| #
72ccea31 |
| 12-Jul-2019 |
Dimitry Andric <[email protected]> |
MFC r349583:
Pull in r360968 from upstream llvm trunk (by Philip Reames):
Clarify comments on helpers used by LFTR [NFC]
I'm slowly wrapping my head around this code, and am making comment
i
MFC r349583:
Pull in r360968 from upstream llvm trunk (by Philip Reames):
Clarify comments on helpers used by LFTR [NFC]
I'm slowly wrapping my head around this code, and am making comment
improvements where I can.
Pull in r360972 from upstream llvm trunk (by Philip Reames):
[LFTR] Factor out a helper function for readability purpose [NFC]
Pull in r360976 from upstream llvm trunk (by Philip Reames):
[IndVars] Don't reimplement Loop::isLoopInvariant [NFC]
Using dominance vs a set membership check is indistinguishable from a
compile time perspective, and the two queries return equivelent
results. Simplify code by using the existing function.
Pull in r360978 from upstream llvm trunk (by Philip Reames):
[LFTR] Strengthen assertions in genLoopLimit [NFCI]
Pull in r362292 from upstream llvm trunk (by Nikita Popov):
[IndVarSimplify] Fixup nowrap flags during LFTR (PR31181)
Fix for https://bugs.llvm.org/show_bug.cgi?id=31181 and partial fix
for LFTR poison handling issues in general.
When LFTR moves a condition from pre-inc to post-inc, it may now
depend on value that is poison due to nowrap flags. To avoid this, we
clear any nowrap flag that SCEV cannot prove for the post-inc addrec.
Additionally, LFTR may switch to a different IV that is dynamically
dead and as such may be arbitrarily poison. This patch will correct
nowrap flags in some but not all cases where this happens. This is
related to the adoption of IR nowrap flags for the pre-inc addrec.
(See some of the switch_to_different_iv tests, where flags are not
dropped or insufficiently dropped.)
Finally, there are likely similar issues with the handling of GEP
inbounds, but we don't have a test case for this yet.
Differential Revision: https://reviews.llvm.org/D60935
Pull in r362971 from upstream llvm trunk (by Philip Reames):
Prepare for multi-exit LFTR [NFC]
This change does the plumbing to wire an ExitingBB parameter through
the LFTR implementation, and reorganizes the code to work in terms of
a set of individual loop exits. Most of it is fairly obvious, but
there's one key complexity which makes it worthy of consideration.
The actual multi-exit LFTR patch is in D62625 for context.
Specifically, it turns out the existing code uses the backedge taken
count from before a IV is widened. Oddly, we can end up with a
different (more expensive, but semantically equivelent) BE count for
the loop when requerying after widening. For the nestedIV example
from elim-extend, we end up with the following BE counts:
BEFORE: (-2 + (-1 * %innercount) + %limit)
AFTER: (-1 + (sext i32 (-1 + %limit) to i64) + (-1 * (sext i32 %innercount to i64))<nsw>)
This is the only test in tree which seems sensitive to this
difference. The actual result of using the wider BETC on this example
is that we actually produce slightly better code. :)
In review, we decided to accept that test change. This patch is
structured to preserve the old behavior, but a separate change will
immediate follow with the behavior change. (I wanted it separate for
problem attribution purposes.)
Differential Revision: https://reviews.llvm.org/D62880
Pull in r362975 from upstream llvm trunk (by Philip Reames):
[LFTR] Use recomputed BE count
This was discussed as part of D62880. The basic thought is that
computing BE taken count after widening should produce (on average)
an equally good backedge taken count as the one before widening.
Since there's only one test in the suite which is impacted by this
change, and it's essentially equivelent codegen, that seems to be a
reasonable assertion. This change was separated from r362971 so that
if this turns out to be problematic, the triggering piece is obvious
and easily revertable.
For the nestedIV example from elim-extend.ll, we end up with the
following BE counts:
BEFORE: (-2 + (-1 * %innercount) + %limit)
AFTER: (-1 + (sext i32 (-1 + %limit) to i64) + (-1 * (sext i32 %innercount to i64))<nsw>)
Note that before is an i32 type, and the after is an i64. Truncating
the i64 produces the i32.
