[Crossposting to both gcc-patches and binutils lists, since this
patch kit touches both source trees].
Binutils devs: GCC 5 gained a way to build GCC as a shared library,
libgccjit.so.
I'm been experimenting with ways of optimizing libgccjit, and the
following patch kit (touching both gcc and binutils) achieves a 5x
speedup of
gcc/testsuite/jit.dg/test-benchmark.c
on this x86_64 box (Fedora 20).
The benchmark constructs IR for a simple function in memory, compiles
it, and runs it, 100 times in a row, in the hope of simulating the
workload of an interpreter/VM/language runtime, where bytecode
functions gradually become "hot" (e.g. interpretation count exceeds
a threshold) and are compiled to machine code, all within one
process.
gcc's backend code emits .s files, and libgccjit currently use pex to
invoke the gcc driver to turn it from .s to a .so file (which in
turn invokes "as" and "ld").
These invocations dominate the time take by libgccjit, so the patch
series attempts to time them, and to move them in-process; doing
so largely eliminates the cost of them.
Here are the performance gains:
jit.dg/test-benchmark.c, 100 iterations at optlevel 0:
Without embedded driver: wallclock of 5.300s (0.053s per iteration)
With embedded driver: wallclock of 4.630s (0.046s per iteration)
With embedded driver & gas: wallclock of 3.510s (0.035s per iteration)
With embedded driver&as&ld: wallclock of 2.130s (0.021s per iteration)
As above, hacking up ld args: wallclock of 1.030s (0.010s per iteration)
i.e. about 5x speedup.
There are some memory leaks, FIXMEs, etc, and it hasn't been fully
tested yet, but I thought it was time to post this for discussion.
The patch kit also generalizes gcc's timevar mechanism in such a way
that it can be used both by jit client code, and by "as" and "ld". An
example of a combined report on the accumulated timings of 100
iterations of jit.dg/test-benchmark.c at optlevel 0:
Execution times (seconds)
Client items:
test_jit : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
0 kB ( 0%) ggc
create_code : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
0 kB ( 0%) ggc
compile : 0.21 (30%) usr 0.13 (45%) sys 0.25 (25%) wall
14939 kB (74%) ggc
verify_code : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
0 kB ( 0%) ggc
GCC items:
phase setup : 0.15 (22%) usr 0.02 ( 7%) sys 0.15 (15%) wall
10661 kB (53%) ggc
phase parsing : 0.02 ( 3%) usr 0.00 ( 0%) sys 0.02 ( 2%) wall
653 kB ( 3%) ggc
callgraph construction : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.02 ( 2%) wall
242 kB ( 1%) ggc
callgraph optimization : 0.01 ( 1%) usr 0.01 ( 3%) sys 0.01 ( 1%) wall
142 kB ( 1%) ggc
cfg construction : 0.01 ( 1%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
17 kB ( 0%) ggc
cfg cleanup : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 1%) wall
0 kB ( 0%) ggc
df live regs : 0.02 ( 3%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
0 kB ( 0%) ggc
df reg dead/unused notes: 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 1%) wall
23 kB ( 0%) ggc
register information : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 1%) wall
0 kB ( 0%) ggc
parser (global) : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 1%) wall
199 kB ( 1%) ggc
tree eh : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 1%) wall
0 kB ( 0%) ggc
tree CFG construction : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 1%) wall
196 kB ( 1%) ggc
tree operand scan : 0.00 ( 0%) usr 0.01 ( 3%) sys 0.00 ( 0%) wall
100 kB ( 0%) ggc
