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Commit Graph

41403 Commits

Author SHA1 Message Date
Justin Lebar
8506de7ef9 [NVPTX] Support .maxnreg annotation.
Reviewers: tra

Subscribers: llvm-commits, jholewinski

Differential Revision: https://reviews.llvm.org/D27638

llvm-svn: 289729
2016-12-14 22:32:50 +00:00
Peter Collingbourne
434cd2f4fe LibDriver: Reject inputs that are not COFF objects or bitcode files.
Fixes PR31372.

Differential Revision: https://reviews.llvm.org/D27776

llvm-svn: 289726
2016-12-14 22:19:22 +00:00
Dehao Chen
4c1d21ec8c Only sets profile summary when it was not preset.
Summary: SampleProfileLoader pass may be invoked twice by LTO. The 2nd pass should not append more summary info as it is already preset by the 1st pass.

Reviewers: eraman, davidxl

Subscribers: mehdi_amini, llvm-commits

Differential Revision: https://reviews.llvm.org/D27733

llvm-svn: 289725
2016-12-14 22:06:49 +00:00
Davide Italiano
204a1f64e7 [LTO] Add the missing datalayout in a test.
llvm-svn: 289720
2016-12-14 21:57:14 +00:00
Davide Italiano
4ca4bcedf1 [LTO] Reject modules without datalayout.
Also, udpate the ~60 failing tests in the tree which did
not contain a valid datalayout.
This fixes PR31123. lld will be updated in a following patch,
immediately after this is committed.

Differential Revision:  https://reviews.llvm.org/D27082

llvm-svn: 289719
2016-12-14 21:57:04 +00:00
Filipe Cabecinhas
0ed7767039 [asan] Don't skip instrumentation of masked load/store unless we've seen a full load/store on that pointer.
Reviewers: kcc, RKSimon

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D27625

llvm-svn: 289718
2016-12-14 21:57:04 +00:00
Filipe Cabecinhas
978d341e1c [asan] Hook ClInstrumentWrites and ClInstrumentReads to masked operation instrumentation.
Reviewers: kcc

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D27548

llvm-svn: 289717
2016-12-14 21:56:59 +00:00
Eli Friedman
c9513096a1 [ARM] Split 128-bit vectors in BUILD_VECTOR lowering
Given that INSERT_VECTOR_ELT operates on D registers anyway, combining
64-bit vectors into a 128-bit vector is basically free. Therefore, try
to split BUILD_VECTOR nodes before giving up and lowering them to a series
of INSERT_VECTOR_ELT instructions. Sometimes this allows dramatically
better lowerings; see testcases for examples. Inspired by similar code
in the x86 backend for AVX.

Differential Revision: https://reviews.llvm.org/D27624

llvm-svn: 289706
2016-12-14 20:44:38 +00:00
Robert Lougher
2f625185c9 [InstCombine] Folding of a compare with RHS const should merge debug locations
If all the operands to a phi node are compares that have a RHS constant,
instcombine will try to pull them through the phi node, combining them into
a single operation. When it does this, the debug location of the new op
should be the merged debug locations of the phi node arguments.

Patch 8 of 8 for D26256.  Folding of a compare that has a RHS constant.

Differential Revision: https://reviews.llvm.org/D26256

llvm-svn: 289704
2016-12-14 20:27:22 +00:00
Eli Friedman
fbd3811bc0 [ARM] Add ARMISD::VLD1DUP to match vld1_dup more consistently.
Currently, there are substantial problems forming vld1_dup even if the
VDUP survives legalization. The lack of an actual node
leads to terrible results: not only can we not form post-increment vld1_dup
instructions, but we form scalar pre-increment and post-increment
loads which force the loaded value into a GPR. This patch fixes that
by combining the vdup+load into an ARMISD node before DAGCombine
messes it up.

Also includes a crash fix for vld2_dup (see testcase @vld2dupi8_postinc_variable).

