Is there a reason why not to use link-time optimization (LTO)?

Question

GCC, MSVC, LLVM, and probably other toolchains have support for link-time (whole program) optimization to allow optimization of calls among compilation units.

Is the

Answer 1

Apart from to this,

Consider a typical example from embedded system,

void function1(void) { /*Do something*/} //located at address 0x1000 
void function2(void) { /*Do something*/} //located at address 0x1100
void function3(void) { /*Do something*/} //located at address 0x1200

With predefined addressed functions can be called through relative addresses like bellow,

 (*0x1000)(); //expected to call function2
 (*0x1100)(); //expected to call function2
 (*0x1200)();  //expected to call function3

LOT can lead to unexpected behavior.