Import LLVM 3.9.1 including clang and lld.

1 files changed, 162 insertions, 29 deletions

diff --git a/gnu/llvm/lib/Analysis/Loads.cpp b/gnu/llvm/lib/Analysis/Loads.cpp
index 4b2fa3c6505..75426b54195 100644
--- a/gnu/llvm/lib/Analysis/Loads.cpp
+++ b/gnu/llvm/lib/Analysis/Loads.cpp
@@ -21,8 +21,125 @@
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Operator.h"
+#include "llvm/IR/Statepoint.h"
+
 using namespace llvm;
 
+static bool isAligned(const Value *Base, const APInt &Offset, unsigned Align,
+                      const DataLayout &DL) {
+  APInt BaseAlign(Offset.getBitWidth(), Base->getPointerAlignment(DL));
+
+  if (!BaseAlign) {
+    Type *Ty = Base->getType()->getPointerElementType();
+    if (!Ty->isSized())
+      return false;
+    BaseAlign = DL.getABITypeAlignment(Ty);
+  }
+
+  APInt Alignment(Offset.getBitWidth(), Align);
+
+  assert(Alignment.isPowerOf2() && "must be a power of 2!");
+  return BaseAlign.uge(Alignment) && !(Offset & (Alignment-1));
+}
+
+static bool isAligned(const Value *Base, unsigned Align, const DataLayout &DL) {
+  Type *Ty = Base->getType();
+  assert(Ty->isSized() && "must be sized");
+  APInt Offset(DL.getTypeStoreSizeInBits(Ty), 0);
+  return isAligned(Base, Offset, Align, DL);
+}
+
+/// Test if V is always a pointer to allocated and suitably aligned memory for
+/// a simple load or store.
+static bool isDereferenceableAndAlignedPointer(
+    const Value *V, unsigned Align, const APInt &Size, const DataLayout &DL,
+    const Instruction *CtxI, const DominatorTree *DT,
+    SmallPtrSetImpl<const Value *> &Visited) {
+  // Note that it is not safe to speculate into a malloc'd region because
+  // malloc may return null.
+
+  // bitcast instructions are no-ops as far as dereferenceability is concerned.
+  if (const BitCastOperator *BC = dyn_cast<BitCastOperator>(V))
+    return isDereferenceableAndAlignedPointer(BC->getOperand(0), Align, Size,
+                                              DL, CtxI, DT, Visited);
+
+  bool CheckForNonNull = false;
+  APInt KnownDerefBytes(Size.getBitWidth(),
+                        V->getPointerDereferenceableBytes(DL, CheckForNonNull));
+  if (KnownDerefBytes.getBoolValue()) {
+    if (KnownDerefBytes.uge(Size))
+      if (!CheckForNonNull || isKnownNonNullAt(V, CtxI, DT))
+        return isAligned(V, Align, DL);
+  }
+
+  // For GEPs, determine if the indexing lands within the allocated object.
+  if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
+    const Value *Base = GEP->getPointerOperand();
+
+    APInt Offset(DL.getPointerTypeSizeInBits(GEP->getType()), 0);
+    if (!GEP->accumulateConstantOffset(DL, Offset) || Offset.isNegative() ||
+        !Offset.urem(APInt(Offset.getBitWidth(), Align)).isMinValue())
+      return false;
+
+    // If the base pointer is dereferenceable for Offset+Size bytes, then the
+    // GEP (== Base + Offset) is dereferenceable for Size bytes.  If the base
+    // pointer is aligned to Align bytes, and the Offset is divisible by Align
+    // then the GEP (== Base + Offset == k_0 * Align + k_1 * Align) is also
+    // aligned to Align bytes.
+
+    return Visited.insert(Base).second &&
+           isDereferenceableAndAlignedPointer(Base, Align, Offset + Size, DL,
+                                              CtxI, DT, Visited);
+  }
+
+  // For gc.relocate, look through relocations
+  if (const GCRelocateInst *RelocateInst = dyn_cast<GCRelocateInst>(V))
+    return isDereferenceableAndAlignedPointer(
+        RelocateInst->getDerivedPtr(), Align, Size, DL, CtxI, DT, Visited);
+
+  if (const AddrSpaceCastInst *ASC = dyn_cast<AddrSpaceCastInst>(V))
+    return isDereferenceableAndAlignedPointer(ASC->getOperand(0), Align, Size,
+                                              DL, CtxI, DT, Visited);
+
+  if (auto CS = ImmutableCallSite(V))
+    if (const Value *RV = CS.getReturnedArgOperand())
+      return isDereferenceableAndAlignedPointer(RV, Align, Size, DL, CtxI, DT,
+                                                Visited);
+
+  // If we don't know, assume the worst.
+  return false;
+}
+
+bool llvm::isDereferenceableAndAlignedPointer(const Value *V, unsigned Align,
+                                              const DataLayout &DL,
+                                              const Instruction *CtxI,
+                                              const DominatorTree *DT) {
+  // When dereferenceability information is provided by a dereferenceable
+  // attribute, we know exactly how many bytes are dereferenceable. If we can
+  // determine the exact offset to the attributed variable, we can use that
+  // information here.
+  Type *VTy = V->getType();
+  Type *Ty = VTy->getPointerElementType();
+
+  // Require ABI alignment for loads without alignment specification
+  if (Align == 0)
+    Align = DL.getABITypeAlignment(Ty);
+
+  if (!Ty->isSized())
+    return false;
+
+  SmallPtrSet<const Value *, 32> Visited;
+  return ::isDereferenceableAndAlignedPointer(
+      V, Align, APInt(DL.getTypeSizeInBits(VTy), DL.getTypeStoreSize(Ty)), DL,
+      CtxI, DT, Visited);
+}
+
+bool llvm::isDereferenceablePointer(const Value *V, const DataLayout &DL,
+                                    const Instruction *CtxI,
+                                    const DominatorTree *DT) {
+  return isDereferenceableAndAlignedPointer(V, 1, DL, CtxI, DT);
+}
+
 /// \brief Test if A and B will obviously have the same value.
 ///
 /// This includes recognizing that %t0 and %t1 will have the same
@@ -56,21 +173,29 @@ static bool AreEquivalentAddressValues(const Value *A, const Value *B) {
 
