Fix SCEVEXpander to handle arbitrary phi expansion. Includes two

related bug fixes and corresponding assertions for uninitialized data
and missing NULL check. Test cases will be included with the new LFTR.

llvm-svn: 135333

2 files changed, 20 insertions, 9 deletions

diff --git a/llvm/include/llvm/Analysis/ScalarEvolutionExpander.h b/llvm/include/llvm/Analysis/ScalarEvolutionExpander.h
index 647a7dcf518..a8c03b2219e 100644
--- a/llvm/include/llvm/Analysis/ScalarEvolutionExpander.h
+++ b/llvm/include/llvm/Analysis/ScalarEvolutionExpander.h
@@ -72,8 +72,8 @@ namespace llvm {
   public:
     /// SCEVExpander - Construct a SCEVExpander in "canonical" mode.
     explicit SCEVExpander(ScalarEvolution &se, const char *name)
-      : SE(se), IVName(name), IVIncInsertLoop(0), CanonicalMode(true),
-        Builder(se.getContext(), TargetFolder(se.TD)) {}
+      : SE(se), IVName(name), IVIncInsertLoop(0), IVIncInsertPos(0),
+        CanonicalMode(true), Builder(se.getContext(), TargetFolder(se.TD)) {}
 
     /// clear - Erase the contents of the InsertedExpressions map so that users
     /// trying to expand the same expression into multiple BasicBlocks or
diff --git a/llvm/lib/Analysis/ScalarEvolutionExpander.cpp b/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
index 9f6063e56ac..478f555fecc 100644
--- a/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -19,6 +19,7 @@
 #include "llvm/LLVMContext.h"
 #include "llvm/Target/TargetData.h"
 #include "llvm/ADT/STLExtras.h"
+
 using namespace llvm;
 
 /// ReuseOrCreateCast - Arrange for there to be a cast of V to Ty at IP,
@@ -848,6 +849,8 @@ SCEVExpander::getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
                                         const Loop *L,
                                         const Type *ExpandTy,
                                         const Type *IntTy) {
+  assert(!IVIncInsertLoop || IVIncInsertPos && "Uninitialized insert position");
+
   // Reuse a previously-inserted PHI, if present.
   for (BasicBlock::iterator I = L->getHeader()->begin();
        PHINode *PN = dyn_cast<PHINode>(I); ++I)
@@ -872,13 +875,15 @@ SCEVExpander::getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
           // If any of the operands don't dominate the insert position, bail.
           // Addrec operands are always loop-invariant, so this can only happen
           // if there are instructions which haven't been hoisted.
-          for (User::op_iterator OI = IncV->op_begin()+1,
-               OE = IncV->op_end(); OI != OE; ++OI)
-            if (Instruction *OInst = dyn_cast<Instruction>(OI))
-              if (!SE.DT->dominates(OInst, IVIncInsertPos)) {
-                IncV = 0;
-                break;
-              }
+          if (L == IVIncInsertLoop) {
+            for (User::op_iterator OI = IncV->op_begin()+1,
+                   OE = IncV->op_end(); OI != OE; ++OI)
+              if (Instruction *OInst = dyn_cast<Instruction>(OI))
+                if (!SE.DT->dominates(OInst, IVIncInsertPos)) {
+                  IncV = 0;
+                  break;
+                }
+          }
           if (!IncV)
             break;
           // Advance to the next instruction.
@@ -920,6 +925,12 @@ SCEVExpander::getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
   Value *StartV = expandCodeFor(Normalized->getStart(), ExpandTy,
                                 L->getHeader()->begin());
 
+  // StartV must be hoisted into L's preheader to dominate the new phi.
+  Instruction *StartI = dyn_cast<Instruction>(StartV);
+  assert(!StartI || SE.DT->properlyDominates(StartI->getParent(),
+                                             L->getHeader()) && "");
+  (void)StartI;
+
   // Expand code for the step value. Insert instructions right before the
   // terminator corresponding to the back-edge. Do this before creating the PHI
   // so that PHI reuse code doesn't see an incomplete PHI. If the stride is