Commit Graph

24443 Commits

Author SHA1 Message Date
Dinesh Dwivedi
c469e543a0 Added inst combine transforms for single bit tests from Chris's note
if ((x & C) == 0) x |= C becomes x |= C
if ((x & C) != 0) x ^= C becomes x &= ~C
if ((x & C) == 0) x ^= C becomes x |= C
if ((x & C) != 0) x &= ~C becomes x &= ~C
if ((x & C) == 0) x &= ~C becomes nothing

Differential Revision: http://reviews.llvm.org/D3777



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210006 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-02 07:24:36 +00:00
Christian Pirker
27e80698ef ARMEB: Fix function return type f64
Reviewed at http://reviews.llvm.org/D3968



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209990 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-01 09:30:52 +00:00
David Blaikie
0d9056d766 DebugInfo: Assert that DbgVariables have associated DIEs
This was previously committed in r209680 and reverted in r209683 after
it caused sanitizer builds to crash.

The issue seems to be that the DebugLoc associated with dbg.value IR
intrinsics isn't necessarily accurate. Instead, we duplicate the
DIVariables and add an InlinedAt field to them to record their
location.

We were using this InlinedAt field to compute the LexicalScope for the
variable, but not using it in the abstract DbgVariable construction and
mapping. This resulted in a formal parameter to the current concrete
function, correctly having no InlinedAt information, but incorrectly
having a DebugLoc that described an inlined location within the
function... thus an abstract DbgVariable was created for the variable,
but its DIE was never constructed (since the LexicalScope had no such
variable). This DbgVariable was silently ignored (by testing for a
non-null DIE on the abstract DbgVariable).

So, fix this by using the right scoping information when constructing
abstract DbgVariables.

In the long run, I suspect we want to undo the work that added this
second kind of location tracking and fix the places where the DebugLoc
propagation on the dbg.value intrinsic fails. This will shrink debug
info (by not duplicating DIVariables), make it more efficient (by not
having to construct new DIVariable metadata nodes to try to map back to
a single variable), and benefit all instructions.

But perhaps there are insurmountable issues with DebugLoc quality that
I'm unaware of... I just don't know how we can't /just keep the DebugLoc
from the dbg.declare to the dbg.values and never get this wrong/.

Some history context:

http://llvm.org/viewvc/llvm-project?view=revision&revision=135629
http://llvm.org/viewvc/llvm-project?view=revision&revision=137253

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209984 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-01 03:38:13 +00:00
Alp Toker
4a0555250d Fix typos
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209982 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-31 21:26:28 +00:00
Benjamin Kramer
37bc2f3216 [Reassociate] Similar to "X + -X" -> "0", added code to handle "X + ~X" -> "-1".
Handle "X + ~X" -> "-1" in the function Value *Reassociate::OptimizeAdd(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
This patch implements:
TODO: We could handle "X + ~X" -> "-1" if we wanted, since "-X = ~X+1".

Patch by Rahul Jain!

Differential Revision: http://reviews.llvm.org/D3835

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209973 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-31 15:01:54 +00:00
Matt Arsenault
da5824d073 R600/SI: Fix [s|u]int_to_fp for i1
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209971 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-31 06:47:42 +00:00
Simon Atanasyan
df96c562a5 [yaml2obj] Add new command line option -docnum.
Input YAML file might contain multiple object file definitions.
New option `-docnum` allows to specify an ordinal number (starting from 1)
of definition used for an object file generation.

Patch reviewed by Sean Silva.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209967 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-31 04:51:07 +00:00
Filipe Cabecinhas
c3648ce2dc Make blend tests more specific
Following the lead set by r209324, I'm making these tests match the whole
instruction, so we can be sure we're lowering them correctly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209947 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-31 00:52:23 +00:00
Alexey Samsonov
014f9fd863 [TSan] Fixup a test case after r209939
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209945 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-31 00:26:03 +00:00
Andrea Di Biagio
1726e2ff15 [X86] Add two combine rules to simplify dag nodes introduced during type legalization when promoting nodes with illegal vector type.
This patch teaches the backend how to simplify/canonicalize dag node
sequences normally introduced by the backend when promoting certain dag nodes
with illegal vector type.

This patch adds two new combine rules:
1) fold (shuffle (bitcast (BINOP A, B)), Undef, <Mask>) ->
        (shuffle (BINOP (bitcast A), (bitcast B)), Undef, <Mask>)

2) fold (BINOP (shuffle (A, Undef, <Mask>)), (shuffle (B, Undef, <Mask>))) ->
        (shuffle (BINOP A, B), Undef, <Mask>).

