Commit Graph

771 Commits

Author SHA1 Message Date
Peter Maydell 378df4b237 Handle CPU interrupts by inline checking of a flag
Fix some of the nasty TCG race conditions and crashes by implementing
cpu_exit() as setting a flag which is checked at the start of each TB.
This avoids crashes if a thread or signal handler calls cpu_exit()
while the execution thread is itself modifying the TB graph (which
may happen in system emulation mode as well as in linux-user mode
with a multithreaded guest binary).

This fixes the crashes seen in LP:668799; however there are another
class of crashes described in LP:1098729 which stem from the fact
that in linux-user with a multithreaded guest all threads will
use and modify the same global TCG date structures (including the
generated code buffer) without any kind of locking. This means that
multithreaded guest binaries are still in the "unsupported"
category.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-03-03 14:28:47 +00:00
Peter Maydell 0980011b4f tcg: Document tcg_qemu_tb_exec() and provide constants for low bit uses
Document tcg_qemu_tb_exec(). In particular, its return value is a
combination of a pointer to the next translation block and some
extra information in the low two bits. Provide some #defines for
the values passed in these bits to improve code clarity.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-03-03 14:28:19 +00:00
Blue Swirl 07ca08bac8 tcg-sparc: fix build
Fix build breakage by 803d805bcef4ea7b7d6ef0b4929263e1160d6b3c:
make tcg_out_addsub2() always available.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-03-03 08:25:50 +00:00
Peter Maydell 989b697ddd qemu-log: default to stderr for logging output
Switch the default for qemu_log logging output from "/tmp/qemu.log"
to stderr. This is an incompatible change in some sense, but logging
is mostly used for debugging purposes so it shouldn't affect production
use. The previous behaviour can be obtained by adding "-D /tmp/qemu.log"
to the command line.

This change requires us to:
 * update all the documentation/help text (we take the opportunity
   to smooth out minor inconsistencies between the phrasing in
   linux-user/bsd-user/system help messages)
 * make linux-user and bsd-user defer to qemu-log for the default
   logging destination rather than overriding it themselves
 * ensure that all logfile closing is done via qemu_log_close()
   and that that function doesn't close stderr
as well as the obvious change to the behaviour of do_qemu_set_log()
when no logfile name has been specified.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-id: 1361901160-28729-1-git-send-email-peter.maydell@linaro.org
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2013-02-26 13:31:47 -06:00
Richard Henderson f1fae40c61 tcg: Apply life analysis to 64-bit multiword arithmetic ops
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-23 17:25:29 +00:00
Richard Henderson f402f38f43 tcg: Implement muls2 with mulu2
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-23 17:25:29 +00:00
Richard Henderson d693e14733 tcg-arm: Implement muls2_i32
We even had the encoding of smull already handy...

Cc: Andrzej Zaborowski <balrogg@gmail.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-23 17:25:29 +00:00
Richard Henderson 624988a53b tcg-i386: Implement multiword arithmetic ops
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-23 17:25:29 +00:00
Richard Henderson f6953a7399 tcg: Implement multiword addition helpers
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-23 17:25:28 +00:00
Richard Henderson 696a8be6a0 tcg: Implement multiword multiply helpers
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-23 17:25:28 +00:00
Richard Henderson 3c51a98507 tcg: Implement a 64-bit to 32-bit extraction helper
We're going to have use for this shortly in implementing other helpers.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-23 17:25:28 +00:00
Richard Henderson 4d3203fd0b tcg: Add signed multiword multiplication operations
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-23 17:25:28 +00:00
Richard Henderson d7156f7ce4 tcg: Add 64-bit multiword arithmetic operations
Matching the 32-bit multiword arithmetic that we already have.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-23 17:25:28 +00:00
Richard Henderson 803d805bce tcg-sparc: Always implement 32-bit multiword ops
Cc: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-23 17:25:28 +00:00
Richard Henderson bbc863bfec tcg-i386: Always implement 32-bit multiword ops
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-23 17:25:28 +00:00
Richard Henderson e6a7273454 tcg: Make 32-bit multiword operations optional for 64-bit hosts
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-23 17:25:28 +00:00
Andreas Färber be96bd3fbf tcg/ppc: Fix build of tcg_qemu_tb_exec()
Commit 0b0d3320db (TCG: Final globals
clean-up) moved code_gen_prologue but forgot to update ppc code.
This broke the build on 32-bit ppc. ppc64 is unaffected.

