Intel Fortran编译器ifort何时启用优化编译选项？

As someone who’s spent plenty of time tuning Fortran code with ifort, I can walk you through the optimizations it handles—including function inlining, interprocedural optimization (IPO), and standard performance tweaks—plus clarify the flags you mentioned:

• -O2 Optimization Level
  This flag triggers ifort’s deep, Fortran-specific optimization suite, and function inlining is a core part of what it does. The compiler automatically spots small, frequently called functions and replaces their calls with the actual function body to cut down on call overhead. Alongside inlining, -O2 also handles things like loop unrolling, smart register allocation, and dead code removal to give your program a solid performance boost.

• -finline-functions
  This option explicitly allows function inlining, but here’s the thing: this is already the default behavior for ifort when you use optimization levels like -O2 or higher. Most folks add this flag either to make their build intent crystal clear (so anyone reading the compile script knows inlining is intentional) or to lock in inlining behavior in edge cases—like when mixing different optimization settings across compile units, where defaults might shift unexpectedly.

• Interprocedural Optimization (IPO)
  While you didn’t mention it directly, IPO (enabled with -ipo) pairs great with the inlining from -O2. It analyzes code across multiple compile units, enabling cross-module inlining, global dead code elimination, and other big-picture optimizations that single-unit inlining can’t touch. It’s a powerful way to squeeze extra performance out of larger Fortran projects.

内容的提问来源于stack exchange，提问作者jvriesem