vendor/llvm/llvm-r114020

1 files changed, 72 insertions, 42 deletions

diff --git a/lib/Analysis/ScalarEvolutionNormalization.cpp b/lib/Analysis/ScalarEvolutionNormalization.cpp
index 563fd2fa96e2e..ac36cef89ebb5 100644
--- a/lib/Analysis/ScalarEvolutionNormalization.cpp
+++ b/lib/Analysis/ScalarEvolutionNormalization.cpp
@@ -26,7 +26,7 @@ using namespace llvm;
 /// post-inc value when we cannot) or it can end up adding extra live-ranges to
 /// the loop, resulting in reg-reg copies (if we use the pre-inc value when we
 /// should use the post-inc value).
-static bool IVUseShouldUsePostIncValue(Instruction *User, Instruction *IV,
+static bool IVUseShouldUsePostIncValue(Instruction *User, Value *Operand,
                                        const Loop *L, DominatorTree *DT) {
   // If the user is in the loop, use the preinc value.
   if (L->contains(User)) return false;
@@ -45,20 +45,17 @@ static bool IVUseShouldUsePostIncValue(Instruction *User, Instruction *IV,
   // their uses occur in the predecessor block, not the block the PHI lives in)
   // should still use the post-inc value.  Check for this case now.
   PHINode *PN = dyn_cast<PHINode>(User);
-  if (!PN) return false;  // not a phi, not dominated by latch block.
+  if (!PN || !Operand) return false; // not a phi, not dominated by latch block.
 
-  // Look at all of the uses of IV by the PHI node.  If any use corresponds to
-  // a block that is not dominated by the latch block, give up and use the
+  // Look at all of the uses of Operand by the PHI node.  If any use corresponds
+  // to a block that is not dominated by the latch block, give up and use the
   // preincremented value.
-  unsigned NumUses = 0;
   for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
-    if (PN->getIncomingValue(i) == IV) {
-      ++NumUses;
-      if (!DT->dominates(LatchBlock, PN->getIncomingBlock(i)))
-        return false;
-    }
+    if (PN->getIncomingValue(i) == Operand &&
+        !DT->dominates(LatchBlock, PN->getIncomingBlock(i)))
+      return false;
 
