Dereferenceable, dereferenceable_or_null metadata for loads

Summary:
Introduce dereferenceable, dereferenceable_or_null metadata for loads
with the same semantic as corresponding attributes.

This patch depends on http://reviews.llvm.org/D9253

Patch by Artur Pilipenko!

Reviewers: hfinkel, sanjoy, reames

Reviewed By: sanjoy, reames

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D9365

llvm-svn: 237720

1 files changed, 20 insertions, 1 deletions

diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 48ac8fbc7db..1ee16f866d6 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -5658,7 +5658,7 @@ Syntax:
 
 ::
 
-      <result> = load [volatile] <ty>, <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>][, !invariant.load !<index>][, !nonnull !<index>]
+      <result> = load [volatile] <ty>, <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>][, !invariant.load !<index>][, !nonnull !<index>][, !dereferenceable !<index>][, !dereferenceable_or_null !<index>]
       <result> = load atomic [volatile] <ty>* <pointer> [singlethread] <ordering>, align <alignment>
       !<index> = !{ i32 1 }
 
@@ -5723,6 +5723,25 @@ never be null.  This is analogous to the ''nonnull'' attribute
 on parameters and return values.  This metadata can only be applied
 to loads of a pointer type.
 
+The optional ``!dereferenceable`` metadata must reference a single
+metadata name ``<index>`` corresponding to a metadata node with one ``i64``
+entry. The existence of the ``!dereferenceable`` metadata on the instruction 
+tells the optimizer that the value loaded is known to be dereferenceable.
+The number of bytes known to be dereferenceable is specified by the integer 
+value in the metadata node. This is analogous to the ''dereferenceable'' 
+attribute on parameters and return values.  This metadata can only be applied 
+to loads of a pointer type.
+
+The optional ``!dereferenceable_or_null`` metadata must reference a single
+metadata name ``<index>`` corresponding to a metadata node with one ``i64``
+entry. The existence of the ``!dereferenceable_or_null`` metadata on the 
+instruction tells the optimizer that the value loaded is known to be either
+dereferenceable or null.
+The number of bytes known to be dereferenceable is specified by the integer 
+value in the metadata node. This is analogous to the ''dereferenceable_or_null'' 
+attribute on parameters and return values.  This metadata can only be applied 
+to loads of a pointer type.
+
 Semantics:
 """"""""""