Hello, I'm trying to optimize my code in time so I used the option window-->C/C++/ selected optimization level 3(-O3) and checked optimize for time. I'm using usb HID in the same project and unfortunately the usb device is not recognized any more. But when I put
#pragma O3 #pragma Otime
before each function in this file, the usb is recognized and there are no problems. So I just want to know if there is a difference between optimizing using the option window in keil or using #pragma.
Well, #pragma will not matter until after that #pragma line.
Command-line switches on the other hand is active before even first source line is processed.
So if it makes a difference with #pragma instead of specifying -O3 for just the file, then you have some part of the file that is compiled differently before you even reach your #pragma.
And if you use -O3 globally for the project, then it obviously affects the full project and not just code inside a specific source file.
Thank you for your help, Is there a way to locate the code that was optimized using keil?
Compare the generated assembler with & without the optimisation?