1 files changed, 105 insertions, 8 deletions

diff --git a/contrib/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp b/contrib/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
index 460f6eb..f1aa98b 100644
--- a/contrib/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
+++ b/contrib/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
@@ -15,6 +15,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Transforms/Utils/Local.h"
 using namespace llvm;
 
 #define DEBUG_TYPE "instcombine"
@@ -245,7 +246,7 @@ Instruction *InstCombiner::FoldPHIArgGEPIntoPHI(PHINode &PN) {
 /// non-address-taken alloca.  Doing so will cause us to not promote the alloca
 /// to a register.
 static bool isSafeAndProfitableToSinkLoad(LoadInst *L) {
-  BasicBlock::iterator BBI = L, E = L->getParent()->end();
+  BasicBlock::iterator BBI = L->getIterator(), E = L->getParent()->end();
 
   for (++BBI; BBI != E; ++BBI)
     if (BBI->mayWriteToMemory())
@@ -349,24 +350,40 @@ Instruction *InstCombiner::FoldPHIArgLoadIntoPHI(PHINode &PN) {
 
   Value *InVal = FirstLI->getOperand(0);
   NewPN->addIncoming(InVal, PN.getIncomingBlock(0));
+  LoadInst *NewLI = new LoadInst(NewPN, "", isVolatile, LoadAlignment);
+
+  unsigned KnownIDs[] = {
+    LLVMContext::MD_tbaa,
+    LLVMContext::MD_range,
+    LLVMContext::MD_invariant_load,
+    LLVMContext::MD_alias_scope,
+    LLVMContext::MD_noalias,
+    LLVMContext::MD_nonnull,
+    LLVMContext::MD_align,
+    LLVMContext::MD_dereferenceable,
+    LLVMContext::MD_dereferenceable_or_null,
+  };
 
-  // Add all operands to the new PHI.
+  for (unsigned ID : KnownIDs)
+    NewLI->setMetadata(ID, FirstLI->getMetadata(ID));
+
+  // Add all operands to the new PHI and combine TBAA metadata.
   for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
-    Value *NewInVal = cast<LoadInst>(PN.getIncomingValue(i))->getOperand(0);
+    LoadInst *LI = cast<LoadInst>(PN.getIncomingValue(i));
+    combineMetadata(NewLI, LI, KnownIDs);
+    Value *NewInVal = LI->getOperand(0);
     if (NewInVal != InVal)
       InVal = nullptr;
     NewPN->addIncoming(NewInVal, PN.getIncomingBlock(i));
   }
 
-  Value *PhiVal;
   if (InVal) {
     // The new PHI unions all of the same values together.  This is really
     // common, so we handle it intelligently here for compile-time speed.
-    PhiVal = InVal;
+    NewLI->setOperand(0, InVal);
     delete NewPN;
   } else {
     InsertNewInstBefore(NewPN, PN);
-    PhiVal = NewPN;
   }
 
   // If this was a volatile load that we are merging, make sure to loop through
@@ -376,17 +393,94 @@ Instruction *InstCombiner::FoldPHIArgLoadIntoPHI(PHINode &PN) {
     for (Value *IncValue : PN.incoming_values())
       cast<LoadInst>(IncValue)->setVolatile(false);
 
-  LoadInst *NewLI = new LoadInst(PhiVal, "", isVolatile, LoadAlignment);
   NewLI->setDebugLoc(FirstLI->getDebugLoc());
   return NewLI;
 }
 
+/// TODO: This function could handle other cast types, but then it might
+/// require special-casing a cast from the 'i1' type. See the comment in
+/// FoldPHIArgOpIntoPHI() about pessimizing illegal integer types.
+Instruction *InstCombiner::FoldPHIArgZextsIntoPHI(PHINode &Phi) {
+  // We cannot create a new instruction after the PHI if the terminator is an
+  // EHPad because there is no valid insertion point.
+  if (TerminatorInst *TI = Phi.getParent()->getTerminator())
+    if (TI->isEHPad())
+      return nullptr;
+
+  // Early exit for the common case of a phi with two operands. These are
+  // handled elsewhere. See the comment below where we check the count of zexts
+  // and constants for more details.
+  unsigned NumIncomingValues = Phi.getNumIncomingValues();
+  if (NumIncomingValues < 3)
+    return nullptr;
 
