From dd9344f3face8f1978a7f9f393c31b628144d1f6 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Fri, 28 May 2010 16:19:17 +0000
Subject: Move FindAvailableLoadedValue isSafeToLoadUnconditionally out of
 lib/Transforms/Utils and into lib/Analysis so that Analysis passes can use
 them.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@104949 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Utils/Local.cpp | 105 -----------------------------------------
 1 file changed, 105 deletions(-)

(limited to 'lib/Transforms/Utils/Local.cpp')

diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index d03f7a69c5..b9fcfd5f5f 100644
--- a/lib/Transforms/Utils/Local.cpp
+++ b/lib/Transforms/Utils/Local.cpp
@@ -34,111 +34,6 @@
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 
-//===----------------------------------------------------------------------===//
-//  Local analysis.
-//
-
-/// 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 Value::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;
-  Value *Base = V;
-  if (TD)
-    Base = getUnderlyingObjectWithOffset(V, TD, ByteOffset);
-
-  const Type *BaseType = 0;
-  unsigned BaseAlign = 0;
-  if (const AllocaInst *AI = dyn_cast<AllocaInst>(Base)) {
-    // 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)) {
-    // Global variables are safe to load from but their size cannot be
-    // guaranteed if they are overridden.
-    if (!isa<GlobalAlias>(GV) && !GV->mayBeOverridden()) {
-      BaseType = GV->getType()->getElementType();
-      BaseAlign = GV->getAlignment();
-    }
-  }
-
-  if (BaseType && BaseType->isSized()) {
-    if (TD && BaseAlign == 0)
-      BaseAlign = TD->getPrefTypeAlignment(BaseType);
-
-    if (Align <= BaseAlign) {
-      if (!TD)
-        return true; // Loading directly from an alloca or global is OK.
-
-      // Check if the load is within the bounds of the underlying object.
-      const PointerType *AddrTy = cast<PointerType>(V->getType());
-      uint64_t LoadSize = TD->getTypeStoreSize(AddrTy->getElementType());
-      if (ByteOffset + LoadSize <= TD->getTypeAllocSize(BaseType) &&
-          (Align == 0 || (ByteOffset % Align) == 0))
-        return true;
-    }
-  }
-
-  // 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,
-  // so there is no harm doing an extra load (also, CSE will later eliminate
-  // the load entirely).
-  BasicBlock::iterator BBI = ScanFrom, E = ScanFrom->getParent()->begin();
-
-  while (BBI != E) {
-    --BBI;
-
-    // If we see a free or a call which may write to memory (i.e. which might do
-    // a free) the pointer could be marked invalid.
-    if (isa<CallInst>(BBI) && BBI->mayWriteToMemory() &&
-        !isa<DbgInfoIntrinsic>(BBI))
-      return false;
-
-    if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
-      if (LI->getOperand(0) == V) return true;
-    } else if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) {
-      if (SI->getOperand(1) == V) return true;
-    }
-  }
-  return false;
-}
-
-
 //===----------------------------------------------------------------------===//
 //  Local constant propagation.
 //
-- 
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