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Yonghong Song 7c423e0690 bpf: generate better lowering code for certain select/setcc instructions 
Currently, for code like below,
===
  inner_map = bpf_map_lookup_elem(outer_map, &port_key);
  if (!inner_map) {
    inner_map = &fallback_map;
  }
===
the compiler generates (pseudo) code like the below:
===
  I1: r1 = bpf_map_lookup_elem(outer_map, &port_key);
  I2: r2 = 0
  I3: if (r1 == r2)
  I4:   r6 = &fallback_map
  I5: ...
===

During kernel verification process, After I1, r1 holds a state
map_ptr_or_null. If I3 condition is not taken
(path [I1, I2, I3, I5]), supposedly r1 should become map_ptr.
Unfortunately, kernel does not recognize this pattern
and r1 remains map_ptr_or_null at insn I5. This will cause
verificaiton failure later on.

Kernel, however, is able to recognize pattern "if (r1 == 0)"
properly and give a map_ptr state to r1 in the above case.

LLVM here generates suboptimal code which causes kernel verification
failure. This patch fixes the issue by changing BPF insn pattern
matching and lowering to generate proper codes if the righthand
parameter of the above condition is a constant. A test case
is also added.

Signed-off-by: Yonghong Song <yhs@fb.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@308080 91177308-0d34-0410-b5e6-96231b3b80d8
2017-07-15 05:41:42 +00:00
bindings [NFC] Remove multiple semicolons 2017-06-28 23:15:16 +00:00
cmake [Solaris] Detect Solaris LD, use detection results to pass Solaris-ld options 2017-07-12 21:43:14 +00:00
docs [lit] add a -vv option to echo all executed commands. 2017-07-13 19:26:27 +00:00
examples fix typos in comments and error messges; NFC 2017-07-13 06:48:39 +00:00
include [TTI] Refine the cost of EXT in getUserCost() 2017-07-15 02:12:16 +00:00
lib bpf: generate better lowering code for certain select/setcc instructions 2017-07-15 05:41:42 +00:00
projects Add temporary workaround to allow in-tree libc++ builds on Windows 2017-05-11 01:44:30 +00:00
resources In MSVC builds embed a VERSIONINFO resource in our exe and DLL files. 2015-06-12 15:58:29 +00:00
runtimes [CMake]Use LLVM_LIBRARY_DIR for lib path. 2017-07-14 00:35:21 +00:00
test bpf: generate better lowering code for certain select/setcc instructions 2017-07-15 05:41:42 +00:00
tools [llvm-readobj] - Teach readobj to print DT_FILTER dynamic tag in human readable form. 2017-07-14 16:00:16 +00:00
unittests [Dominators] Fix reachable visitation and reenable a unit test 2017-07-15 01:27:16 +00:00
utils [TableGen][MC] Fix a few places where we didn't hide the underlying type of LaneBitmask very well. 2017-07-14 18:30:09 +00:00
.arcconfig project_id is from another era in phabricator land and does not provide any value. 2016-09-27 15:47:29 +00:00
.clang-format Test commit. 2014-03-02 13:08:46 +00:00
.clang-tidy .clang-tidy: correct style name is 'camelBack' not 'lowerCase'. 2016-09-13 19:04:26 +00:00
.gitignore gitignore: Ignore .vs folder (VS2017 config files) 2017-04-08 00:16:58 +00:00
CMakeLists.txt CMake: Add LLVM_UTILS_INSTALL_DIR option 2017-07-05 12:57:30 +00:00
CODE_OWNERS.TXT Remove the BBVectorize pass. 2017-06-30 07:09:08 +00:00
configure Remove autoconf support 2016-01-26 21:29:08 +00:00
CREDITS.TXT Another test commit 2017-07-01 03:24:06 +00:00
LICENSE.TXT Bump year to 2017 in LICENSE.txt 2017-01-12 18:02:42 +00:00
llvm.spec.in [Sparc] Implement i64 load/store support for 32-bit sparc. 2015-08-10 19:11:39 +00:00
LLVMBuild.txt Remove the very substantial, largely unmaintained legacy PGO 2013-10-02 15:42:23 +00:00
README.txt Test commit. Added a blank line. 2017-03-06 20:45:33 +00:00
RELEASE_TESTERS.TXT [RelTest] Diana is doing both releases now 2017-07-14 08:33:52 +00:00

README.txt 

Low Level Virtual Machine (LLVM)
================================

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Please see the documentation provided in docs/ for further
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