Changeset 7d7b2a3 in rtems for make/custom/mvme167.cfg

Timestamp:

02/24/99 15:46:25 (24 years ago)

Author:

Joel Sherrill <joel.sherrill@…>

Branches:

4.10, 4.11, 4.8, 4.9, 5, master

Children:

32a98d2

Parents:

4e4e691

Message:

Patch from Charles Gauthier <Charles.Gauthier@@iit.nrc.ca> to address
FP issues on this target:

The default variants of libc, libm and libgcc assume that a 68881
coprocessor is present. Without the FPSP, any floating point operation,
including printf() with a "%f" format specifier, is likely to cause an
unimplemented instruction exception.

The FPSP works with the default variants of libc, libm and libgcc. It does not
work in conjunction with the msoft-float variants. The paranoia test goes into
an infinite loop at milestone 40. I am guessing that floor() is returning an
incorrect value.

The msoft-float variants of libc, libm and libgcc appear to do floating point
I/O properly. They only failed in paranoia. Offhand, I can't think of why they
would conflict with the FPSP, so I think that there is something wrong with the
msoft-float code. It might be my installation.

Given my experiences, I decided to install the FPSP in bsp_start(), and to link
against the default variants of libc, libm and libgcc. This causes the
executables to increase in size by about 60 KB. The README file and the
mvme167.cfg specify how to remove the FPSP, and how to link against the
msoft-float variants of the libraries. This is not what Eric Norum had done: on
my host, his gen68360_040 port links RTEMS code with the msoft-float variants
of libc and libm, and the default variant of libgcc. In this configuration, the
output of printf() with "%f" is garbage on my target.

File:

• make/custom/mvme167.cfg (modified) (3 diffs)

make/custom/mvme167.cfg

@@ -5 +5 @@
 #
 
-include $(RTEMS_ROOT)/make/custom/default.cfg
-
 RTEMS_CPU=m68k
 RTEMS_CPU_MODEL=m68040
+
+include $(RTEMS_ROOT)/make/custom/default.cfg
 
 # This is the actual bsp directory used during the build process.
@@ -24 +24 @@
 CFLAGS_OPTIMIZE_V=-O4 -fomit-frame-pointer
 
-# This target does NOT support the TCP/IP stack so ignore requests
+# This target does NOT support the TCP/IP stack (yet) so ignore requests
 # to enable it.
 HAS_NETWORKING=no
@@ -57 +57 @@
 
 ifeq ($(RTEMS_USE_GCC272),yes)
+
+# The MC68040 does not implement all MC68881/MC68882 instructions, so use
+# either the gcc floating-point software support (msoft-float libraries), or
+# use the Motorola FPSP floating-point emulator in
+#   rtems/c/src/lib/libcpu/m68k/m68040/fpsp
+# The default is to use the FPSP. 
+# To use the msoft-float libraries, uncomment the three lines below.
+# You then should comment the M68KFPSPInstallExceptionHandlers() statement
+# in rtems/c/src/lib/libbsp/m68k/mvme167/startup/bststart.c in bsp_start().
+# Floating-point support will then be limited. See the mvme167 README file
+# for more details.
+
+# LIBC_LIBC = $(RTEMS_LIBC_DIR)/lib/msoft-float/libc.a
+# LIBC_LIBM = $(RTEMS_LIBC_DIR)/lib/msoft-float/libm.a
+# LIBGCC = $(shell $(CC) -msoft-float -print-libgcc-file-name)
+
 define make-exe
         $(LD) $(LDFLAGS) -N -T $(LINKCMDS) -o $(basename $@).exe \