Cc: Evgeny Voevodin <evgenyvoevodin@gmail.com>
Cc: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Andreas Färber <andreas.faerber@web.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-17 14:27:36 +00:00
Peter Maydell 24537a0191 qemu-log: Rename the public-facing cpu_set_log function to qemu_set_log
Rename the public-facing function cpu_set_log to qemu_set_log. This
requires us to rename the internal-only qemu_set_log() to
do_qemu_set_log().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-16 10:44:44 +00:00
Evgeny Voevodin 5e5f07e08f TCG: Move translation block variables to new context inside tcg_ctx: tb_ctx
It's worth to clean-up translation blocks variables and move them
into one context as was suggested by Swirl.
Also if we use this context directly inside tcg_ctx, then it
speeds up code generation a bit.

Signed-off-by: Evgeny Voevodin <evgenyvoevodin@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-16 10:41:16 +00:00
Evgeny Voevodin 0b0d3320db TCG: Final globals clean-up
Signed-off-by: Evgeny Voevodin <evgenyvoevodin@gmail.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-16 10:40:56 +00:00
Peter Maydell 5256a7208a tcg/target-arm: Add missing parens to assertions
Silence a (legitimate) complaint about missing parentheses:

tcg/arm/tcg-target.c: In function ‘tcg_out_qemu_ld’:
tcg/arm/tcg-target.c:1148:5: error: suggest parentheses around
comparison in operand of ‘&’ [-Werror=parentheses]
tcg/arm/tcg-target.c: In function ‘tcg_out_qemu_st’:
tcg/arm/tcg-target.c:1357:5: error: suggest parentheses around
comparison in operand of ‘&’ [-Werror=parentheses]

which meant that we would mistakenly always assert if running
a QEMU built with debug enabled on ARM.

Signed-off-by: Peter Maydell <peter.maydelL@linaro.org>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-01-19 10:27:45 +00:00
Paolo Bonzini 633f650254 optimize: optimize using nonzero bits
This adds two optimizations using the non-zero bit mask.  In some cases
involving shifts or ANDs the value can become zero, and can thus be
optimized to a move of zero.  Second, useless zero-extension or an
AND with constant can be detected that would only zero bits that are
already zero.

The main advantage of this optimization is that it turns zero-extensions
into moves, thus enabling much better copy propagation (around 1% code
reduction).  Here is for example a "test $0xff0000,%ecx + je" before
optimization:

 mov_i64 tmp0,rcx
 movi_i64 tmp1,$0xff0000
 discard cc_src
 and_i64 cc_dst,tmp0,tmp1
 movi_i32 cc_op,$0x1c
 ext32u_i64 tmp0,cc_dst
 movi_i64 tmp12,$0x0
 brcond_i64 tmp0,tmp12,eq,$0x0

and after (without patch on the left, with on the right):

 movi_i64 tmp1,$0xff0000                 movi_i64 tmp1,$0xff0000
 discard cc_src                          discard cc_src
 and_i64 cc_dst,rcx,tmp1                 and_i64 cc_dst,rcx,tmp1
 movi_i32 cc_op,$0x1c                    movi_i32 cc_op,$0x1c
 ext32u_i64 tmp0,cc_dst
 movi_i64 tmp12,$0x0                     movi_i64 tmp12,$0x0
 brcond_i64 tmp0,tmp12,eq,$0x0           brcond_i64 cc_dst,tmp12,eq,$0x0

Other similar cases: "test %eax, %eax + jne" where eax is already 32-bit
(after optimization, without patch on the left, with on the right):

 discard cc_src                          discard cc_src
 mov_i64 cc_dst,rax                      mov_i64 cc_dst,rax
 movi_i32 cc_op,$0x1c                    movi_i32 cc_op,$0x1c
 ext32u_i64 tmp0,cc_dst
 movi_i64 tmp12,$0x0                     movi_i64 tmp12,$0x0
 brcond_i64 tmp0,tmp12,ne,$0x0           brcond_i64 rax,tmp12,ne,$0x0

"test $0x1, %dl + je":

 movi_i64 tmp1,$0x1                      movi_i64 tmp1,$0x1
 discard cc_src                          discard cc_src
 and_i64 cc_dst,rdx,tmp1                 and_i64 cc_dst,rdx,tmp1
 movi_i32 cc_op,$0x1a                    movi_i32 cc_op,$0x1a
 ext8u_i64 tmp0,cc_dst
 movi_i64 tmp12,$0x0                     movi_i64 tmp12,$0x0
 brcond_i64 tmp0,tmp12,eq,$0x0           brcond_i64 cc_dst,tmp12,eq,$0x0

In some cases TCG even outsmarts GCC. :)  Here the input code has
"and $0x2,%eax + movslq %eax,%rbx + test %rbx, %rbx" and the optimizer,
thanks to copy propagation, does the following:

 movi_i64 tmp12,$0x2                     movi_i64 tmp12,$0x2
 and_i64 rax,rax,tmp12                   and_i64 rax,rax,tmp12
 mov_i64 cc_dst,rax                      mov_i64 cc_dst,rax
 ext32s_i64 tmp0,rax                  -> nop
 mov_i64 rbx,tmp0                     -> mov_i64 rbx,cc_dst
 and_i64 cc_dst,rbx,rbx               -> nop