Both rules are only triggered on the type-legalized DAG.
In particular, rule 1. is a target specific combine rule that attempts
to sink a bitconvert into the operands of a binary operation.
Rule 2. is a target independet rule that attempts to move a shuffle
immediately after a binary operation.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209930 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 23:17:53 +00:00
Filipe Cabecinhas
d99cefbad1 Convert a vselect into a concat_vector if possible
Summary:
If both vector args to vselect are concat_vectors and the condition is
constant and picks half a vector from each argument, convert the vselect
into a concat_vectors.

Added a test.

The ConvertSelectToConcatVector is assuming it doesn't get vselects with
arguments of, for example, <undef, undef, true, true>. Those get taken
care of in the checks above its call.

Reviewers: nadav, delena, grosbach, hfinkel

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D3916

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209929 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 23:03:11 +00:00
Filipe Cabecinhas
94141a42ed Separate the check for blend shuffle_vector masks
Summary:
Separate the check for blend shuffle_vector masks into isBlendMask.
This function will also be used to check if a vector shuffle is legal. No
change in functionality was intended, but we ended up improving codegen on
two tests, which were being (more) optimized only if the resulting shuffle
was legal.

Reviewers: nadav, delena, andreadb

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D3964

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209923 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 21:31:21 +00:00
Matt Arsenault
c4e0611d86 Make bitcast, extractelement, and insertelement considered cheap for speculation.
This helps more branches into selects. On R600,
vectors are cheap and anything that helps
remove branches is very good.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209914 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 18:34:43 +00:00
Logan Chien
731d23ed42 Fix MIPS exception personality encoding.
For MIPS, we have to encode the personality routine with
an indirect pointer to absptr; otherwise, some link warning
warning will be raised, and the program might crash in some
early MIPS Android device.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209907 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 16:48:56 +00:00
Tim Northover
ba735134d7 MachO: move test to ARM directory.
This test specifies an ARM triple, so it needs ARM as a registered
target.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209905 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 16:01:29 +00:00
Rafael Espindola
fcb9926813 PR19753: Optimize comparisons with "ashr exact" of a constanst.
Patch by suyog sarda.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209903 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 15:54:32 +00:00
Rafael Espindola
6319c0c520 [pr19636] Fix known bit computation in urem instruction with power of two.
Patch by Andrey Kuharev.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209902 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 15:00:45 +00:00
Tim Northover
3a45d4c621 SelectionDAG: skip barriers for unordered atomic operations
Unordered is strictly weaker than monotonic, so if the latter doesn't have any
barriers then the former certainly shouldn't.

rdar://problem/16548260

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209901 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 14:41:51 +00:00
Tim Northover
645c5b94e2 ARM: use AAPCS-style prologues for embedded MachO.
Darwin prologues save their GPRs in two stages: a narrow push of r0-r7 & lr,
followed by a wide push of the remaining registers if there are any. AAPCS uses
a single push.w instruction.

It turns out that, on average, enough registers get pushed that code is smaller
in the AAPCS prologue, which is a nice property for M-class programmers. They
also have other options available for back-traces, so can hopefully deal with
the fact that FP & LR aren't adjacent in memory.

rdar://problem/15909583

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209895 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 13:23:06 +00:00
Tim Northover
98f8bc9323 MachO: support N_INDR aliases in assembly files.
This makes LLVM create N_INDR aliases (to be resolved by the linker) when
appropriate.

rdar://problem/15125513

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209894 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 13:22:59 +00:00
Tim Northover
910dc41e24 AArch64 & ARM: disable generic test that relies on no CFG changes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209885 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 10:56:12 +00:00
Tim Northover
d0dbe02fd2 ARM & AArch64: make use of common cmpxchg idioms after expansion
The C and C++ semantics for compare_exchange require it to return a bool
indicating success. This gets mapped to LLVM IR which follows each cmpxchg with
an icmp of the value loaded against the desired value.

When lowered to ldxr/stxr loops, this extra comparison is redundant: its
results are implicit in the control-flow of the function.

This commit makes two changes: it replaces that icmp with appropriate PHI
nodes, and then makes sure earlyCSE is called after expansion to actually make
use of the opportunities revealed.