Pull in r362980 from upstream llvm trunk (by Philip Reames):
Factor out a helper function for readability and reuse in a future
patch [NFC]
Pull in r363613 from upstream llvm trunk (by Philip Reames):
Fix a bug w/inbounds invalidation in LFTR (recommit)
Recommit r363289 with a bug fix for crash identified in pr42279.
Issue was that a loop exit test does not have to be an icmp, leading
to a null dereference crash when new logic was exercised for that
case. Test case previously committed in r363601.
Original commit comment follows:
This contains fixes for two cases where we might invalidate inbounds
and leave it stale in the IR (a miscompile). Case 1 is when switching
to an IV with no dynamically live uses, and case 2 is when doing
pre-to-post conversion on the same pointer type IV.
The basic scheme used is to prove that using the given IV (pre or
post increment forms) would have to already trigger UB on the path to
the test we're modifying. As such, our potential UB triggering use
does not change the semantics of the original program.
As was pointed out in the review thread by Nikita, this is defending
against a separate issue from the hasConcreteDef case. This is about
poison, that's about undef. Unfortunately, the two are different, see
Nikita's comment for a fuller explanation, he explains it well.
(Note: I'm going to address Nikita's last style comment in a separate
commit just to minimize chance of subtle bugs being introduced due to
typos.)
Differential Revision: https://reviews.llvm.org/D62939
Pull in r363875 from upstream llvm trunk (by Philip Reames):
[LFTR] Rename variable to minimize confusion [NFC]
(Recommit of r363293 which was reverted when a dependent patch was.)
As pointed out by Nikita in D62625, BackedgeTakenCount is generally
used to refer to the backedge taken count of the loop. A conditional
backedge taken count - one which only applies if a particular exit is
taken - is called a ExitCount in SCEV code, so be consistent here.
Pull in r363877 from upstream llvm trunk (by Philip Reames):
[LFTR] Stylistic cleanup as suggested in last review comment of
D62939 [NFC]
(Resumbit of r363292 which was reverted along w/an earlier patch)
Pull in r364346 from upstream llvm trunk (by Philip Reames):
[LFTR] Adjust debug output to include extensions (if any)
Pull in r364693 from upstream llvm trunk (by Philip Reames):
[IndVars] Remove a bit of manual constant folding [NFC]
SCEV is more than capable of folding (add x, trunc(0)) to x.
Pull in r364709 from upstream llvm trunk (by Nikita Popov):
[LFTR] Fix post-inc pointer IV with truncated exit count (PR41998)
Fixes https://bugs.llvm.org/show_bug.cgi?id=41998. Usually when we
have a truncated exit count we'll truncate the IV when comparing
against the limit, in which case exit count overflow in post-inc form
doesn't matter. However, for pointer IVs we don't do that, so we have
to be careful about incrementing the IV in the wide type.
I'm fixing this by removing the IVCount variable (which was ExitCount
or ExitCount+1) and replacing it with a UsePostInc flag, and then
moving the actual limit adjustment to the individual cases (which
are: pointer IV where we add to the wide type, integer IV where we
add to the narrow type, and constant integer IV where we add to the
wide type).
Differential Revision: https://reviews.llvm.org/D63686
Together, these should fix a hang when building the textproc/htmldoc
port, due to an incorrect loop optimization.
PR: 237515
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| #
b5893f02 |
| 12-Apr-2019 |
Dimitry Andric <[email protected]> |
Merge llvm, clang, compiler-rt, libc++, libunwind, lld, lldb and openmp
8.0.0 final release r356365.
MFC r340287 (by emaste):
Consolidate gcov entries in OptionalObsoleteFiles
Sponsored by: The Fr
Merge llvm, clang, compiler-rt, libc++, libunwind, lld, lldb and openmp
8.0.0 final release r356365.
MFC r340287 (by emaste):
Consolidate gcov entries in OptionalObsoleteFiles
Sponsored by: The FreeBSD Foundation
MFC r340289 (by emaste):
llvm-cov: also install as gcov (if GNU gcov is disabled)
llvm-cov provides a gcov-compatible interface when invoked as gcov.
Reviewed by: dim, markj
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D17923
MFC r340296 (by emaste):
Move llvm-profdata build into MK_LLVM_COV block
llvm-profdata is used with llvm-cov for code coverage (although llvm-cov
can also operate independently in a gcov-compatible mode).