Differential Revision: https://reviews.llvm.org/D27694

llvm-svn: 289703
2016-12-14 20:25:26 +00:00
Robert Lougher
4f006e8400 [InstCombine] Folding of a binop with RHS const should merge the debug locations
If all the operands to a phi node are a binop with a RHS constant, instcombine
will try to pull them through the phi node, combining them into a single
operation. When it does this, the debug location of the new op should be the
merged debug locations of the phi node arguments.

Patch 7 of 8 for D26256.  Folding of a binop with RHS constant.

Differential Revision: https://reviews.llvm.org/D26256

llvm-svn: 289699
2016-12-14 20:07:49 +00:00
Geoff Berry
e0fc91243e [GVNHoist] Move GVNHoist to function simplification part of pipeline.
Summary:
Move GVNHoist to later in the optimization pipeline, specifically, to
the function simplification part of the pipeline.  The new pipeline
location allows GVNHoist to run on a function after its callees have
been inlined but before the function has been considered for inlining
into its callers, exposing more opportunities for hoisting.

Performance results on AArch64 kryo:
Improvements:
  Benchmarks/CoyoteBench/fftbench  -24.952%
  spec2006/bzip2                    -4.071%
  internal bmark                    -3.177%
  Benchmarks/PAQ8p/paq8p            -1.754%
  spec2000/perlbmk                  -1.328%
  spec2006/h264ref                  -1.140%

Regressions:
  internal bmark                    +1.818%
  Benchmarks/mafft/pairlocalalign   +1.084%

Reviewers: sebpop, dberlin, hiraditya

Subscribers: aemerson, mehdi_amini, mcrosier, llvm-commits

Differential Revision: https://reviews.llvm.org/D27722

llvm-svn: 289696
2016-12-14 19:38:22 +00:00
Robert Lougher
af1853c43a [InstCombine] When folding casts through a phi node merge the debug locations
If all the operands to a phi node are a cast, instcombine will try to pull
them through the phi node, combining them into a single cast. When it does
this, the debug location of the new cast should be the merged debug locations
of the phi node arguments.

Patch 6 of 8 for D26256.  Folding of a cast operation.

Differential Revision: https://reviews.llvm.org/D26256

llvm-svn: 289693
2016-12-14 19:24:01 +00:00
Robert Lougher
66b5fbb84d [InstCombine] Folding loads through a phi node should merge the debug locations
If all the operands to a phi node are a load, instcombine will try to pull
them through the phi node, combining them into a single load. When it does
this, the debug location of the new load should be the merged debug locations
of the phi node arguments.

Patch 5 of 8 for D26256.  Folding of a load operation.

Differential Revision: https://reviews.llvm.org/D26256

llvm-svn: 289688
2016-12-14 19:02:14 +00:00
Robert Lougher
6783059cee [InstCombine] When folding GEP through a phi node merge the debug locations
If all the operands to a phi node are getelementptr, instcombine
will try to pull them through the phi node, combining them into a single
operation.  When it does this, the debug location of the new getelementptr
should be the merged debug locations of the phi node arguments.

Patch 4 of 8 for D26256.  Folding of a getelementptr operation.

Differential Revision: https://reviews.llvm.org/D26256

llvm-svn: 289684
2016-12-14 18:37:50 +00:00
Robert Lougher
ac0e540aa5 [InstCombine] Merge debug locations when folding through a phi node
If all the operands to a phi node are of the same operation, instcombine
will try to pull them through the phi node, combining them into a single
operation.  When it does this, the debug location of the operation should
be the merged debug locations of the phi node arguments.

Patch 3 of 8 for D26256.  Folding of a compare operation.

Differential Revision: https://reviews.llvm.org/D26256

llvm-svn: 289681
2016-12-14 18:14:57 +00:00
Robert Lougher
bf534d3173 [InstCombine] Merge debug locations when folding through a phi node
If all the operands to a phi node are of the same operation, instcombine
will try to pull them through the phi node, combining them into a single
operation.  When it does this, the debug location of the operation should
be the merged debug locations of the phi node arguments.

