[cfe-commits] [PATCH/RFC] Extend TBAA to handle OpenCL address spaces

Peter Collingbourne peter at pcc.me.uk
Fri Oct 14 11:57:31 PDT 2011

On Fri, Oct 14, 2011 at 02:01:46PM -0400, Justin Holewinski wrote:
> -llvm::MDNode *CodeGenTBAA::getChar() {
> +llvm::MDNode *CodeGenTBAA::getChar(Qualifiers& Quals) {

Qualifiers is a lightweight type, and should be passed by value.

>  llvm::MDNode *
> -CodeGenTBAA::getTBAAInfo(QualType QTy) {
> +CodeGenTBAA::getTBAAInfo(QualType QTy, Qualifiers *Override) {

I think it's best if you split getTBAAInfo into two functions:
one which takes a QualType and the other which takes a canonical
SplitQualType.  The former would check for the may_alias attribute,
while the latter would contain the rest of the code (and be called
recursively for the unsigned->signed mapping).  To call the latter from
the former, you can obtain a SplitQualType using the QualType::split
function on the canonical type.

> @@ -42,10 +43,12 @@
>    MangleContext &MContext;
>    /// MetadataCache - This maps clang::Types to llvm::MDNodes describing them.
> -  llvm::DenseMap<const Type *, llvm::MDNode *> MetadataCache;
> +  llvm::DenseMap<std::pair<const Type *, unsigned>, llvm::MDNode *>
> +    MetadataCache;
>    llvm::MDNode *Root;
> -  llvm::MDNode *Char;
> +
> +  llvm::DenseMap<unsigned, llvm::MDNode *> CharCache;

A cheaper way of defining MetadataCache and CharCache would be
as arrays of (respectively) DenseMaps or MDNode pointers of size
LangAS::Count+1.  You can then define a function which defines
a mapping from a Qualifiers object to an integer between 0 and
LangAS::Count (the return value of which conceptually represents a
set of aliasing qualifiers) which would be used to index the arrays.


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