xref: /freebsd/sys/conf/kern.mk (revision 5521ff5a4d1929056e7ffc982fac3341ca54df7c)
1# $FreeBSD$
2
3#
4# Warning flags for compiling the kernel and components of the kernel.
5#
6# Note that the newly added -Wcast-qual is responsible for generating
7# most of the remaining warnings.  Warnings introduced with -Wall will
8# also pop up, but are easier to fix.
9#
10CWARNFLAGS?=	-Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
11		-Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual \
12		-fformat-extensions -ansi
13#
14# The following flags are next up for working on:
15#	-W
16#
17# When working on removing warnings from code, the `-Werror' flag should be
18# of material assistance.
19#
20
21#
22# On the i386, do not align the stack to 16-byte boundaries.  Otherwise GCC
23# 2.95 adds code to the entry and exit point of every function to align the
24# stack to 16-byte boundaries -- thus wasting approximately 12 bytes of stack
25# per function call.  While the 16-byte alignment may benefit micro benchmarks,
26# it is probably an overall loss as it makes the code bigger (less efficient
27# use of code cache tag lines) and uses more stack (less efficient use of data
28# cache tag lines)
29#
30.if ${MACHINE_ARCH} == "i386"
31CFLAGS+=	-mpreferred-stack-boundary=2
32.endif
33
34#
35# On the alpha, make sure that we don't use floating-point registers and
36# allow the use of EV56 instructions (only needed for low-level i/o).
37# Also, reserve register t7 to point at per-cpu global variables.
38#
39.if ${MACHINE_ARCH} == "alpha"
40CFLAGS+=	-mno-fp-regs -ffixed-8 -Wa,-mev56
41.endif
42
43#
44# For IA-64, we use r13 for the kernel globals pointer and we only use
45# a very small subset of float registers for integer divides.
46#
47.if ${MACHINE_ARCH} == "ia64"
48CFLAGS+=	-ffixed-r13 -mfixed-range=f32-f127
49.endif
50