Allocating an arbitrarily-sized array of tbs results in either
(a) a lot of memory wasted or (b) unnecessary flushes of the code
cache when we run out of TB structs in the array.
An obvious solution would be to just malloc a TB struct when needed,
and keep the TB array as an array of pointers (recall that tb_find_pc()
needs the TB array to run in O(log n)).
Perhaps a better solution, which is implemented in this patch, is to
allocate TB's right before the translated code they describe. This
results in some memory waste due to padding to have code and TBs in
separate cache lines--for instance, I measured 4.7% of padding in the
used portion of code_gen_buffer when booting aarch64 Linux on a
host with 64-byte cache lines. However, it can allow for optimizations
in some host architectures, since TCG backends could safely assume that
the TB and the corresponding translated code are very close to each
other in memory. See this message by rth for a detailed explanation:
https://lists.gnu.org/archive/html/qemu-devel/2017-03/msg05172.html
Subject: Re: GSoC 2017 Proposal: TCG performance enhancements
Backports commit 6e3b2bfd6af488a896f7936e99ef160f8f37e6f2 from qemu
Instead of exporting goto_ptr directly to TCG frontends, export
tcg_gen_lookup_and_goto_ptr(), which calls goto_ptr with the pointer
returned by the lookup_tb_ptr() helper. This is the only use case
we have for goto_ptr and lookup_tb_ptr, so having this function is
very convenient. Furthermore, it trivially allows us to avoid calling
the lookup helper if goto_ptr is not implemented by the backend.
Backports commit cedbcb01529cb6cf9a2289cdbebbc63f6149fc18 from qemu
This allows an output operand to match an input operand
only when the input operand needs a register.
Backports commit 17280ff4a5f264e01e55ae514ee6d3586f9577b2 from qemu
This will let us choose how to interpret a given constraint
depending on whether the opcode is 32- or 64-bit. Which will
let us share more constraint combinations between opcodes.
At the same time, change the interface to return the advanced
pointer instead of passing it in/out by reference.
Backports commit 069ea736b50b75fdec99c9b8cc603b97bd98419e from qemu
This will allow the target to tailor the constraints to the
auto-detected ISA extensions.
Backports commit f69d277ece43c42c7ab0144c2ff05ba740f6706b from qemu
This comes from free from unifying tcg_reg_alloc_mov and
tcg_reg_alloc_movi's handling of TEMP_VAL_CONST. It triggers
often on moves to cc_dst, such as the following translation
of "sub $0x3c,%esp":
before: after:
subl $0x3c,%ebp subl $0x3c,%ebp
movl %ebp,0x10(%r14) movl %ebp,0x10(%r14)
movl $0x3c,%ebx movl $0x3c,0x2c(%r14)
movl %ebx,0x2c(%r14)
Backports commit 0fe4fca4e1a5e06a270127dd80bb753d4dda61c6 from qemu
Rather than rely on recursion during the middle of register allocation,
lower indirect registers to loads and stores off the indirect base into
plain temps.
For an x86_64 host, with sufficient registers, this results in identical
code, modulo the actual register assignments.
For an i686 host, with insufficient registers, this means that temps can
be (temporarily) spilled to the stack in order to satisfy an allocation.
This as opposed to the possibility of not being able to spill, to allocate
a register for the indirect base, in order to perform a spill.
Backports commit 5a18407f55ade924aa6397c9a043a9ffd59645fe from qemu
We only need two bits per temporary. Fold the two bytes into one,
and reduce the memory and cachelines required during compilation.
Backports commit c70fbf0a9938baf3b4f843355a77c17a7e945b98 from qemu
Reduce the size of other bitfields to make room.
This reduces the cache footprint of compilation.
Backports commit bee158cb4dde35c41632a3a129c869f14a32f8f0 from qemu
Instead of using -1 as end of chain, use 0, and link through the 0
entry as a fully circular double-linked list.
Backports commit dcb8e75870e2de199db853697f8839cb603beefe from qemu
This reduces both memory usage and per-insn cacheline usage
during code generation.
Backports commit a1b3c48d2b23d6eaeb4529d3e1183d2648731bf8 from qemu
Some architectures (e.g. ARMv8) need the address which is aligned
to a size more than the size of the memory access.
To support such check it's enough the current costless alignment
check implementation in QEMU, but we need to support
an alignment size specifying.
Backports commit 1f00b27f17518a1bcb4cedca49eaec96a4d560bd from qemu
While we can store constants via constrants on INDEX_op_st_i32 et al,
we weren't able to spill constants to backing store.
Add a new backend interface, tcg_out_sti, which may store the constant
(and is allowed to fail). Rearrange the temp_* helpers so that we only
attempt to directly store a constant when the temp is becoming dead/free.
Backports commit 59d7c14eeff8d2ad7f61aed86ce5a176113bc153 from qemu
exec-all.h contains TCG-specific definitions. It is not needed outside
TCG-specific files such as translate.c, exec.c or *helper.c.
One generic function had snuck into include/exec/exec-all.h; move it to
include/qom/cpu.h.
Backports commit 63c915526d6a54a95919ebece83fa9ca631b2508 from qemu
The TCG code is quite performance sensitive, but at the same time can
also be quite tricky. That is why asserts that can be enabled with the
--enable-debug-tcg configure option.
