Reverting r171325 & r172363. This was causing a mis-compile on the self-hosted LTO build bots.

Okay, here's how to reproduce the problem:

1) Build a Release (or Release+Asserts) version of clang in the normal way.

2) Using the clang & clang++ binaries from (1), build a Release (or
   Release+Asserts) version of the same sources, but this time enable LTO ---
   specify the `-flto' flag on the command line.

3) Run the ARC migrator tests:

    $ arcmt-test --args -triple x86_64-apple-darwin10 -fsyntax-only -x objective-c++ ./src/tools/clang/test/ARCMT/cxx-rewrite.mm

You'll see that the output isn't correct (the whitespace is off).

The mis-compile is in the function `RewriteBuffer::RemoveText' in the
clang/lib/Rewrite/Core/Rewriter.cpp file. When that function and RewriteRope.cpp
are compiled with LTO and the `arcmt-test' executable is regenerated, you'll see
the error. When those files are not LTO'ed, then the output of the `arcmt-test'
is fine.

It is *really* hard to get a testcase out of this. I'll file a PR with what I
have currently.

--- Reverse-merging r172363 into '.':
U    include/llvm/Analysis/MemoryBuiltins.h
U    lib/Analysis/MemoryBuiltins.cpp

--- Reverse-merging r171325 into '.':
U    test/Transforms/InstCombine/objsize.ll
G    include/llvm/Analysis/MemoryBuiltins.h
G    lib/Analysis/MemoryBuiltins.cpp




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172756 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 13 insertions, 160 deletions

diff --git a/include/llvm/Analysis/MemoryBuiltins.h b/include/llvm/Analysis/MemoryBuiltins.h
index 2a9cd75ee7..f07658fbc6 100644
--- a/include/llvm/Analysis/MemoryBuiltins.h
+++ b/include/llvm/Analysis/MemoryBuiltins.h
@@ -153,14 +153,12 @@ 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/MemoryBuiltins.cpp b/lib/Analysis/MemoryBuiltins.cpp
index 1d27a83d93..0fc05505dd 100644
--- a/lib/Analysis/MemoryBuiltins.cpp
+++ b/lib/Analysis/MemoryBuiltins.cpp
@@ -385,23 +385,16 @@ 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))
@@ -415,6 +408,8 @@ 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
@@ -548,21 +543,9 @@ 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
-}