Revert r176408 and r176407 to address PR15540.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179111 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 43 insertions, 189 deletions

diff --git a/include/llvm/Analysis/MemoryBuiltins.h b/include/llvm/Analysis/MemoryBuiltins.h
index 63262eb9a3..488338302a 100644
--- a/include/llvm/Analysis/MemoryBuiltins.h
+++ b/include/llvm/Analysis/MemoryBuiltins.h
@@ -146,14 +146,6 @@ static inline CallInst *isFreeCall(Value *I, const TargetLibraryInfo *TLI) {
 bool getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout *TD,
                    const TargetLibraryInfo *TLI, bool RoundToAlign = false);
 
-/// \brief Compute the size of the underlying object pointed by Ptr. Returns
-/// true and the object size in Size if successful, and false otherwise.
-/// If RoundToAlign is true, then Size is rounded up to the aligment of allocas,
-/// byval arguments, and global variables.
-bool getUnderlyingObjectSize(const Value *Ptr, uint64_t &Size,
-                             const DataLayout *TD, const TargetLibraryInfo *TLI,
-                             bool RoundToAlign = false);
-
 
 
 typedef std::pair<APInt, APInt> SizeOffsetType;
@@ -163,14 +155,12 @@ typedef std::pair<APInt, APInt> SizeOffsetType;
 class ObjectSizeOffsetVisitor
   : public InstVisitor<ObjectSizeOffsetVisitor, SizeOffsetType> {
 
-  typedef DenseMap<const Value*, SizeOffsetType> CacheMapTy;
-
   const DataLayout *TD;
   const TargetLibraryInfo *TLI;
   bool RoundToAlign;
   unsigned IntTyBits;
   APInt Zero;
-  CacheMapTy CacheMap;
+  SmallPtrSet<Instruction *, 8> SeenInsts;
 
   APInt align(APInt Size, uint64_t Align);
 
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index ae6da1af0c..f8509dd070 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -88,7 +88,7 @@ static uint64_t getObjectSize(const Value *V, const DataLayout &TD,
                               const TargetLibraryInfo &TLI,
                               bool RoundToAlign = false) {
   uint64_t Size;
-  if (getUnderlyingObjectSize(V, Size, &TD, &TLI, RoundToAlign))
+  if (getObjectSize(V, Size, &TD, &TLI, RoundToAlign))
     return Size;
   return AliasAnalysis::UnknownSize;
 }
@@ -98,6 +98,35 @@ static uint64_t getObjectSize(const Value *V, const DataLayout &TD,
 static bool isObjectSmallerThan(const Value *V, uint64_t Size,
                                 const DataLayout &TD,
                                 const TargetLibraryInfo &TLI) {
+  // Note that the meanings of the "object" are slightly different in the
+  // following contexts:
+  //    c1: llvm::getObjectSize()
+  //    c2: llvm.objectsize() intrinsic
+  //    c3: isObjectSmallerThan()
+  // c1 and c2 share the same meaning; however, the meaning of "object" in c3
+  // refers to the "entire object".
+  //
+  //  Consider this example:
+  //     char *p = (char*)malloc(100)
+  //     char *q = p+80;
+  //
+  //  In the context of c1 and c2, the "object" pointed by q refers to the
+  // stretch of memory of q[0:19]. So, getObjectSize(q) should return 20.
+  //
+  //  However, in the context of c3, the "object" refers to the chunk of memory
+  // being allocated. So, the "object" has 100 bytes, and q points to the middle
+  // the "object". In case q is passed to isObjectSmallerThan() as the 1st
+  // parameter, before the llvm::getObjectSize() is called to get the size of
+  // entire object, we should:
+  //    - either rewind the pointer q to the base-address of the object in
+  //      question (in this case rewind to p), or
+  //    - just give up. It is up to caller to make sure the pointer is pointing
+  //      to the base address the object.
+  // 
+  // We go for 2nd option for simplicity.
+  if (!isIdentifiedObject(V))
+    return false;
+
   // This function needs to use the aligned object size because we allow
   // reads a bit past the end given sufficient alignment.
   uint64_t ObjectSize = getObjectSize(V, TD, TLI, /*RoundToAlign*/true);
diff --git a/lib/Analysis/MemoryBuiltins.cpp b/lib/Analysis/MemoryBuiltins.cpp
index d490d5419f..9c0d8ac6a3 100644
--- a/lib/Analysis/MemoryBuiltins.cpp
+++ b/lib/Analysis/MemoryBuiltins.cpp
@@ -364,26 +364,6 @@ bool llvm::getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout *TD,
   return true;
 }
 
