From 31ea6d1590ce79845504b8d928f07cb71bd4be80 Mon Sep 17 00:00:00 2001 From: Sanjoy Das Date: Thu, 16 Apr 2015 20:29:50 +0000 Subject: [IR] Introduce a dereferenceable_or_null(N) attribute. Summary: If a pointer is marked as dereferenceable_or_null(N), LLVM assumes it is either `null` or `dereferenceable(N)` or both. This change only introduces the attribute and adds a token test case for the `llvm-as` / `llvm-dis`. It does not hook up other parts of the optimizer to actually exploit the attribute -- those changes will come later. For pointers in address space 0, `dereferenceable(N)` is now exactly equivalent to `dereferenceable_or_null(N)` && `nonnull`. For other address spaces, `dereferenceable(N)` is potentially weaker than `dereferenceable_or_null(N)` && `nonnull` (since we could have a null `dereferenceable(N)` pointer). The motivating case for this change is Java (and other managed languages), where pointers are either `null` or dereferenceable up to some usually known-at-compile-time constant offset. Reviewers: rafael, hfinkel Reviewed By: hfinkel Subscribers: nicholas, llvm-commits Differential Revision: http://reviews.llvm.org/D8650 llvm-svn: 235132 --- llvm/lib/Bitcode/Writer/BitcodeWriter.cpp | 2 ++ 1 file changed, 2 insertions(+) (limited to 'llvm/lib/Bitcode/Writer/BitcodeWriter.cpp') diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp index 743ffe3cb1fd..aa4a6a4c28a1 100644 --- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp +++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp @@ -200,6 +200,8 @@ static uint64_t getAttrKindEncoding(Attribute::AttrKind Kind) { return bitc::ATTR_KIND_NON_NULL; case Attribute::Dereferenceable: return bitc::ATTR_KIND_DEREFERENCEABLE; + case Attribute::DereferenceableOrNull: + return bitc::ATTR_KIND_DEREFERENCEABLE_OR_NULL; case Attribute::NoRedZone: return bitc::ATTR_KIND_NO_RED_ZONE; case Attribute::NoReturn: -- cgit v1.2.3