The new placement of the TB means that we can use one insn
to load the goto_tb destination directly from the TB.
Backports commit 308714e6bc945389c64faf1b9213e2c0d3f03391 from qemu
The new placement of the TB means that we can use one insn
to load the return value for exit_tb returning the TB pointer.
Backports commit cc74d332ff9a78684374847375ef63fc4bd10436 from qemu
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
In theory this would re-enable usage of QEMU on an armv4 host.
Whether this is worthwhile is debatable -- we've been unconditionally
issuing the armv5t BX instruction in the prologue since 2011 without
complaint. Possibly we should simply require an armv6 host.
Backports commit 702a947484eb3e615183dafc93de590ab0679f60 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
Users of tcg_gen_atomic_cmpxchg and do_atomic_op rightfully utilize
the output. Even though this code is dead, it gets translated, and
without the initialization we encounter a tcg_error.
Backports commit 79b1af906245558c30e0a5faf26cb52b63f83cce from qemu
We already require gcc 4.1 or newer (for the atomic
support), so the fallback codepaths for older gcc
versions than that are now dead code and we can
just delete them.
NB: clang reports itself as gcc 4.2 (regardless of
clang version), so clang won't be using the fallbacks
either.
Backports commit fa54abb8c298f892639ffc4bc2f61448ac3be4a1 from qemu
The C store helper functions take the address argument as a
target_ulong type; if this is 32 bit but the host is 64 bit
then the SPARC calling convention requires that the caller
must zero extend the value. We weren't doing this, which
meant we could pass values to the caller with high bits set
and QEMU would crash if it was compiled with optimizations.
In particular, the i386 BIOS would not start.
Backports commit 5c32be5baf41aec4f4675d2bf24f9948756abf3c from qemu
The C store helper functions take the data argument as a uint8_t,
uint16_t, etc depending on the store size. The SPARC calling
convention requires that data types smaller than the register
size must be extended by the caller. We weren't doing this,
which meant that if QEMU was compiled with optimizations enabled
we could end up storing incorrect values to guest memory.
(In particular the i386 guest BIOS would crash on startup.)
Add code to the trampolines that call the store helpers to
do the zero extension as required.
Backports commit 709a340d679d95a0c6cbb9b5f654498f04345b50 from qemu
To fix the following warnings:
In file included from /users/pranith/qemu/tcg/tcg.c:255:
/users/pranith/qemu/tcg/aarch64/tcg-target.inc.c:879:24: warning: implicit conversion from enumeration type 'TCGMemOp' (aka 'enum TCGMemOp') to different enumeration type 'TCGType' (aka 'enum TCGType')
[-Wenum-conversion]
tcg_out_cmp(s, ext, a, b, b_const);
~~~~~~~~~~~ ^~~
/users/pranith/qemu/tcg/aarch64/tcg-target.inc.c:893:36: warning: implicit conversion from enumeration type 'TCGMemOp' (aka 'enum TCGMemOp') to different enumeration type 'TCGType' (aka 'enum TCGType')
[-Wenum-conversion]
tcg_out_insn(s, 3201, CBZ, ext, a, offset);
~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~
/users/pranith/qemu/tcg/aarch64/tcg-target.inc.c:389:65: note: expanded from macro 'tcg_out_insn'
glue(tcg_out_insn_,FMT)(S, glue(glue(glue(I,FMT),_),OP), ## __VA_ARGS__)
^
/users/pranith/qemu/tcg/aarch64/tcg-target.inc.c:895:37: warning: implicit conversion from enumeration type 'TCGMemOp' (aka 'enum TCGMemOp') to different enumeration type 'TCGType' (aka 'enum TCGType')
[-Wenum-conversion]
tcg_out_insn(s, 3201, CBNZ, ext, a, offset);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~
/users/pranith/qemu/tcg/aarch64/tcg-target.inc.c:389:65: note: expanded from macro 'tcg_out_insn'
glue(tcg_out_insn_,FMT)(S, glue(glue(glue(I,FMT),_),OP), ## __VA_ARGS__)
^
/users/pranith/qemu/tcg/aarch64/tcg-target.inc.c:1610:27: warning: implicit conversion from enumeration type 'TCGType' (aka 'enum TCGType') to different enumeration type 'TCGMemOp' (aka 'enum TCGMemOp')
[-Wenum-conversion]
tcg_out_brcond(s, ext, a2, a0, a1, const_args[1], arg_label(args[3]));
~~~~~~~~~~~~~~ ^~~
backports commit dc1eccd661ada3b746ca4438e444993c36a0f04f from qemu
This enables the multi-threaded system emulation by default for ARMv7
and ARMv8 guests using the x86_64 TCG backend. This is because on the
guest side:
- The ARM translate.c/translate-64.c have been converted to
- use MTTCG safe atomic primitives
- emit the appropriate barrier ops
- The ARM machine has been updated to
- hold the BQL when modifying shared cross-vCPU state
- defer powerctl changes to async safe work
All the host backends support the barrier and atomic primitives but
need to provide same-or-better support for normal load/store
operations.
Backports commit ca759f9e387db87e1719911f019bc60c74be9ed8 from qemu
We know there will be cases where MTTCG won't work until additional work
is done in the front/back ends to support. It will however be useful to
be able to turn it on.
As a result MTTCG will default to off unless the combination is
supported. However the user can turn it on for the sake of testing.
Backports commit 8d4e9146b3568022ea5730d92841345d41275d66 from qemu
We'll be using the memory ordering definitions to define values for
both the host and guest. To avoid fighting with circular header
dependencies just move these types into their own minimal header.
Backports commit 20937143145b8f5a4194e5c407731ba38797864e from qemu
Particularly when andc is also available, this is two insns
shorter than using clz to compute ctz.
Backports commit 14e99210f6c6cede461a54b2e0f9b4cd55175f00 from qemu
The number of actual invocations of ctpop itself does not warrent
an opcode, but it is very helpful for POWER7 to use in generating
an expansion for ctz.
Backports commit a768e4e99247911f00c5c0267c12d4e207d5f6cc from qemu
The number of actual invocations does not warrent an opcode,
and the backends generating it. But at least we can eliminate
redundant helpers.
Backports commit 086920c2c8008f125fd38781072fa25c3ad158ea from qemu
Previously we could not have different constraints for different ISA levels,
which prevented us from eliding the matching constraint for shifts.
We do now have to make sure that the operands match for constant shifts.
We can also handle some small left shifts via lea.
Backports commit 6a5aed4bdc7078838a8098336588d56c9ce09d1d from qemu
Use a switch instead of searching a table. Share constraints between
32-bit and 64-bit, when at all possible.
Backports commit cd26449a505f808e479af4fdd539e05767e09c06 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
Since we can no longer use matching constraints, this does
mean we must handle that data movement by hand.
Backports commit 752b1be94757de906b9c24ebc8f5e6aa54b96b23 from qemu
This lets us expose facilities to TCG_TARGET_HAS_* defines
directly, rather than hiding behind function calls.
Backports commit b2c98d9d392c87c9b9e975d30f79924719d9cbbe from qemu