Patch 2 of 8 for D26256.  Folding of a binary operation.

Differential Revision: https://reviews.llvm.org/D26256

llvm-svn: 289679
2016-12-14 17:49:19 +00:00
Yaxun Liu
98de4b3c84 AMDGPU: Emit runtime metadata version 2 as YAML
Differential Revision: https://reviews.llvm.org/D25046

llvm-svn: 289674
2016-12-14 17:16:52 +00:00
Derek Schuff
faf0eebd7e lit.cfg: Check value of build config rather than converting to boolean
This is a CMake var which never evaluates to false.

llvm-svn: 289673
2016-12-14 17:05:34 +00:00
Nirav Dave
9fd3ae9cf9 Revert "In visitSTORE, always use FindBetterChain, rather than only when UseAA is enabled."
Reverting due to ARM MCJIT and MIPS LLD error.

This reverts commit r289659.

llvm-svn: 289667
2016-12-14 16:43:44 +00:00
Matt Arsenault
c74ace61e1 AMDGPU: Change vintrp printing
llvm-svn: 289664
2016-12-14 16:36:12 +00:00
Derek Schuff
8d68fc19a9 Revert gold part of change, just liblto
llvm-svn: 289663
2016-12-14 16:20:25 +00:00
Derek Schuff
25d8d3aa71 Disable libLTO tests when libLTO is not built
Summary:
The current test only checks whether ld64 is available, causing tests
to fail when ld64 is avilable but libLTO is not built.

Reviewers: beanz, mehdi_amini

Subscribers: mehdi_amini, llvm-commits

Differential Revision: https://reviews.llvm.org/D27739

llvm-svn: 289662
2016-12-14 16:20:22 +00:00
Nirav Dave
afe2eccae3 In visitSTORE, always use FindBetterChain, rather than only when UseAA is enabled.
Retrying after fixing after removing load-store factoring through
token factors in favor of improved token factor operand pruning

Simplify Consecutive Merge Store Candidate Search

Now that address aliasing is much less conservative, push through
simplified store merging search which only checks for parallel stores
through the chain subgraph. This is cleaner as the separation of
non-interfering loads/stores from the store-merging logic.

Whem merging stores, search up the chain through a single load, and
finds all possible stores by looking down from through a load and a
TokenFactor to all stores visited. This improves the quality of the
output SelectionDAG and generally the output CodeGen (with some
exceptions).

Additional Minor Changes:

   1. Finishes removing unused AliasLoad code
   2. Unifies the the chain aggregation in the merged stores across
      code paths
   3. Re-add the Store node to the worklist after calling
      SimplifyDemandedBits.
   4. Increase GatherAllAliasesMaxDepth from 6 to 18. That number is
      arbitrary, but seemed sufficient to not cause regressions in
      tests.

This finishes the change Matt Arsenault started in r246307 and
jyknight's original patch.

Many tests required some changes as memory operations are now
reorderable. Some tests relying on the order were changed to use
volatile memory operations

Noteworthy tests:

    CodeGen/AArch64/argument-blocks.ll -
      It's not entirely clear what the test_varargs_stackalign test is
      supposed to be asserting, but the new code looks right.

    CodeGen/AArch64/arm64-memset-inline.lli -
    CodeGen/AArch64/arm64-stur.ll -
    CodeGen/ARM/memset-inline.ll -

      The backend now generates *worse* code due to store merging
      succeeding, as we do do a 16-byte constant-zero store efficiently.

    CodeGen/AArch64/merge-store.ll -
      Improved, but there still seems to be an extraneous vector insert
      from an element to itself?

    CodeGen/PowerPC/ppc64-align-long-double.ll -
      Worse code emitted in this case, due to the improved store->load
      forwarding.

