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

@@ -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);
 }

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
+}