xref: /freebsd/sys/conf/kern.mk (revision 262e143bd46171a6415a5b28af260a5efa2a3db8)
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.if ${CC} == "icc"
10#CWARNFLAGS=	-w2	# use this if you are terribly bored
11CWARNFLAGS=
12.else
13CWARNFLAGS?=	-Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
14		-Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual \
15		-fformat-extensions -std=c99
16.endif
17#
18# The following flags are next up for working on:
19#	-W
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).  Explicitly prohibit the use of SSE and other SIMD
29# operations inside the kernel itself.  These operations are exclusively
30# reserved for user applications.
31#
32.if ${MACHINE_ARCH} == "i386" && ${CC} != "icc"
33CFLAGS+=	-mno-align-long-strings -mpreferred-stack-boundary=2 \
34		-mno-mmx -mno-3dnow -mno-sse -mno-sse2 -mno-sse3
35INLINE_LIMIT?=	8000
36.endif
37
38#
39# On the alpha, make sure that we don't use floating-point registers and
40# allow the use of BWX etc instructions (only needed for low-level i/o).
41# Also, reserve register t7 to point at per-cpu global variables.
42#
43.if ${MACHINE_ARCH} == "alpha"
44CFLAGS+=	-mno-fp-regs -ffixed-8 -Wa,-mev6
45INLINE_LIMIT?=	15000
46.endif
47
48.if ${MACHINE_ARCH} == "arm"
49INLINE_LIMIT?=	8000
50.endif
51#
52# For IA-64, we use r13 for the kernel globals pointer and we only use
53# a very small subset of float registers for integer divides.
54#
55.if ${MACHINE_ARCH} == "ia64"
56CFLAGS+=	-ffixed-r13 -mfixed-range=f32-f127 -mno-sdata
57INLINE_LIMIT?=	15000
58.endif
59
60#
61# For sparc64 we want medlow code model, and we tell gcc to use floating
62# point emulation.  This avoids using floating point registers for integer
63# operations which it has a tendency to do.
64#
65.if ${MACHINE_ARCH} == "sparc64"
66CFLAGS+=	-mcmodel=medlow -msoft-float
67INLINE_LIMIT?=	15000
68.endif
69
70#
71# For AMD64, we explicitly prohibit the use of FPU, SSE and other SIMD
72# operations inside the kernel itself.  These operations are exclusively
73# reserved for user applications.
74#
75.if ${MACHINE_ARCH} == "amd64"
76CFLAGS+=	-mcmodel=kernel -mno-red-zone \
77		-mfpmath=387 -mno-sse -mno-sse2 -mno-mmx -mno-3dnow \
78		-msoft-float -fno-asynchronous-unwind-tables
79INLINE_LIMIT?=	8000
80.endif
81
82#
83# For PowerPC we tell gcc to use floating point emulation.  This avoids using
84# floating point registers for integer operations which it has a tendency to do.
85#
86.if ${MACHINE_ARCH} == "powerpc"
87CFLAGS+=	-msoft-float
88INLINE_LIMIT?=	15000
89.endif
90
91#
92# GCC 3.0 and above like to do certain optimizations based on the
93# assumption that the program is linked against libc.  Stop this.
94#
95.if ${CC} == "icc"
96CFLAGS+=	-nolib_inline
97.else
98CFLAGS+=	-ffreestanding
99.endif
100
101.if ${CC} == "icc"
102CFLAGS+=	-restrict
103.endif
104