fix PR17635: false positive with packed structures

LLVM optimizers may widen accesses to packed structures that overflow the structure itself, but should be in bounds up to the alignment of the object

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193317 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 38 insertions, 5 deletions

diff --git a/include/llvm/Analysis/MemoryBuiltins.h b/include/llvm/Analysis/MemoryBuiltins.h
index c54b7e6..91224ad 100644
--- a/include/llvm/Analysis/MemoryBuiltins.h
+++ b/include/llvm/Analysis/MemoryBuiltins.h
@@ -228,6 +228,7 @@ class ObjectSizeOffsetEvaluator
   Value *Zero;
   CacheMapTy CacheMap;
   PtrSetTy SeenVals;
+  bool RoundToAlign;
 
   SizeOffsetEvalType unknown() {
     return std::make_pair((Value*)0, (Value*)0);
@@ -236,7 +237,7 @@ class ObjectSizeOffsetEvaluator
 
 public:
   ObjectSizeOffsetEvaluator(const DataLayout *DL, const TargetLibraryInfo *TLI,
-                            LLVMContext &Context);
+                            LLVMContext &Context, bool RoundToAlign = false);
   SizeOffsetEvalType compute(Value *V);
 
   bool knownSize(SizeOffsetEvalType SizeOffset) {
diff --git a/lib/Analysis/MemoryBuiltins.cpp b/lib/Analysis/MemoryBuiltins.cpp
index a2fb544..1db0f63 100644
--- a/lib/Analysis/MemoryBuiltins.cpp
+++ b/lib/Analysis/MemoryBuiltins.cpp
@@ -588,8 +588,10 @@ SizeOffsetType ObjectSizeOffsetVisitor::visitInstruction(Instruction &I) {
 
 ObjectSizeOffsetEvaluator::ObjectSizeOffsetEvaluator(const DataLayout *DL,
                                                      const TargetLibraryInfo *TLI,
-                                                     LLVMContext &Context)
-: DL(DL), TLI(TLI), Context(Context), Builder(Context, TargetFolder(DL)) {
+                                                     LLVMContext &Context,
+                                                     bool RoundToAlign)
+: DL(DL), TLI(TLI), Context(Context), Builder(Context, TargetFolder(DL)),
+  RoundToAlign(RoundToAlign) {
   IntTy = DL->getIntPtrType(Context);
   Zero = ConstantInt::get(IntTy, 0);
 }
@@ -614,7 +616,7 @@ SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute(Value *V) {
 }
 
 SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute_(Value *V) {
-  ObjectSizeOffsetVisitor Visitor(DL, TLI, Context);
+  ObjectSizeOffsetVisitor Visitor(DL, TLI, Context, RoundToAlign);
   SizeOffsetType Const = Visitor.compute(V);
   if (Visitor.bothKnown(Const))
     return std::make_pair(ConstantInt::get(Context, Const.first),
diff --git a/lib/Transforms/Instrumentation/BoundsChecking.cpp b/lib/Transforms/Instrumentation/BoundsChecking.cpp
index 4a9e950..7a9f0f6 100644
--- a/lib/Transforms/Instrumentation/BoundsChecking.cpp
+++ b/lib/Transforms/Instrumentation/BoundsChecking.cpp
@@ -172,7 +172,8 @@ bool BoundsChecking::runOnFunction(Function &F) {
   TrapBB = 0;
   BuilderTy TheBuilder(F.getContext(), TargetFolder(TD));
   Builder = &TheBuilder;
-  ObjectSizeOffsetEvaluator TheObjSizeEval(TD, TLI, F.getContext());
+  ObjectSizeOffsetEvaluator TheObjSizeEval(TD, TLI, F.getContext(),
+                                           /*RoundToAlign=*/true);
   ObjSizeEval = &TheObjSizeEval;
 
   // check HANDLE_MEMORY_INST in include/llvm/Instruction.def for memory
diff --git a/test/Instrumentation/BoundsChecking/simple-32.ll b/test/Instrumentation/BoundsChecking/simple-32.ll
new file mode 100644
index 0000000..38b210f
--- /dev/null
+++ b/test/Instrumentation/BoundsChecking/simple-32.ll
@@ -0,0 +1,29 @@
+; RUN: opt < %s -bounds-checking -S | FileCheck %s
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32-S128"
+
+%struct.s2_packed = type <{ i64, i32, i32, i32, i16, i8 }>
+
+; CHECK-LABEL: @f
+; CHECK-NOT: trap
+define i16 @f() {
+entry:
+  %packed1 = alloca %struct.s2_packed, align 8
+  %gep = getelementptr inbounds %struct.s2_packed* %packed1, i32 0, i32 4
+  %ptr = bitcast i16* %gep to i32*
+  %val = load i32* %ptr, align 4
+  %valt = trunc i32 %val to i16
+  ret i16 %valt
+}
+
+; CHECK-LABEL: @f
+; CHECK: call void @llvm.trap()
+define i16 @f2() {
+entry:
+  %packed1 = alloca %struct.s2_packed, align 8
+  %gep = getelementptr inbounds %struct.s2_packed* %packed1, i32 0, i32 4
+  %ptr = bitcast i16* %gep to i48*
+  %val = load i48* %ptr, align 4
+  %valt = trunc i48 %val to i16
+  ret i16 %valt
+}