Facundo Ciccioli writes: > I wrote a function which modifies esp register through some asm > instructions (it pushes things to the stack). Everything works perfect > for now because the function takes care of restauring the content of > esp issuing an add instruction too so that it can return allright. Right. Good. asms shouldn't clobber SP. SP is controlled by the compiler. > But reading GCC docs I found this: > > "If you refer to a particular hardware register from the assembler > code, you will probably have to list the register after the third > colon to tell the compiler the register's value is modified." > > Ok, so I do that. But looking at the assembler code generated by the > compiler I notice that it is exactly the same than before I did what > the docs say. So I wonder, why does the compiler needs to know if I > execute an instruction that modifies some register? And also (maybe > the answer to the former would respond this) why does the code doesn't > change? If you use a specific hardware register, say R7, then you need to tell the compiler you have done so, so that the compiler doesn't use that register to store a temporary. Andrew.
