rvalues, as C++11 constant evaluation semantics require. DeclRefs referring to
references can now use the normal initialization-caching codepath, which
incidentally fixes a crash in cyclic initialization of references.
llvm-svn: 142844
This commit removes the major functional dependency on the ExprEngine::Builder
member variable.
In some cases the code became more verbose. Particularly, we call takeNodes()
and addNodes() to move responsibility for the nodes from one builder to another.
This will get simplified later on.
llvm-svn: 142831
To convert iteratively, we take the nodes the local builder will
process from the from the global builder and add the generated nodes
after the short lived builder is done. PureStmtNodeBuilder is the
one we should eventually use everywhere. Added Stmt index and Builder
context as ExprEngine globals. To avoid passing them around.
llvm-svn: 142828
First step toward removing the global Stmt builder. Added several transitional methods (like takeNodes/addNodes).
+ Stop early if the set of exploded nodes for the next iteration is empty.
llvm-svn: 142827
This moves the responsibility for storing the output node set from the
builder to the clients. The builder is just responsible for transforming
an input set into the output set: {SrcSet/SrcNode} -> {Frontier}.
llvm-svn: 142826
introduce no-return or unreachable heuristics.
The return heuristics from the Ball and Larus paper don't work well in
practice as they pessimize early return paths. The only good hitrate
return heuristics are those for:
- NULL return
- Constant return
- negative integer return
Only the last of these three can possibly require significant code for
the returning block, and even the last is fairly rare and usually also
a constant. As a consequence, even for the cold return paths, there is
little code on that return path, and so little code density to be gained
by sinking it. The places where sinking these blocks is valuable (inner
loops) will already be weighted appropriately as the edge is a loop-exit
branch.
All of this aside, early returns are nearly as common as all three of
these return categories, and should actually be predicted as taken!
Rather than muddy the waters of the static predictions, just remain
silent on returns and let the CFG itself dictate any layout or other
issues.
However, the return heuristic was flagging one very important case:
unreachable. Unfortunately it still gave a 1/4 chance of the
branch-to-unreachable occuring. It also didn't do a rigorous job of
finding those blocks which post-dominate an unreachable block.
This patch builds a more powerful analysis that should flag all branches
to blocks known to then reach unreachable. It also has better worst-case
runtime complexity by not looping through successors for each block. The
previous code would perform an N^2 walk in the event of a single entry
block branching to N successors with a switch where each successor falls
through to the next and they finally fall through to a return.
Test case added for noreturn heuristics. Also doxygen comments improved
along the way.
llvm-svn: 142793
two more subtle routines to the bottom and expand on their cautionary
comments a bit. No functionality or actual interface change here.
llvm-svn: 142789
Anna Zaks