    CodeGen/X86/dag-merge-fast-accesses.ll -
    CodeGen/X86/MergeConsecutiveStores.ll -
    CodeGen/X86/stores-merging.ll -
    CodeGen/Mips/load-store-left-right.ll -
      Restored correct merging of non-aligned stores

    CodeGen/AMDGPU/promote-alloca-stored-pointer-value.ll -
      Improved. Correctly merges buffer_store_dword calls

    CodeGen/AMDGPU/si-triv-disjoint-mem-access.ll -
      Improved. Sidesteps loading a stored value and
      merges two stores

    CodeGen/X86/pr18023.ll -
      This test has been removed, as it was asserting incorrect
      behavior. Non-volatile stores *CAN* be moved past volatile loads,
      and now are.

    CodeGen/X86/vector-idiv.ll -
    CodeGen/X86/vector-lzcnt-128.ll -
      It's basically impossible to tell what these tests are actually
      testing. But, looks like the code got better due to the memory
      operations being recognized as non-aliasing.

    CodeGen/X86/win32-eh.ll -
      Both loads of the securitycookie are now merged.

Reviewers: arsenm, hfinkel, tstellarAMD, jyknight, nhaehnle

Subscribers: wdng, nhaehnle, nemanjai, arsenm, weimingz, niravd, RKSimon, aemerson, qcolombet, dsanders, resistor, tstellarAMD, t.p.northover, spatel

Differential Revision: https://reviews.llvm.org/D14834

llvm-svn: 289659
2016-12-14 15:44:26 +00:00
Simon Pilgrim
f05854a8a9 [DAGCombiner] Try to use SelectionDAG::isKnownToBeAPowerOfTwo instead of just APInt::isPowerOf2
Generalize sdiv/udiv/srem/urem combines using APInt::isPowerOf2, which only works for const/splat-const values, to call SelectionDAG::isKnownToBeAPowerOfTwo instead which recognises many more cases.

Added a DAGCombiner::BuildLogBase2 helper since PowerOf2 combines often involve taking the log2 of such a value.

Differential Revision: https://reviews.llvm.org/D27714

llvm-svn: 289654
2016-12-14 15:08:13 +00:00
Michael Zuckerman
2aaf4b3071 Fix bug 30945- [AVX512] Failure to flip vector comparison to remove not mask instruction
adding new optimization opportunity by adding new X86ISelLowering pattern. The test case was shown in https://llvm.org/bugs/show_bug.cgi?id=30945.

Test explanation:
Select gets three arguments mask, op and op2. In this case, the Mask is a result of ICMP. The ICMP instruction compares (with equal operand) the zero initializer vector and the result of the first ICMP.

In general, The result of "cmp eq, op1, zero initializers" is "not(op1)" where op1 is a mask. By rearranging of the two arguments inside the Select instruction, we can get the same result. Without the necessary of the middle phase ("cmp eq, op1, zero initializers").

Missed optimization opportunity: 
vpcmpled %zmm0, %zmm1, %k0
knotw %k0, %k1

can be combine to 
vpcmpgtd %zmm0, %zmm2, %k1

Reviewers: 
1. delena
2. igorb 

Commited after check all 
Differential Revision: https://reviews.llvm.org/D27160

llvm-svn: 289653
2016-12-14 14:57:10 +00:00
Simon Pilgrim
e235162ad6 [X86][SSE] Add AVX1 tests to sdiv/udiv srem/urem combine tests
As requested on D27714

llvm-svn: 289652
2016-12-14 14:39:51 +00:00
Renato Golin
8d9c51307d Revert "[AVR] Add the very first on-target test"
This reverts commit r289648, as it's an execution test and relies on the
emulator/dispatcher being available on all builders.

llvm-svn: 289651
2016-12-14 13:24:20 +00:00
Dylan McKay
ebd67f8b91 [AVR] Add the very first on-target test
This test runs on actual AVR hardware.

llvm-svn: 289648
2016-12-14 12:03:39 +00:00
Oliver Stannard
f0a90b93e6 [Assembler] Better error messages for .org directive
Currently, the error messages we emit for the .org directive when the
expression is not absolute or is out of range do not include the line
number of the directive, so it can be hard to track down the problem if
a file contains many .org directives.

