freebsd-dev/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.
CWARNFLAGS?=	-Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
		-Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual \
		-fformat-extensions -std=c99
#
# 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)
#
.if ${MACHINE_ARCH} == "i386"
CFLAGS+=	-mno-align-long-strings -mpreferred-stack-boundary=2
.endif

#
# On the alpha, make sure that we don't use floating-point registers and
# allow the use of BWX etc instructions (only needed for low-level i/o).
# Also, reserve register t7 to point at per-cpu global variables.
#
.if ${MACHINE_ARCH} == "alpha"
CFLAGS+=	-mno-fp-regs -ffixed-8 -Wa,-mev6
.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 -mno-sdata
.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_ARCH} == "sparc64"
CFLAGS+=	-mcmodel=medlow -msoft-float
.endif

#
# For AMD64, use a medium model for now.  We'll switch to "kernel"
# once pmap is ready.  Be excessively careful to not generate FPU code.
#
.if ${MACHINE_ARCH} == "amd64"
CFLAGS+=	-mcmodel=kernel -mno-red-zone \
		-mfpmath=387 -mno-sse -mno-sse2 -mno-mmx -mno-3dnow \
		-msoft-float -fno-asynchronous-unwind-tables
.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