WholeProgramDevirt: Teach the pass to handle structs of arrays.

This will become necessary in some cases once D22296 lands.

llvm-svn: 289165

lib/Transforms/IPO/WholeProgramDevirt.cpp

@@ -293,7 +293,7 @@ struct DevirtModule {
   void buildTypeIdentifierMap(
       std::vector<VTableBits> &Bits,
       DenseMap<Metadata *, std::set<TypeMemberInfo>> &TypeIdMap);
-  Constant *getValueAtOffset(Constant *I, uint64_t Offset);
+  Constant *getPointerAtOffset(Constant *I, uint64_t Offset);
   bool
   tryFindVirtualCallTargets(std::vector<VirtualCallTarget> &TargetsForSlot,
                             const std::set<TypeMemberInfo> &TypeMemberInfos,
@@ -383,36 +383,36 @@ void DevirtModule::buildTypeIdentifierMap(
   }
 }
 
-Constant *DevirtModule::getValueAtOffset(Constant *I, uint64_t Offset) {
+Constant *DevirtModule::getPointerAtOffset(Constant *I, uint64_t Offset) {
+  if (I->getType()->isPointerTy()) {
+    if (Offset == 0)
+      return I;
+    return nullptr;
+  }
+
   const DataLayout &DL = M.getDataLayout();
-  unsigned Op;
 
   if (auto *C = dyn_cast<ConstantStruct>(I)) {
     const StructLayout *SL = DL.getStructLayout(C->getType());
-
     if (Offset >= SL->getSizeInBytes())
       return nullptr;
 
-    Op = SL->getElementContainingOffset(Offset);
+    unsigned Op = SL->getElementContainingOffset(Offset);
-
+    return getPointerAtOffset(cast<Constant>(I->getOperand(Op)),
-    if (Offset != SL->getElementOffset(Op))
+                              Offset - SL->getElementOffset(Op));
-      return nullptr;
+  }
-
+  if (auto *C = dyn_cast<ConstantArray>(I)) {
-  } else if (auto *C = dyn_cast<ConstantArray>(I)) {
     ArrayType *VTableTy = C->getType();
     uint64_t ElemSize = DL.getTypeAllocSize(VTableTy->getElementType());
 
-    if (Offset % ElemSize != 0)
+    unsigned Op = Offset / ElemSize;
-      return nullptr;
-
-    Op = Offset / ElemSize;
-
     if (Op >= C->getNumOperands())
       return nullptr;
-  } else
-    return nullptr;
 
-  return cast<Constant>(I->getOperand(Op));
+    return getPointerAtOffset(cast<Constant>(I->getOperand(Op)),
+                              Offset % ElemSize);
+  }
+  return nullptr;
 }
 
 bool DevirtModule::tryFindVirtualCallTargets(
@@ -422,13 +422,12 @@ bool DevirtModule::tryFindVirtualCallTargets(
     if (!TM.Bits->GV->isConstant())
       return false;
 
-    Constant *I = TM.Bits->GV->getInitializer();
+    Constant *Ptr = getPointerAtOffset(TM.Bits->GV->getInitializer(),
-    Value *V = getValueAtOffset(I, TM.Offset + ByteOffset);
+                                       TM.Offset + ByteOffset);
-
+    if (!Ptr)
-    if (!V)
       return false;
 
-    auto Fn = dyn_cast<Function>(V->stripPointerCasts());
+    auto Fn = dyn_cast<Function>(Ptr->stripPointerCasts());
     if (!Fn)
       return false;
 

test/Transforms/WholeProgramDevirt/bad-read-from-vtable.ll

@@ -3,14 +3,15 @@
 target datalayout = "e-p:64:64"
 target triple = "x86_64-unknown-linux-gnu"
 
-@vt = global [2 x i8*] [i8* zeroinitializer, i8* bitcast (void (i8*)* @vf to i8*)], !type !0
+@vt1 = global [2 x i8*] [i8* zeroinitializer, i8* bitcast (void (i8*)* @vf to i8*)], !type !0
+@vt2 = global i8* bitcast (void (i8*)* @vf to i8*), !type !1
 
 define void @vf(i8* %this) {
   ret void
 }
 
-; CHECK: define void @unaligned
+; CHECK: define void @unaligned1
-define void @unaligned(i8* %obj) {
+define void @unaligned1(i8* %obj) {
   %vtableptr = bitcast i8* %obj to [1 x i8*]**
   %vtable = load [1 x i8*]*, [1 x i8*]** %vtableptr
   %vtablei8 = bitcast [1 x i8*]* %vtable to i8*
@@ -25,6 +26,22 @@ define void @unaligned(i8* %obj) {
   ret void
 }
 