I've also added -{arm,aarch64}-enable-atomic-tidy options, so that
existing fragile tests aren't perturbed too much by the change. Many
of them either rely on undef/unreachable too pervasively to be
restored to something well-defined (particularly while making sure
they test the same obscure assert from many years ago), or depend on a
particular CFG shape, which is disrupted by SimplifyCFG.

rdar://problem/16227836

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209883 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 10:09:59 +00:00
Tim Northover
7be505ae88 AArch64 & ARM: remove undefined behaviour from some tests.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209880 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 08:59:55 +00:00
Hao Liu
fd481d05be Test cases named with dates is a legacy rule not used now. Rename several test cases.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209877 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 05:58:19 +00:00
Karthik Bhat
8ffc96a163 Allow vectorization of intrinsics such as powi,cttz and ctlz in Loop and SLP Vectorizer.
This patch adds support to vectorize intrinsics such as powi, cttz and ctlz in Vectorizer. These intrinsics are different from other
intrinsics as second argument to these function must be same in order to vectorize them and it should be represented as a scalar.
Review: http://reviews.llvm.org/D3851#inline-32769 and http://reviews.llvm.org/D3937#inline-32857


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209873 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 04:31:24 +00:00
Nick Lewycky
a35be5ab67 When analyzing params/args for readnone/readonly, don't forget to consider that a pointer argument may be passed through a callsite to the return, and that we may need to analyze it. Fixes a bug reported on llvm-dev: http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-May/073098.html
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209870 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-30 02:31:27 +00:00
Adam Nemet
0997206ac4 [X86] Move test from r209863 to CodeGen/X86
We should only run this if X86 is in the targets.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209866 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 23:52:53 +00:00
Adam Nemet
7cd893a985 [X86] Remove AVX1 vbroadcast intrinsics
The corresponding CFE patch replaces these intrinsics with vector initializers
in avxintrin.h.  This patch removes the LLVM intrinsics from the backend.

We now stop lowering at X86ISD::VBROADCAST custom node rather than lowering
that further to the intrinsics.

The patch only changes VBROADCASTS* and leaves VBROADCAST[FI]128 to continue
to use intrinsics.  As explained in the CFE patch, the reason is that we
currently don't generate as good code for them without the intrinsics.

CodeGen/X86/avx-vbroadcast.ll already provides coverage for this change.  It
checks that for a series of insertelements we generate the appropriate
vbroadcast instruction.

Also verified that there was no assembly change in the test-suite before and
after this patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209864 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 23:35:36 +00:00
Adam Nemet
23356d4d64 [X86] Auto-upgrade AVX1 vbroadcast intrinsics
They are replaced with the same IR that is generated for the
vector-initializers in avxintrin.h.

The test verifies that we get back the original instruction.  I haven't seen
this approach to be used in other auto-upgrade tests (i.e. llc + FileCheck)
but I think it's the most direct way to test this case.  I believe this should
work because llc upgrades calls during parsing.  (Other tests mostly check
that assembling and disassembling yields the upgraded IR.)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209863 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 23:35:33 +00:00
Arnold Schwaighofer
06413cd0f0 LoopVectorizer: Add a check that the backedge taken count + 1 does not overflow
The loop vectorizer instantiates be-taken-count + 1 as the loop iteration count.
If this expression overflows the generated code was invalid.

In case of overflow the code now jumps to the scalar loop.

Fixes PR17288.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209854 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 22:10:01 +00:00
Filipe Cabecinhas
ade072c1a9 Added tests for shufflevector lowering to blend instrs.
These tests ensure that a change I will propose in clang works as
expected.

Summary:
Added tests for the generation of blend+immediate instructions from a
shufflevector.
These tests were proposed along with a patch that was dropped. I'm
committing the tests anyway to protect against possible regressions in
codegen.

Reviewers: nadav, bkramer

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D3600

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209853 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 22:04:42 +00:00
Louis Gerbarg
78874456fc Add support for combining GEPs across PHI nodes
Currently LLVM will generally merge GEPs. This allows backends to use more
complex addressing modes. In some cases this is not happening because there
is PHI inbetween the two GEPs:

  GEP1--\
        |-->PHI1-->GEP3
  GEP2--/

This patch checks to see if GEP1 and GEP2 are similiar enough that they can be
cloned (GEP12) in GEP3's BB, allowing GEP->GEP merging (GEP123):

  GEP1--\                     --\                           --\
        |-->PHI1-->GEP3  ==>    |-->PHI2->GEP12->GEP3 == >    |-->PHI2->GEP123
  GEP2--/                     --/                           --/

This also breaks certain use chains that are preventing GEP->GEP merges that the
the existing instcombine would merge otherwise.

Tests included.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209843 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 20:29:47 +00:00
Rafael Espindola
d4aff6892b Rename alias variables to make it easier to add new tests to the file.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209822 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 16:16:12 +00:00
Rafael Espindola
289a9d75de [PPC] Use alias symbols in address computation.
This seems to match what gcc does for ppc and what every other llvm
backend does.

