GCC and IAR compiler comparison
From NXTGCC
With the recent release of the IAR compiler for Lego Mindstorms NXT, it is possible to compare the size of the firmware that the two compilers generate. Start by looking at the memory layout. The table below shows the size of the compiled firmware in the flash and RAM of NXT. The term "packing" refers to packing of structs.
| Compiler (1.05 sources) | Size of .text (Flash bytes) | Size of .data (RAM bytes) | Speed #loops (using a benchmark) |
|---|---|---|---|
| GCC (pack all) | 202052 | 54548 | - |
| NXTGCC (pack selected) | 180104 | 54144 | 615 |
| GCC (pack none) | 162136 | 54228 | - |
| IAR (speed optimization) | 127552 | 49831 | - |
| IAR (size optimization) | 122440 | 49763 | 640 |
IAR produce a smaller and faster image than GCC.
IAR Compiler
You can set the speed or size optimization flags here:
Then choose Rebuild All, and read the numbers from the IAR map output. Check the IAR linker reference for a good explanation of the segments. The .text (Flash) size is CODE + CONST, and .data (RAM) is the DATA segment:
GCC
In NXTGCC you can also read the numbers after a firmware build. The RAM requirement is .data + .bss. It is indicated how to produce the numbers when (1)all structs are packed, (2)some are packed (NXTGCC default), and (3)none are packed:
