[cfe-commits] r117043 - in /cfe/trunk/lib/CodeGen: CodeGenTBAA.cpp CodeGenTBAA.h
Dan Gohman
gohman at apple.com
Thu Oct 21 11:49:12 PDT 2010
Author: djg
Date: Thu Oct 21 13:49:12 2010
New Revision: 117043
URL: http://llvm.org/viewvc/llvm-project?rev=117043&view=rev
Log:
Add some more comments.
Modified:
cfe/trunk/lib/CodeGen/CodeGenTBAA.cpp
cfe/trunk/lib/CodeGen/CodeGenTBAA.h
Modified: cfe/trunk/lib/CodeGen/CodeGenTBAA.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenTBAA.cpp?rev=117043&r1=117042&r2=117043&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenTBAA.cpp (original)
+++ cfe/trunk/lib/CodeGen/CodeGenTBAA.cpp Thu Oct 21 13:49:12 2010
@@ -7,8 +7,8 @@
//
//===----------------------------------------------------------------------===//
//
-// This is the code that manages TBAA information. Relevant standards
-// text includes:
+// This is the code that manages TBAA information and defines the TBAA policy
+// for the optimizer to use. Relevant standards text includes:
//
// C99 6.5p7
// C++ [basic.lval] (p10 in n3126, p15 in some earlier versions)
@@ -32,6 +32,8 @@
CodeGenTBAA::~CodeGenTBAA() {
}
+/// getTBAAInfoForNamedType - Create a TBAA tree node with the given string
+/// as its identifier, and the given Parent node as its tree parent.
llvm::MDNode *CodeGenTBAA::getTBAAInfoForNamedType(llvm::StringRef NameStr,
llvm::MDNode *Parent) {
llvm::Value *Ops[] = {
@@ -49,12 +51,22 @@
if (llvm::MDNode *N = MetadataCache[Ty])
return N;
+ // If this is our first node, create the initial tree.
if (!Root) {
+ // Define the root of the tree. This identifies the tree, so that
+ // if our LLVM IR is linked with LLVM IR from a different front-end
+ // (or a different version of this front-end), their TBAA trees will
+ // remain distinct, and the optimizer will treat them conservatively.
Root = getTBAAInfoForNamedType("Experimental TBAA", 0);
+
+ // Define the root of the tree for user-accessible memory. C and C++
+ // give special powers to char and certain similar types. However,
+ // these special powers only cover user-accessible memory, and doesn't
+ // include things like vtables.
Char = getTBAAInfoForNamedType("omnipotent char", Root);
}
- // For now, just emit a very minimal tree.
+ // Handle builtin types.
if (const BuiltinType *BTy = dyn_cast<BuiltinType>(Ty)) {
switch (BTy->getKind()) {
// Character types are special and can alias anything.
@@ -89,6 +101,7 @@
}
}
+ // Handle pointers.
// TODO: Implement C++'s type "similarity" and consider dis-"similar"
// pointers distinct.
if (Ty->isPointerType())
Modified: cfe/trunk/lib/CodeGen/CodeGenTBAA.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenTBAA.h?rev=117043&r1=117042&r2=117043&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenTBAA.h (original)
+++ cfe/trunk/lib/CodeGen/CodeGenTBAA.h Thu Oct 21 13:49:12 2010
@@ -7,7 +7,8 @@
//
//===----------------------------------------------------------------------===//
//
-// This is the code that manages TBAA information.
+// This is the code that manages TBAA information and defines the TBAA policy
+// for the optimizer to use.
//
//===----------------------------------------------------------------------===//
@@ -60,6 +61,8 @@
MangleContext &MContext);
~CodeGenTBAA();
+ /// getTBAAInfo - Get the TBAA MDNode to be used for a dereference
+ /// of the given type.
llvm::MDNode *getTBAAInfo(QualType QTy);
};
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