There are two cases handled here:
1) a branch on undef
2) a switch with an undef condition.
Both cases are currently handled by ResolvedUndefsIn. If we have
a branch on undef, we force its value to false (which is trivially
foldable). If we have a switch on undef, we force to the first
constant (which is also foldable).
llvm-svn: 288725
so we can stop using DW_OP_bit_piece with the wrong semantics.
The entire back story can be found here:
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20161114/405934.html
The gist is that in LLVM we've been misinterpreting DW_OP_bit_piece's
offset field to mean the offset into the source variable rather than
the offset into the location at the top the DWARF expression stack. In
order to be able to fix this in a subsequent patch, this patch
introduces a dedicated DW_OP_LLVM_fragment operation with the
semantics that we used to apply to DW_OP_bit_piece, which is what we
actually need while inside of LLVM. This patch is complete with a
bitcode upgrade for expressions using the old format. It does not yet
fix the DWARF backend to use DW_OP_bit_piece correctly.
Implementation note: We discussed several options for implementing
this, including reserving a dedicated field in DIExpression for the
fragment size and offset, but using an custom operator at the end of
the expression works just fine and is more efficient because we then
only pay for it when we need it.
Differential Revision: https://reviews.llvm.org/D27361
rdar://problem/29335809
llvm-svn: 288683
Now that PointerType is no longer a SequentialType, all SequentialTypes
have an associated number of elements, so we can move that information to
the base class, allowing for a number of simplifications.
Differential Revision: https://reviews.llvm.org/D27122
llvm-svn: 288464
As proposed on llvm-dev:
http://lists.llvm.org/pipermail/llvm-dev/2016-October/106640.html
This is for a couple of reasons:
- Values of type PointerType are unlike the other SequentialTypes (arrays
and vectors) in that they do not hold values of the element type. By moving
PointerType we can unify certain aspects of how the other SequentialTypes
are handled.
- PointerType will have no place in the SequentialType hierarchy once
pointee types are removed, so this is a necessary step towards removing
pointee types.
Differential Revision: https://reviews.llvm.org/D26595
llvm-svn: 288462
Instead, expose whether the current type is an array or a struct, if an array
what the upper bound is, and if a struct the struct type itself. This is
in preparation for a later change which will make PointerType derive from
Type rather than SequentialType.
Differential Revision: https://reviews.llvm.org/D26594
llvm-svn: 288458
This just extracts out the transfer rules for constant ranges into a single shared point. As it happens, neither bit of code actually overlaps in terms of the handled operators, but with this change that could easily be tweaked in the future.
I also want to have this separated out to make experimenting with a eager value info implementation and possibly a ValueTracking-like fixed depth recursion peephole version. There's no reason all four of these can't share a common implementation which reduces the chances of bugs.
Differential Revision: https://reviews.llvm.org/D27294
llvm-svn: 288413
[recommitting after the fix in r288307]
This requires some changes to the opt-diag API. Hal and I have
discussed this at the Dev Meeting and came up with a streaming delimiter
(setExtraArgs) to solve this.
Arguments after this delimiter are only included in the optimization
records and not in the remarks printed in the compiler output. (Note,
how in the test the content of the YAML file changes but the remarks on
the compiler output don't.)
This implements the green GVN message with a bug fix at line
http://lab.llvm.org:8080/artifacts/opt-view_test-suite/build/SingleSource/Benchmarks/Dhrystone/CMakeFiles/dry.dir/html/_org_test-suite_SingleSource_Benchmarks_Dhrystone_dry.c.html#L446
The fix is that now we properly include the constant value in the
message: "load of type i32 eliminated in favor of 7"
Differential Revision: https://reviews.llvm.org/D26489
llvm-svn: 288380
If LoopInfo is available during GVN, BasicAA will use it. However
MergeBlockIntoPredecessor does not update LI as it merges blocks.
This didn't use to cause problems because LI was freed before
GVN/BasicAA. Now with OptimizationRemarkEmitter, the lifetime of LI is
extended so LI needs to be kept up-to-date during GVN.
Differential Revision: https://reviews.llvm.org/D27288
llvm-svn: 288307
Summary:
Fix a case when first register in a search has maximum
RegUses.getUsedByIndices(Reg).count()
Reviewers: qcolombet
Differential Revision: http://reviews.llvm.org/D26877
From: Evgeny Stupachenko <evstupac@gmail.com>
llvm-svn: 288278
This implements PGO-driven loop peeling.
The basic idea is that when the average dynamic trip-count of a loop is known,
based on PGO, to be low, we can expect a performance win by peeling off the
first several iterations of that loop.
Unlike unrolling based on a known trip count, or a trip count multiple, this
doesn't save us the conditional check and branch on each iteration. However,
it does allow us to simplify the straight-line code we get (constant-folding,
etc.). This is important given that we know that we will usually only hit this
code, and not the actual loop.