Although llvm-profdata can be used independently of llvm-cov it makes
sense to group these under one option.
Also handle these in OptionalObsoleteFiles.inc while here.
Sponsored by: The FreeBSD Foundation
MFC r340300 (by emaste):
libllvm: Move SampleProfWriter to SRCS_MIN
It is required by llvm-profdata, now built by default under the
LLVM_COV knob. The additional complexity that would come from avoiding
building it if CLANG_EXTRAS and LLVM_COV are both disabled is not worth
the small savings in build time.
Sponsored by: The FreeBSD Foundation
MFC r340972 (by emaste):
llvm-objdump: initial man page
Based on llvm-objdump's online documentation and usage information.
This serves as a starting point; additional detail and cleanup still
required.
Also being submitted upstream in LLVM review D54864. I expect to use
this bespoke copy while we have LLVM 6.0 or 7.0 in FreeBSD; when we
update to LLVM 8.0 it should be upstream and we will switch to it.
PR: 233437
Reviewed by: bcr (man formatting)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D18309
MFC r340973 (by emaste):
llvm-objdump.1: remove invalid options
Some options appear in llvm-objdump's usage information as a side effect
of its option parsing implementation and are not actually llvm-objdump
options. Reported in LLVM review https://reviews.llvm.org/D54864.
Reported by: Fangrui Song
Sponsored by: The FreeBSD Foundation
MFC r340975 (by emaste):
llvm-objdump.1: fix igor / mandoc -Tlint warnings
Accidentally omitted from r340972.
MFC r341055 (by emaste):
llvm-objdump.1: remove more unintentional options
Some options come from static constructors in LLVM libraries and are
automatically added to llvm's usage output. They're not really supposed
to be llvm-objdump options.
Reported by: Fangrui Song in LLVM review D54864
Sponsored by: The FreeBSD Foundation
MFC r344779:
Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
the upstream release_80 branch r355313 (effectively, 8.0.0 rc3). The
release will follow very soon, but no more functional changes are
expected.
Release notes for llvm, clang and lld 8.0.0 will soon be available here:
<https://releases.llvm.org/8.0.0/docs/ReleaseNotes.html>
<https://releases.llvm.org/8.0.0/tools/clang/docs/ReleaseNotes.html>
<https://releases.llvm.org/8.0.0/tools/lld/docs/ReleaseNotes.html>
PR: 236062
Relnotes: yes
MFC r344798 (by emaste):
libllvm: promote WithColor and xxhash to SRCS_MIN
The armv6 build failed in CI due to missing symbols (from these two
source files) in the bootstrap Clang.
This affected only armv6 because other Clang-using archs are using LLD
as the bootstrap linker, and thus include SRCS_MIW via LLD_BOOTSTRAP.
Reported by: CI, via lwhsu
Sponsored by: The FreeBSD Foundation
MFC r344825:
Add a few missed files to the MK_LLVM_TARGET_BPF=yes case, otherwise
clang and various other executables will fail to link with undefined
symbols.
Reported by: O. Hartmann <[email protected]>
MFC r344852:
Put in a temporary workaround for what is likely a gcc 6 bug (it does
not occur with gcc 7 or later). This should prevent the following error
from breaking the head-amd64-gcc CI builds:
In file included from /workspace/src/contrib/llvm/tools/lldb/source/API/SBMemoryRegionInfo.cpp:14:0:
/workspace/src/contrib/llvm/tools/lldb/include/lldb/Target/MemoryRegionInfo.h:128:54: error: 'template<class _InputIterator> lldb_private::MemoryRegionInfos::MemoryRegionInfos(_InputIterator, _InputIterator, const allocator_type&)' inherited from 'std::__1::vector<lldb_private::MemoryRegionInfo>'
using std::vector<lldb_private::MemoryRegionInfo>::vector;
^~~~~~
/workspace/src/contrib/llvm/tools/lldb/include/lldb/Target/MemoryRegionInfo.h:128:54: error: conflicts with version inherited from 'std::__1::vector<lldb_private::MemoryRegionInfo>'
Reported by: CI
MFC r344896:
Pull in r354937 from upstream clang trunk (by Jörg Sonnenberger):
Fix inline assembler constraint validation
The current constraint logic is both too lax and too strict. It fails
for input outside the [INT_MIN..INT_MAX] range, but it also
implicitly accepts 0 as value when it should not. Adjust logic to
handle both correctly.