-/// \brief Compute the size of the underlying object pointed by Ptr. Returns
-/// true and the object size in Size if successful, and false otherwise.
-/// If RoundToAlign is true, then Size is rounded up to the aligment of allocas,
-/// byval arguments, and global variables.
-bool llvm::getUnderlyingObjectSize(const Value *Ptr, uint64_t &Size,
-                                   const DataLayout *TD,
-                                   const TargetLibraryInfo *TLI,
-                                   bool RoundToAlign) {
-  if (!TD)
-    return false;
-
-  ObjectSizeOffsetVisitor Visitor(TD, TLI, Ptr->getContext(), RoundToAlign);
-  SizeOffsetType Data = Visitor.compute(const_cast<Value*>(Ptr));
-  if (!Visitor.knownSize(Data))
-    return false;
-
-  Size = Data.first.getZExtValue();
-  return true;
-}
-
 
 STATISTIC(ObjectVisitorArgument,
           "Number of arguments with unsolved size and offset");
@@ -409,23 +389,16 @@ ObjectSizeOffsetVisitor::ObjectSizeOffsetVisitor(const DataLayout *TD,
 
 SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
   V = V->stripPointerCasts();
+  if (Instruction *I = dyn_cast<Instruction>(V)) {
+    // If we have already seen this instruction, bail out. Cycles can happen in
+    // unreachable code after constant propagation.
+    if (!SeenInsts.insert(I))
+      return unknown();
 
-  if (isa<Instruction>(V) || isa<GEPOperator>(V)) {
-    // Return cached value or insert unknown in cache if size of V was not
-    // computed yet in order to avoid recursions in PHis.
-    std::pair<CacheMapTy::iterator, bool> CacheVal =
-      CacheMap.insert(std::make_pair(V, unknown()));
-    if (!CacheVal.second)
-      return CacheVal.first->second;
-
-    SizeOffsetType Result;
     if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
-      Result = visitGEPOperator(*GEP);
-    else
-      Result = visit(cast<Instruction>(*V));
-    return CacheMap[V] = Result;
+      return visitGEPOperator(*GEP);
+    return visit(*I);
   }
-
   if (Argument *A = dyn_cast<Argument>(V))
     return visitArgument(*A);
   if (ConstantPointerNull *P = dyn_cast<ConstantPointerNull>(V))
@@ -439,6 +412,8 @@ SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
     if (CE->getOpcode() == Instruction::IntToPtr)
       return unknown(); // clueless
+    if (CE->getOpcode() == Instruction::GetElementPtr)
+      return visitGEPOperator(cast<GEPOperator>(*CE));
   }
 
   DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: " << *V
@@ -572,21 +547,9 @@ SizeOffsetType ObjectSizeOffsetVisitor::visitLoadInst(LoadInst&) {
   return unknown();
 }
 
-SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode &PHI) {
-  if (PHI.getNumIncomingValues() == 0)
-    return unknown();
-
-  SizeOffsetType Ret = compute(PHI.getIncomingValue(0));
-  if (!bothKnown(Ret))
-    return unknown();
-
-  // Verify that all PHI incoming pointers have the same size and offset.
-  for (unsigned i = 1, e = PHI.getNumIncomingValues(); i != e; ++i) {
-    SizeOffsetType EdgeData = compute(PHI.getIncomingValue(i));
-    if (!bothKnown(EdgeData) || EdgeData != Ret)
-      return unknown();
-  }
-  return Ret;
+SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) {
+  // too complex to analyze statically.
+  return unknown();
 }
 
 SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) {
diff --git a/test/Transforms/InstCombine/objsize.ll b/test/Transforms/InstCombine/objsize.ll
index 0ead9d1237..31a3cb46e4 100644
--- a/test/Transforms/InstCombine/objsize.ll
+++ b/test/Transforms/InstCombine/objsize.ll
@@ -256,131 +256,3 @@ xpto:
 return:
   ret i32 7
 }
-
-declare noalias i8* @valloc(i32) nounwind
-
-; CHECK: @test14
-; CHECK: ret i32 6
-define i32 @test14(i32 %a) nounwind {
-  switch i32 %a, label %sw.default [
-    i32 1, label %sw.bb
-    i32 2, label %sw.bb1
-  ]
-
-sw.bb:
-  %call = tail call noalias i8* @malloc(i32 6) nounwind
-  br label %sw.epilog
-
-sw.bb1:
-  %call2 = tail call noalias i8* @calloc(i32 3, i32 2) nounwind
-  br label %sw.epilog
-
-sw.default:
-  %call3 = tail call noalias i8* @valloc(i32 6) nounwind
-  br label %sw.epilog
-
-sw.epilog:
-  %b.0 = phi i8* [ %call3, %sw.default ], [ %call2, %sw.bb1 ], [ %call, %sw.bb ]
-  %1 = tail call i32 @llvm.objectsize.i32(i8* %b.0, i1 false)
-  ret i32 %1
-}
-
-; CHECK: @test15
-; CHECK: llvm.objectsize
-define i32 @test15(i32 %a) nounwind {
-  switch i32 %a, label %sw.default [
-    i32 1, label %sw.bb
-    i32 2, label %sw.bb1
-  ]
-
-sw.bb:
-  %call = tail call noalias i8* @malloc(i32 3) nounwind
-  br label %sw.epilog
-
-sw.bb1:
-  %call2 = tail call noalias i8* @calloc(i32 2, i32 1) nounwind
-  br label %sw.epilog
-
-sw.default:
-  %call3 = tail call noalias i8* @valloc(i32 3) nounwind
-  br label %sw.epilog
-
-sw.epilog:
-  %b.0 = phi i8* [ %call3, %sw.default ], [ %call2, %sw.bb1 ], [ %call, %sw.bb ]
-  %1 = tail call i32 @llvm.objectsize.i32(i8* %b.0, i1 false)
-  ret i32 %1
-}
-
-; CHECK: @test16
-; CHECK: llvm.objectsize
-define i32 @test16(i8* %a, i32 %n) nounwind {
-  %b = alloca [5 x i8], align 1
-  %c = alloca [5 x i8], align 1
-  switch i32 %n, label %sw.default [
-    i32 1, label %sw.bb
-    i32 2, label %sw.bb1
-  ]
-
-sw.bb:
-  %bp = bitcast [5 x i8]* %b to i8*
-  br label %sw.epilog
-
-sw.bb1:
-  %cp = bitcast [5 x i8]* %c to i8*
-  br label %sw.epilog
-
-sw.default:
-  br label %sw.epilog
-
-sw.epilog:
-  %phi = phi i8* [ %a, %sw.default ], [ %cp, %sw.bb1 ], [ %bp, %sw.bb ]
-  %sz = call i32 @llvm.objectsize.i32(i8* %phi, i1 false)
-  ret i32 %sz
-}
-
-; CHECK: @test17
-; CHECK: ret i32 5
-define i32 @test17(i32 %n) nounwind {
-  %b = alloca [5 x i8], align 1
-  %c = alloca [5 x i8], align 1
-  %bp = bitcast [5 x i8]* %b to i8*
-  switch i32 %n, label %sw.default [
-    i32 1, label %sw.bb
-    i32 2, label %sw.bb1
-  ]
-
-sw.bb:
-  br label %sw.epilog
-
-sw.bb1:
-  %cp = bitcast [5 x i8]* %c to i8*
-  br label %sw.epilog
-
-sw.default:
-  br label %sw.epilog
-
-sw.epilog:
-  %phi = phi i8* [ %bp, %sw.default ], [ %cp, %sw.bb1 ], [ %bp, %sw.bb ]
-  %sz = call i32 @llvm.objectsize.i32(i8* %phi, i1 false)
-  ret i32 %sz
-}
-
-@globalalias = alias internal [60 x i8]* @a
-
-; CHECK: @test18
-; CHECK-NEXT: ret i32 60
-define i32 @test18() {
-  %bc = bitcast [60 x i8]* @globalalias to i8*
-  %1 = call i32 @llvm.objectsize.i32(i8* %bc, i1 false)
-  ret i32 %1
-}
-
-@globalalias2 = alias weak [60 x i8]* @a
-
-; CHECK: @test19
-; CHECK: llvm.objectsize
-define i32 @test19() {
-  %bc = bitcast [60 x i8]* @globalalias2 to i8*
-  %1 = call i32 @llvm.objectsize.i32(i8* %bc, i1 false)
-  ret i32 %1
-}