6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-11-01 00:17:01 +00:00
Code Issues Projects Releases Wiki Activity

[IR] Introduce a dereferenceable_or_null(N) attribute.

Browse Source 
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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235132 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjoy Das
2015-04-16 20:29:50 +00:00
parent 3054c3e982
commit 5ff5907996
17 changed files with 181 additions and 31 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
include/llvm/IR/Instructions.h
View File

@@ -1412,6 +1412,10 @@ public:
/// \brief adds the dereferenceable attribute to the list of attributes.
void addDereferenceableAttr(unsigned i, uint64_t Bytes);
/// \brief adds the dereferenceable_or_null attribute to the list of
/// attributes.
void addDereferenceableOrNullAttr(unsigned i, uint64_t Bytes);
/// \brief Determine whether this call has the given attribute.
bool hasFnAttr(Attribute::AttrKind A) const {
assert(A != Attribute::NoBuiltin &&
@@ -3104,6 +3108,10 @@ public:
/// \brief adds the dereferenceable attribute to the list of attributes.
void addDereferenceableAttr(unsigned i, uint64_t Bytes);
/// \brief adds the dereferenceable_or_null attribute to the list of
/// attributes.
void addDereferenceableOrNullAttr(unsigned i, uint64_t Bytes);
/// \brief Determine whether this call has the given attribute.
bool hasFnAttr(Attribute::AttrKind A) const {
assert(A != Attribute::NoBuiltin &&