FreeBSD/Linux Kernel Cross Reference
sys/conf/kern.mk

     # $FreeBSD: releng/9.0/sys/conf/kern.mk 222248 2011-05-24 09:01:56Z brucec $
     
     #
     # Warning flags for compiling the kernel and components of the kernel:
     #
     CWARNFLAGS?=    -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
                     -Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual \
                     -Wundef -Wno-pointer-sign -fformat-extensions \
                     -Wmissing-include-dirs -fdiagnostics-show-option
    #
    # The following flags are next up for working on:
    #       -Wextra
    
    #
    # On i386, do not align the stack to 16-byte boundaries.  Otherwise GCC 2.95
    # and above adds code to the entry and exit point of every function to align the
    # stack to 16-byte boundaries -- thus wasting approximately 12 bytes of stack
    # per function call.  While the 16-byte alignment may benefit micro benchmarks,
    # it is probably an overall loss as it makes the code bigger (less efficient
    # use of code cache tag lines) and uses more stack (less efficient use of data
    # cache tag lines).  Explicitly prohibit the use of FPU, SSE and other SIMD
    # operations inside the kernel itself.  These operations are exclusively
    # reserved for user applications.
    #
    # gcc:
    # Setting -mno-mmx implies -mno-3dnow
    # Setting -mno-sse implies -mno-sse2, -mno-sse3 and -mno-ssse3
    #
    # clang:
    # Setting -mno-mmx implies -mno-3dnow, -mno-3dnowa, -mno-sse, -mno-sse2,
    #                          -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
    #
    .if ${MACHINE_CPUARCH} == "i386"
    .if ${CC:T:Mclang} != "clang"
    CFLAGS+=        -mno-align-long-strings -mpreferred-stack-boundary=2 -mno-sse
    .else
    CFLAGS+=        -mno-aes -mno-avx
    .endif
    CFLAGS+=        -mno-mmx -msoft-float
    INLINE_LIMIT?=  8000
    .endif
    
    .if ${MACHINE_CPUARCH} == "arm"
    INLINE_LIMIT?=  8000
    .endif
    
    #
    # For IA-64, we use r13 for the kernel globals pointer and we only use
    # a very small subset of float registers for integer divides.
    #
    .if ${MACHINE_CPUARCH} == "ia64"
    CFLAGS+=        -ffixed-r13 -mfixed-range=f32-f127 -fpic #-mno-sdata
    INLINE_LIMIT?=  15000
    .endif
    
    #
    # For sparc64 we want medlow code model, and we tell gcc to use floating
    # point emulation.  This avoids using floating point registers for integer
    # operations which it has a tendency to do.
    #
    .if ${MACHINE_CPUARCH} == "sparc64"
    CFLAGS+=        -mcmodel=medany -msoft-float
    INLINE_LIMIT?=  15000
    .endif
    
    #
    # For AMD64, we explicitly prohibit the use of FPU, SSE and other SIMD
    # operations inside the kernel itself.  These operations are exclusively
    # reserved for user applications.
    #
    # gcc:
    # Setting -mno-mmx implies -mno-3dnow
    # Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3 and -mfpmath=387
    #
    # clang:
    # Setting -mno-mmx implies -mno-3dnow, -mno-3dnowa, -mno-sse, -mno-sse2,
    #                          -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
    # (-mfpmath= is not supported)
    #
    .if ${MACHINE_CPUARCH} == "amd64"
    .if ${CC:T:Mclang} != "clang"
    CFLAGS+=        -mno-sse
    .else
    CFLAGS+=        -mno-aes -mno-avx
    .endif
    CFLAGS+=        -mcmodel=kernel -mno-red-zone -mno-mmx -msoft-float \
                    -fno-asynchronous-unwind-tables
    INLINE_LIMIT?=  8000
    .endif
    
    #
    # For PowerPC we tell gcc to use floating point emulation.  This avoids using
    # floating point registers for integer operations which it has a tendency to do.
    # Also explicitly disable Altivec instructions inside the kernel.
    #
    .if ${MACHINE_CPUARCH} == "powerpc"
    CFLAGS+=        -msoft-float -mno-altivec
    INLINE_LIMIT?=  15000
    .endif
   
   #
   # Use dot symbols on powerpc64 to make ddb happy
   #
   .if ${MACHINE_ARCH} == "powerpc64"
   CFLAGS+=        -mcall-aixdesc
   .endif
   
   #
   # For MIPS we also tell gcc to use floating point emulation
   #
   .if ${MACHINE_CPUARCH} == "mips"
   CFLAGS+=        -msoft-float
   INLINE_LIMIT?=  8000
   .endif
   
   #
   # GCC 3.0 and above like to do certain optimizations based on the
   # assumption that the program is linked against libc.  Stop this.
   #
   CFLAGS+=        -ffreestanding
   
   #
   # GCC SSP support
   #
   .if ${MK_SSP} != "no" && ${MACHINE_CPUARCH} != "ia64" && \
       ${MACHINE_CPUARCH} != "arm" && ${MACHINE_CPUARCH} != "mips"
   CFLAGS+=        -fstack-protector
   .endif
   
   #
   # Enable CTF conversation on request
   #
   .if defined(WITH_CTF)
   .undef NO_CTF
   .endif

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