Improve the accuracy of the inlining heuristic looking for the

case where a static caller is itself inlined everywhere else, and
thus may go away if it doesn't get too big due to inlining other
things into it.  If there are references to the caller other than
calls, it will not be removed; account for this.
This results in same-day completion of the case in PR8853.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122821 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/IPO/Inliner.cpp b/lib/Transforms/IPO/Inliner.cpp
index ae904354ee2c699c250dd1f081e66ec263bbe6bf..37eafd723bf80e47d4233615b4fb005cac4d0978 100644 (file)
--- a/lib/Transforms/IPO/Inliner.cpp
+++ b/lib/Transforms/IPO/Inliner.cpp
@@ -252,20 +252,25 @@ bool Inliner::shouldInline(CallSite CS) {
   if (Caller->hasLocalLinkage()) {
     int TotalSecondaryCost = 0;
     bool outerCallsFound = false;
-    bool allOuterCallsWillBeInlined = true;
-    bool someOuterCallWouldNotBeInlined = false;
+    // This bool tracks what happens if we do NOT inline C into B.
+    bool callerWillBeRemoved = true;
+    // This bool tracks what happens if we DO inline C into B.
+    bool inliningPreventsSomeOuterInline = false;
     for (Value::use_iterator I = Caller->use_begin(), E =Caller->use_end(); 
          I != E; ++I) {
       CallSite CS2(*I);
 
       // If this isn't a call to Caller (it could be some other sort
-      // of reference) skip it.
-      if (!CS2 || CS2.getCalledFunction() != Caller)
+      // of reference) skip it.  Such references will prevent the caller
+      // from being removed.
+      if (!CS2 || CS2.getCalledFunction() != Caller) {
+        callerWillBeRemoved = false;
         continue;
+      }
 
       InlineCost IC2 = getInlineCost(CS2);
       if (IC2.isNever())
-        allOuterCallsWillBeInlined = false;
+        callerWillBeRemoved = false;
       if (IC2.isAlways() || IC2.isNever())
         continue;
 
@@ -275,14 +280,14 @@ bool Inliner::shouldInline(CallSite CS) {
       float FudgeFactor2 = getInlineFudgeFactor(CS2);
 
       if (Cost2 >= (int)(CurrentThreshold2 * FudgeFactor2))
-        allOuterCallsWillBeInlined = false;
+        callerWillBeRemoved = false;
 
       // See if we have this case.  We subtract off the penalty
       // for the call instruction, which we would be deleting.
       if (Cost2 < (int)(CurrentThreshold2 * FudgeFactor2) &&
           Cost2 + Cost - (InlineConstants::CallPenalty + 1) >= 
                 (int)(CurrentThreshold2 * FudgeFactor2)) {
-        someOuterCallWouldNotBeInlined = true;
+        inliningPreventsSomeOuterInline = true;
         TotalSecondaryCost += Cost2;
       }
     }
@@ -290,10 +295,10 @@ bool Inliner::shouldInline(CallSite CS) {
     // one is set very low by getInlineCost, in anticipation that Caller will
     // be removed entirely.  We did not account for this above unless there
     // is only one caller of Caller.
-    if (allOuterCallsWillBeInlined && Caller->use_begin() != Caller->use_end())
+    if (callerWillBeRemoved && Caller->use_begin() != Caller->use_end())
       TotalSecondaryCost += InlineConstants::LastCallToStaticBonus;
 
-    if (outerCallsFound && someOuterCallWouldNotBeInlined && 
+    if (outerCallsFound && inliningPreventsSomeOuterInline &&
         TotalSecondaryCost < Cost) {
       DEBUG(dbgs() << "    NOT Inlining: " << *CS.getInstruction() << 
            " Cost = " << Cost <<