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/Reader/BitcodeReader.cpp | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'llvm/lib/Bitcode/Reader/BitcodeReader.cpp') diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp index 6caec344d1f..5366f5fb4ea 100644 --- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp +++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp @@ -1098,6 +1098,8 @@ static Attribute::AttrKind GetAttrFromCode(uint64_t Code) { return Attribute::NonNull; case bitc::ATTR_KIND_DEREFERENCEABLE: return Attribute::Dereferenceable; + case bitc::ATTR_KIND_DEREFERENCEABLE_OR_NULL: + return Attribute::DereferenceableOrNull; case bitc::ATTR_KIND_NO_RED_ZONE: return Attribute::NoRedZone; case bitc::ATTR_KIND_NO_RETURN: @@ -1214,6 +1216,8 @@ std::error_code BitcodeReader::ParseAttributeGroupBlock() { B.addStackAlignmentAttr(Record[++i]); else if (Kind == Attribute::Dereferenceable) B.addDereferenceableAttr(Record[++i]); + else if (Kind == Attribute::DereferenceableOrNull) + B.addDereferenceableOrNullAttr(Record[++i]); } else { // String attribute assert((Record[i] == 3 || Record[i] == 4) && "Invalid attribute group entry"); -- cgit v1.2.3