Temporarily revert r110987 as it's causing some miscompares in

vector heavy code.  I'll re-enable when we've tracked down the problem.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111318 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 64 insertions, 123 deletions

diff --git a/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index fea85094c4..a58124d703 100644
--- a/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -448,8 +448,10 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
   if (isa<UndefValue>(SVI.getOperand(2)))
     return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType()));
   
-  unsigned VWidth = Mask.size();
-  unsigned LHSWidth = cast<VectorType>(LHS->getType())->getNumElements();
+  unsigned VWidth = cast<VectorType>(SVI.getType())->getNumElements();
+  
+  if (VWidth != cast<VectorType>(LHS->getType())->getNumElements())
+    return 0;
   
   APInt UndefElts(VWidth, 0);
   APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
@@ -462,12 +464,14 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
   // Canonicalize shuffle(x    ,x,mask) -> shuffle(x, undef,mask')
   // Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask').
   if (LHS == RHS || isa<UndefValue>(LHS)) {
-    if (isa<UndefValue>(LHS) && LHS == RHS)
-      return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType()));
+    if (isa<UndefValue>(LHS) && LHS == RHS) {
+      // shuffle(undef,undef,mask) -> undef.
+      return ReplaceInstUsesWith(SVI, LHS);
+    }
     
     // Remap any references to RHS to use LHS.
     std::vector<Constant*> Elts;
-    for (unsigned i = 0, e = LHSWidth; i != VWidth; ++i) {
+    for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
       if (Mask[i] >= 2*e)
         Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext())));
       else {
@@ -491,130 +495,67 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
   }
   
   // Analyze the shuffle, are the LHS or RHS and identity shuffles?
-  if (VWidth == LHSWidth) {
-    bool isLHSID = true, isRHSID = true;
-    
-    for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
-      if (Mask[i] >= e*2) continue;  // Ignore undef values.
-      // Is this an identity shuffle of the LHS value?
-      isLHSID &= (Mask[i] == i);
-      
-      // Is this an identity shuffle of the RHS value?
-      isRHSID &= (Mask[i]-e == i);
-    }
+  bool isLHSID = true, isRHSID = true;
   
-    // Eliminate identity shuffles.
-    if (isLHSID) return ReplaceInstUsesWith(SVI, LHS);
-    if (isRHSID) return ReplaceInstUsesWith(SVI, RHS);
-  }
-  
-  // Check for a handful of important shuffle(shuffle()) combinations.
-  ShuffleVectorInst *LSVI = dyn_cast<ShuffleVectorInst>(LHS);
-  if (!LSVI)
-    return MadeChange ? &SVI : 0;
-
-  LHS = LSVI->getOperand(0);
-  std::vector<unsigned> LHSMask = getShuffleMask(LSVI);
-  unsigned LHSInNElts = cast<VectorType>(LHS->getType())->getNumElements();
-  
-  // If the LHS is an identity shuffle, or if SVI + LHS form a full unpack 
-  // operation, merge the LHS and SVI shuffles. This allows llvm to emit 
-  // efficient code for matrix transposes written with generic vector ops.
-  bool isLHSLoExtract = true, isLHSHiExtract = true;
-  bool isUnpackLo = isPowerOf2_32(VWidth);
-  bool isUnpackHi = isPowerOf2_32(VWidth);
-  for (unsigned i = 0, e = LHSMask.size(); i != e; ++i) {
-    if (LHSMask[i] >= LHSInNElts*2) continue; // Ignore undef values;
-    isLHSLoExtract &= (LHSMask[i] == i);
-    isLHSHiExtract &= (LHSMask[i] == i+(LHSInNElts/2));
-    isUnpackLo &= (LHSMask[i] == (i/2));
-    isUnpackHi &= (LHSMask[i] == (i/2) + (e/2));
-  }
-  for (unsigned i = 0, e = Mask.size(); i != e && (isUnpackLo || isUnpackHi);
-       i += 2) {
-    isUnpackLo &= (Mask[i] == i) && (Mask[i+1] == (i/2)+e);
-    isUnpackHi &= (Mask[i] == i) && (Mask[i+1] == (i/2)+e+(e/2));
-  }
-  if ((isLHSLoExtract || isLHSHiExtract || isUnpackLo || isUnpackHi) && 
-      (isa<UndefValue>(RHS) || (LHSWidth == LHSInNElts))) {
-    std::vector<Constant*> Elts;
-    for (unsigned i = 0, e = VWidth; i != e; ++i) {
-      if (Mask[i] >= 2*LHSWidth)
-        Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext())));
-      else if (Mask[i] >= e)
-        Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()),
-                                        Mask[i]));
-      else
-        Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()),
-                                        LHSMask[Mask[i]]));
-    }
-    if (isa<UndefValue>(RHS))
-      RHS = UndefValue::get(LHS->getType());
-    return new ShuffleVectorInst(LHS, RHS, ConstantVector::get(Elts));
-  }
-
-  // If rhs is shuffle + identity, propagate.
-  if (ShuffleVectorInst *RSVI = dyn_cast<ShuffleVectorInst>(RHS)) {
-    std::vector<unsigned> RHSMask = getShuffleMask(RSVI);
-    unsigned RHSInNElts = 
-      cast<VectorType>(RSVI->getOperand(0)->getType())->getNumElements();
-
-    // If rhs is identity, propagate
-    bool isRHSLoExtract = true, isRHSHiExtract = true;
-    for (unsigned i = 0, e = RHSMask.size(); i != e; ++i) {
-      if (RHSMask[i] >= RHSInNElts*2) continue; // Ignore undef values;
-      isRHSLoExtract &= (RHSMask[i] == i);
-      isRHSHiExtract &= (RHSMask[i] == i+(RHSInNElts/2));
-    }
-    if ((isRHSLoExtract || isRHSHiExtract) && (LHSWidth == RHSInNElts)) {
-      std::vector<Constant*> Elts;
-      for (unsigned i = 0, e = VWidth; i != e; ++i) {
-        if (Mask[i] >= 2*LHSWidth)
-          Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext())));
-        else if (Mask[i] < LHSWidth)
-          Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()),
-                                          Mask[i]));
-        else
-          Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()),
-                                          RHSMask[Mask[i]-LHSWidth]+LHSWidth));
-      }
-      SVI.setOperand(1, RSVI->getOperand(0));
-      SVI.setOperand(2, ConstantVector::get(Elts));
-      return &SVI;
-    }
+  for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
+    if (Mask[i] >= e*2) continue;  // Ignore undef values.
+    // Is this an identity shuffle of the LHS value?
+    isLHSID &= (Mask[i] == i);
+    
+    // Is this an identity shuffle of the RHS value?
+    isRHSID &= (Mask[i]-e == i);
   }
   