This used to work the following way:
| #include "config.h"
|
| ...
|
| #if !defined(CONFIG_DEBUG_TCG) && !defined(NDEBUG)
| /* define it to suppress various consistency checks (faster) */
| #define NDEBUG
| #endif
|
| ...
|
| #include <assert.h>
Since commit 757e725b (tcg: Clean up includes) "config.h" as been
replaced by "qemu/osdep.h" which itself includes <assert.h>. As a
consequence the assertions are always enabled, even when using
--disable-debug-tcg, causing a performance regression, especially on
targets with many registers. For instance on qemu-system-ppc the
speed difference is about 15%.
tcg_debug_assert is controlled directly by CONFIG_DEBUG_TCG and already
uses in some places. This patch replaces all the calls to assert into
calss to tcg_debug_assert.
Backports commit eabb7b91b36b202b4dac2df2d59d698e3aff197a from qemu
qemu-log: dfilter-ise exec, out_asm, op and opt_op
This ensures the code generation debug code will honour -dfilter if set.
For the "exec" tracing I've added a new inline macro for efficiency's
sake.
Backports commit d977e1c2dbc9e63454b2000f91954d02543bf43b from qemu
My later debugging patches need access to the origin PC which is held in
the TranslationBlock structure. Pass down the whole structure as it also
holds the information about the code start point.
Backports commit 5bd2ec3d7b47b2252745882795d79aef36380fb7 from qemu
Move declarations out of qemu-common.h for functions declared in
utils/ files: e.g. include/qemu/path.h for utils/path.c.
Move inline functions out of qemu-common.h and into new files (e.g.
include/qemu/bcd.h)
Backports commit f348b6d1a53e5271cf1c9f9acc4646b4b98c1771 from qemu
Rename the per-architecture tcg-target.c files to tcg-target.inc.c.
This makes it clearer that they are not intended to be standalone
C files, but are instead #included into another source file.
Backports commit ce151109813e2770fd3cee2f37bfa2cdd01a12b9 from qemu
Since we've not got liveness analysis for indirect bases,
placing them at the end of the call-saved registers makes
it more likely that it'll stay live.
Backports commit 91478cefaaf2fa678e56df8635b34957f4d5d565 from qemu
That is, global_mem registers whose base is another global_mem
register, rather than a fixed register.
Backports commit b3915dbbdcdb2e04753f3d34a1b0865eea005069 from qemu
A previous patch patch changed the type of REG from int
to enum TCGReg, which provokes the following bug in clang:
https://llvm.org/bugs/show_bug.cgi?id=16154
Backports commit 869938ae2a284fe730cb6f807ea0f9e324e0f87c from qemu
A subsequent patch patch will change the type of REG from int
to enum TCGReg, which provokes the following bug in clang:
https://llvm.org/bugs/show_bug.cgi?id=16154
Backports commit c8074023204e8e8a213399961ab56e2814aa6116 from qemu
In particular, make sure the memory is memset before use.
Continues the increased use of TCGTemp pointers instead of
integer indices where appropriate.
Backports commit 7ca4b752feaab647b0c1a147bd3815fcdb479a59 from qemu
Undo the workaround at b17a6d3390f87620735f7efb03bb1c96682ff449.
If there are lots of memory operations in a TB, the slow path code
can exceed the highwater reservation. Add a check within the loop.
Backports commit 23dceda62a3643f734b7aa474fa6052593ae1a70 from qemu
Clean up includes so that osdep.h is included first and headers
which it implies are not included manually.
This commit was created with scripts/clean-includes.
Backports commit 757e725b58c57d3ebb66a31fd2210df977a12154 from qemu
A simple typo in the variable to use when comparing vs the highwater mark.
Reports are that qemu can in fact segfault occasionally due to this mistake.
Backports commit 644da9b39e477caa80bab69d2847dfcb468f0d33 from qemu
We currently pre-compute an worst case code size for any TB, which
works out to be 122kB. Since the average TB size is near 1kB, this
wastes quite a lot of storage.
Instead, check for overflow in between generating code for each opcode.
The overhead of the check isn't measurable and wastage is minimized.
Backports commit b125f9dc7bd68cd4c57189db4da83b0620b28a72 from qemu
By putting the prologue at the end, we risk overwriting the
prologue should our estimate of maximum TB size. Given the
two different placements of the call to tcg_prologue_init,
move the high water mark computation into tcg_prologue_init.
Backports commit 8163b74938d8b7d12e70597c4553dd0dc49443d5 from qemu
The gen_opc_* arrays are already redundant with the data stored in
the insn_start arguments. Transition restore_state_to_opc to use
data from the latter.
Backports commit bad729e272387de7dbfa3ec4319036552fc6c107 from qemu
tcg_op_defs (and the _max) are both needed by the TCI disassembler. For
multi-arch, tcg.c will be multiple-compiled (arch-obj) with its symbols
hidden from common code. So split the definition off to new file,
tcg-common.c which will remain a regular obj-y for use by both the TCI
disas as well as the multiple tcg.c's.
Backports commit 7d8f787d9d261d6880b69e35ed682241e3f9242f from qemu
With an eye toward having this data replace the gen_opc_* arrays
that each target collects in order to enable restore_state_from_tb.
Backports commit 9aef40ed1f6e2bd794bbb3ba8c8b773e506334c9 from qemu
