From: Chandler Carruth <chandlerc@gmail.com>
Date: Fri, 25 Apr 2014 06:38:58 +0000 (+0000)
Subject: [LCG] Now that the loop structure of the core SCC finding routine is
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=fe0f0187be88afc697514c0626fa2c4ba87b7466;p=oota-llvm.git

[LCG] Now that the loop structure of the core SCC finding routine is
factored into a more reasonable form, replace the tail call with
a simple outer-loop continuation. It's sad that C++ makes this so
awkward to write, but it seems more direct and clear than the tail call
at this point.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207201 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Analysis/LazyCallGraph.cpp b/lib/Analysis/LazyCallGraph.cpp
index 2e4fad3996e..c9cc0dd4ecb 100644
--- a/lib/Analysis/LazyCallGraph.cpp
+++ b/lib/Analysis/LazyCallGraph.cpp
@@ -449,6 +449,7 @@ LazyCallGraph::SCC *LazyCallGraph::getNextSCCInPostOrder() {
     assert(N->DFSNumber != 0 && "We should always assign a DFS number "
                                 "before placing a node onto the stack.");
 
+    bool Recurse = false; // Used to simulate recursing onto a child.
     for (auto I = DFSStack.back().second, E = N->end(); I != E; ++I) {
       Node &ChildN = *I;
       if (ChildN.DFSNumber == 0) {
@@ -463,7 +464,8 @@ LazyCallGraph::SCC *LazyCallGraph::getNextSCCInPostOrder() {
         ChildN.LowLink = ChildN.DFSNumber = NextDFSNumber++;
         SCCEntryNodes.remove(&ChildN.getFunction());
         DFSStack.push_back(std::make_pair(&ChildN, ChildN.begin()));
-        return LazyCallGraph::getNextSCCInPostOrder();
+        Recurse = true;
+        break;
       }
 
       // Track the lowest link of the childen, if any are still in the stack.
@@ -472,6 +474,11 @@ LazyCallGraph::SCC *LazyCallGraph::getNextSCCInPostOrder() {
       if (ChildN.LowLink >= 0 && ChildN.LowLink < N->LowLink)
         N->LowLink = ChildN.LowLink;
     }
+    if (Recurse)
+      // Continue the outer loop when we exit the inner loop in order to
+      // recurse onto a child.
+      continue;
+
     // No more children to process here, pop the node off the stack.
     DFSStack.pop_back();