 /// \brief Check if executing a load of this pointer value cannot trap.
 ///
+/// If DT and ScanFrom are specified this method performs context-sensitive
+/// analysis and returns true if it is safe to load immediately before ScanFrom.
+///
 /// If it is not obviously safe to load from the specified pointer, we do
 /// a quick local scan of the basic block containing \c ScanFrom, to determine
 /// if the address is already accessed.
 ///
 /// This uses the pointee type to determine how many bytes need to be safe to
 /// load from the pointer.
-bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
-                                       unsigned Align) {
-  const DataLayout &DL = ScanFrom->getModule()->getDataLayout();
-
+bool llvm::isSafeToLoadUnconditionally(Value *V, unsigned Align,
+                                       const DataLayout &DL,
+                                       Instruction *ScanFrom,
+                                       const DominatorTree *DT) {
   // Zero alignment means that the load has the ABI alignment for the target
   if (Align == 0)
     Align = DL.getABITypeAlignment(V->getType()->getPointerElementType());
   assert(isPowerOf2_32(Align));
 
+  // If DT is not specified we can't make context-sensitive query
+  const Instruction* CtxI = DT ? ScanFrom : nullptr;
+  if (isDereferenceableAndAlignedPointer(V, Align, DL, CtxI, DT))
+    return true;
+
   int64_t ByteOffset = 0;
   Value *Base = V;
   Base = GetPointerBaseWithConstantOffset(V, ByteOffset, DL);
@@ -86,9 +211,9 @@ bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
     BaseAlign = AI->getAlignment();
   } else if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Base)) {
     // Global variables are not necessarily safe to load from if they are
-    // overridden. Their size may change or they may be weak and require a test
-    // to determine if they were in fact provided.
-    if (!GV->mayBeOverridden()) {
+    // interposed arbitrarily. Their size may change or they may be weak and
+    // require a test to determine if they were in fact provided.
+    if (!GV->isInterposable()) {
       BaseType = GV->getType()->getElementType();
       BaseAlign = GV->getAlignment();
     }
@@ -113,6 +238,9 @@ bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
     }
   }
 
