Revert "Do not inline self-recursive functions into other functions."

This reverts commit dc65f70 since it
looks like the updated test is broken on some configurations.

I'll investigate, fix, and reapply soon.

Author: rudkx

lib/SILPasses/IPO/PerformanceInliner.cpp

@@ -542,16 +542,6 @@ bool SILPerformanceInliner::hasInliningCycle(SILFunction *Caller,
   return InlinedBefore;
 }
 
-
-static bool calleeIsSelfRecursive(SILFunction *Callee) {
-  for (auto &BB : *Callee)
-    for (auto &I : BB)
-      if (auto Apply = FullApplySite::isa(&I))
-        if (Apply.getCalleeFunction() == Callee)
-          return true;
-  return false;
-}
-
 // Returns the callee of an apply_inst if it is basically inlinable.
 SILFunction *SILPerformanceInliner::getEligibleFunction(FullApplySite AI) {
 
@@ -634,16 +624,6 @@ SILFunction *SILPerformanceInliner::getEligibleFunction(FullApplySite AI) {
           Callee->getName() << ".\n");
     return nullptr;
   }
-
-  // Inlining self-recursive functions into other functions can result
-  // in excessive code duplication since we run the inliner multiple
-  // times in our pipeline.
-  if (calleeIsSelfRecursive(Callee)) {
-    DEBUG(llvm::dbgs() << "        FAIL: Callee is self-recursive in " <<
-          Callee->getName() << ".\n");
-    return nullptr;
-  }
-
   DEBUG(llvm::dbgs() << "        Eligible callee: " <<
         Callee->getName() << "\n");
 

test/SILPasses/inline_recursive.swift

@@ -7,17 +7,13 @@ private func recFunc(x: Int) -> Int {
   return 0
 }
 
-// Ensure that we do not inline self-recursive functions into other
-// functions since doing so can result in large code growth if we run
-// the inlining pass multiple times.
-
-// CHECK-LABEL: sil hidden @_TF16inline_recursive6callitFT_Si
+//CHECK-LABEL: sil {{.*}}callit
 // CHECK: bb0:
-// CHECK: [[FN:%.*]] = function_ref @_TF16inline_recursiveP33_38E63D320CFF538A1F98BBC31453B1EB7recFuncFSiSi
-// CHECK: [[BUILTIN_INT:%.*]] = integer_literal $Builtin.Int64, 3
-// CHECK: [[INT:%.*]] = struct $Int ([[BUILTIN_INT]] : $Builtin.Int64)
-// CHECK: [[APPLY:%.*]] = apply [[FN]]([[INT]])
-// CHECK: return [[APPLY]]
+// CHECK-NEXT: integer_literal {{.*}}, 0
+// CHECK-NEXT: struct
+// CHECK-NEXT: return
+
 func callit() -> Int {
   return recFunc(3)
 }
+