out of ssa : 0.00 ( 0%) usr 0.02 ( 7%) sys 0.01 ( 1%) wall
0 kB ( 0%) ggc
expand : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 1%) wall
398 kB ( 2%) ggc
loop init : 0.01 ( 1%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
67 kB ( 0%) ggc
integrated RA : 0.07 (10%) usr 0.02 ( 7%) sys 0.02 ( 2%) wall
2468 kB (12%) ggc
LRA virtuals elimination: 0.01 ( 1%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
56 kB ( 0%) ggc
machine dep reorg : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 1%) wall
0 kB ( 0%) ggc
shorten branches : 0.01 ( 1%) usr 0.00 ( 0%) sys 0.02 ( 2%) wall
0 kB ( 0%) ggc
final : 0.01 ( 1%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
216 kB ( 1%) ggc
initialize rtl : 0.01 ( 1%) usr 0.00 ( 0%) sys 0.01 ( 1%) wall
12 kB ( 0%) ggc
rest of compilation : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.03 ( 3%) wall
232 kB ( 1%) ggc
unaccounted todo : 0.01 ( 1%) usr 0.00 ( 0%) sys 0.02 ( 2%) wall
0 kB ( 0%) ggc
replay of JIT client activity: 0.01 ( 1%) usr 0.00 ( 0%) sys 0.01 ( 1%)
wall 309 kB ( 2%) ggc
driver : 0.01 ( 1%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
0 kB ( 0%) ggc
driver: setup : 0.04 ( 6%) usr 0.00 ( 0%) sys 0.06 ( 6%) wall
0 kB ( 0%) ggc
driver: do spec on infiles: 0.01 ( 1%) usr 0.00 ( 0%) sys 0.02 ( 2%)
wall 0 kB ( 0%) ggc
driver: run linker : 0.00 ( 0%) usr 0.01 ( 3%) sys 0.02 ( 2%) wall
0 kB ( 0%) ggc
driver: embedded assembler: 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 1%)
wall 0 kB ( 0%) ggc
driver: embedded linker : 0.04 ( 6%) usr 0.02 ( 7%) sys 0.04 ( 4%) wall
0 kB ( 0%) ggc
load JIT result : 0.01 ( 1%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
0 kB ( 0%) ggc
Embedded 'as':
gas_main : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
0 kB ( 0%) ggc
before pass : 0.03 ( 4%) usr 0.02 ( 7%) sys 0.13 (13%) wall
0 kB ( 0%) ggc
perform_an_assembly_pass: 0.06 ( 9%) usr 0.01 ( 3%) sys 0.06 ( 6%) wall
0 kB ( 0%) ggc
after pass : 0.04 ( 6%) usr 0.00 ( 0%) sys 0.03 ( 3%) wall
0 kB ( 0%) ggc
cleanup : 0.02 ( 3%) usr 0.00 ( 0%) sys 0.03 ( 3%) wall
0 kB ( 0%) ggc
Embedded 'ld':
ld_internal_main: init : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
0 kB ( 0%) ggc
ldmain.c: lang_final : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
0 kB ( 0%) ggc
ldmain.c: lang_process : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
0 kB ( 0%) ggc
lang_process: 1st half : 0.00 ( 0%) usr 0.02 ( 7%) sys 0.02 ( 2%) wall
0 kB ( 0%) ggc
open_output : 0.01 ( 1%) usr 0.00 ( 0%) sys 0.01 ( 1%) wall
0 kB ( 0%) ggc
open_input_bfds : 0.01 ( 1%) usr 0.02 ( 7%) sys 0.01 ( 1%) wall
0 kB ( 0%) ggc
lang_input_statement_enum: 0.00 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
0 kB ( 0%) ggc
open_input_bfds:load_symbols: 0.00 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%)
wall 0 kB ( 0%) ggc
load_symbols: ldfile_open_file: 0.00 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%)
wall 0 kB ( 0%) ggc
ldlang_add_file : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
0 kB ( 0%) ggc
load_symbols: bfd_link_add_symbols: 0.02 ( 3%) usr 0.00 ( 0%) sys 0.00 (
0%) wall 0 kB ( 0%) ggc
lang_process: 2nd half : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.04 ( 4%) wall
0 kB ( 0%) ggc
ldmain.c: ldwrite : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.03 ( 3%) wall
0 kB ( 0%) ggc
ld_main cleanup : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.00 ( 0%) wall
0 kB ( 0%) ggc
TOTAL : 0.69 0.29 0.99
20298 kB
Thoughts?
--
1.8.5.3
