Here is a diff to switch GCC 8 to defaulting to i586 on i386.
Index: Makefile
===================================================================
RCS file: /home/cvs/ports/lang/gcc/8/Makefile,v
retrieving revision 1.31
diff -u -p -u -p -r1.31 Makefile
--- Makefile 5 Apr 2020 15:44:52 -0000 1.31
+++ Makefile 7 Aug 2020 11:27:24 -0000
@@ -16,7 +16,7 @@ USE_LLD = No
DPB_PROPERTIES = parallel
V = 8.3.0
-REVISION = 5
+REVISION = 6
FULL_VERSION = $V
FULL_PKGVERSION = $V
Index: patches/patch-gcc_config_gcc
===================================================================
RCS file: /home/cvs/ports/lang/gcc/8/patches/patch-gcc_config_gcc,v
retrieving revision 1.2
diff -u -p -u -p -r1.2 patch-gcc_config_gcc
--- patches/patch-gcc_config_gcc 25 Mar 2019 20:17:47 -0000 1.2
+++ patches/patch-gcc_config_gcc 7 Aug 2020 11:40:30 -0000
@@ -1,4 +1,5 @@
$OpenBSD: patch-gcc_config_gcc,v 1.2 2019/03/25 20:17:47 pascal Exp $
+
Index: gcc/config.gcc
--- gcc/config.gcc.orig
+++ gcc/config.gcc
@@ -131,7 +132,7 @@ Index: gcc/config.gcc
+ arch_without_64bit=yes
+ ;;
+ i386-*-openbsd*)
-+ arch=i486
++ arch=pentium
cpu=generic
arch_without_sse2=yes
arch_without_64bit=yes
Index: patches/patch-gcc_config_i386_openbsdelf_h
===================================================================
RCS file:
/home/cvs/ports/lang/gcc/8/patches/patch-gcc_config_i386_openbsdelf_h,v
retrieving revision 1.2
diff -u -p -u -p -r1.2 patch-gcc_config_i386_openbsdelf_h
--- patches/patch-gcc_config_i386_openbsdelf_h 20 May 2019 14:59:05 -0000
1.2
+++ patches/patch-gcc_config_i386_openbsdelf_h 7 Aug 2020 11:40:40 -0000
@@ -1,4 +1,5 @@
$OpenBSD: patch-gcc_config_i386_openbsdelf_h,v 1.2 2019/05/20 14:59:05 pascal
Exp $
+
Index: gcc/config/i386/openbsdelf.h
--- gcc/config/i386/openbsdelf.h.orig
+++ gcc/config/i386/openbsdelf.h
@@ -17,7 +18,7 @@ Index: gcc/config/i386/openbsdelf.h
- %{!shared: %{pg:gcrt0%O%s} %{!pg:%{p:gcrt0%O%s} %{!p:crt0%O%s}} \
- crtbegin%O%s} %{shared:crtbeginS%O%s}"
-+#define SUBTARGET32_DEFAULT_CPU "i486"
++#define SUBTARGET32_DEFAULT_CPU "i586"
+#define STARTFILE_SPEC "\
+ %{!shared: %{pg:gcrt0%O%s} %{!pg:%{p:gcrt0%O%s} \
+ %{!p:%{!static:crt0%O%s} %{static:%{nopie:crt0%O%s} \
