I have been making some videos using TRACE32 the debugger that is free for the Portenta which shows the Assembly Language for each of your C/C++ commands, so I thought I should try to do some Assembly using the asm(); function. Well it took a full day of searching for Arduino assembly code that did not work.
Here is what I finally got working. It basically just does what
myLoop++; would do.
Using TRACE32 you can watch as the registers change.
Video should be available soon here
//myLoop += 1; // was set with int myLoop = 0;
// Lets mess with myLoop using assembly Language
// Note: #0x1 for HEX, #1 for numbers, #0b00000001 for bits
asm("ldr r0, =(myLoop) "); // load myLoop address into R0
asm("ldr r1, [r0] "); // Load value of myLoop into r1
asm("add r2, r1, #0x1 "); // Add r1 and "1" into r2,
asm("str r2, [r0] "); // Store value in r2 back to myLoop
Serial.println("Loop #: "+ String(myLoop));