[CodeGen] Propagate may-alias'ness of lvalues with TBAA info

This patch fixes various places in clang to propagate may-alias
TBAA access descriptors during construction of lvalues, thus
eliminating the need for the LValueBaseInfo::MayAlias flag.

This is part of D38126 reworked to be a separate patch to
simplify review.

Differential Revision: https://reviews.llvm.org/D39008


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@316988 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 43 insertions, 47 deletions

diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index d3c2f47093..d3b03e556f 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -1538,8 +1538,6 @@ llvm::Value *CodeGenFunction::EmitLoadOfScalar(Address Addr, bool Volatile,
     Load->setMetadata(CGM.getModule().getMDKindID("nontemporal"), Node);
   }
 
-  if (BaseInfo.getMayAlias())
-    TBAAInfo = CGM.getTBAAMayAliasAccessInfo();
   CGM.DecorateInstructionWithTBAA(Load, TBAAInfo);
 
   if (EmitScalarRangeCheck(Load, Ty, Loc)) {
@@ -1622,8 +1620,6 @@ void CodeGenFunction::EmitStoreOfScalar(llvm::Value *Value, Address Addr,
     Store->setMetadata(CGM.getModule().getMDKindID("nontemporal"), Node);
   }
 
-  if (BaseInfo.getMayAlias())
-    TBAAInfo = CGM.getTBAAMayAliasAccessInfo();
   CGM.DecorateInstructionWithTBAA(Store, TBAAInfo);
 }
 
@@ -2170,10 +2166,7 @@ CodeGenFunction::EmitLoadOfReference(LValue RefLVal,
                                      TBAAAccessInfo *PointeeTBAAInfo) {
   llvm::LoadInst *Load = Builder.CreateLoad(RefLVal.getAddress(),
                                             RefLVal.isVolatile());
-  TBAAAccessInfo RefTBAAInfo = RefLVal.getTBAAInfo();
-  if (RefLVal.getBaseInfo().getMayAlias())
-    RefTBAAInfo = CGM.getTBAAMayAliasAccessInfo();
-  CGM.DecorateInstructionWithTBAA(Load, RefTBAAInfo);
+  CGM.DecorateInstructionWithTBAA(Load, RefLVal.getTBAAInfo());
 
   CharUnits Align = getNaturalTypeAlignment(RefLVal.getType()->getPointeeType(),
                                             PointeeBaseInfo, PointeeTBAAInfo,
@@ -2356,11 +2349,10 @@ LValue CodeGenFunction::EmitDeclRefLValue(const DeclRefExpr *E) {
         LValue CapLVal =
             EmitCapturedFieldLValue(*this, CapturedStmtInfo->lookup(VD),
                                     CapturedStmtInfo->getContextValue());
-        bool MayAlias = CapLVal.getBaseInfo().getMayAlias();
         return MakeAddrLValue(
             Address(CapLVal.getPointer(), getContext().getDeclAlign(VD)),
-            CapLVal.getType(), LValueBaseInfo(AlignmentSource::Decl, MayAlias),
-            CGM.getTBAAAccessInfo(CapLVal.getType()));
+            CapLVal.getType(), LValueBaseInfo(AlignmentSource::Decl),
+            CapLVal.getTBAAInfo());
       }
 
       assert(isa<BlockDecl>(CurCodeDecl));
@@ -2504,7 +2496,7 @@ LValue CodeGenFunction::EmitUnaryOpLValue(const UnaryOperator *E) {
          ? emitAddrOfRealComponent(LV.getAddress(), LV.getType())
          : emitAddrOfImagComponent(LV.getAddress(), LV.getType()));
     LValue ElemLV = MakeAddrLValue(Component, T, LV.getBaseInfo(),
-                                   CGM.getTBAAAccessInfo(T));
+                                   CGM.getTBAAInfoForSubobject(LV, T));
     ElemLV.getQuals().addQualifiers(LV.getQuals());
     return ElemLV;
   }
@@ -3242,18 +3234,18 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E,
     Addr = emitArraySubscriptGEP(*this, Addr, Idx, EltType, /*inbounds*/ true,
                                  SignedIndices, E->getExprLoc());
     return MakeAddrLValue(Addr, EltType, LV.getBaseInfo(),
-                          CGM.getTBAAAccessInfo(EltType));
+                          CGM.getTBAAInfoForSubobject(LV, EltType));
   }
 
