X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FLoads.cpp;h=0902a39a9f8199898ff6f37572f412d30d57bb69;hb=08368387a450dc2b5681000e2728ec702a8f1197;hp=1f554a3da26c155bf101a1bc8e994e2934149c90;hpb=db125cfaf57cc83e7dd7453de2d509bc8efd0e5e;p=oota-llvm.git

diff --git a/lib/Analysis/Loads.cpp b/lib/Analysis/Loads.cpp
index 1f554a3da26..0902a39a9f8 100644
--- a/lib/Analysis/Loads.cpp
+++ b/lib/Analysis/Loads.cpp
@@ -13,11 +13,13 @@
 
 #include "llvm/Analysis/Loads.h"
 #include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Target/TargetData.h"
-#include "llvm/GlobalAlias.h"
-#include "llvm/GlobalVariable.h"
-#include "llvm/IntrinsicInst.h"
-#include "llvm/Operator.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/GlobalAlias.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Operator.h"
 using namespace llvm;
 
 /// AreEquivalentAddressValues - Test if A and B will obviously have the same
@@ -47,48 +49,18 @@ static bool AreEquivalentAddressValues(const Value *A, const Value *B) {
   return false;
 }
 
-/// getUnderlyingObjectWithOffset - Strip off up to MaxLookup GEPs and
-/// bitcasts to get back to the underlying object being addressed, keeping
-/// track of the offset in bytes from the GEPs relative to the result.
-/// This is closely related to GetUnderlyingObject but is located
-/// here to avoid making VMCore depend on TargetData.
-static Value *getUnderlyingObjectWithOffset(Value *V, const TargetData *TD,
-                                            uint64_t &ByteOffset,
-                                            unsigned MaxLookup = 6) {
-  if (!V->getType()->isPointerTy())
-    return V;
-  for (unsigned Count = 0; MaxLookup == 0 || Count < MaxLookup; ++Count) {
-    if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
-      if (!GEP->hasAllConstantIndices())
-        return V;
-      SmallVector<Value*, 8> Indices(GEP->op_begin() + 1, GEP->op_end());
-      ByteOffset += TD->getIndexedOffset(GEP->getPointerOperandType(),
-                                         &Indices[0], Indices.size());
-      V = GEP->getPointerOperand();
-    } else if (Operator::getOpcode(V) == Instruction::BitCast) {
-      V = cast<Operator>(V)->getOperand(0);
-    } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
-      if (GA->mayBeOverridden())
-        return V;
-      V = GA->getAliasee();
-    } else {
-      return V;
-    }
-    assert(V->getType()->isPointerTy() && "Unexpected operand type!");
-  }
-  return V;
-}
-
 /// isSafeToLoadUnconditionally - Return true if we know that executing a load
 /// from this value cannot trap.  If it is not obviously safe to load from the
 /// specified pointer, we do a quick local scan of the basic block containing
 /// ScanFrom, to determine if the address is already accessed.
 bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
-                                       unsigned Align, const TargetData *TD) {
-  uint64_t ByteOffset = 0;
+                                       unsigned Align, const DataLayout *TD) {
+  int64_t ByteOffset = 0;
   Value *Base = V;
-  if (TD)
-    Base = getUnderlyingObjectWithOffset(V, TD, ByteOffset);
+  Base = GetPointerBaseWithConstantOffset(V, ByteOffset, TD);
+
+  if (ByteOffset < 0) // out of bounds
+    return false;
 
   Type *BaseType = 0;
   unsigned BaseAlign = 0;
@@ -96,10 +68,10 @@ bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
     // An alloca is safe to load from as load as it is suitably aligned.
     BaseType = AI->getAllocatedType();
     BaseAlign = AI->getAlignment();
-  } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(Base)) {
+  } else if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Base)) {
     // Global variables are safe to load from but their size cannot be
     // guaranteed if they are overridden.
-    if (!isa<GlobalAlias>(GV) && !GV->mayBeOverridden()) {
+    if (!GV->mayBeOverridden()) {
       BaseType = GV->getType()->getElementType();
       BaseAlign = GV->getAlignment();
     }
@@ -160,10 +132,15 @@ bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
 /// MaxInstsToScan specifies the maximum instructions to scan in the block.  If
 /// it is set to 0, it will scan the whole block. You can also optionally
 /// specify an alias analysis implementation, which makes this more precise.
+///
+/// If TBAATag is non-null and a load or store is found, the TBAA tag from the
+/// load or store is recorded there.  If there is no TBAA tag or if no access
+/// is found, it is left unmodified.
 Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
                                       BasicBlock::iterator &ScanFrom,
                                       unsigned MaxInstsToScan,
-                                      AliasAnalysis *AA) {
+                                      AliasAnalysis *AA,
+                                      MDNode **TBAATag) {
   if (MaxInstsToScan == 0) MaxInstsToScan = ~0U;
 
   // If we're using alias analysis to disambiguate get the size of *Ptr.
@@ -188,14 +165,22 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
     
     --ScanFrom;
     // If this is a load of Ptr, the loaded value is available.
+    // (This is true even if the load is volatile or atomic, although
+    // those cases are unlikely.)
     if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
-      if (AreEquivalentAddressValues(LI->getOperand(0), Ptr))
+      if (AreEquivalentAddressValues(LI->getOperand(0), Ptr)) {
+        if (TBAATag) *TBAATag = LI->getMetadata(LLVMContext::MD_tbaa);
         return LI;
+      }
     
     if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
       // If this is a store through Ptr, the value is available!
-      if (AreEquivalentAddressValues(SI->getOperand(1), Ptr))
+      // (This is true even if the store is volatile or atomic, although
+      // those cases are unlikely.)
+      if (AreEquivalentAddressValues(SI->getOperand(1), Ptr)) {
+        if (TBAATag) *TBAATag = SI->getMetadata(LLVMContext::MD_tbaa);
         return SI->getOperand(0);
+      }
       
       // If Ptr is an alloca and this is a store to a different alloca, ignore
       // the store.  This is a trivial form of alias analysis that is important