-// getInlineCost - The heuristic used to determine if we should inline the
-// function call or not.
-//
-int SimpleInliner::getInlineCost(CallSite CS) {
- Instruction *TheCall = CS.getInstruction();
- const Function *Callee = CS.getCalledFunction();
- const Function *Caller = TheCall->getParent()->getParent();
-
- // Don't inline a directly recursive call.
- if (Caller == Callee) return 2000000000;
-
- // InlineCost - This value measures how good of an inline candidate this call
- // site is to inline. A lower inline cost make is more likely for the call to
- // be inlined. This value may go negative.
- //
- int InlineCost = 0;
-
- // If there is only one call of the function, and it has internal linkage,
- // make it almost guaranteed to be inlined.
- //
- if (Callee->use_size() == 1 && Callee->hasInternalLinkage())
- InlineCost -= 30000;
-
- // Add to the inline quality for properties that make the call valueable to
- // inline. This includes factors that indicate that the result of inlining
- // the function will be optimizable. Currently this just looks at arguments
- // passed into the function.
- //
- for (CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
- I != E; ++I) {
- // Each argument passed in has a cost at both the caller and the callee
- // sides. This favors functions that take many arguments over functions
- // that take few arguments.
- InlineCost -= 20;
-
- // If this is a function being passed in, it is very likely that we will be
- // able to turn an indirect function call into a direct function call.
- if (isa<Function>(I))
- InlineCost -= 100;
-
- // If a constant, global variable or alloca is passed in, inlining this
- // function is likely to allow significant future optimization possibilities
- // (constant propagation, scalar promotion, and scalarization), so encourage
- // the inlining of the function.
- //
- else if (isa<Constant>(I) || isa<GlobalVariable>(I) || isa<AllocaInst>(I))
- InlineCost -= 60;