3 files changed, 67 insertions, 4 deletions
diff --git a/lib/Analysis/LoopInfo.cpp b/lib/Analysis/LoopInfo.cpp
index eb355537f7..858cc642f4 100644
--- a/lib/Analysis/LoopInfo.cpp
+++ b/lib/Analysis/LoopInfo.cpp
@@ -19,6 +19,7 @@
 #include "llvm/Instructions.h"
 #include "llvm/Analysis/Dominators.h"
 #include "llvm/Analysis/LoopIterator.h"
+#include "llvm/Analysis/ValueTracking.h"
 #include "llvm/Assembly/Writer.h"
 #include "llvm/Support/CFG.h"
 #include "llvm/Support/CommandLine.h"
@@ -95,7 +96,7 @@ bool Loop::makeLoopInvariant(Instruction *I, bool &Changed,
   // Test if the value is already loop-invariant.
   if (isLoopInvariant(I))
     return true;
-  if (!I->isSafeToSpeculativelyExecute())
+  if (!isSafeToSpeculativelyExecute(I))
     return false;
   if (I->mayReadFromMemory())
     return false;
diff --git a/lib/Analysis/PHITransAddr.cpp b/lib/Analysis/PHITransAddr.cpp
index 86d915ff0a..80ea219cd8 100644
--- a/lib/Analysis/PHITransAddr.cpp
+++ b/lib/Analysis/PHITransAddr.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Analysis/PHITransAddr.h"
+#include "llvm/Analysis/ValueTracking.h"
 #include "llvm/Constants.h"
 #include "llvm/Instructions.h"
 #include "llvm/Analysis/Dominators.h"
@@ -27,7 +28,7 @@ static bool CanPHITrans(Instruction *Inst) {
     return true;
 
   if (isa<CastInst>(Inst) &&
-      Inst->isSafeToSpeculativelyExecute())
+      isSafeToSpeculativelyExecute(Inst))
     return true;
 
   if (Inst->getOpcode() == Instruction::Add &&
@@ -186,7 +187,7 @@ Value *PHITransAddr::PHITranslateSubExpr(Value *V, BasicBlock *CurBB,
   // operands need to be phi translated, and if so, reconstruct it.
 
   if (CastInst *Cast = dyn_cast<CastInst>(Inst)) {
-    if (!Cast->isSafeToSpeculativelyExecute()) return 0;
+    if (!isSafeToSpeculativelyExecute(Cast)) return 0;
     Value *PHIIn = PHITranslateSubExpr(Cast->getOperand(0), CurBB, PredBB, DT);
     if (PHIIn == 0) return 0;
     if (PHIIn == Cast->getOperand(0))
@@ -381,7 +382,7 @@ InsertPHITranslatedSubExpr(Value *InVal, BasicBlock *CurBB,
 
   // Handle cast of PHI translatable value.
   if (CastInst *Cast = dyn_cast<CastInst>(Inst)) {
-    if (!Cast->isSafeToSpeculativelyExecute()) return 0;
+    if (!isSafeToSpeculativelyExecute(Cast)) return 0;
     Value *OpVal = InsertPHITranslatedSubExpr(Cast->getOperand(0),
                                               CurBB, PredBB, DT, NewInsts);
     if (OpVal == 0) return 0;
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index ecc83dfceb..ef19e065b7 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -1875,3 +1875,64 @@ bool llvm::onlyUsedByLifetimeMarkers(const Value *V) {
   }
   return true;
 }
+
+bool llvm::isSafeToSpeculativelyExecute(const Instruction *Inst,
+                                        const TargetData *TD) {
+  for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i)
+    if (Constant *C = dyn_cast<Constant>(Inst->getOperand(i)))
+      if (C->canTrap())
+        return false;
+
+  switch (Inst->getOpcode()) {
+  default:
+    return true;
+  case Instruction::UDiv:
+  case Instruction::URem:
+    // x / y is undefined if y == 0, but calcuations like x / 3 are safe.
+    return isKnownNonZero(Inst->getOperand(1), TD);
+  case Instruction::SDiv:
+  case Instruction::SRem: {
+    Value *Op = Inst->getOperand(1);
+    // x / y is undefined if y == 0
+    if (!isKnownNonZero(Op, TD))
+      return false;
+    // x / y might be undefined if y == -1
+    unsigned BitWidth = getBitWidth(Op->getType(), TD);
+    if (BitWidth == 0)
+      return false;
+    APInt KnownZero(BitWidth, 0);
+    APInt KnownOne(BitWidth, 0);
+    ComputeMaskedBits(Op, APInt::getAllOnesValue(BitWidth),
+                      KnownZero, KnownOne, TD);
+    return !!KnownZero;
+  }
+  case Instruction::Load: {
+    const LoadInst *LI = cast<LoadInst>(Inst);
+    if (!LI->isUnordered())
+      return false;
+    return LI->getPointerOperand()->isDereferenceablePointer();
+  }
+  case Instruction::Call:
+    return false; // The called function could have undefined behavior or
+                  // side-effects.
+                  // FIXME: We should special-case some intrinsics (bswap,
+                  // overflow-checking arithmetic, etc.)
+  case Instruction::VAArg:
+  case Instruction::Alloca:
+  case Instruction::Invoke:
+  case Instruction::PHI:
+  case Instruction::Store:
+  case Instruction::Ret:
+  case Instruction::Br:
+  case Instruction::IndirectBr:
+  case Instruction::Switch:
+  case Instruction::Unwind:
+  case Instruction::Unreachable:
+  case Instruction::Fence:
+  case Instruction::LandingPad:
+  case Instruction::AtomicRMW:
+  case Instruction::AtomicCmpXchg:
+  case Instruction::Resume:
+    return false; // Misc instructions which have effects
+  }
+}