Hello all,
I compiled the following C++ function with CW 10.1 for Kinetis and found what I believe to be a volatile optimization bug.
void DebugResetFTM0Status(){ volatile uint32* pReg = &FTM0_STATUS; *pReg = *pReg & 0;}I expect the assembly code to read the FTM register and write back a 0. The Freescale FlexTimer has interrupt flags with a "write 0 after reading 1" reset protocol, so I really care for the read. If I want reads and writes optimized away, I leave out the "volatile".
The disassembly (from the debugger) shows that the C++ compiler optimized the volatile read-write combination away.
00010120: movw r5,#0x805000010124: movt r5,#0x400300010128: movs r0,#00001012a: str r0,[r5,#0] ; Blind store of 0 into the FTM register!; followed by an uninteresting epilogue, ldm this, add sp that.
Version info: CodeWarrior for MCU Version: 10.1 Build Id:110204, with whatever C++ compiler that brings along. I compiled for the K60 derivate on the TWR K60 board.
Greetings, KA