Differential Revision: https://reviews.llvm.org/D58649
Pull in r355491 from upstream clang trunk (by Hans Wennborg):
Inline asm constraints: allow ICE-like pointers for the "n"
constraint (PR40890)
Apparently GCC allows this, and there's code relying on it (see bug).
The idea is to allow expression that would have been allowed if they
were cast to int. So I based the code on how such a cast would be
done (the CK_PointerToIntegral case in
IntExprEvaluator::VisitCastExpr()).
Differential Revision: https://reviews.llvm.org/D58821
These should fix assertions and errors when using the inline assembly
"n" constraint in certain ways.
In case of devel/valgrind, a pointer was used as the input for the
constraint, which lead to "Assertion failed: (isInt() && "Invalid
accessor"), function getInt".
In case of math/secp256k1, a very large integer value was used as input
for the constraint, which lead to "error: value '4624529908474429119'
out of range for constraint 'n'".
PR: 236216, 236194
MFC r344951:
Merge llvm, clang, compiler-rt, libc++, lld, and lldb release_80 branch
r355677 (effectively, 8.0.0 rc4), resolve conflicts, and bump version
numbers.
PR: 236062
MFC r345018:
Merge LLVM libunwind trunk r351319, from just before upstream's
release_80 branch point. Afterwards, we will merge the rest of the
changes in the actual release_80 branch.
PR: 236062
MFC r345019:
Merge LLVM libunwind release_80 branch r355677 (effectively, 8.0.0 rc4).
PR: 236062
MFC r345021:
Pull in r355854 from upstream llvm trunk (by Jonas Paulsson):
[RegAlloc] Avoid compile time regression with multiple copy hints.
As a fix for https://bugs.llvm.org/show_bug.cgi?id=40986 ("excessive
compile time building opencollada"), this patch makes sure that no
phys reg is hinted more than once from getRegAllocationHints().
This handles the case were many virtual registers are assigned to the
same physreg. The previous compile time fix (r343686) in
weightCalcHelper() only made sure that physical/virtual registers are
passed no more than once to addRegAllocationHint().
Review: Dimitry Andric, Quentin Colombet
https://reviews.llvm.org/D59201
This should fix a hang when compiling certain generated .cpp files in
the graphics/opencollada port.
PR: 236313
MFC r345068 (by jhb):
Move libunwind out of contrib/llvm/projects.
Move LLVM's libunwind to its own contrib/ directory similar to other
runtime libraries like libc++ and libcxxrt.
Reviewed by: dim, emaste
Differential Revision: https://reviews.freebsd.org/D19534
MFC r345073:
Revert r308867 (which was originally committed in the clang390-import
project branch):
Work around LLVM PR30879, which is about a bad interaction between
X86 Call Frame Optimization on i386 and libunwind, by disallowing the
optimization for i386-freebsd12.
This should fix some instances of broken exception handling when
frame pointers are omitted, in particular some unittests run during
the build of editors/libreoffice.
This hack will be removed as soon as upstream has implemented a more
permanent fix for this problem.
And indeed, after r345018 and r345019, which updated LLVM libunwind to
the most recent version, the above workaround is no longer needed. The
upstream commit which fixed this is:
https://llvm.org/viewvc/llvm-project?view=revision&revision=292723
Specifically, 32 bit (i386-freebsd) executables optimized with omitted
frame pointers and Call Frame Optimization should now behave correctly
when a C++ exception is thrown, and the stack is unwound.
Upstream PR: https://llvm.org/bugs/show_bug.cgi?id=30879
PR: 236062
MFC r345152:
Merge llvm, clang, compiler-rt, libc++, libunwind, lld, and lldb
release_80 branch r356034 (effectively, 8.0.0 rc5), resolve conflicts,
and bump version numbers.
PR: 236062
MFC r345231:
Add LLVM openmp trunk r351319 (just before the release_80 branch point)
to contrib/llvm. This is not yet connected to the build, the glue for
that will come in a follow-up commit.
PR: 236062
MFC r345232:
Bootstrap svn:mergeinfo on contrib/openmp.
PR: 236062
MFC r345233:
Merge openmp release_80 branch r356034 (effectively, 8.0.0 rc5).