+; CHECK: define void @unaligned2
+define void @unaligned2(i8* %obj) {
+  %vtableptr = bitcast i8* %obj to [1 x i8*]**
+  %vtable = load [1 x i8*]*, [1 x i8*]** %vtableptr
+  %vtablei8 = bitcast [1 x i8*]* %vtable to i8*
+  %p = call i1 @llvm.type.test(i8* %vtablei8, metadata !"typeid2")
+  call void @llvm.assume(i1 %p)
+  %fptrptr = getelementptr i8, i8* %vtablei8, i32 1
+  %fptrptr_casted = bitcast i8* %fptrptr to i8**
+  %fptr = load i8*, i8** %fptrptr_casted
+  %fptr_casted = bitcast i8* %fptr to void (i8*)*
+  ; CHECK: call void %
+  call void %fptr_casted(i8* %obj)
+  ret void
+}
+
 ; CHECK: define void @outofbounds
 define void @outofbounds(i8* %obj) {
   %vtableptr = bitcast i8* %obj to [1 x i8*]**
@@ -61,3 +78,4 @@ declare i1 @llvm.type.test(i8*, metadata)
 declare void @llvm.assume(i1)
 
 !0 = !{i32 0, !"typeid"}
+!1 = !{i32 0, !"typeid2"}

test/Transforms/WholeProgramDevirt/pointer-vtable.ll

@@ -19,7 +19,7 @@ define void @call(i8* %obj) {
   %fptrptr = getelementptr [1 x i8*], [1 x i8*]* %vtable, i32 0, i32 0
   %fptr = load i8*, i8** %fptrptr
   %fptr_casted = bitcast i8* %fptr to void (i8*)*
-  ; CHECK: call void %
+  ; CHECK: call void @vf(
   call void %fptr_casted(i8* %obj)
   ret void
 }

test/Transforms/WholeProgramDevirt/soa-vtable.ll

@@ -0,0 +1,52 @@
+; RUN: opt -S -wholeprogramdevirt %s | FileCheck %s
+
+target datalayout = "e-p:64:64"
+target triple = "x86_64-unknown-linux-gnu"
+
+%vtTy = type { [2 x void (i8*)*], [2 x void (i8*)*] }
+
+@vt = constant %vtTy { [2 x void (i8*)*] [void (i8*)* null, void (i8*)* @vf1], [2 x void (i8*)*] [void (i8*)* null, void (i8*)* @vf2] }, !type !0, !type !1
+
+define void @vf1(i8* %this) {
+  ret void
+}
+
+define void @vf2(i8* %this) {
+  ret void
+}
+
+; CHECK: define void @call1
+define void @call1(i8* %obj) {
+  %vtableptr = bitcast i8* %obj to [1 x i8*]**
+  %vtable = load [1 x i8*]*, [1 x i8*]** %vtableptr
+  %vtablei8 = bitcast [1 x i8*]* %vtable to i8*
+  %p = call i1 @llvm.type.test(i8* %vtablei8, metadata !"typeid1")
+  call void @llvm.assume(i1 %p)
+  %fptrptr = getelementptr [1 x i8*], [1 x i8*]* %vtable, i32 0, i32 0
+  %fptr = load i8*, i8** %fptrptr
+  %fptr_casted = bitcast i8* %fptr to void (i8*)*
+  ; CHECK: call void @vf1(
+  call void %fptr_casted(i8* %obj)
+  ret void
+}
+
+; CHECK: define void @call2
+define void @call2(i8* %obj) {
+  %vtableptr = bitcast i8* %obj to [1 x i8*]**
+  %vtable = load [1 x i8*]*, [1 x i8*]** %vtableptr
+  %vtablei8 = bitcast [1 x i8*]* %vtable to i8*
+  %p = call i1 @llvm.type.test(i8* %vtablei8, metadata !"typeid2")
+  call void @llvm.assume(i1 %p)
+  %fptrptr = getelementptr [1 x i8*], [1 x i8*]* %vtable, i32 0, i32 0
+  %fptr = load i8*, i8** %fptrptr
+  %fptr_casted = bitcast i8* %fptr to void (i8*)*
+  ; CHECK: call void @vf2(
+  call void %fptr_casted(i8* %obj)
+  ret void
+}
+
+declare i1 @llvm.type.test(i8*, metadata)
+declare void @llvm.assume(i1)
+
+!0 = !{i32 8, !"typeid1"}
+!1 = !{i32 24, !"typeid2"}