Some BPF JIT backends would want to optimize memcpy in their own
architecture specific way.
However, at the moment, there is no way for JIT backends to see memcpy
semantics in a reliable way. This is due to LLVM BPF backend is expanding
memcpy into load/store sequences and could possibly schedule them apart from
each other further. So, BPF JIT backends inside kernel can't reliably
recognize memcpy semantics by peephole BPF sequence.
This patch introduce new intrinsic expand infrastructure to memcpy.
To get stable in-order load/store sequence from memcpy, we first lower
memcpy into BPF::MEMCPY node which then expanded into in-order load/store
sequences in expandPostRAPseudo pass which will happen after instruction
scheduling. By this way, kernel JIT backends could reliably recognize
memcpy through scanning BPF sequence.
This new memcpy expand infrastructure is gated by a new option:
-bpf-expand-memcpy-in-order
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
llvm-svn: 337977
Commit e4507fb8c94b ("bpf: disable DwarfUsesRelocationsAcrossSections")
disables MCAsmInfo DwarfUsesRelocationsAcrossSections unconditionally
so that dwarf will not use cross section (between dwarf and symbol table)
relocations. This new debug format enables pahole to dump structures
correctly as libdwarves.so does not have BPF backend support yet.
This new debug format, however, breaks bcc (https://github.com/iovisor/bcc)
source debug output as llvm in-memory Dwarf support has some issues to
handle it. More specifically, with DwarfUsesRelocationsAcrossSections
disabled, JIT compiler does not generate .debug_abbrev and Dwarf
DIE (debug info entry) processing is not happy about this.
This patch introduces a new flag -mattr=dwarfris
(dwarf relocation in section) to disable DwarfUsesRelocationsAcrossSections.
DwarfUsesRelocationsAcrossSections is true by default.
Signed-off-by: Yonghong Song <yhs@fb.com>
llvm-svn: 326505
This new attribute aims to control the enablement of 32-bit subregister
support on eBPF backend.
Name the interface as "alu32" is because we in particular want to enable
the generation of BPF_ALU32 instructions by enable subregister support.
This attribute could be used in the following format with llc:
llc -mtriple=bpf -mattr=[+|-]alu32
It is disabled at default.
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Reviewed-by: Yonghong Song <yhs@fb.com>
llvm-svn: 325982
All these headers already depend on CodeGen headers so moving them into
CodeGen fixes the layering (since CodeGen depends on Target, not the
other way around).
llvm-svn: 318490
-mcpu=# will support:
. generic: the default insn set
. v1: insn set version 1, the same as generic
. v2: insn set version 2, version 1 + additional jmp insns
. probe: the compiler will probe the underlying kernel to
decide proper version of insn set.
We did not not use -mcpu=native since llc/llvm will interpret -mcpu=native
as the underlying hardware architecture regardless of -march value.
Currently, only x86_64 supports -mcpu=probe. Other architecture will
silently revert to "generic".
Also added -mcpu=help to print available cpu parameters.
llvm will print out the information only if there are at least one
cpu and at least one feature. Add an unused dummy feature to
enable the printout.
Examples for usage:
$ llc -march=bpf -mcpu=v1 -filetype=asm t.ll
$ llc -march=bpf -mcpu=v2 -filetype=asm t.ll
$ llc -march=bpf -mcpu=generic -filetype=asm t.ll
$ llc -march=bpf -mcpu=probe -filetype=asm t.ll
$ llc -march=bpf -mcpu=v3 -filetype=asm t.ll
'v3' is not a recognized processor for this target (ignoring processor)
...
$ llc -march=bpf -mcpu=help -filetype=asm t.ll
Available CPUs for this target:
generic - Select the generic processor.
probe - Select the probe processor.
v1 - Select the v1 processor.
v2 - Select the v2 processor.
Available features for this target:
dummy - unused feature.
Use +feature to enable a feature, or -feature to disable it.
For example, llc -mcpu=mycpu -mattr=+feature1,-feature2
...
