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Re: Réf. : Re: Soft-float compiler for ARM


Hi,
Even I got the same errors while compiling. I thought gcc might still generate proper code after searching in google (someone had said about this HF-SF conflict earlier). I knew the toolchain what I had generated pure soft-float code. I spent some considerable time verifying the generated .o , .s files with my small test programs. Above everything the compiled programs ran without using the kernel float emulation.


with regards
senthil kumar

arnaud.zanetti@sagem.com wrote:

Looks like it's the same problem I got with gcc-3.3.2 and binutils-031031 :
- the default option for gcc is soft-float
- however, this default option isn't passed down to the assembler
this result in having an object file containing no hard-float instruction
but being tagged as hard-FP. So the link-hack should work fine.
However, I solved the problem for my own target by patching the default
option
in gcc and patching the option in the multilib process.

Here is the patch that leads to a full working multilib :


diff -urpN gcc-3.3.2/gcc/config/arm/elf.h gcc-3.3.2.patch/gcc/config/arm/elf.h --- gcc-3.3.2/gcc/config/arm/elf.h 2002-11-21 22:29:24.000000000 +0100 +++ gcc-3.3.2.patch/gcc/config/arm/elf.h 2003-12-27 11:54:50.000000000 +0100 @@ -111,7 +111,7 @@ Boston, MA 02111-1307, USA. */

#ifndef MULTILIB_DEFAULTS
#define MULTILIB_DEFAULTS \
-  { "marm", "mlittle-endian", "msoft-float", "mapcs-32",
"mno-thumb-interwork", "fno-leading-underscore" }
+  { "marm", "mlittle-endian", "mhard-float", "mapcs-32",
"mno-thumb-interwork", "fno-leading-underscore" }
#endif


diff -urpN gcc-3.3.2/gcc/config/arm/t-arm-elf gcc-3.3.2.patch/gcc/config/arm/t-arm-elf --- gcc-3.3.2/gcc/config/arm/t-arm-elf 2002-05-08 17:01:13.000000000 +0200 +++ gcc-3.3.2.patch/gcc/config/arm/t-arm-elf 2003-12-27 11:55:26.000000000 +0100 @@ -25,23 +25,23 @@ MULTILIB_OPTIONS = marm/mthumb MULTILIB_DIRNAMES = arm thumb MULTILIB_EXCEPTIONS =

-# MULTILIB_OPTIONS     += mlittle-endian/mbig-endian
-# MULTILIB_DIRNAMES    += le be
-# MULTILIB_EXCEPTIONS  =
-# MULTILIB_MATCHES     = mbig-endian=mbe mlittle-endian=mle
-#
-# MULTILIB_OPTIONS    += mhard-float/msoft-float
-# MULTILIB_DIRNAMES   += fpu soft
-# MULTILIB_EXCEPTIONS += *mthumb/*mhard-float*
-#
+MULTILIB_OPTIONS     += mlittle-endian/mbig-endian
+MULTILIB_DIRNAMES    += le be
+MULTILIB_EXCEPTIONS  =
+MULTILIB_MATCHES     = mbig-endian=mbe mlittle-endian=mle
+
+MULTILIB_OPTIONS    += mhard-float/msoft-float
+MULTILIB_DIRNAMES   += fpu soft
+MULTILIB_EXCEPTIONS += *mthumb/*mhard-float*
+
# MULTILIB_OPTIONS    += mapcs-32/mapcs-26
# MULTILIB_DIRNAMES   += 32bit 26bit
# MULTILIB_EXCEPTIONS += *mthumb/*mapcs-26*
-#
-# MULTILIB_OPTIONS    += mno-thumb-interwork/mthumb-interwork
-# MULTILIB_DIRNAMES   += normal interwork
-# MULTILIB_EXCEPTIONS += *mapcs-26/*mthumb-interwork*
-#
+
+MULTILIB_OPTIONS    += mno-thumb-interwork/mthumb-interwork
+MULTILIB_DIRNAMES   += normal interwork
+MULTILIB_EXCEPTIONS += *mapcs-26/*mthumb-interwork*
+
# MULTILIB_OPTIONS    += fno-leading-underscore/fleading-underscore
# MULTILIB_DIRNAMES   += elf under
#

This has the default to lead to longer multilib generation process. But now
all combination
of soft/hard FP, Thumb/ARM, little/big Endian and interworking are usable.
But I have to specify the exact location of the libc and libgcc at the link
stage :

LIBS= -L /usr/local/arm-elf/arm-elf/lib/thumb/soft/interwork -lc
\
     -L /usr/local/arm-elf/lib/gcc-lib/arm-elf/3.3.2/thumb/soft/interwork
-lgcc





Robert Schwebel <robert@schwebel.de> Pour : senthil <senthilnow@netscape.net> cc : robert@schwebel.de, crossgcc@sources.redhat.com, (ccc : Arnaud Envoyé par : ZANETTI/DSEC/SAGEM) crossgcc-owner@sources Objet : Re: Soft-float compiler for ARM .redhat.com 28/01/2004 07:47 Remis le : 28/01/2004 07:46




On Wed, Jan 28, 2004 at 01:31:13PM -0500, senthil wrote:


Hi,
you will have to use something like this,
arm-linux-gcc -static -L./ -msoft-float -Xlinker --no-warn-mismatch
hello.c, you can also use -lfloat option if needed (use netwinder
libfloat or nico's libfloat)

--no-warn-mismatch will allow you to continue linking
but sometimes I have noticed gcc putting hard-float instructions aswell
as definitions from softfloat (I used nicolas pitre's soft-float glibc
replacement ) if the arguments were passed in
a different order, but this one works fine for me. I am using gcc3.2.1.



This looks like a hack to me; I don't really want to change anything in the compiler call as it works quite fine with gcc-2.95.3 and just ommitting the warning smells like a hack - the real problem seems to be that libgcc only has (or at least claims to have) hard fp support compiled in.

Robert
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