Commit Graph

2 Commits

Author SHA1 Message Date
Hal Finkel 9e440c08a9 Make Value::isDereferenceablePointer handle offsets to pointer types with dereferenceable attributes
When we have a parameter (or call site return) with a dereferenceable
attribute, it can specify the size of an array pointed to by that parameter. If
we have a value for which we can accumulate a constant offset to such a
parameter, then we can use that offset in a direct comparison with the size
specified by the dereferenceable attribute.

This enables us to handle cases like this:

  int foo(int a[static 3]) {
    return a[2]; /* this is always dereferenceable */
  }

llvm-svn: 213447
2014-07-19 03:25:16 +00:00
Hal Finkel b0407ba071 Add a dereferenceable attribute
This attribute indicates that the parameter or return pointer is
dereferenceable. Practically speaking, loads from such a pointer within the
associated byte range are safe to speculatively execute. Such pointer
parameters are common in source languages (C++ references, for example).

llvm-svn: 213385
2014-07-18 15:51:28 +00:00