-  LValueBaseInfo BaseInfo;
-  TBAAAccessInfo TBAAInfo;
+  LValueBaseInfo EltBaseInfo;
+  TBAAAccessInfo EltTBAAInfo;
   Address Addr = Address::invalid();
   if (const VariableArrayType *vla =
            getContext().getAsVariableArrayType(E->getType())) {
     // The base must be a pointer, which is not an aggregate.  Emit
     // it.  It needs to be emitted first in case it's what captures
     // the VLA bounds.
-    Addr = EmitPointerWithAlignment(E->getBase(), &BaseInfo, &TBAAInfo);
+    Addr = EmitPointerWithAlignment(E->getBase(), &EltBaseInfo, &EltTBAAInfo);
     auto *Idx = EmitIdxAfterBase(/*Promote*/true);
 
     // The element count here is the total number of non-VLA elements.
@@ -3277,7 +3269,7 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E,
     // Indexing over an interface, as in "NSString *P; P[4];"
 
     // Emit the base pointer.
-    Addr = EmitPointerWithAlignment(E->getBase(), &BaseInfo, &TBAAInfo);
+    Addr = EmitPointerWithAlignment(E->getBase(), &EltBaseInfo, &EltTBAAInfo);
     auto *Idx = EmitIdxAfterBase(/*Promote*/true);
 
     CharUnits InterfaceSize = getContext().getTypeSizeInChars(OIT);
@@ -3324,18 +3316,18 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E,
         *this, ArrayLV.getAddress(), {CGM.getSize(CharUnits::Zero()), Idx},
         E->getType(), !getLangOpts().isSignedOverflowDefined(), SignedIndices,
         E->getExprLoc());
-    BaseInfo = ArrayLV.getBaseInfo();
-    TBAAInfo = CGM.getTBAAAccessInfo(E->getType());
+    EltBaseInfo = ArrayLV.getBaseInfo();
+    EltTBAAInfo = CGM.getTBAAInfoForSubobject(ArrayLV, E->getType());
   } else {
     // The base must be a pointer; emit it with an estimate of its alignment.
-    Addr = EmitPointerWithAlignment(E->getBase(), &BaseInfo, &TBAAInfo);
+    Addr = EmitPointerWithAlignment(E->getBase(), &EltBaseInfo, &EltTBAAInfo);
     auto *Idx = EmitIdxAfterBase(/*Promote*/true);
     Addr = emitArraySubscriptGEP(*this, Addr, Idx, E->getType(),
                                  !getLangOpts().isSignedOverflowDefined(),
                                  SignedIndices, E->getExprLoc());
   }
 
-  LValue LV = MakeAddrLValue(Addr, E->getType(), BaseInfo, TBAAInfo);
+  LValue LV = MakeAddrLValue(Addr, E->getType(), EltBaseInfo, EltTBAAInfo);
 
