MIPS: Fix build with binutils 2.24.51+

Starting with version 2.24.51.20140728 MIPS binutils complain loudly
about mixing soft-float and hard-float object files, leading to this
build failure since GCC is invoked with "-msoft-float" on MIPS:

{standard input}: Warning: .gnu_attribute 4,3 requires `softfloat'
  LD      arch/mips/alchemy/common/built-in.o
mipsel-softfloat-linux-gnu-ld: Warning: arch/mips/alchemy/common/built-in.o
 uses -msoft-float (set by arch/mips/alchemy/common/prom.o),
 arch/mips/alchemy/common/sleeper.o uses -mhard-float

To fix this, we detect if GAS is new enough to support "-msoft-float" command
option, and if it does, we can let GCC pass it to GAS;  but then we also need
to sprinkle the files which make use of floating point registers with the
necessary ".set hardfloat" directives.

Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
Cc: Linux-MIPS <linux-mips@linux-mips.org>
Cc: Matthew Fortune <Matthew.Fortune@imgtec.com>
Cc: Markos Chandras <Markos.Chandras@imgtec.com>
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/8355/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 10 insertions, 1 deletions

diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
index cf3b580c3df6..b46cd220a018 100644
--- a/arch/mips/include/asm/mipsregs.h
+++ b/arch/mips/include/asm/mipsregs.h
@@ -1324,7 +1324,7 @@ do {									\
 /*
  * Macros to access the floating point coprocessor control registers
  */
-#define read_32bit_cp1_register(source)                                 \
+#define _read_32bit_cp1_register(source, gas_hardfloat)                 \
 ({                                                                      \
         int __res;                                                      \
                                                                         \
@@ -1334,12 +1334,21 @@ do {									\
         "       # gas fails to assemble cfc1 for some archs,    \n"     \
         "       # like Octeon.                                  \n"     \
         "       .set    mips1                                   \n"     \
+        "       "STR(gas_hardfloat)"                            \n"     \
         "       cfc1    %0,"STR(source)"                        \n"     \
         "       .set    pop                                     \n"     \
         : "=r" (__res));                                                \
         __res;                                                          \
 })
 
+#ifdef GAS_HAS_SET_HARDFLOAT
+#define read_32bit_cp1_register(source)                                 \
+        _read_32bit_cp1_register(source, .set hardfloat)
+#else
+#define read_32bit_cp1_register(source)                                 \
+        _read_32bit_cp1_register(source, )
+#endif
+
 #ifdef HAVE_AS_DSP
 #define rddsp(mask)                                                     \
 ({                                                                      \