+  if (!ScanFrom)
+    return false;
+
   // Otherwise, be a little bit aggressive by scanning the local block where we
   // want to check to see if the pointer is already being loaded or stored
   // from/to.  If so, the previous load or store would have already trapped,
@@ -174,33 +302,24 @@ llvm::DefMaxInstsToScan("available-load-scan-limit", cl::init(6), cl::Hidden,
            "to scan backward from a given instruction, when searching for "
            "available loaded value"));
 
-/// \brief Scan the ScanBB block backwards to see if we have the value at the
-/// memory address *Ptr locally available within a small number of instructions.
-///
-/// The scan starts from \c ScanFrom. \c MaxInstsToScan specifies the maximum
-/// instructions to scan in the block. If it is set to \c 0, it will scan the whole
-/// block.
-///
-/// If the value is available, this function returns it. If not, it returns the
-/// iterator for the last validated instruction that the value would be live
-/// through. If we scanned the entire block and didn't find something that
-/// invalidates \c *Ptr or provides it, \c ScanFrom is left at the last
-/// instruction processed and this returns null.
-///
-/// You can also optionally specify an alias analysis implementation, which
-/// makes this more precise.
-///
-/// If \c AATags is non-null and a load or store is found, the AA tags from the
-/// load or store are recorded there. If there are no AA tags or if no access is
-/// found, it is left unmodified.
-Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
+Value *llvm::FindAvailableLoadedValue(LoadInst *Load, BasicBlock *ScanBB,
                                       BasicBlock::iterator &ScanFrom,
                                       unsigned MaxInstsToScan,
-                                      AliasAnalysis *AA, AAMDNodes *AATags) {
+                                      AliasAnalysis *AA, AAMDNodes *AATags,
+                                      bool *IsLoadCSE) {
   if (MaxInstsToScan == 0)
     MaxInstsToScan = ~0U;
 
-  Type *AccessTy = cast<PointerType>(Ptr->getType())->getElementType();
+  Value *Ptr = Load->getPointerOperand();
+  Type *AccessTy = Load->getType();
+
+  // We can never remove a volatile load
+  if (Load->isVolatile())
+    return nullptr;
+
+  // Anything stronger than unordered is currently unimplemented.
+  if (!Load->isUnordered())
+    return nullptr;
 
   const DataLayout &DL = ScanBB->getModule()->getDataLayout();
 
@@ -231,8 +350,16 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
       if (AreEquivalentAddressValues(
               LI->getPointerOperand()->stripPointerCasts(), StrippedPtr) &&
           CastInst::isBitOrNoopPointerCastable(LI->getType(), AccessTy, DL)) {
+
+        // We can value forward from an atomic to a non-atomic, but not the
+        // other way around.
+        if (LI->isAtomic() < Load->isAtomic())
+          return nullptr;
+
         if (AATags)
           LI->getAAMetadata(*AATags);
+        if (IsLoadCSE)
+            *IsLoadCSE = true;
         return LI;
       }
 
@@ -244,6 +371,12 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
       if (AreEquivalentAddressValues(StorePtr, StrippedPtr) &&
           CastInst::isBitOrNoopPointerCastable(SI->getValueOperand()->getType(),
                                                AccessTy, DL)) {
+
+        // We can value forward from an atomic to a non-atomic, but not the
+        // other way around.
+        if (SI->isAtomic() < Load->isAtomic())
+          return nullptr;
+
         if (AATags)
           SI->getAAMetadata(*AATags);
         return SI->getOperand(0);