The order in which instructions are truncated in truncateToMinimalBitwidths
effects code generation. Switch to a map with a determinisic order, since the
iteration order over a DenseMap is not defined.
This code is not hot, so the difference in container performance isn't
interesting.
Many thanks to David Blaikie for making me aware of MapVector!
Fixes PR25490.
Differential Revision: http://reviews.llvm.org/D14981
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@254179 91177308-0d34-0410-b5e6-96231b3b80d8
Implemented as many of Michael's suggestions as were possible:
* clang-format the added code while it is still fresh.
* tried to change Value* to Instruction* in many places in computeMinimumValueSizes - unfortunately there are several places where Constants need to be handled so this wasn't possible.
* Reduce the pass list on loop-vectorization-factors.ll.
* Fix a bug where we were querying MinBWs for I->getOperand(0) but using MinBWs[I].
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252469 91177308-0d34-0410-b5e6-96231b3b80d8
C semantics force sub-int-sized values (e.g. i8, i16) to be promoted to int
type (e.g. i32) whenever arithmetic is performed on them.
For targets with native i8 or i16 operations, usually InstCombine can shrink
the arithmetic type down again. However InstCombine refuses to create illegal
types, so for targets without i8 or i16 registers, the lengthening and
shrinking remains.
Most SIMD ISAs (e.g. NEON) however support vectors of i8 or i16 even when
their scalar equivalents do not, so during vectorization it is important to
remove these lengthens and truncates when deciding the profitability of
vectorization.
The algorithm this uses starts at truncs and icmps, trawling their use-def
chains until they terminate or instructions outside the loop are found (or
unsafe instructions like inttoptr casts are found). If the use-def chains
starting from different root instructions (truncs/icmps) meet, they are
unioned. The demanded bits of each node in the graph are ORed together to form
an overall mask of the demanded bits in the entire graph. The minimum bitwidth
that graph can be truncated to is the bitwidth minus the number of leading
zeroes in the overall mask.
The intention is that this algorithm should "first do no harm", so it will
never insert extra cast instructions. This is why the use-def graphs are
unioned, so that subgraphs with different minimum bitwidths do not need casts
inserted between them.
This algorithm works hard to reduce compile time impact. DemandedBits are only
queried if there are extends of illegal types and if a truncate to an illegal
type is seen. In the general case, this results in a simple linear scan of the
instructions in the loop.
No non-noise compile time impact was seen on a clang bootstrap build.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@250032 91177308-0d34-0410-b5e6-96231b3b80d8
This reverts commit r246379. It seems that the commit was not the culprit,
and the bot will be investigated for instability.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@246380 91177308-0d34-0410-b5e6-96231b3b80d8
This reverts commit r246371, as it cause a rather obscure bug in AArch64
test-suite paq8p (time outs, seg-faults). I'll investigate it before
reapplying.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@246379 91177308-0d34-0410-b5e6-96231b3b80d8
Value *getSplatValue(Value *Val);
It complements the CreateVectorSplat(), which creates 2 instructions - insertelement and shuffle with all-zero mask.
The new function recognizes the pattern - insertelement+shuffle and returns the splat value (or nullptr).
It also returns a splat value form ConstantDataVector, for completeness.
Differential Revision: http://reviews.llvm.org/D11124
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@246371 91177308-0d34-0410-b5e6-96231b3b80d8
The following functions are moved from the LoopVectorizer to VectorUtils:
- getGEPInductionOperand
- stripGetElementPtr
- getUniqueCastUse
- getStrideFromPointer
These used to be static functions in LoopVectorize, but will also be used by
the upcoming loop versioning LICM transformation.
Patch by Ashutosh Nema!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241980 91177308-0d34-0410-b5e6-96231b3b80d8
