From 49da93396eb2058fcf19ed7da2b73e854955fff8 Mon Sep 17 00:00:00 2001
From: Chandler Carruth <chandlerc@gmail.com>
Date: Fri, 6 Apr 2012 17:21:31 +0000
Subject: [PATCH] Sink the collection of return instructions until after *all*
 simplification has been performed. This is a bit less efficient (requires
 another ilist walk of the basic blocks) but shouldn't matter in practice.
 More importantly, it's just too much work to keep track of all the various
 ways the return instructions can be mutated while simplifying them. This
 fixes yet another crasher, reported by Daniel Dunbar.

llvm-svn: 154179
---
 llvm/lib/Transforms/Utils/CloneFunction.cpp   | 16 ++++----
 llvm/test/Transforms/Inline/inline_cleanup.ll | 37 +++++++++++++++++++
 2 files changed, 46 insertions(+), 7 deletions(-)

diff --git a/llvm/lib/Transforms/Utils/CloneFunction.cpp b/llvm/lib/Transforms/Utils/CloneFunction.cpp
index 423f47d22bf0..20052a412277 100644
--- a/llvm/lib/Transforms/Utils/CloneFunction.cpp
+++ b/llvm/lib/Transforms/Utils/CloneFunction.cpp
@@ -532,13 +532,6 @@ void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
     // and we still want to prune the dead code as early as possible.
     ConstantFoldTerminator(I);
 
-    // Track all of the newly-inserted returns.
-    if (ReturnInst *RI = dyn_cast<ReturnInst>(I->getTerminator())) {
-      Returns.push_back(RI);
-      ++I;
-      continue;
-    }
-
     BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
     if (!BI || BI->isConditional()) { ++I; continue; }
     
@@ -566,4 +559,13 @@ void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
     
     // Do not increment I, iteratively merge all things this block branches to.
   }
+
+  // Make a final pass over the basic blocks from theh old function to gather
+  // any return instructions which survived folding. We have to do this here
+  // because we can iteratively remove and merge returns above.
+  for (Function::iterator I = cast<BasicBlock>(VMap[&OldFunc->getEntryBlock()]),
+                          E = NewFunc->end();
+       I != E; ++I)
+    if (ReturnInst *RI = dyn_cast<ReturnInst>(I->getTerminator()))
+      Returns.push_back(RI);
 }
diff --git a/llvm/test/Transforms/Inline/inline_cleanup.ll b/llvm/test/Transforms/Inline/inline_cleanup.ll
index ee73b0e30305..3898aa7044ac 100644
--- a/llvm/test/Transforms/Inline/inline_cleanup.ll
+++ b/llvm/test/Transforms/Inline/inline_cleanup.ll
@@ -174,3 +174,40 @@ entry:
   call void @PR12470_inner(i16 signext 1)
   ret void
 }
+
+define void @crasher_inner() nounwind uwtable {
+entry:
+  br i1 false, label %for.end28, label %for.body6
+
+for.body6:
+  br i1 undef, label %for.body6, label %for.cond12.for.inc26_crit_edge
+
+for.cond12.for.inc26_crit_edge:
+  br label %for.body6.1
+
+for.end28:
+  ret void
+
+for.body6.1:
+  br i1 undef, label %for.body6.1, label %for.cond12.for.inc26_crit_edge.1
+
+for.cond12.for.inc26_crit_edge.1:
+  br label %for.body6.2
+
+for.body6.2:
+  br i1 undef, label %for.body6.2, label %for.cond12.for.inc26_crit_edge.2
+
+for.cond12.for.inc26_crit_edge.2:
+  br label %for.end28
+}
+
+define void @crasher_outer() {
+; CHECK: @crasher_outer
+; CHECK-NOT: call
+; CHECK: ret void
+; CHECK-NOT: ret
+; CHECK: }
+entry:
+  tail call void @crasher_inner()
+  ret void
+}