4 # Warning flags for compiling the kernel and components of the kernel.
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.
10 #CWARNFLAGS= -w2 # use this if you are terribly bored
13 CWARNFLAGS?= -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
14 -Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual \
15 -fformat-extensions -std=c99
18 # The following flags are next up for working on:
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.
32 .if ${MACHINE_ARCH} == "i386" && ${CC} != "icc"
33 CFLAGS+= -mno-align-long-strings -mpreferred-stack-boundary=2 \
34 -mno-mmx -mno-3dnow -mno-sse -mno-sse2
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.
43 .if ${MACHINE_ARCH} == "alpha"
44 CFLAGS+= -mno-fp-regs -ffixed-8 -Wa,-mev6
48 .if ${MACHINE_ARCH} == "arm"
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.
55 .if ${MACHINE_ARCH} == "ia64"
56 CFLAGS+= -ffixed-r13 -mfixed-range=f32-f127 -mno-sdata
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.
65 .if ${MACHINE_ARCH} == "sparc64"
66 CFLAGS+= -mcmodel=medlow -msoft-float
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.
75 .if ${MACHINE_ARCH} == "amd64"
76 CFLAGS+= -mcmodel=kernel -mno-red-zone \
77 -mfpmath=387 -mno-sse -mno-sse2 -mno-mmx -mno-3dnow \
78 -msoft-float -fno-asynchronous-unwind-tables
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.
86 .if ${MACHINE_ARCH} == "powerpc"
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.
96 CFLAGS+= -nolib_inline
98 CFLAGS+= -ffreestanding