llvm/lib/Transforms/IPO, branch release_31

Add a Fixme.

2012-04-16T04:23:52Z

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154793 91177308-0d34-0410-b5e6-96231b3b80d8

By default, use Early-CSE instead of GVN for vectorization cleanup.

2012-04-13T17:15:33Z

As has been suggested by Duncan and others, Early-CSE and GVN should do similar redundancy elimination, but Early-CSE is much less expensive. Most of my autovectorization benchmarks show a performance regresion, but all of these are < 0.1%, and so I think that it is still worth using the less expensive pass. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154673 91177308-0d34-0410-b5e6-96231b3b80d8

Code-gen may inject code into the IR before it emits the ASM. The linker

2012-04-13T01:06:27Z

obviously cannot know that this code is present, let alone used. So prevent the internalize pass from internalizing those global values which code-gen may insert. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154645 91177308-0d34-0410-b5e6-96231b3b80d8

Add two statistics to help track how we are computing the inline cost.

2012-04-11T10:15:10Z

Yea, 'NumCallerCallersAnalyzed' isn't a great name, suggestions welcome. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154492 91177308-0d34-0410-b5e6-96231b3b80d8

Add an option to turn off the expensive GVN load PRE part of GVN.

2012-04-02T22:16:50Z

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153902 91177308-0d34-0410-b5e6-96231b3b80d8

Belatedly address some code review from Chris.

2012-04-01T10:41:24Z

As a side note, I really dislike array_pod_sort... Do we really still care about any STL implementations that get this so wrong? Does libc++? git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153834 91177308-0d34-0410-b5e6-96231b3b80d8

Fix a pretty scary bug I introduced into the always inliner with

2012-04-01T10:21:05Z

a single missing character. Somehow, this had gone untested. I've added tests for returns-twice logic specifically with the always-inliner that would have caught this, and fixed the bug. Thanks to Matt for the careful review and spotting this!!! =D git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153832 91177308-0d34-0410-b5e6-96231b3b80d8

Give the always-inliner its own custom filter. It shouldn't have to pay

2012-03-31T13:17:18Z

the very high overhead of the complex inline cost analysis when all it wants to do is detect three patterns which must not be inlined. Comment the code, clean it up, and leave some hints about possible performance improvements if this ever shows up on a profile. Moving this off of the (now more expensive) inline cost analysis is particularly important because we have to run this inliner even at -O0. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153814 91177308-0d34-0410-b5e6-96231b3b80d8

Remove a bunch of empty, dead, and no-op methods from all of these

2012-03-31T12:48:08Z

interfaces. These methods were used in the old inline cost system where there was a persistent cache that had to be updated, invalidated, and cleared. We're now doing more direct computations that don't require this intricate dance. Even if we resume some level of caching, it would almost certainly have a simpler and more narrow interface than this. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153813 91177308-0d34-0410-b5e6-96231b3b80d8

Initial commit for the rewrite of the inline cost analysis to operate

2012-03-31T12:42:41Z

on a per-callsite walk of the called function's instructions, in breadth-first order over the potentially reachable set of basic blocks. This is a major shift in how inline cost analysis works to improve the accuracy and rationality of inlining decisions. A brief outline of the algorithm this moves to: - Build a simplification mapping based on the callsite arguments to the function arguments. - Push the entry block onto a worklist of potentially-live basic blocks. - Pop the first block off of the *front* of the worklist (for breadth-first ordering) and walk its instructions using a custom InstVisitor. - For each instruction's operands, re-map them based on the simplification mappings available for the given callsite. - Compute any simplification possible of the instruction after re-mapping, and store that back int othe simplification mapping. - Compute any bonuses, costs, or other impacts of the instruction on the cost metric. - When the terminator is reached, replace any conditional value in the terminator with any simplifications from the mapping we have, and add any successors which are not proven to be dead from these simplifications to the worklist. - Pop the next block off of the front of the worklist, and repeat. - As soon as the cost of inlining exceeds the threshold for the callsite, stop analyzing the function in order to bound cost. The primary goal of this algorithm is to perfectly handle dead code paths. We do not want any code in trivially dead code paths to impact inlining decisions. The previous metric was *extremely* flawed here, and would always subtract the average cost of two successors of a conditional branch when it was proven to become an unconditional branch at the callsite. There was no handling of wildly different costs between the two successors, which would cause inlining when the path actually taken was too large, and no inlining when the path actually taken was trivially simple. There was also no handling of the code *path*, only the immediate successors. These problems vanish completely now. See the added regression tests for the shiny new features -- we skip recursive function calls, SROA-killing instructions, and high cost complex CFG structures when dead at the callsite being analyzed. Switching to this algorithm required refactoring the inline cost interface to accept the actual threshold rather than simply returning a single cost. The resulting interface is pretty bad, and I'm planning to do lots of interface cleanup after this patch. Several other refactorings fell out of this, but I've tried to minimize them for this patch. =/ There is still more cleanup that can be done here. Please point out anything that you see in review. I've worked really hard to try to mirror at least the spirit of all of the previous heuristics in the new model. It's not clear that they are all correct any more, but I wanted to minimize the change in this single patch, it's already a bit ridiculous. One heuristic that is *not* yet mirrored is to allow inlining of functions with a dynamic alloca *if* the caller has a dynamic alloca. I will add this back, but I think the most reasonable way requires changes to the inliner itself rather than just the cost metric, and so I've deferred this for a subsequent patch. The test case is XFAIL-ed until then. As mentioned in the review mail, this seems to make Clang run about 1% to 2% faster in -O0, but makes its binary size grow by just under 4%. I've looked into the 4% growth, and it can be fixed, but requires changes to other parts of the inliner. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153812 91177308-0d34-0410-b5e6-96231b3b80d8