http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58689
Bug ID: 58689
Summary: Enhance returns_nonnull
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Keywords: diagnostic, missed-optimization
Severity: enhancement
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: glisse at gcc dot gnu.org
Depends on: 21856, 24825
For PR 20318, we added an attribute "returns_nonnull". For now, it is quite
basic and only used by fold-const and VRP to assert in callers that the return
value is != 0. However, there are many other things that could be done with it,
see this conversation for details:
http://gcc.gnu.org/ml/gcc-patches/2013-10/msg00498.html
http://gcc.gnu.org/ml/gcc-patches/2013-10/msg00501.html
http://gcc.gnu.org/ml/gcc-patches/2013-10/msg00509.html
This includes in particular:
1) warn if a returns_nonnull function returns null (both using static analysis
and runtime tests);
2) optimize the callee, back-propagating this non-null property and marking as
unreachable the paths that would return 0;
3) preserve the nonnull property when inlining the function (assert_expr?);
4) mark a number of gcc functions with this attribute.
A number of these changes could be shared with the nonnull attribute and
pointer dereferencing.