This patch stores the source location in the MCOrgFragment, so that it
can be used for diagnostics emitted during layout.

Since layout is an iterative process, and the errors are detected during
each iteration, it would have been possible for errors to be reported
multiple times. To prevent this, I've made the assembler bail out after
each iteration if any errors have been reported. This will still allow
multiple unrelated errors to be reported in the common case where they
are all detected in the first round of layout.

Differential Revision: https://reviews.llvm.org/D27411

llvm-svn: 289643
2016-12-14 10:43:58 +00:00
Dylan McKay
fea5788d65 [AVR] Add a function instrumentation pass
This will be used for an on-chip test suite.

llvm-svn: 289641
2016-12-14 10:15:00 +00:00
Craig Topper
a7a943094c [X86][InstCombine] Handle demanded elements for operand of AVX-512 scalar floating point to integer conversion intrinsics.
llvm-svn: 289639
2016-12-14 07:46:12 +00:00
Hal Finkel
972f16ac78 [PowerPC] Fix logic dealing with nop after calls (and tail-call eligibility)
This change aims to unify and correct our logic for when we need to allow for
the possibility of the linker adding a TOC restoration instruction after a
call. This comes up in two contexts:

 1. When determining tail-call eligibility. If we make a tail call (i.e.
    directly branch to a function) then there is no place for the linker to add
    a TOC restoration.
 2. When determining when we need to add a nop instruction after a call.
    Likewise, if there is a possibility that the linker might need to add a
    TOC restoration after a call, then we need to put a nop after the call
    (the bl instruction).

First problem: We were using similar, but different, logic to decide (1) and
(2). This is just wrong. Both the resideInSameModule function (used when
determining tail-call eligibility) and the isLocalCall function (used when
deciding if the post-call nop is needed) were supposed to be determining the
same underlying fact (i.e. might a TOC restoration be needed after the call).
The same logic should be used in both places.

Second problem: The logic in both places was wrong. We only know that two
functions will share the same TOC when both functions come from the same
section of the same object. Otherwise the linker might cause the functions to
use different TOC base addresses (unless the multi-TOC linker option is
disabled, in which case only shared-library boundaries are relevant). There are
a number of factors that can cause functions to be placed in different sections
or come from different objects (-ffunction-sections, explicitly-specified
section names, COMDAT, weak linkage, etc.). All of these need to be checked.
The existing logic only checked properties of the callee, but the properties of
the caller must also be checked (for example, calling from a function in a
COMDAT section means calling between sections).

There was a conceptual error in the resideInSameModule function in that it
allowed tail calls to functions with weak linkage and protected/hidden
visibility. While protected/hidden visibility does prevent the function
implementation from being replaced at runtime (via interposition), it does not
prevent the linker from using an alternate implementation at link time (i.e.
using some strong definition to replace the provided weak one during linking).
If this happens, then we're still potentially looking at a required TOC
restoration upon return.

Otherwise, in general, the post-call nop is needed wherever ELF interposition
needs to be supported. We don't currently support ELF interposition at the IR
level (see http://lists.llvm.org/pipermail/llvm-dev/2016-November/107625.html
for more information), and I don't think we should try to make it appear to
work in the backend in spite of that fact. This will yield subtle bugs if
interposition is attempted. As a result, regardless of whether we're in PIC
mode, we don't assume that we need to add the nop to support the possibility of
ELF interposition. However, the necessary check is in place (i.e. calling
GV->isInterposable and TM.shouldAssumeDSOLocal) so when we have functions for
which interposition is allowed at the IR level, we'll add the nop as necessary.
In the mean time, we'll generate more tail calls and fewer nops when compiling
position-independent code.

