Please don't ignore this, support for MIPS r5900 was already ignored for ~10 years. Just apply the patch when you don't know what I am talking about. The fix for mips16 is very important. The patch has impact only on MIPS r5900.
> Gesendet: Sonntag, 15. Juni 2014 um 22:08 Uhr > Von: "Jürgen Urban" <juergenur...@gmx.de> > An: gcc-patches@gcc.gnu.org > Cc: juergenur...@gmx.de > Betreff: [MIPS r5900] libgcc floating point fixes > > Hello, > > I found a problem in GCC on MIPS r5900: When printf() is used with type > float, the converter function __extendsfdf2() is called. Parameters to > printf() are always passed as double and not float. The function > __extendsfdf2() calls itself to convert 32 bit float to 64 bit float. With > Linux the __extendsfdf2() leads to a segfault when the stack limit is reached. > Here is the wrong code (mipsel-linux-gnu): > > 00402af0 <__extendsfdf2>: > 402af0: 3c1c0002 lui gp,0x2 > 402af4: 279c9b30 addiu gp,gp,-25808 > 402af8: 0399e021 addu gp,gp,t9 > 402afc: 8f9980a0 lw t9,-32608(gp) # Load pointer to > __extendsfdf2 into t9 > 402b00: 27bdffe0 addiu sp,sp,-32 > 402b04: afbf001c sw ra,28(sp) > 402b08: 0320f809 jalr t9 # Calls __extendsfdf2 > (itself) > 402b0c: afbc0010 sw gp,16(sp) > 402b10: 8fbf001c lw ra,28(sp) > 402b14: 03e00008 jr ra > 402b18: 27bd0020 addiu sp,sp,32 > 402b1c: 00000000 nop > > The problem happens with the r5900 hard float configurations, e.g.: > configure --target=mipsel-linux-gnu --with-float=hard --with-fpu=single > --with-arch=r5900 > I created the attached patch which fixes this problem for r5900 and another > problem explained later. > The fixed code generates the following code which should be correct > (mipsr5900el-ps2-elf): > > 00105440 <__extendsfdf2>: > 105440: 27bdffc8 addiu sp,sp,-56 > 105444: 27a40028 addiu a0,sp,40 > 105448: 27a50018 addiu a1,sp,24 > 10544c: afbf0034 sw ra,52(sp) > 105450: 0c0417b5 jal 105ed4 <__unpack_f> > 105454: e7ac0028 swc1 $f12,40(sp) > 105458: 8fa20024 lw v0,36(sp) > 10545c: 8fa40018 lw a0,24(sp) > 105460: 8fa5001c lw a1,28(sp) > 105464: 8fa60020 lw a2,32(sp) > 105468: 00021882 srl v1,v0,0x2 > 10546c: 00021780 sll v0,v0,0x1e > 105470: afa20010 sw v0,16(sp) > 105474: 0c041789 jal 105e24 <__make_dp> > 105478: afa30014 sw v1,20(sp) > 10547c: 8fbf0034 lw ra,52(sp) > 105480: 03e00008 jr ra > 105484: 27bd0038 addiu sp,sp,56 > > The default targets mipsr5900el and mips64r5900el are not affected by the > problem, because soft float is the default. > > It also seems that the same problem occurs with the following configuration: > configure --target=mipsel-linux-gnu --with-float=hard --with-fpu=single > I expected that this combination should work and a problem should already be > detected. Can somebody confirm that the problem also occurs with default > mipsel? > > The second part of the patch fixes the following configuration: > configure --target=mipsel-linux-gnu --with-arch=r5900 > It disables the mips16 stuff in the libgcc. This can't be compiled on r5900. > This was already disabled for targets mipsr5900*el. I detected the problem, > because the buildroot project uses this style which leads to less problems > with existing software (because "mipsel" or "mips64el" is hardcoded in most > configure scripts and don't expect "mipsr5900el" or "mips64r5900el"). > > Can someone please add the patch to the official GCC repository? > > I am not sure whether I fixed all self-calling implementations. Does somebody > know a way of finding selfcalling implementations? > > I tried to find a FPU testsuite, but the testsuites are not designed to test > non-standard FPUs or use double instead of float. So there can be more > problems with FPU on r5900 which I don't see at the moment. > > Best regards > Jürgen Urban