-  // Okay, all uses of IV by PN are in predecessor blocks that really are
+  // Okay, all uses of Operand by PN are in predecessor blocks that really are
   // dominated by the latch block.  Use the post-incremented value.
   return true;
 }
@@ -72,6 +69,7 @@ const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
                                          DominatorTree &DT) {
   if (isa<SCEVConstant>(S) || isa<SCEVUnknown>(S))
     return S;
+
   if (const SCEVCastExpr *X = dyn_cast<SCEVCastExpr>(S)) {
     const SCEV *O = X->getOperand();
     const SCEV *N = TransformForPostIncUse(Kind, O, User, OperandValToReplace,
@@ -85,9 +83,69 @@ const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
       }
     return S;
   }
+
+  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
+    // An addrec. This is the interesting part.
+    SmallVector<const SCEV *, 8> Operands;
+    const Loop *L = AR->getLoop();
+    // The addrec conceptually uses its operands at loop entry.
+    Instruction *LUser = L->getHeader()->begin();
+    // Transform each operand.
+    for (SCEVNAryExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
+         I != E; ++I) {
+      const SCEV *O = *I;
+      const SCEV *N = TransformForPostIncUse(Kind, O, LUser, 0, Loops, SE, DT);
+      Operands.push_back(N);
+    }
+    const SCEV *Result = SE.getAddRecExpr(Operands, L);
+    switch (Kind) {
+    default: llvm_unreachable("Unexpected transform name!");
+    case NormalizeAutodetect:
+      if (IVUseShouldUsePostIncValue(User, OperandValToReplace, L, &DT)) {
+        const SCEV *TransformedStep =
+          TransformForPostIncUse(Kind, AR->getStepRecurrence(SE),
+                                 User, OperandValToReplace, Loops, SE, DT);
+        Result = SE.getMinusSCEV(Result, TransformedStep);
+        Loops.insert(L);
+      }
+#if 0
+      // This assert is conceptually correct, but ScalarEvolution currently
+      // sometimes fails to canonicalize two equal SCEVs to exactly the same
+      // form. It's possibly a pessimization when this happens, but it isn't a
+      // correctness problem, so disable this assert for now.
+      assert(S == TransformForPostIncUse(Denormalize, Result,
+                                         User, OperandValToReplace,
+                                         Loops, SE, DT) &&
+             "SCEV normalization is not invertible!");
+#endif
+      break;
+    case Normalize:
+      if (Loops.count(L)) {
+        const SCEV *TransformedStep =
+          TransformForPostIncUse(Kind, AR->getStepRecurrence(SE),
+                                 User, OperandValToReplace, Loops, SE, DT);
+        Result = SE.getMinusSCEV(Result, TransformedStep);
+      }
+#if 0
+      // See the comment on the assert above.
+      assert(S == TransformForPostIncUse(Denormalize, Result,
+                                         User, OperandValToReplace,
+                                         Loops, SE, DT) &&
+             "SCEV normalization is not invertible!");
+#endif
+      break;
+    case Denormalize:
+      if (Loops.count(L))
+        Result = cast<SCEVAddRecExpr>(Result)->getPostIncExpr(SE);
+      break;
+    }
+    return Result;
+  }
+
   if (const SCEVNAryExpr *X = dyn_cast<SCEVNAryExpr>(S)) {
     SmallVector<const SCEV *, 8> Operands;
     bool Changed = false;
+    // Transform each operand.
     for (SCEVNAryExpr::op_iterator I = X->op_begin(), E = X->op_end();
          I != E; ++I) {
       const SCEV *O = *I;
@@ -96,37 +154,7 @@ const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
       Changed |= N != O;
       Operands.push_back(N);
     }
-    if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
-      // An addrec. This is the interesting part.
-      const Loop *L = AR->getLoop();
-      const SCEV *Result = SE.getAddRecExpr(Operands, L);
-      switch (Kind) {
-      default: llvm_unreachable("Unexpected transform name!");
-      case NormalizeAutodetect:
-        if (Instruction *OI = dyn_cast<Instruction>(OperandValToReplace))
-          if (IVUseShouldUsePostIncValue(User, OI, L, &DT)) {
-            const SCEV *TransformedStep =
-              TransformForPostIncUse(Kind, AR->getStepRecurrence(SE),
-                                     User, OperandValToReplace, Loops, SE, DT);
-            Result = SE.getMinusSCEV(Result, TransformedStep);
-            Loops.insert(L);
-          }
-        break;
-      case Normalize:
-        if (Loops.count(L)) {
-          const SCEV *TransformedStep =
-            TransformForPostIncUse(Kind, AR->getStepRecurrence(SE),
-                                   User, OperandValToReplace, Loops, SE, DT);
-          Result = SE.getMinusSCEV(Result, TransformedStep);
-        }
-        break;
-      case Denormalize:
-        if (Loops.count(L))
-          Result = SE.getAddExpr(Result, AR->getStepRecurrence(SE));
-        break;
-      }
-      return Result;
-    }
+    // If any operand actually changed, return a transformed result.
     if (Changed)
       switch (S->getSCEVType()) {
       case scAddExpr: return SE.getAddExpr(Operands);
@@ -137,6 +165,7 @@ const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
       }
     return S;
   }
+
   if (const SCEVUDivExpr *X = dyn_cast<SCEVUDivExpr>(S)) {
     const SCEV *LO = X->getLHS();
     const SCEV *RO = X->getRHS();
@@ -148,6 +177,7 @@ const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
       return SE.getUDivExpr(LN, RN);
     return S;
   }
+
   llvm_unreachable("Unexpected SCEV kind!");
   return 0;
 }