This is currently disabled by default.
Differential Revision: https://reviews.llvm.org/D25963
llvm-svn: 288274
Michel Dänzer reported that r288051, "[StructurizeCFG] Use range-based
for loops", introduced a bug into rebuildSSA, wherein we were iterating
over an instruction's use list while modifying it, without taking care
to do this correctly.
llvm-svn: 288200
The flag was introduced because the optimization controlled by the flag initially caused regressions. All the regressions were fixed some time ago and the flag has been false for quite a while.
llvm-svn: 288154
Enable scalar hoisting at -Oz as it is safe to hoist scalars to a place
where they are partially needed.
Differential Revision: https://reviews.llvm.org/D27111
llvm-svn: 288141
Preserving lifetime markers isn't as important as allowing promotion,
so just drop the lifetime markers if necessary.
This also fixes an assertion failure where other parts of SROA assumed
that lifetime markers never block promotion.
Fixes https://llvm.org/bugs/show_bug.cgi?id=29139.
Differential Revision: https://reviews.llvm.org/D24854
llvm-svn: 288074
Summary:
As far as I can tell, doing our own computations in
NearestCommonDominator is a false optimization -- DomTree will build up
what appears to be exactly this data when it decides it's worthwhile.
Moreover, by building the cache ourselves, we cannot take advantage of
the cache that the domtree might have available.
In addition, I am not convinced of the correctness of the original code.
In particular, setting ResultIndex = 1 on the first addBlock instead of
setting it to 0 is quite fishy. Similarly, it's not clear to me that
setting IndexMap[Node] = 0 for every node as we walk up the tree finding
a common parent is correct. But rather than ponder over these
questions, I'd rather just make the code do the obviously-correct thing.
This patch also changes the NearestCommonDominator API a bit, improving
the names and getting rid of the boolean parameter in addBlock -- see
http://jlebar.com/2011/12/16/Boolean_parameters_to_API_functions_considered_harmful..html
Reviewers: arsenm
Subscribers: aemerson, wdng, llvm-commits
Differential Revision: https://reviews.llvm.org/D26998
llvm-svn: 288050
Summary:
The iterative algorithm for Loop Unswitching may render some of the branches unreachable in the unswitched loops.
Given the exponential nature of the algorithm, this is quite an overhead.
This patch fixes this problem by selectively unswitching only those branches within a loop that are reachable from the loop header.
Reviewers: Michael Zolothukin, Anna Thomas, Weiming Zhao.
Subscribers: llvm-commits.
Differential Revision: http://reviews.llvm.org/D26299
llvm-svn: 287925
Summary:
No need to copy the RPOT vector before using it. Switch from std::map
to SmallDenseMap. Get rid of an unused variable (TempVisited). Get rid
of a typedef, RNVector, which is now used only once.
Differential Revision: https://reviews.llvm.org/D26997
llvm-svn: 287721
Summary:
"addRequired" and "addPreserved" look very similar when squished up next
to each other -- without the newline this code looked to me like it was
addRequired'ing DominatorTreeWrapperPass twice.
Reviewers: arsenm
Subscribers: wdng, llvm-commits
Differential Revision: https://reviews.llvm.org/D26996
llvm-svn: 287720
Summary: Lets us get rid of one member variable too.
Reviewers: arsenm
Subscribers: wdng, llvm-commits
Differential Revision: https://reviews.llvm.org/D26992
llvm-svn: 287716
We visit and/or, we try to derive a lattice value for the
instruction even if one of the operands is overdefined.
If the non-overdefined value is still 'unknown' just return and wait
for ResolvedUndefsIn to "plug in" the correct value. This simplifies
the logic a bit. While I'm here add tests for missing cases.
llvm-svn: 287709
Allow using an instruction other than a mul or phi as the base for
root-finding. For example, the included testcase includes a loop
which requires using a getelementptr as the base for root-finding.
Differential Revision: https://reviews.llvm.org/D26529
llvm-svn: 287588
This patch updates a bunch of places where add_dependencies was being explicitly called to add dependencies on intrinsics_gen to instead use the DEPENDS named parameter. This cleanup is needed for a patch I'm working on to add a dependency debugging mode to the build system.
llvm-svn: 287206
Summary:
For flat loop, even if it is hot, it is not a good idea to unroll in runtime, thus we set a lower partial unroll threshold.
For hot loop, we set a higher unroll threshold and allows expensive tripcount computation to allow more aggressive unrolling.
Reviewers: davidxl, mzolotukhin
Subscribers: sanjoy, mehdi_amini, llvm-commits
Differential Revision: https://reviews.llvm.org/D26527
llvm-svn: 287186
Davide Italiano