On Thu, 21 Feb 2013 11:40:54 -0500 Nicolas Pitre <n...@fluxnic.net> wrote:
> On Thu, 21 Feb 2013, Kim Phillips wrote: > > > On Wed, 20 Feb 2013 23:29:58 -0500 > > Nicolas Pitre <n...@fluxnic.net> wrote: > > > > > On Wed, 20 Feb 2013, Kim Phillips wrote: > > > > > > > On Wed, 20 Feb 2013 10:43:18 -0500 > > > > Nicolas Pitre <n...@fluxnic.net> wrote: > > > > > > > > > On Wed, 20 Feb 2013, Woodhouse, David wrote: > > > > > > On Wed, 2013-02-20 at 09:06 -0500, Nicolas Pitre wrote: > > > > > > > ... in which case there is no harm shipping a .c file and > > > > > > > trivially > > > > > > > enforcing -O2, the rest being equal. > > > > > > > > > > > > For today's compilers, unless the wind changes. > > > > > > > > > > We'll adapt if necessary. Going with -O2 should remain pretty safe > > > > > anyway. > > > > > > > > Alas, not so for gcc 4.4 - I had forgotten I had tested > > > > Ubuntu/Linaro 4.4.7-1ubuntu2 here: > > > > > > > > https://patchwork.kernel.org/patch/2101491/ > > > > > > > > add -O2 to that test script and gcc 4.4 *always* emits calls to > > > > __bswap[sd]i2, even with -march=armv6k+. > > > > argh, sorry - that script was testing support for > > __builtin_bswap{16,32,64} directly, which isn't the same as testing > > code generation of a byte swap pattern in C. > > Still, I'm not as confident as I was about this. which part exactly? Having -O2 as "protection"? Yes, me neither. > > I'll still try the assembly approach - gcc 4.4's armv6 output looks > > worse than both the pre-armv6 and post-armv6 __arch_swab32 > > implementations currently in use: > > > > mov ip, sp > > push {fp, ip, lr, pc} > > sub fp, ip, #4 > > You should use -fomit-frame-pointer to compile this. We don't need a > frame pointer here, especially for a leaf function that the compiler > decides to call on its own. > > > and r2, r0, #65280 ; 0xff00 > > lsl ip, r0, #24 > > orr r1, ip, r0, lsr #24 > > and r0, r0, #16711680 ; 0xff0000 > > orr r3, r1, r2, lsl #8 > > orr r0, r3, r0, lsr #8 > > Other than that, it is true that the above is slightly suboptimal. Here's the asm version I'm working on now, based on compiler output of the C version. Haven't tested beyond defconfig builds, which pass ok. Is there anything I have to do for thumb mode? If so, how to test? diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index dedf02b..e8a41d0 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -59,6 +59,7 @@ config ARM select CLONE_BACKWARDS select OLD_SIGSUSPEND3 select OLD_SIGACTION + select ARCH_USE_BUILTIN_BSWAP help The ARM series is a line of low-power-consumption RISC chip designs licensed by ARM Ltd and targeted at embedded applications and diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile index 5cad8a6..a277e97 100644 --- a/arch/arm/boot/compressed/Makefile +++ b/arch/arm/boot/compressed/Makefile @@ -108,12 +108,12 @@ endif targets := vmlinux vmlinux.lds \ piggy.$(suffix_y) piggy.