Differential Revision: https://reviews.llvm.org/D27231

llvm-svn: 289638
2016-12-14 07:24:50 +00:00
Craig Topper
402d6bf13b [X86][InstCombine] Teach SimplifyDemandedVectorElts to handle masked scalar add/sub/mul/div/max/min intrinsics better.
Now we can remove these intrinsics if element 0 isn't used. Also fix undef element tracking.

llvm-svn: 289636
2016-12-14 06:06:58 +00:00
Mehdi Amini
1c61c19903 [ThinLTO] Add an API to trigger file-based API for returning objects to the linker
Summary:
The motivation is to support better the -object_path_lto option on
Darwin. The linker needs to write down the generate object files on
disk for later use by lldb or dsymutil (debug info are not present
in the final binary). We're moving this into libLTO so that we can
be smarter when a cache is enabled and hard-link when possible
instead of duplicating the files.

Reviewers: tejohnson, deadalnix, pcc

Subscribers: dexonsmith, llvm-commits

Differential Revision: https://reviews.llvm.org/D27507

llvm-svn: 289631
2016-12-14 04:56:42 +00:00
Peter Collingbourne
3b1ff75ab8 LTO: Add support for multi-module bitcode files.
Differential Revision: https://reviews.llvm.org/D27313

llvm-svn: 289621
2016-12-14 01:17:59 +00:00
Paul Robinson
fee2a350dc [DWARF] Preserve column number when emitting 'line 0' record
Follow-up to r289256, address a FIXME to avoid resetting the column
number. This reduced .debug_line by 2.6% in a RelWithDebInfo
self-build of clang.

llvm-svn: 289620
2016-12-14 00:27:35 +00:00
Evandro Menezes
f2e582c435 [ARM] Fix typo in checking prefix
llvm-svn: 289617
2016-12-14 00:02:03 +00:00
Evandro Menezes
d6a1cb395c Add support for Samsung Exynos M3 (NFC)
llvm-svn: 289613
2016-12-13 23:31:41 +00:00
Chris Bieneman
4bed4ed8ab [llvm-config] Add --ignore-libllvm
This flag forces off linking libLLVM. This should resolve some issues reported on llvm-commits.

llvm-svn: 289605
2016-12-13 22:17:59 +00:00
Anna Thomas
d7d47f4ccb [IRCE] Avoid loop optimizations on pre and post loops
Summary:
This patch will add loop metadata on the pre and post loops generated by IRCE.
Currently, we have metadata for disabling optimizations such as vectorization,
unrolling, loop distribution and LICM versioning (and confirmed that these
optimizations check for the metadata before proceeding with the transformation).

The pre and post loops generated by IRCE need not go through loop opts (since
these are slow paths).

Added two test cases as well.

Reviewers: sanjoy, reames

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D26806

llvm-svn: 289588
2016-12-13 21:05:21 +00:00
Michael Kuperstein
2c0f3dbd6f [LV] Don't vectorize when we have a small static bound on trip count
We currently check if the exact trip count is known and is smaller than the
"tiny loop" bound. We should be checking the maximum bound on the trip count
instead.

Differential Revision: https://reviews.llvm.org/D27690

llvm-svn: 289583
2016-12-13 20:38:18 +00:00
Peter Collingbourne
87a2fe46d9 Object: Make IRObjectFile own multiple modules and enumerate symbols from all modules.
This implements multi-module support in IRObjectFile.

Differential Revision: https://reviews.llvm.org/D26951

llvm-svn: 289578
2016-12-13 20:20:17 +00:00
Alina Sbirlea
81ca226117 Generalize strided store pattern in interleave access pass
Summary:
This patch aims to generalize matching of the strided store accesses to more general masks.
The more general rule is to have consecutive accesses based on the stride:
[x, y, ... z, x+1, y+1, ...z+1, x+2, y+2, ...z+2, ...]
All elements in the masks need not form a contiguous space, there may be gaps.
As before, undefs are allowed and filled in with adjacent element loads.

