61caf7cce9
in arm64 Let's see how the following code looks like in assembly
volatile cpu_set_t g_cpu_set;
cpu_set_t set_cpu_set_t_set(int cpu) {
g_cpu_set &= ~(1 << cpu);
return g_cpu_set;
}
when
typedef volatile uint32_t cpu_set_t;
Dump of assembler code for function set_cpu_set_t_set:
0x0000000040288570 <+0>: adrp x2, 0x403ce000 <g_irqvector+1160>
0x0000000040288574 <+4>: ldr w3, [x2, #2368]
0x0000000040288578 <+8>: mov w1, #0x1
0x000000004028857c <+12>: lsl w1, w1, w0
0x0000000040288580 <+16>: bic w1, w3, w1
0x0000000040288584 <+20>: str w1, [x2, #2368]
0x0000000040288588 <+24>: ldr w0, [x2, #2368]
0x000000004028858c <+28>: ret
when
typedef volatile uint8_t cpu_set_t;
Dump of assembler code for function set_cpu_set_t_set:
0x000000004028856c <+0>: adrp x2, 0x403ce000 <g_irqvector+1192>
0x0000000040288570 <+4>: ldrb w3, [x2, #2336]
0x0000000040288574 <+8>: mov w1, #0x1
0x0000000040288578 <+12>: and w3, w3, #0xff // At this time, there will be one more instruction
0x000000004028857c <+16>: lsl w1, w1, w0
0x0000000040288580 <+20>: bic w1, w3, w1
0x0000000040288584 <+24>: strb w1, [x2, #2336]
0x0000000040288588 <+28>: ldrb w0, [x2, #2336]
0x000000004028858c <+32>: ret
test:
We can use qemu for testing.
compiling
make distclean -j20; ./tools/configure.sh -l qemu-armv8a:nsh_smp ;make -j20
running
qemu-system-aarch64 -cpu cortex-a53 -smp 4 -nographic -machine virt,virtualization=on,gic-version=3 -net none -chardev stdio,id=con,mux=on -serial chardev:con -mon chardev=con,mode=readline -kernel ./nuttx
Signed-off-by: hujun5 <hujun5@xiaomi.com>
Apache NuttX is a real-time operating system (RTOS) with an emphasis on standards compliance and small footprint. Scalable from 8-bit to 64-bit microcontroller environments, the primary governing standards in NuttX are POSIX and ANSI standards. Additional standard APIs from Unix and other common RTOSs (such as VxWorks) are adopted for functionality not available under these standards, or for functionality that is not appropriate for deeply-embedded environments (such as fork()).
For brevity, many parts of the documentation will refer to Apache NuttX as simply NuttX.
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If you wish to contribute to the NuttX project, read the Contributing guidelines for information on Git usage, coding standard, workflow and the NuttX principles.
License
The code in this repository is under either the Apache 2 license, or a license compatible with the Apache 2 license. See the License Page for more information.