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I found out that the ARM-compiler armcc V5.05 does not compile uint64_t correctly into assembly code. It uses only one register instead of two so the result is truncated to 32 bits (though the compiler is not complaining). As a workaround I used the gcc compiler, put the generated assembler code into a separate asm file and ran the ARM assembler. The target could not be created due to the error:

This register combination results in UNPREDICTABLE behaviour

which is really fatal, I suppose. After the C- "return" statement at the end of a function gcc inserts an offending SUB SP,R11,#0 or ADD SP,R11,#0 command before the ASM-return command BX LR. This is true with or without uint64_t. Can I rely on gcc or is it a bug in armcc/armasm?

trylimits
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keyboardwizard
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  • Hello trylimits, thanks for formatting ! I just wanted to make things clearer when I saw that the source code wasn't complete. After completion there are no more `SUB SP` or `ADD SP` so gcc is reliable of course. But it doesn't compile uint64_t correctly, the same way armcc does. – keyboardwizard Nov 03 '18 at 15:15

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