+  // Find the narrower type specified by the first zext.
+  Type *NarrowType = nullptr;
+  for (Value *V : Phi.incoming_values()) {
+    if (auto *Zext = dyn_cast<ZExtInst>(V)) {
+      NarrowType = Zext->getSrcTy();
+      break;
+    }
+  }
+  if (!NarrowType)
+    return nullptr;
+
+  // Walk the phi operands checking that we only have zexts or constants that
+  // we can shrink for free. Store the new operands for the new phi.
+  SmallVector<Value *, 4> NewIncoming;
+  unsigned NumZexts = 0;
+  unsigned NumConsts = 0;
+  for (Value *V : Phi.incoming_values()) {
+    if (auto *Zext = dyn_cast<ZExtInst>(V)) {
+      // All zexts must be identical and have one use.
+      if (Zext->getSrcTy() != NarrowType || !Zext->hasOneUse())
+        return nullptr;
+      NewIncoming.push_back(Zext->getOperand(0));
+      NumZexts++;
+    } else if (auto *C = dyn_cast<Constant>(V)) {
+      // Make sure that constants can fit in the new type.
+      Constant *Trunc = ConstantExpr::getTrunc(C, NarrowType);
+      if (ConstantExpr::getZExt(Trunc, C->getType()) != C)
+        return nullptr;
+      NewIncoming.push_back(Trunc);
+      NumConsts++;
+    } else {
+      // If it's not a cast or a constant, bail out.
+      return nullptr;
+    }
+  }
+
+  // The more common cases of a phi with no constant operands or just one
+  // variable operand are handled by FoldPHIArgOpIntoPHI() and FoldOpIntoPhi()
+  // respectively. FoldOpIntoPhi() wants to do the opposite transform that is
+  // performed here. It tries to replicate a cast in the phi operand's basic
+  // block to expose other folding opportunities. Thus, InstCombine will
+  // infinite loop without this check.
+  if (NumConsts == 0 || NumZexts < 2)
+    return nullptr;
+
+  // All incoming values are zexts or constants that are safe to truncate.
+  // Create a new phi node of the narrow type, phi together all of the new
+  // operands, and zext the result back to the original type.
+  PHINode *NewPhi = PHINode::Create(NarrowType, NumIncomingValues,
+                                    Phi.getName() + ".shrunk");
+  for (unsigned i = 0; i != NumIncomingValues; ++i)
+    NewPhi->addIncoming(NewIncoming[i], Phi.getIncomingBlock(i));
+
+  InsertNewInstBefore(NewPhi, Phi);
+  return CastInst::CreateZExtOrBitCast(NewPhi, Phi.getType());
+}
 
 /// If all operands to a PHI node are the same "unary" operator and they all are
 /// only used by the PHI, PHI together their inputs, and do the operation once,
 /// to the result of the PHI.
 Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
+  // We cannot create a new instruction after the PHI if the terminator is an
+  // EHPad because there is no valid insertion point.
+  if (TerminatorInst *TI = PN.getParent()->getTerminator())
+    if (TI->isEHPad())
+      return nullptr;
+
   Instruction *FirstInst = cast<Instruction>(PN.getIncomingValue(0));
 
   if (isa<GetElementPtrInst>(FirstInst))
@@ -740,7 +834,7 @@ Instruction *InstCombiner::SliceUpIllegalIntegerPHI(PHINode &FirstPhi) {
         }
 
         // Otherwise, do an extract in the predecessor.
-        Builder->SetInsertPoint(Pred, Pred->getTerminator());
+        Builder->SetInsertPoint(Pred->getTerminator());
         Value *Res = InVal;
         if (Offset)
           Res = Builder->CreateLShr(Res, ConstantInt::get(InVal->getType(),
@@ -787,6 +881,9 @@ Instruction *InstCombiner::visitPHINode(PHINode &PN) {
   if (Value *V = SimplifyInstruction(&PN, DL, TLI, DT, AC))
     return ReplaceInstUsesWith(PN, V);
 
+  if (Instruction *Result = FoldPHIArgZextsIntoPHI(PN))
+    return Result;
+
   // If all PHI operands are the same operation, pull them through the PHI,
   // reducing code size.
   if (isa<Instruction>(PN.getIncomingValue(0)) &&