Hard FPU unsupported instruction - vcvt.f64.f32

Hello Evgene,

Is the FPU Unit and Lazy Stacking Enabled?

Regards

Amit

Hi Amit.

The FPU is enabled and working, since some other FPU instructions doing well. I am not sure about lazy stacking, will check it tomorrow, but I think it is on default state which is on AFAIK. Should it be off? Why would it matter?

Thank you

Hello Evgene,

It is not enabled by default, so having it on would be useful. I have seen such a problem in the past on FPU instruction and got it fixed using the Lazy Stacking. Also if you can send the gcc compile and link options, I can try to reproduce the same with the code snippet.

Regards

Amit

If I understand this correctly, the cause is an unsupported double precision instruction (VCVT.F64).

Hello f.m.

Yes, you are right "right deserve a verified answer". It seems that the FPU option is used for a cortex-r4/5 series will generate the instruction. I do want to make sure that once we get the compilation/link options in gcc it turns out to be the use of r4 cpu option.

Regards

Amit

Thank you for your replies

Since I am using eclipse to manage my build configs, I'll just post here just the command outputs from the console, sorry for the mess:

make all 
'Building file: ../src/main.c'
'Invoking: Cross ARM C Compiler'
arm-eabi-gcc -mcpu=cortex-m4 -mthumb -mthumb-interwork -mfloat-abi=hard -mfpu=fpv4-sp-d16 -O0 -fmessage-length=0 -fsigned-char -ffunction-sections -fdata-sections -Wall  -g3 -DTARGET_IS_TM4C123_RB1 -DPART_TM4C123GH6PM -D__FPU_PRESENT -I"C:\Projects\Gen2_TI\driver" -I"C:\ti\TivaWare_C_Series" -std=gnu11 -MMD -MP -MF"src/main.d" -MT"src/main.o" -c -o "src/main.o" "../src/main.c"
../src/main.c: In function 'main':
../src/main.c:29:14: warning: unused variable 'r' [-Wunused-variable]
     uint32_t r = crash(0.22, 156);
              ^
'Finished building: ../src/main.c'
' '
'Building file: ../src/startup_gcc.c'
'Invoking: Cross ARM C Compiler'
arm-eabi-gcc -mcpu=cortex-m4 -mthumb -mthumb-interwork -mfloat-abi=hard -mfpu=fpv4-sp-d16 -O0 -fmessage-length=0 -fsigned-char -ffunction-sections -fdata-sections -Wall  -g3 -DTARGET_IS_TM4C123_RB1 -DPART_TM4C123GH6PM -D__FPU_PRESENT -I"C:\Projects\Gen2_TI\driver" -I"C:\ti\TivaWare_C_Series" -std=gnu11 -MMD -MP -MF"src/startup_gcc.d" -MT"src/startup_gcc.o" -c -o "src/startup_gcc.o" "../src/startup_gcc.c"
'Finished building: ../src/startup_gcc.c'
' '
'Building target: fpu_test.elf'
'Invoking: Cross ARM C Linker'
arm-eabi-gcc -mcpu=cortex-m4 -mthumb -mthumb-interwork -mfloat-abi=hard -mfpu=fpv4-sp-d16 -O0 -fmessage-length=0 -fsigned-char -ffunction-sections -fdata-sections -Wall  -g3 -T "C:\Projects\Gen2_TI\fpu_test\linkerscript\tm4c123g.ld" -nostartfiles -Xlinker --gc-sections -L"C:\Projects\Gen2_TI\driver\Debug" -Wl,-Map,"fpu_test.map" -o "fpu_test.elf"  ./src/main.o ./src/startup_gcc.o   -ldriver
'Finished building target: fpu_test.elf'

For the sake of completenessI've attached the sources and the linker script 8306.src.zip .

Just an update.

I have switched to a different toolchain build, and it is generating a different code for the same settings, such that this issue does not present anymore.

The toolchain with the problem is this

The "good" toolchain is this