PR: 236062
MFC r345234:
Add openmp __kmp_gettid() wrapper, using pthread_getthreadid_np(3).
This has also been submitted upstream.
PR: 236062
MFC r345283:
Enable building libomp.so for 32-bit x86. This is done by selectively
enabling the functions that save and restore MXCSR, since access to this
register requires SSE support.
Note that you may run into other issues with OpenMP on i386, since this
*not* yet supported upstream, and certainly not extensively tested.
PR: 236062, 236582
MFC r345345:
Merge llvm, clang, compiler-rt, libc++, libunwind, lld, lldb and openmp
8.0.0 final release r356365. There were no functional changes since the
most recent merge, of 8.0.0 rc5.
Release notes for llvm, clang, lld and libc++ 8.0.0 are now available:
https://llvm.org/releases/8.0.0/docs/ReleaseNotes.html
https://llvm.org/releases/8.0.0/tools/clang/docs/ReleaseNotes.html
https://llvm.org/releases/8.0.0/tools/lld/docs/ReleaseNotes.html
https://llvm.org/releases/8.0.0/projects/libcxx/docs/ReleaseNotes.html
PR: 236062
MFC r345349:
Pull in r352826 from upstream lld trunk (by Fangrui Song):
[ELF] Support --{,no-}allow-shlib-undefined
Summary:
In ld.bfd/gold, --no-allow-shlib-undefined is the default when
linking an executable. This patch implements a check to error on
undefined symbols in a shared object, if all of its DT_NEEDED entries
are seen.
Our approach resembles the one used in gold, achieves a good balance
to be useful but not too smart (ld.bfd traces all DSOs and emulates
the behavior of a dynamic linker to catch more cases).
The error is issued based on the symbol table, different from
undefined reference errors issued for relocations. It is most
effective when there are DSOs that were not linked with -z defs (e.g.
when static sanitizers runtime is used).
gold has a comment that some system libraries on GNU/Linux may have
spurious undefined references and thus system libraries should be
excluded (https://sourceware.org/bugzilla/show_bug.cgi?id=6811). The
story may have changed now but we make --allow-shlib-undefined the
default for now. Its interaction with -shared can be discussed in the
future.
Reviewers: ruiu, grimar, pcc, espindola
Reviewed By: ruiu
Subscribers: joerg, emaste, arichardson, llvm-commits
Differential Revision: https://reviews.llvm.org/D57385
Pull in r352943 from upstream lld trunk (by Fangrui Song):
[ELF] Default to --no-allow-shlib-undefined for executables
Summary:
This follows the ld.bfd/gold behavior.
The error check is useful as it captures a common type of ld.so
undefined symbol errors as link-time errors:
// a.cc => a.so (not linked with -z defs)
void f(); // f is undefined
void g() { f(); }
// b.cc => executable with a DT_NEEDED entry on a.so
void g();
int main() { g(); }
// ld.so errors when g() is executed (lazy binding) or when the program is started (-z now)
// symbol lookup error: ... undefined symbol: f
Reviewers: ruiu, grimar, pcc, espindola
Reviewed By: ruiu
Subscribers: llvm-commits, emaste, arichardson
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D57569
Together, these add support for --no-allow-shlib-undefined, and make it
the default for executables, so they will fail to link if any symbols
from needed shared libraries are undefined.
Reported by: jbeich
PR: 236062, 236141
MFC r345449:
Pull in r356809 from upstream llvm trunk (by Eli Friedman):
[ARM] Don't form "ands" when it isn't scheduled correctly.
In r322972/r323136, the iteration here was changed to catch cases at
the beginning of a basic block... but we accidentally deleted an
important safety check. Restore that check to the way it was.
Fixes https://bugs.llvm.org/show_bug.cgi?id=41116
Differential Revision: https://reviews.llvm.org/D59680
This should fix "Assertion failed: (LiveCPSR && "CPSR liveness tracking
is wrong!"), function UpdateCPSRUse" errors when building the devel/xwpe
port for armv7.
PR: 236062, 236568
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| #
4ba319b5 |
| 16-Feb-2019 |
Dimitry Andric <[email protected]> |
Merge clang 7.0.1 and several follow-up changes
MFC r341825:
Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
the upstream release_70 branch r348686 (effectively, 7.0.1 rc3).