This is a fixed version of r209638. The difference is to avoid any change
in behavior for functions. The logic for using constant pools for function
addresseses is spread over a few places and we have to keep them in sync.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209821 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 15:41:38 +00:00
Rafael Espindola
f5df18bff0 Add a test showing the ppc code sequence for getting a function pointer.
This would have found the miscompile in r209638.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209820 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 15:13:23 +00:00
Rafael Espindola
843ac4747a Revert "Revert "Revert "InstCombine: Improvement to check if signed addition overflows."""
This reverts commit r209776.

It was miscompiling llvm::SelectionDAGISel::MorphNode.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209817 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 14:39:16 +00:00
Artyom Skrobov
897fd5f0ed Restore getInvertedCondCode() from the phased-out backend, fixing disassembly for NV
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209803 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 11:34:50 +00:00
Artyom Skrobov
684122e84e Add missing check when MatchInstructionImpl() reports failure
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209802 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 11:26:15 +00:00
Simon Atanasyan
ce538c7834 [elf2yaml][ELF] Move Info field to the RelocationSection structure. This
field represents ELF section header sh_info field and does not have any
sense for regular sections. Its interpretation depends on section type.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209801 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 11:05:31 +00:00
Hao Liu
086a708135 Rename a test case to contain correct date info.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209799 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 09:21:23 +00:00
Hao Liu
bb7f18abf8 Fix an assertion failure caused by v1i64 in DAGCombiner Shrink.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209798 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 09:19:07 +00:00
Dinesh Dwivedi
2a747bf1c5 LCSSA should be performed on the outermost affected loop while unrolling loop.
During loop-unroll, loop exits from the current loop may end up in in different
outer loop. This requires to re-form LCSSA recursively for one level down from
the outer most loop where loop exits are landed during unroll. This fixes PR18861.

Differential Revision: http://reviews.llvm.org/D2976



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209796 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 06:47:23 +00:00
Michael J. Spencer
8bfb46e790 Add LoadCombine pass.
This pass is disabled by default. Use -combine-loads to enable in -O[1-3]

Differential revision: http://reviews.llvm.org/D3580

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209791 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 01:55:07 +00:00
Michael J. Spencer
11ef9456a8 [x86] Fold extract_vector_elt of a load into the Load's address computation.
An address only use of an extract element of a load can be simplified to a
load. Without this the result of the extract element is spilled to the
stack so that an address is available.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209788 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 01:42:45 +00:00
Alexey Samsonov
b18eabd2d8 [ASan] Use llvm.global_ctors to insert init-order checking calls into ASan runtime.
Don't assume that dynamically initialized globals are all initialized from
_GLOBAL__<module_name>I_ function. Instead, scan the llvm.global_ctors and
insert poison/unpoison calls to each function there.

Patch by Nico Weber!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209780 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-29 00:51:15 +00:00
Rafael Espindola
c81cf72ef3 Revert "Revert "InstCombine: Improvement to check if signed addition overflows.""
This reverts commit r209762, bringing back r209746. It was not responsible for the libc++ build failure

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209776 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-28 21:43:52 +00:00
Rafael Espindola
836475b2e2 Revert "Add support for combining GEPs across PHI nodes"
This reverts commit r209755.

it was the real cause of the libc++ build failure.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209775 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-28 21:41:21 +00:00
Rafael Espindola
e04c0e3f8d Revert "InstCombine: Improvement to check if signed addition overflows."
This reverts commit r209746.

It looks it is causing a crash while building libcxx. I am trying to get a
reduced testcase.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209762 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-28 18:48:10 +00:00
Rafael Espindola
665d42accf [pr19844] Add thread local mode to aliases.
This matches gcc's behavior. It also seems natural given that aliases
contain other properties that govern how it is accessed (linkage,
visibility, dll storage).

Clang still has to be updated to expose this feature to C.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209759 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-28 18:15:43 +00:00
Louis Gerbarg
a5423f2598 Add support for combining GEPs across PHI nodes
Currently LLVM will generally merge GEPs. This allows backends to use more
complex addressing modes. In some cases this is not happening because there
is PHI inbetween the two GEPs:

  GEP1--\
        |-->PHI1-->GEP3
  GEP2--/

This patch checks to see if GEP1 and GEP2 are similiar enough that they can be
cloned (GEP12) in GEP3's BB, allowing GEP->GEP merging (GEP123):

  GEP1--\                     --\                           --\
        |-->PHI1-->GEP3  ==>    |-->PHI2->GEP12->GEP3 == >    |-->PHI2->GEP123
  GEP2--/                     --/                           --/

This also breaks certain use chains that are preventing GEP->GEP merges that the
the existing instcombine would merge otherwise.

Tests included.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209755 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-28 17:38:31 +00:00