   if (getLangOpts().ObjC1 &&
       getLangOpts().getGC() != LangOptions::NonGC) {
@@ -3374,9 +3366,12 @@ static Address emitOMPArraySectionBase(CodeGenFunction &CGF, const Expr *Base,
       return CGF.Builder.CreateElementBitCast(Addr,
                                               CGF.ConvertTypeForMem(ElTy));
     }
-    LValueBaseInfo TypeInfo;
-    CharUnits Align = CGF.getNaturalTypeAlignment(ElTy, &TypeInfo);
-    BaseInfo.mergeForCast(TypeInfo);
+    LValueBaseInfo TypeBaseInfo;
+    TBAAAccessInfo TypeTBAAInfo;
+    CharUnits Align = CGF.getNaturalTypeAlignment(ElTy, &TypeBaseInfo,
+                                                  &TypeTBAAInfo);
+    BaseInfo.mergeForCast(TypeBaseInfo);
+    TBAAInfo = CGF.CGM.mergeTBAAInfoForCast(TBAAInfo, TypeTBAAInfo);
     return Address(CGF.Builder.CreateLoad(BaseLVal.getAddress()), Align);
   }
   return CGF.EmitPointerWithAlignment(Base, &BaseInfo, &TBAAInfo);
@@ -3522,7 +3517,7 @@ LValue CodeGenFunction::EmitOMPArraySectionExpr(const OMPArraySectionExpr *E,
         ResultExprTy, !getLangOpts().isSignedOverflowDefined(),
         /*SignedIndices=*/false, E->getExprLoc());
     BaseInfo = ArrayLV.getBaseInfo();
-    TBAAInfo = CGM.getTBAAAccessInfo(ResultExprTy);
+    TBAAInfo = CGM.getTBAAInfoForSubobject(ArrayLV, ResultExprTy);
   } else {
     Address Base = emitOMPArraySectionBase(*this, E->getBase(), BaseInfo,
                                            TBAAInfo, BaseTy, ResultExprTy,
@@ -3712,7 +3707,7 @@ LValue CodeGenFunction::EmitLValueForField(LValue base,
     QualType fieldType =
       field->getType().withCVRQualifiers(base.getVRQualifiers());
     // TODO: Support TBAA for bit fields.
-    LValueBaseInfo FieldBaseInfo(BaseInfo.getAlignmentSource(), false);
+    LValueBaseInfo FieldBaseInfo(BaseInfo.getAlignmentSource());
     return LValue::MakeBitfield(Addr, Info, fieldType, FieldBaseInfo,
                                 TBAAAccessInfo());
   }
@@ -3723,16 +3718,14 @@ LValue CodeGenFunction::EmitLValueForField(LValue base,
   QualType FieldType = field->getType();
   const RecordDecl *rec = field->getParent();
   AlignmentSource BaseAlignSource = BaseInfo.getAlignmentSource();
-  LValueBaseInfo FieldBaseInfo(getFieldAlignmentSource(BaseAlignSource), false);
+  LValueBaseInfo FieldBaseInfo(getFieldAlignmentSource(BaseAlignSource));
   TBAAAccessInfo FieldTBAAInfo;
-  if (BaseInfo.getMayAlias() || rec->hasAttr<MayAliasAttr>() ||
-          FieldType->isVectorType()) {
-    FieldBaseInfo.setMayAlias(true);
-    FieldTBAAInfo = CGM.getTBAAMayAliasAccessInfo();
+  if (base.getTBAAInfo().isMayAlias() ||
+          rec->hasAttr<MayAliasAttr>() || FieldType->isVectorType()) {
+    FieldTBAAInfo = TBAAAccessInfo::getMayAliasInfo();
   } else if (rec->isUnion()) {
     // TODO: Support TBAA for unions.
-    FieldBaseInfo.setMayAlias(true);
-    FieldTBAAInfo = CGM.getTBAAMayAliasAccessInfo();
+    FieldTBAAInfo = TBAAAccessInfo::getMayAliasInfo();
   } else {
     // If no base type been assigned for the base access, then try to generate
     // one for this base lvalue.
@@ -3818,13 +3811,14 @@ CodeGenFunction::EmitLValueForFieldInitialization(LValue Base,
   llvm::Type *llvmType = ConvertTypeForMem(FieldType);
   V = Builder.CreateElementBitCast(V, llvmType, Field->getName());
 