Merge clang 7.0.1 and several follow-up changes
MFC r341825:
Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
the upstream release_70 branch r348686 (effectively, 7.0.1 rc3). The
release will follow very soon, but no more functional changes are
expected.
Release notes for llvm, clang and lld 7.0.0 are available here:
<http://releases.llvm.org/7.0.0/docs/ReleaseNotes.html>
<http://releases.llvm.org/7.0.0/tools/clang/docs/ReleaseNotes.html>
<http://releases.llvm.org/7.0.0/tools/lld/docs/ReleaseNotes.html>
PR: 230240, 230355
Relnotes: yes
MFC r342123:
Update clang, llvm, lld, lldb, compiler-rt and libc++ version number to
7.0.1 release r349250. There were no functional changes since the 7.0.1
rc3 import.
PR: 230240, 230355
Relnotes: yes
r343429 | emaste | 2019-01-25 15:46:13 +0100 (Fri, 25 Jan 2019) | 16 lines
clang: default to DWARF 4 as of FreeBSD 13
FreeBSD previously defaulted to DWARF 2 because several tools (gdb,
ctfconvert, etc.) did not support later versions. These have either
been fixed or are deprecated.
Note that gdb 6 still exists but has been moved out of $PATH into
/usr/libexec and is intended only for use by crashinfo(8). The kernel
build sets the DWARF version explicitly via -gdwarf2, so this should
have no effect there.
PR: 234887 [exp-run]
Reviewed by: markj
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D17930
MFC r343916:
Pull in r352607 from upstream llvm trunk (by Craig Topper):
[X86] Add FPSW as a Def on some FP instructions that were missing it.
Pull in r353141 from upstream llvm trunk (by Craig Topper):
[X86] Connect the default fpsr and dirflag clobbers in inline
assembly to the registers we have defined for them.
Summary:
We don't currently map these constraints to physical register numbers
so they don't make it to the MachineIR representation of inline
assembly.
This could have problems for proper dependency tracking in the
machine schedulers though I don't have a test case that shows that.
Reviewers: rnk
Reviewed By: rnk
Subscribers: eraman, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D57641
Pull in r353489 from upstream llvm trunk (by Craig Topper):
[X86] Add FPCW as a register and start using it as an implicit use on
floating point instructions.
Summary:
FPCW contains the rounding mode control which we manipulate to
implement fp to integer conversion by changing the roudning mode,
storing the value to the stack, and then changing the rounding mode
back. Because we didn't model FPCW and its dependency chain, other
instructions could be scheduled into the middle of the sequence.
This patch introduces the register and adds it as an implciit def of
FLDCW and implicit use of the FP binary arithmetic instructions and
store instructions. There are more instructions that need to be
updated, but this is a good start. I believe this fixes at least the
reduced test case from PR40529.
Reviewers: RKSimon, spatel, rnk, efriedma, andrew.w.kaylor
Subscribers: dim, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D57735
These should fix a problem in clang 7.0 where it would sometimes emit
long double floating point instructions in a slightly wrong order,
leading to failures in our libm tests. In particular, the cbrt_test
test case 'cbrtl_powl' and the trig_test test case 'reduction'.
Also bump __FreeBSD_cc_version, to be able to detect this in our test
suite.
Reported by: lwhsu
PR: 234040
Upstream PR: https://bugs.llvm.org/show_bug.cgi?id=40206
MFC r344056:
Pull in r339734 from upstream llvm trunk (by Eli Friedman):
[ARM] Make PerformSHLSimplify add nodes to the DAG worklist correctly.
Intentionally excluding nodes from the DAGCombine worklist is likely
to lead to weird optimizations and infinite loops, so it's generally
a bad idea.
To avoid the infinite loops, fix DAGCombine to use the
isDesirableToCommuteWithShift target hook before performing the
transforms in question, and implement the target hook in the ARM
backend disable the transforms in question.
Fixes https://bugs.llvm.org/show_bug.cgi?id=38530 . (I don't have a
reduced testcase for that bug. But we should have sufficient test
coverage for PerformSHLSimplify given that we're not playing weird
tricks with the worklist. I can try to bugpoint it if necessary,
though.)
Differential Revision: https://reviews.llvm.org/D50667
This should fix a possible hang when compiling sys/dev/nxge/if_nxge.c
(which exists now only in the stable/11 branch) for arm.
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