Reviewers: HaoLiu, mssimpso

Subscribers: mkuper, delena, llvm-commits

Differential Revision: https://reviews.llvm.org/D23646

llvm-svn: 289573
2016-12-13 19:32:36 +00:00
Matthias Braun
98ab51d843 Revert "AArch64CollectLOH: Rewrite as block-local analysis."
This is not always behaving as expected as it turns out block live-in
lists are only correct most of the time. Still waiting for reviews on
https://reviews.llvm.org/D27559 to have them correct all of the time.

See also http://llvm.org/PR31361, rdar://25117107

This reverts commit r288567.
This reverts commit r288561.

llvm-svn: 289570
2016-12-13 19:08:17 +00:00
Tim Northover
24088c5166 GlobalISel: fix GOT accesses on AArch64.
We were using the correct pseudo-instruction, but because the operand's flags
weren't set correctly we still ended up emitting incorrect relocations during
MC lowering.

llvm-svn: 289566
2016-12-13 18:25:38 +00:00
Rong Xu
e788cd0e3c Fix the test cases committed in r289521.
llvm-svn: 289556
2016-12-13 17:34:29 +00:00
Simon Pilgrim
7b2c71035d [X86][SSE] Regenerate vector of pointers tests
llvm-svn: 289555
2016-12-13 17:22:39 +00:00
David Callahan
86eb682529 [ADCE] Add code to remove dead branches
Summary:
This is last in of a series of patches to evolve ADCE.cpp to support
removing of unnecessary control flow.

This patch adds the code to update the control and data flow graphs
to remove the dead control flow.

Also update unit tests to test the capability to remove dead,
may-be-infinite loop which is enabled by the switch
-adce-remove-loops.

Previous patches:

D23824 [ADCE] Add handling of PHI nodes when removing control flow
D23559 [ADCE] Add control dependence computation
D23225 [ADCE] Modify data structures to support removing control flow
D23065 [ADCE] Refactor anticipating new functionality (NFC)
D23102 [ADCE] Refactoring for new functionality (NFC)

Reviewers: dberlin, majnemer, nadav, mehdi_amini

Subscribers: llvm-commits, david2050, freik, twoh

Differential Revision: https://reviews.llvm.org/D24918

llvm-svn: 289548
2016-12-13 16:42:18 +00:00
Artur Pilipenko
5f36ddf06d [DAGCombiner] Match load by bytes idiom and fold it into a single load
Match a pattern where a wide type scalar value is loaded by several narrow loads and combined by shifts and ors. Fold it into a single load or a load and a bswap if the targets supports it.

Assuming little endian target:
  i8 *a = ...
  i32 val = a[0] | (a[1] << 8) | (a[2] << 16) | (a[3] << 24)
=>
  i32 val = *((i32)a)

  i8 *a = ...
  i32 val = (a[0] << 24) | (a[1] << 16) | (a[2] << 8) | a[3]
=>
  i32 val = BSWAP(*((i32)a))

This optimization was discussed on llvm-dev some time ago in "Load combine pass" thread. We came to the conclusion that we want to do this transformation late in the pipeline because in presence of atomic loads load widening is irreversible transformation and it might hinder other optimizations.

Eventually we'd like to support folding patterns like this where the offset has a variable and a constant part:
  i32 val = a[i] | (a[i + 1] << 8) | (a[i + 2] << 16) | (a[i + 3] << 24)

Matching the pattern above is easier at SelectionDAG level since address reassociation has already happened and the fact that the loads are adjacent is clear. Understanding that these loads are adjacent at IR level would have involved looking through geps/zexts/adds while looking at the addresses.

The general scheme is to match OR expressions by recursively calculating the origin of individual bits which constitute the resulting OR value. If all the OR bits come from memory verify that they are adjacent and match with little or big endian encoding of a wider value. If so and the load of the wider type (and bswap if needed) is allowed by the target generate a load and a bswap if needed.

Reviewed By: hfinkel, RKSimon, filcab

Differential Revision: https://reviews.llvm.org/D26149

llvm-svn: 289538
2016-12-13 14:21:14 +00:00