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

     # $FreeBSD$
     
     #
     # Warning flags for compiling the kernel and components of the kernel.
     #
     # Note that the newly added -Wcast-qual is responsible for generating 
     # most of the remaining warnings.  Warnings introduced with -Wall will
     # also pop up, but are easier to fix.
     .if ${CC} == "icc"
    #CWARNFLAGS=    -w2     # use this if you are terribly bored
    CWARNFLAGS=
    .else
    CWARNFLAGS?=    -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
                    -Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual \
                    ${_wundef} ${_Wno_pointer_sign} -fformat-extensions
    .if !defined(WITH_GCC3)
    _Wno_pointer_sign=-Wno-pointer-sign
    .endif
    .if !defined(NO_UNDEF)
    _wundef=        -Wundef
    .endif
    .endif
    #
    # The following flags are next up for working on:
    #       -W
    
    #
    # On the i386, do not align the stack to 16-byte boundaries.  Otherwise GCC
    # 2.95 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 SSE and other SIMD
    # operations inside the kernel itself.  These operations are exclusively
    # reserved for user applications.
    #
    .if ${MACHINE_ARCH} == "i386" && ${CC} != "icc"
    CFLAGS+=        -mno-align-long-strings -mpreferred-stack-boundary=2 \
                    -mno-mmx -mno-3dnow -mno-sse -mno-sse2 -mno-sse3
    INLINE_LIMIT?=  8000
    .endif
    
    .if ${MACHINE_ARCH} == "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_ARCH} == "ia64"
    CFLAGS+=        -ffixed-r13 -mfixed-range=f32-f127 -fpic #-mno-sdata
    INLINE_LIMIT?=  15000
    .endif
    
    #
    # For sparc64 we want the medany code model so modules may be located
    # anywhere in the 64-bit address space.  We also 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_ARCH} == "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.
    #
    .if ${MACHINE_ARCH} == "amd64"
    CFLAGS+=        -mcmodel=kernel -mno-red-zone \
                    -mfpmath=387 -mno-sse -mno-sse2 -mno-sse3 -mno-mmx -mno-3dnow \
                    -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_ARCH} == "powerpc"
    CFLAGS+=        -msoft-float -mno-altivec
    INLINE_LIMIT?=  15000
    .endif
    
    #
    # For MIPS we also tell gcc to use floating point emulation and 
    # disable MIPS DSP ASE Instruction set.
    #
    .if ${MACHINE_ARCH} == "mips"
    CFLAGS+=        -msoft-float -mno-dsp
    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.
   #
   .if ${CC} == "icc"
   CFLAGS+=        -nolib_inline
   .else
   CFLAGS+=        -ffreestanding
   .endif
   
   .if ${CC} == "icc"
   CFLAGS+=        -restrict
   .endif
   
   #
   # GCC SSP support.
   #
   .if ${MK_SSP} != "no" && ${CC} != "icc" && ${MACHINE_ARCH} != "ia64" && \
           ${MACHINE_ARCH} != "arm" && ${MACHINE_ARCH} != "mips"
   CFLAGS+=        -fstack-protector
   .endif

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