-  // Be extremely conservative when merging shufflevector instructions.  It is 
-  // difficult for the code generator to recognize a merged shuffle, which 
-  // usually leads to worse code from merging a shuffle.
-  if (!isa<UndefValue>(RHS))
-    return MadeChange ? &SVI : 0;
-  
-  // If the merged shuffle mask is one of the two input shuffle masks, which
-  // just removes one instruction.  This should handle splat(splat) -> splat.
-  if (LHSMask.size() == Mask.size()) {
-    std::vector<unsigned> NewMask;
-    for (unsigned i = 0, e = Mask.size(); i != e; ++i)
-      if (Mask[i] >= e)
-        NewMask.push_back(2*e);
-      else
-        NewMask.push_back(LHSMask[Mask[i]]);
-    
-    // If the result mask is equal to the src shuffle or this shuffle mask,
-    // do the replacement.
-    if (NewMask == LHSMask || NewMask == Mask) {
-      std::vector<Constant*> Elts;
-      for (unsigned i = 0, e = NewMask.size(); i != e; ++i) {
-        if (NewMask[i] >= LHSInNElts*2) {
-          Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext())));
-        } else {
-          Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()),
-                                          NewMask[i]));
+  // Eliminate identity shuffles.
+  if (isLHSID) return ReplaceInstUsesWith(SVI, LHS);
+  if (isRHSID) return ReplaceInstUsesWith(SVI, RHS);
+  
+  // If the LHS is a shufflevector itself, see if we can combine it with this
+  // one without producing an unusual shuffle.  Here we are really conservative:
+  // we are absolutely afraid of producing a shuffle mask not in the input
+  // program, because the code gen may not be smart enough to turn a merged
+  // shuffle into two specific shuffles: it may produce worse code.  As such,
+  // we only merge two shuffles if the result is one of the two input shuffle
+  // masks.  In this case, merging the shuffles just removes one instruction,
+  // which we know is safe.  This is good for things like turning:
+  // (splat(splat)) -> splat.
+  if (ShuffleVectorInst *LHSSVI = dyn_cast<ShuffleVectorInst>(LHS)) {
+    if (isa<UndefValue>(RHS)) {
+      std::vector<unsigned> LHSMask = getShuffleMask(LHSSVI);
+      
+      if (LHSMask.size() == Mask.size()) {
+        std::vector<unsigned> NewMask;
+        for (unsigned i = 0, e = Mask.size(); i != e; ++i)
+          if (Mask[i] >= e)
+            NewMask.push_back(2*e);
+          else
+            NewMask.push_back(LHSMask[Mask[i]]);
+        
+        // If the result mask is equal to the src shuffle or this
+        // shuffle mask, do the replacement.
+        if (NewMask == LHSMask || NewMask == Mask) {
+          unsigned LHSInNElts =
+          cast<VectorType>(LHSSVI->getOperand(0)->getType())->
+          getNumElements();
+          std::vector<Constant*> Elts;
+          for (unsigned i = 0, e = NewMask.size(); i != e; ++i) {
+            if (NewMask[i] >= LHSInNElts*2) {
+              Elts.push_back(UndefValue::get(
+                                             Type::getInt32Ty(SVI.getContext())));
+            } else {
+              Elts.push_back(ConstantInt::get(
+                                              Type::getInt32Ty(SVI.getContext()),
+                                              NewMask[i]));
+            }
+          }
+          return new ShuffleVectorInst(LHSSVI->getOperand(0),
+                                       LHSSVI->getOperand(1),
+                                       ConstantVector::get(Elts));
         }
       }
-      return new ShuffleVectorInst(LHS, LSVI->getOperand(1),
-                                   ConstantVector::get(Elts));
     }
   }
+  
   return MadeChange ? &SVI : 0;
 }
+