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
llvm-svn: 311522
The patch is generated using this command:
tools/clang/tools/extra/clang-tidy/tool/run-clang-tidy.py -fix \
-checks=-*,llvm-namespace-comment -header-filter='llvm/.*|clang/.*' \
llvm/lib/
Thanks to Eugene Kosov for the original patch!
llvm-svn: 240137
Summary:
This continues the patch series to eliminate StringRef forms of GNU triples
from the internals of LLVM that began in r239036.
Reviewers: rafael
Reviewed By: rafael
Subscribers: rafael, ted, jfb, llvm-commits, rengolin, jholewinski
Differential Revision: http://reviews.llvm.org/D10311
llvm-svn: 239467
Summary:
V8->V9:
- cleanup tests
V7->V8:
- addressed feedback from David:
- switched to range-based 'for' loops
- fixed formatting of tests
V6->V7:
- rebased and adjusted AsmPrinter args
- CamelCased .td, fixed formatting, cleaned up names, removed unused patterns
- diffstat: 3 files changed, 203 insertions(+), 227 deletions(-)
V5->V6:
- addressed feedback from Chandler:
- reinstated full verbose standard banner in all files
- fixed variables that were not in CamelCase
- fixed names of #ifdef in header files
- removed redundant braces in if/else chains with single statements
- fixed comments
- removed trailing empty line
- dropped debug annotations from tests
- diffstat of these changes:
46 files changed, 456 insertions(+), 469 deletions(-)
V4->V5:
- fix setLoadExtAction() interface
- clang-formated all where it made sense
V3->V4:
- added CODE_OWNERS entry for BPF backend
V2->V3:
- fix metadata in tests
V1->V2:
- addressed feedback from Tom and Matt
- removed top level change to configure (now everything via 'experimental-backend')
- reworked error reporting via DiagnosticInfo (similar to R600)
- added few more tests
- added cmake build
- added Triple::bpf
- tested on linux and darwin
V1 cover letter:
---------------------
recently linux gained "universal in-kernel virtual machine" which is called
eBPF or extended BPF. The name comes from "Berkeley Packet Filter", since
new instruction set is based on it.
This patch adds a new backend that emits extended BPF instruction set.
The concept and development are covered by the following articles:
http://lwn.net/Articles/599755/http://lwn.net/Articles/575531/http://lwn.net/Articles/603983/http://lwn.net/Articles/606089/http://lwn.net/Articles/612878/
One of use cases: dtrace/systemtap alternative.
bpf syscall manpage:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=b4fc1a460f3017e958e6a8ea560ea0afd91bf6fe
instruction set description and differences vs classic BPF:
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/networking/filter.txt
Short summary of instruction set:
- 64-bit registers
R0 - return value from in-kernel function, and exit value for BPF program
R1 - R5 - arguments from BPF program to in-kernel function
R6 - R9 - callee saved registers that in-kernel function will preserve
R10 - read-only frame pointer to access stack
- two-operand instructions like +, -, *, mov, load/store
- implicit prologue/epilogue (invisible stack pointer)
- no floating point, no simd
Short history of extended BPF in kernel:
interpreter in 3.15, x64 JIT in 3.16, arm64 JIT, verifier, bpf syscall in 3.18, more to come in the future.
It's a very small and simple backend.
There is no support for global variables, arbitrary function calls, floating point, varargs,
exceptions, indirect jumps, arbitrary pointer arithmetic, alloca, etc.
From C front-end point of view it's very restricted. It's done on purpose, since kernel
rejects all programs that it cannot prove safe. It rejects programs with loops
and with memory accesses via arbitrary pointers. When kernel accepts the program it is
guaranteed that program will terminate and will not crash the kernel.
This patch implements all 'must have' bits. There are several things on TODO list,
so this is not the end of development.
Most of the code is a boiler plate code, copy-pasted from other backends.
Only odd things are lack or < and <= instructions, specialized load_byte intrinsics
and 'compare and goto' as single instruction.
Current instruction set is fixed, but more instructions can be added in the future.
Signed-off-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Subscribers: majnemer, chandlerc, echristo, joerg, pete, rengolin, kristof.beyls, arsenm, t.p.northover, tstellarAMD, aemerson, llvm-commits
Differential Revision: http://reviews.llvm.org/D6494
llvm-svn: 227008
Yonghong Song