$(suffix_y).o \ - lib1funcs.o lib1funcs.S ashldi3.o ashldi3.S \ + lib1funcs.o lib1funcs.S ashldi3.o ashldi3.S bswapsdi2.o \ font.o font.c head.o misc.o $(OBJS) # Make sure files are removed during clean extra-y += piggy.gzip piggy.lzo piggy.lzma piggy.xzkern \ - lib1funcs.S ashldi3.S $(libfdt) $(libfdt_hdrs) + lib1funcs.S ashldi3.S bswapsdi2.o $(libfdt) $(libfdt_hdrs) ifeq ($(CONFIG_FUNCTION_TRACER),y) ORIG_CFLAGS := $(KBUILD_CFLAGS) @@ -155,6 +155,12 @@ ashldi3 = $(obj)/ashldi3.o $(obj)/ashldi3.S: $(srctree)/arch/$(SRCARCH)/lib/ashldi3.S $(call cmd,shipped) +# For __bswapsi2, __bswapdi2 +bswapsdi2 = $(obj)/bswapsdi2.o + +$(obj)/bswapsdi2.S: $(srctree)/arch/$(SRCARCH)/lib/bswapsdi2.S + $(call cmd,shipped) + # We need to prevent any GOTOFF relocs being used with references # to symbols in the .bss section since we cannot relocate them # independently from the rest at run time. This can be achieved by @@ -176,7 +182,8 @@ if [ $(words $(ZRELADDR)) -gt 1 -a "$(CONFIG_AUTO_ZRELADDR)" = "" ]; then \ fi $(obj)/vmlinux: $(obj)/vmlinux.lds $(obj)/$(HEAD) $(obj)/piggy.$(suffix_y).o \ - $(addprefix $(obj)/, $(OBJS)) $(lib1funcs) $(ashldi3) FORCE + $(addprefix $(obj)/, $(OBJS)) $(lib1funcs) $(ashldi3) \ + $(bswapsdi2) FORCE @$(check_for_multiple_zreladdr) $(call if_changed,ld) @$(check_for_bad_syms) diff --git a/arch/arm/kernel/armksyms.c b/arch/arm/kernel/armksyms.c index 60d3b73..ba578f7 100644 --- a/arch/arm/kernel/armksyms.c +++ b/arch/arm/kernel/armksyms.c @@ -35,6 +35,8 @@ extern void __ucmpdi2(void); extern void __udivsi3(void); extern void __umodsi3(void); extern void __do_div64(void); +extern void __bswapsi2(void); +extern void __bswapdi2(void); extern void __aeabi_idiv(void); extern void __aeabi_idivmod(void); @@ -114,6 +116,8 @@ EXPORT_SYMBOL(__ucmpdi2); EXPORT_SYMBOL(__udivsi3); EXPORT_SYMBOL(__umodsi3); EXPORT_SYMBOL(__do_div64); +EXPORT_SYMBOL(__bswapsi2); +EXPORT_SYMBOL(__bswapdi2); #ifdef CONFIG_AEABI EXPORT_SYMBOL(__aeabi_idiv); diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile index af72969..5383df7 100644 --- a/arch/arm/lib/Makefile +++ b/arch/arm/lib/Makefile @@ -13,7 +13,7 @@ lib-y := backtrace.o changebit.o csumipv6.o csumpartial.o \ ashldi3.o ashrdi3.o lshrdi3.o muldi3.o \ ucmpdi2.o lib1funcs.o div64.o \ io-readsb.o io-writesb.o io-readsl.o io-writesl.o \ - call_with_stack.o + call_with_stack.o bswapsdi2.o mmu-y := clear_user.o copy_page.o getuser.o putuser.o diff --git a/arch/arm/lib/bswapsdi2.S b/arch/arm/lib/bswapsdi2.S new file mode 100644 index 0000000..e9c8ca7 --- /dev/null +++ b/arch/arm/lib/bswapsdi2.S @@ -0,0 +1,36 @@ +#include <linux/linkage.h> + +#if __LINUX_ARM_ARCH__ >= 6 +ENTRY(__bswapsi2) + rev r0, r0 + bx lr +ENDPROC(__bswapsi2) + +ENTRY(__bswapdi2) + rev r3, r0 + rev r0, r1 + mov r1, r3 + bx lr +ENDPROC(__bswapdi2) +#else +ENTRY(__bswapsi2) + eor r3, r0, r0, ror #16 + lsr r3, r3, #8 + bic r3, r3, #65280 @ 0xff00 + eor r0, r3, r0, ror #8 + mov pc, lr +ENDPROC(__bswapsi2) + +ENTRY(__bswapdi2) + mov ip, r1 + eor r3, ip, ip, ror #16 + eor r1, r0, r0, ror #16 + lsr r1, r1, #8 + lsr r3, r3, #8 + bic r3, r3, #65280 @ 0xff00 + bic r1, r1, #65280 @ 0xff00 + eor r1, r1, r0, ror #8 + eor r0, r3, ip, ror #8 + mov pc, lr +ENDPROC(__bswapdi2) +#endif Thanks, Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
