[polly] r184128 - revert r183799: scop detection: remove an iteration over all uses

[Sebastian Pop]

Author: spop
Date: Mon Jun 17 16:43:10 2013
New Revision: 184128

URL: http://llvm.org/viewvc/llvm-project?rev=184128&view=rev
Log:
revert r183799: scop detection: remove an iteration over all uses

Modified:
    polly/trunk/lib/Analysis/ScopDetection.cpp

Modified: polly/trunk/lib/Analysis/ScopDetection.cpp
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/lib/Analysis/ScopDetection.cpp?rev=184128&r1=184127&r2=184128&view=diff
==============================================================================
--- polly/trunk/lib/Analysis/ScopDetection.cpp (original)
+++ polly/trunk/lib/Analysis/ScopDetection.cpp Mon Jun 17 16:43:10 2013
@@ -142,6 +142,7 @@ BADSCOP_STAT(IndEdge, "Found invalid reg
 BADSCOP_STAT(LoopBound, "Loop bounds can not be computed");
 BADSCOP_STAT(FuncCall, "Function call with side effects appeared");
 BADSCOP_STAT(AffFunc, "Expression not affine");
+BADSCOP_STAT(Scalar, "Found scalar dependency");
 BADSCOP_STAT(Alias, "Found base address alias");
 BADSCOP_STAT(SimpleLoop, "Loop not in -loop-simplify form");
 BADSCOP_STAT(Other, "Others");
@@ -326,6 +327,30 @@ bool ScopDetection::isValidMemoryAccess(
   return true;
 }
 
+bool ScopDetection::hasScalarDependency(Instruction &Inst,
+                                        Region &RefRegion) const {
+  for (Instruction::use_iterator UI = Inst.use_begin(), UE = Inst.use_end();
+       UI != UE; ++UI)
+    if (Instruction *Use = dyn_cast<Instruction>(*UI))
+      if (!RefRegion.contains(Use->getParent())) {
+        // DirtyHack 1: PHINode user outside the Scop is not allow, if this
+        // PHINode is induction variable, the scalar to array transform may
+        // break it and introduce a non-indvar PHINode, which is not allow in
+        // Scop.
+        // This can be fix by:
+        // Introduce a IndependentBlockPrepare pass, which translate all
+        // PHINodes not in Scop to array.
+        // The IndependentBlockPrepare pass can also split the entry block of
+        // the function to hold the alloca instruction created by scalar to
+        // array.  and split the exit block of the Scop so the new create load
+        // instruction for escape users will not break other Scops.
+        if (isa<PHINode>(Use))
+          return true;
+      }
+
+  return false;
+}
+
 bool ScopDetection::isValidInstruction(Instruction &Inst,
                                        DetectionContext &Context) const {
   if (PHINode *PN = dyn_cast<PHINode>(&Inst))
@@ -337,6 +362,10 @@ bool ScopDetection::isValidInstruction(I
         INVALID(IndVar, "Non canonical PHI node: " << Inst);
     }
 
+  // Scalar dependencies are not allowed.
+  if (hasScalarDependency(Inst, Context.CurRegion))
+    INVALID(Scalar, "Scalar dependency found: " << Inst);
+
   // We only check the call instruction but not invoke instruction.
   if (CallInst *CI = dyn_cast<CallInst>(&Inst)) {
     if (isValidCallInst(*CI))