-  // TODO: access-path TBAA?
+  // TODO: Generate TBAA information that describes this access as a structure
+  // member access and not just an access to an object of the field's type. This
+  // should be similar to what we do in EmitLValueForField().
   LValueBaseInfo BaseInfo = Base.getBaseInfo();
-  LValueBaseInfo FieldBaseInfo(
-      getFieldAlignmentSource(BaseInfo.getAlignmentSource()),
-      BaseInfo.getMayAlias());
+  AlignmentSource FieldAlignSource = BaseInfo.getAlignmentSource();
+  LValueBaseInfo FieldBaseInfo(getFieldAlignmentSource(FieldAlignSource));
   return MakeAddrLValue(V, FieldType, FieldBaseInfo,
-                        CGM.getTBAAAccessInfo(FieldType));
+                        CGM.getTBAAInfoForSubobject(Base, FieldType));
 }
 
 LValue CodeGenFunction::EmitCompoundLiteralLValue(const CompoundLiteralExpr *E){
@@ -3937,11 +3931,10 @@ EmitConditionalOperatorLValue(const AbstractConditionalOperator *expr) {
     AlignmentSource alignSource =
       std::max(lhs->getBaseInfo().getAlignmentSource(),
                rhs->getBaseInfo().getAlignmentSource());
-    bool MayAlias = lhs->getBaseInfo().getMayAlias() ||
-                    rhs->getBaseInfo().getMayAlias();
-    return MakeAddrLValue(result, expr->getType(),
-                          LValueBaseInfo(alignSource, MayAlias),
-                          CGM.getTBAAAccessInfo(expr->getType()));
+    TBAAAccessInfo TBAAInfo = CGM.mergeTBAAInfoForConditionalOperator(
+        lhs->getTBAAInfo(), rhs->getTBAAInfo());
+    return MakeAddrLValue(result, expr->getType(), LValueBaseInfo(alignSource),
+                          TBAAInfo);
   } else {
     assert((lhs || rhs) &&
            "both operands of glvalue conditional are throw-expressions?");
@@ -4039,8 +4032,11 @@ LValue CodeGenFunction::EmitCastLValue(const CastExpr *E) {
         This, DerivedClassDecl, E->path_begin(), E->path_end(),
         /*NullCheckValue=*/false, E->getExprLoc());
 
+    // TODO: Support accesses to members of base classes in TBAA. For now, we
+    // conservatively pretend that the complete object is of the base class
+    // type.
     return MakeAddrLValue(Base, E->getType(), LV.getBaseInfo(),
-                          CGM.getTBAAAccessInfo(E->getType()));
+                          CGM.getTBAAInfoForSubobject(LV, E->getType()));
   }
   case CK_ToUnion:
     return EmitAggExprToLValue(E);
@@ -4068,7 +4064,7 @@ LValue CodeGenFunction::EmitCastLValue(const CastExpr *E) {
                                 CFITCK_DerivedCast, E->getLocStart());
 
     return MakeAddrLValue(Derived, E->getType(), LV.getBaseInfo(),
-                          CGM.getTBAAAccessInfo(E->getType()));
+                          CGM.getTBAAInfoForSubobject(LV, E->getType()));
   }
   case CK_LValueBitCast: {
     // This must be a reinterpret_cast (or c-style equivalent).
@@ -4085,14 +4081,14 @@ LValue CodeGenFunction::EmitCastLValue(const CastExpr *E) {
                                 CFITCK_UnrelatedCast, E->getLocStart());
 
     return MakeAddrLValue(V, E->getType(), LV.getBaseInfo(),
-                          CGM.getTBAAAccessInfo(E->getType()));
+                          CGM.getTBAAInfoForSubobject(LV, E->getType()));
   }
   case CK_ObjCObjectLValueCast: {
     LValue LV = EmitLValue(E->getSubExpr());
     Address V = Builder.CreateElementBitCast(LV.getAddress(),
                                              ConvertType(E->getType()));
     return MakeAddrLValue(V, E->getType(), LV.getBaseInfo(),
-                          CGM.getTBAAAccessInfo(E->getType()));
+                          CGM.getTBAAInfoForSubobject(LV, E->getType()));
   }
   case CK_ZeroToOCLQueue:
     llvm_unreachable("NULL to OpenCL queue lvalue cast is not valid");