-I${.CURDIR}/../../common \
 	-I${.CURDIR}/../btx/lib -I. \
@@ -62,6 +60,23 @@ CFLAGS=	-elf -ffreestanding -Os -fno-builtin -fno-stack-protector \
 	-Wmissing-declarations -Wmissing-prototypes -Wnested-externs \
 	-Wpointer-arith -Wshadow -Wstrict-prototypes -Wwrite-strings
 
+# -mrtd will produce bad code (missing stack pops) when combined with
+# gcc-3.4's (default on) unit-at-a-time optimization.  See the code
+# generated for 'xputc' as an example.
+#
+.if ${CCVER} == "gcc2"
+CFLAGS+= -mrtd
+.endif
+
+# Unfortunately, unit-at-a-time creates other issues as well, as yet
+# not tracked down, in boot2, so we have to turn it off.  Note that
+# the problem has been narrowed down to the 'boot2' code.  The /boot/loader
+# doesn't seem to have a problem.
+#
+.if ${CCVER} != "gcc2"
+CFLAGS+= -fno-unit-at-a-time
+.endif
+
 LDFLAGS=-nostdlib -static -N --gc-sections
 
 all: boot1 boot2 boot
diff --git a/sys/boot/pc32/boot2/Makefile b/sys/boot/pc32/boot2/Makefile
index 8253d20c97..15473566e8 100644
--- a/sys/boot/pc32/boot2/Makefile
+++ b/sys/boot/pc32/boot2/Makefile
@@ -1,5 +1,5 @@
 # $FreeBSD: src/sys/boot/i386/boot2/Makefile,v 1.47 2003/06/26 03:51:57 peter Exp $
-# $DragonFly: src/sys/boot/pc32/boot2/Makefile,v 1.10 2004/07/27 19:37:17 dillon Exp $
+# $DragonFly: src/sys/boot/pc32/boot2/Makefile,v 1.11 2004/08/06 20:50:35 dillon Exp $
 
 PROG=		boot2
 NOMAN=
@@ -51,10 +51,8 @@ BOOT2_UFS?=	UFS1_ONLY
 # gcc3.x
 #	-fno-guess-branch-probability
 #	-mno-align-long-strings
-
 CFLAGS=	-elf -ffreestanding -Os -fno-builtin -fno-stack-protector \
 	-fomit-frame-pointer \
-	-mrtd \
 	-D${BOOT2_UFS} \
 	-I${.CURDIR}/../../common \
 	-I${.CURDIR}/../btx/lib -I. \
@@ -62,6 +60,23 @@ CFLAGS=	-elf -ffreestanding -Os -fno-builtin -fno-stack-protector \
 	-Wmissing-declarations -Wmissing-prototypes -Wnested-externs \
 	-Wpointer-arith -Wshadow -Wstrict-prototypes -Wwrite-strings
 
+# -mrtd will produce bad code (missing stack pops) when combined with
+# gcc-3.4's (default on) unit-at-a-time optimization.  See the code
+# generated for 'xputc' as an example.
+#
+.if ${CCVER} == "gcc2"
+CFLAGS+= -mrtd
+.endif
+
+# Unfortunately, unit-at-a-time creates other issues as well, as yet
+# not tracked down, in boot2, so we have to turn it off.  Note that
+# the problem has been narrowed down to the 'boot2' code.  The /boot/loader
+# doesn't seem to have a problem.
+#
+.if ${CCVER} != "gcc2"
+CFLAGS+= -fno-unit-at-a-time
+.endif
+
 LDFLAGS=-nostdlib -static -N --gc-sections
 
 all: boot1 boot2 boot