This adds a propagation heuristic to convert instruction samples
into branch weights. It implements a similar heuristic to the one
implemented by Dehao Chen on GCC.
The propagation proceeds in 3 phases:
1- Assignment of block weights. All the basic blocks in the function
are initial assigned the same weight as their most frequently
executed instruction.
2- Creation of equivalence classes. Since samples may be missing from
blocks, we can fill in the gaps by setting the weights of all the
blocks in the same equivalence class to the same weight. To compute
the concept of equivalence, we use dominance and loop information.
Two blocks B1 and B2 are in the same equivalence class if B1
dominates B2, B2 post-dominates B1 and both are in the same loop.
3- Propagation of block weights into edges. This uses a simple
propagation heuristic. The following rules are applied to every
block B in the CFG:
- If B has a single predecessor/successor, then the weight
of that edge is the weight of the block.
- If all the edges are known except one, and the weight of the
block is already known, the weight of the unknown edge will
be the weight of the block minus the sum of all the known
edges. If the sum of all the known edges is larger than B's weight,
we set the unknown edge weight to zero.
- If there is a self-referential edge, and the weight of the block is
known, the weight for that edge is set to the weight of the block
minus the weight of the other incoming edges to that block (if
known).
Since this propagation is not guaranteed to finalize for every CFG, we
only allow it to proceed for a limited number of iterations (controlled
by -sample-profile-max-propagate-iterations). It currently uses the same
GCC default of 100.
Before propagation starts, the pass builds (for each block) a list of
unique predecessors and successors. This is necessary to handle
identical edges in multiway branches. Since we visit all blocks and all
edges of the CFG, it is cleaner to build these lists once at the start
of the pass.
Finally, the patch fixes the computation of relative line locations.
The profiler emits lines relative to the function header. To discover
it, we traverse the compilation unit looking for the subprogram
corresponding to the function. The line number of that subprogram is the
line where the function begins. That becomes line zero for all the
relative locations.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198972 91177308-0d34-0410-b5e6-96231b3b80d8
for (i = 0; i < N; ++i)
A[i * Stride1] += B[i * Stride2];
We take loops like this and check that the symbolic strides 'Strided1/2' are one
and drop to the scalar loop if they are not.
This is currently disabled by default and hidden behind the flag
'enable-mem-access-versioning'.
radar://13075509
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198950 91177308-0d34-0410-b5e6-96231b3b80d8
An upcoming loop vectorizer commit will want to replace a SCEVUnknown(Value*)
by a SCEVConstant. This commit modifies the SCEVParameterRewriter to support
this. The SCEVParameterRewriter constructor can optionally specify to follow
this behavior.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198949 91177308-0d34-0410-b5e6-96231b3b80d8
The disassembler would no longer be able to disambiguage between the two
variants (explicit immediate #0 vs implicit, omitted #0) for the ldrt, strt,
ldrbt, strbt mnemonics as both versions indicated the disassembler routine.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198944 91177308-0d34-0410-b5e6-96231b3b80d8
The GNU assembler supports prefixing the expression with a '#' to indiciate that
the value that is being moved is infact a constant. This improves the
compatibility of the integrated assembler's parser for this.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198916 91177308-0d34-0410-b5e6-96231b3b80d8
The GNU assembler has an extension that allows for the elision of the paired
register (dt2) for the LDRD and STRD mnemonics. Add support for this in the
assembly parser. Canonicalise the usage during the instruction parsing from
the specified version.
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The ARM ARM indicates the mnemonics as follows:
ldrbt{<c>}{<q>} <Rt>, [<Rn>], {, #+/-<imm>}
ldrt{<c>}{<q>} <Rt>, [<Rn>] {, #+/-<imm>}
strbt{<c>}{<q>} <Rt>, [<Rn>] {, #<imm>}
strt{<c>}{<q>} <Rt>, [<Rn>] {, #+/-<imm>}
This improves the parser to deal with the implicit immediate 0 for the mnemonics
as per the specification.
Thanks to Joerg Sonnenberger for the tests!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198914 91177308-0d34-0410-b5e6-96231b3b80d8
This reverts commit r198865 which reverts r198851.
ASan identified a use-of-uninitialized of the DwarfTypeUnit::Ty variable
in skeleton type units.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198908 91177308-0d34-0410-b5e6-96231b3b80d8
contributors to submit patches to the LLVM project. Thanks to Danny,
Chris, Alp, and others for reviewing.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198901 91177308-0d34-0410-b5e6-96231b3b80d8
I would not normally add tests like these, but the copy constructor is not
used at all in our codebase with c++11, so having this tests might prevent
breaking the c++03 build again.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198886 91177308-0d34-0410-b5e6-96231b3b80d8
To declare or define reserved identifers is undefined behaviour in standard
C++. This needs to be addressed in compiler-rt before it can be used in LLVM.
See the list discussion for details.
This reverts commit r198858.
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The zext handling added in r197802 wasn't right for RNSBG. This patch
restricts it to ROSBG, RXSBG and RISBG. (The tests for RISBG were added
in r197802 since RISBG was the motivating example.)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198862 91177308-0d34-0410-b5e6-96231b3b80d8
At the moment we expect rotates to have the form:
(or (shl X, Y), (shr X, Z))
where Y == bitsize(X) - Z or Z == bitsize(X) - Y. This form means that
the (or ...) is undefined for Y == 0 or Z == 0. This undefinedness can
be avoided by using Y == (C * bitsize(X) - Z) & (bitsize(X) - 1) or
Z == (C * bitsize(X) - Y) & (bitsize(X) - 1) for any integer C
(including 0, the most natural choice).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198861 91177308-0d34-0410-b5e6-96231b3b80d8
InstCombine converts (sub 32, (add X, C)) into (sub 32-C, X),
so a rotate left of a 32-bit Y by X+C could appear as either:
(or (shl Y, (add X, C)), (shr Y, (sub 32, (add X, C))))
without InstCombine or:
(or (shl Y, (add X, C)), (shr Y, (sub 32-C, X)))
with it.
We already matched the first form. This patch handles the second too.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198860 91177308-0d34-0410-b5e6-96231b3b80d8
