thumb

问题 I am currently trying to speed up some of my C functions on a Cortex-M0 (Freescale KL25Z) using assembly. I get a problem with this minimal test program: @.syntax unified .cpu cortex-m0 .text .global test .code 16 test: mov r0, #0 adds r0, r0, #1 bx lr When I try to assemble my .s file to a .o file, I get this error $ arm-none-eabi-as test.s -o test.o test.s: Assembler messages: test.s:8: Error: instruction not supported in Thumb16 mode -- `adds r0,r0,#1' The error message doesn't make sense

来源： https://stackoverflow.com/questions/60371470/how-is-part-of-ldm-r1-r2-instruction-in-armv6-m-architecture-encoded

问题 I have generated a code base using STM32Cube for STM32F205RB to be used within Atollic TrueSTUDIO. The project does not build, giving the error: arm-atollic-eabi-gcc -c -mthumb -std=gnu90 -DUSE_HAL_DRIVER -DSTM32F205xx -IC:\Users\Elliott\Atollic\TrueSTUDIO\ARM_workspace\USBInterfaceCUBE\USBInterfaceCube/Inc -IC:\Users\Elliott\Atollic\TrueSTUDIO\ARM_workspace\USBInterfaceCUBE\USBInterfaceCube/Drivers/STM32F2xx_HAL_Driver/Inc -IC:\Users\Elliott\Atollic\TrueSTUDIO\ARM_workspace\USBInterfaceCUBE

问题 I'm just getting started with the ARM architecture on my Nucleo STM32F303RE, and I'm trying to understand how the instructions are encoded. I have running a simple LED-blinking program, and the first few disassembled application instructions are: 08000188: push {lr} 0800018a: sub sp, #12 235 __initialize_hardware_early (); 0800018c: bl 0x80005b8 <__initialize_hardware_early> These instructions resolve to the following in the hex file (displayed weird in Eclipse -- each 32-bit word is in MSB

问题 I'm currently playing around a bit with assembler on a Cortex-M3 microcontroller. I'm not sure if this is important, but here you go. I need to write a value into to a certain address in memory. Here is what I tried: LDR R4, =__cs3_interrupt_vector_cortex_m STR R4, [=VTOR] But it seems like I need to reference the VTOR address relative to the PC register. The question is if there is a way to not reference the address relativ and let this do automatically (so that it would basically look like

问题 So it's fairly easy to figure out what kind of CPU an iOS device runs by querying sysctlbyname("hw.cpusubtype", ...) , but there seems to be no obvious way to figure out what features the CPU actually has (think VFP, NEON, Thumb, ...). Can someone think of a way to do this? Basically, what I need is something similar to getauxval(AT_HWCAP) on Linux/Android, which returns a bit mask of features supported by the CPU. A few things to note: The information must be retrieved at runtime from the OS

问题 In ARM architecture, if an ARM to Thumb mode switch occurs, will a pipeline stall occur? If so, how many cycles are affected? Is this same for Thumb to ARM mode switching ? Does this behavior vary with different ARM processors ? 回答1: Assuming you switch in the sensible way (with BLX / BX LR ), any modern core will predict that (assuming the branch predictor isn't turned off, of course). Writing to the PC directly is a little more variable - generally, big cores might predict it but little

问题 I have this C code: int test(signed char anim_col) { if (anim_col >= 31) { return 1; } else if (anim_col <= -15) { return -2; } return 0; } That compiles to the following thumb code with -Os -mthumb using Android NDK r4b: test: mov r3, #1 cmp r0, #30 bgt .L3 mov r3, #0 add r0, r0, #14 bge .L3 mov r3, #2 neg r3, r3 .L3: mov r0, r3 bx lr But with the latest Android NDK r5 it compiles to this broken code: test: mov r3, #1 cmp r0, #30 bgt .L3 lsl r0, r0, #24 lsr r0, r0, #24 mov r3, #0 cmp r0,

问题 I'm working on an iPhone/iPad project, and I want to update the status register during some (not all) arithmetic operations. By default, Xcode uses 'Compile for Thumb' and I don't want to change it. The following GCC inline assembly code works fine under ARM, but results in a compile error under Thumb: 'instruction not supported in Thumb16 mode - adds r6,r4,r5'. The problem lies in the status register update. (I'm also aware that movcs and strcs will need to be changed). Does Thumb have an

问题 Help me please with gnu assembler for arm926ejs cpu. I try to build a simple program(test.S): .global _start _start: mov r0, #2 bx lr and success build it: arm-none-linux-gnueabi-as -mthumb -o test.o test.S arm-none-linux-gnueabi-ld -o test test.o but when I run the program in the arm target linux environment, I get an error: ./test Segmentation fault What am I doing wrong? Can _start function be the thumb func? or It is always arm func? 回答1: Can _start be a thumb function (in a Linux user