Expose InsertPreheaderForLoop from LoopSimplify to other passes

Other passes, PPC counter-loop formation for example, also need to add loop
preheaders outside of the regular loop simplification pass. This makes
InsertPreheaderForLoop a global function so that it can be used by other
passes.

No functionality change intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182299 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Transforms/Utils/LoopSimplify.h

@@ -0,0 +1,26 @@
+//===- llvm/Transforms/Utils/LoopSimplify.h - Loop utilities -*- C++ -*-======//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines some loop transformation utilities.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_UTILS_LOOPSIMPLIFY_H
+#define LLVM_TRANSFORMS_UTILS_LOOPSIMPLIFY_H
+
+namespace llvm {
+
+class Loop;
+class Pass;
+
+BasicBlock *InsertPreheaderForLoop(Loop *L, Pass *P);
+
+}
+
+#endif

lib/Transforms/Utils/LoopSimplify.cpp

@@ -59,6 +59,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Utils/LoopSimplify.h"
 using namespace llvm;
 
 STATISTIC(NumInserted, "Number of pre-header or exit blocks inserted");
@@ -100,16 +101,16 @@ namespace {
   private:
     bool ProcessLoop(Loop *L, LPPassManager &LPM);
     BasicBlock *RewriteLoopExitBlock(Loop *L, BasicBlock *Exit);
-    BasicBlock *InsertPreheaderForLoop(Loop *L);
     Loop *SeparateNestedLoop(Loop *L, LPPassManager &LPM,
                              BasicBlock *Preheader);
     BasicBlock *InsertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader);
-    void PlaceSplitBlockCarefully(BasicBlock *NewBB,
-                                  SmallVectorImpl<BasicBlock*> &SplitPreds,
-                                  Loop *L);
   };
 }
 
+static void PlaceSplitBlockCarefully(BasicBlock *NewBB,
+                                     SmallVectorImpl<BasicBlock*> &SplitPreds,
+                                     Loop *L);
+
 char LoopSimplify::ID = 0;
 INITIALIZE_PASS_BEGIN(LoopSimplify, "loop-simplify",
                 "Canonicalize natural loops", true, false)
@@ -208,7 +209,7 @@ ReprocessLoop:
   // Does the loop already have a preheader?  If so, don't insert one.
   BasicBlock *Preheader = L->getLoopPreheader();
   if (!Preheader) {
-    Preheader = InsertPreheaderForLoop(L);
+    Preheader = InsertPreheaderForLoop(L, this);
     if (Preheader) {
       ++NumInserted;
       Changed = true;
@@ -367,7 +368,7 @@ ReprocessLoop:
 /// preheader, this method is called to insert one.  This method has two phases:
 /// preheader insertion and analysis updating.
 ///
-BasicBlock *LoopSimplify::InsertPreheaderForLoop(Loop *L) {
+BasicBlock *llvm::InsertPreheaderForLoop(Loop *L, Pass *PP) {
   BasicBlock *Header = L->getHeader();
 
   // Compute the set of predecessors of the loop that are not in the loop.
@@ -390,11 +391,11 @@ BasicBlock *LoopSimplify::InsertPreheaderForLoop(Loop *L) {
   BasicBlock *PreheaderBB;
   if (!Header->isLandingPad()) {
     PreheaderBB = SplitBlockPredecessors(Header, OutsideBlocks, ".preheader",
-                                         this);
+                                         PP);
   } else {
     SmallVector<BasicBlock*, 2> NewBBs;
     SplitLandingPadPredecessors(Header, OutsideBlocks, ".preheader",
-                                ".split-lp", this, NewBBs);
+                                ".split-lp", PP, NewBBs);
     PreheaderBB = NewBBs[0];
   }
 
@@ -491,9 +492,9 @@ static PHINode *FindPHIToPartitionLoops(Loop *L, DominatorTree *DT,
 // PlaceSplitBlockCarefully - If the block isn't already, move the new block to
 // right after some 'outside block' block.  This prevents the preheader from
 // being placed inside the loop body, e.g. when the loop hasn't been rotated.
-void LoopSimplify::PlaceSplitBlockCarefully(BasicBlock *NewBB,
-                                       SmallVectorImpl<BasicBlock*> &SplitPreds,
-                                            Loop *L) {
+void PlaceSplitBlockCarefully(BasicBlock *NewBB,
+                              SmallVectorImpl<BasicBlock*> &SplitPreds,
+                              Loop *L) {
   // Check to see if NewBB is already well placed.
   Function::iterator BBI = NewBB; --BBI;
   for (unsigned i = 0, e = SplitPreds.size(); i != e; ++i) {