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-01-19 10:13:16 +00:00
Paolo Bonzini 3a9d8b179b optimize: track nonzero bits of registers
Add a "mask" field to the tcg_temp_info struct.  A bit that is zero
in "mask" will always be zero in the corresponding temporary.
Zero bits in the mask can be produced from moves of immediates,
zero-extensions, ANDs with constants, shifts; they can then be
be propagated by logical operations, shifts, sign-extensions,
negations, deposit operations, and conditional moves.  Other
operations will just reset the mask to all-ones, i.e. unknown.

[rth: s/target_ulong/tcg_target_ulong/]

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-01-19 10:13:14 +00:00
Paolo Bonzini d193a14a2c optimize: only write to state when clearing optimizer data
The next patch will add to the TCG optimizer a field that should be
non-zero in the default case.  Thus, replace the memset of the
temps array with a loop.  Only the state field has to be up-to-date,
because others are not used except if the state is TCG_TEMP_COPY
or TCG_TEMP_CONST.

[rth: Extracted the loop to a function.]

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-01-19 10:13:13 +00:00
Paolo Bonzini 163fa4b09d tcg-i386: use LEA for 3-operand 64-bit addition
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-01-12 12:45:56 +00:00
Stefan Weil 9a8a5ae69d tcg: Remove unneeded assertion
Commit 7f6f0ae5b9 added two assertions.

One of these assertions is not needed:
The pointer ts is never NULL because it is initialized with the
address of an array element.

Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2013-01-02 11:23:21 -06:00
Richard Henderson 753d99d38b tcg-hppa: Fix typo in brcond2
Reported-by: Stuart Brady <sdb@zubnet.me.uk>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2012-12-29 12:21:53 +00:00
Richard Henderson 76a347e1cd tcg-i386: Perform cmov detection at runtime for 32-bit.
Existing compile-time detection is spotty at best.  Convert
it all to runtime detection instead.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2012-12-29 12:21:16 +00:00
Richard Henderson afcb92beac tcg: Add TCGV_IS_UNUSED_*
Cc: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2012-12-29 12:14:07 +00:00
Paolo Bonzini 1de7afc984 misc: move include files to include/qemu/
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-12-19 08:32:39 +01:00
Paolo Bonzini 022c62cbbc exec: move include files to include/exec/
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-12-19 08:31:31 +01:00
Paolo Bonzini cb9c377f54 janitor: add guards to headers
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-12-19 08:31:31 +01:00
Anthony Liguori 7c12fd9b29 Merge remote-tracking branch 'stefanha/trivial-patches' into staging
* stefanha/trivial-patches:
  pc_sysfw: Plug memory leak on pc_fw_add_pflash_drv() error path
  qemu-options: Fix space at EOL
  Fix spelling in comments and documentation
  Clean up pci_drive_hot_add()'s use of BlockInterfaceType
  arm: a9mpcore: remove un-used ptimer_iomem field
  target-sparc: Remove t0, t1 from CPUSPARCState
  target-m68k: Remove t1 from CPUM68KState
  target-alpha: Remove t0, t1 from CPUAlphaState
  s390x: Spelling fixes (endianess -> endianness, occured -> occurred)
  Fix comments (adress -> address, layed -> laid, wierd -> weird)
  Fix spelling (prefered -> preferred)
  configure: Remove stray debug output
  sd: Send debug printfery to stderr not stdout

Conflicts:
	configure

Resolve spelling conflict in configure.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2012-12-10 08:34:29 -06:00
Evgeny Voevodin c3a43607d9 tcg/tcg.h: Duplicate global TCG gen_opc_ arrays into TCGContext.
Signed-off-by: Evgeny Voevodin <e.voevodin@samsung.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2012-12-08 14:24:41 +00:00
Stefan Weil a93cf9dfba Fix comments (adress -> address, layed -> laid, wierd -> weird)
Remove also a duplicated 'the'.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2012-12-07 12:34:11 +01:00
Aurelien Jarno e5138db510 tcg: mark local temps as MEM in dead_temp()
In dead_temp, local temps should always be marked as back to memory,
even if they have not been allocated (i.e. they are discared before
cross a basic block).

It fixes the following assertion in target-xtensa:

    qemu-system-xtensa: tcg/tcg.c:1665: temp_save: Assertion `s->temps[temp].val_type == 2 || s->temps[temp].fixed_reg' failed.
    Aborted

Reported-by: Max Filippov <jcmvbkbc@gmail.com>
Tested-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
2012-11-24 13:24:13 +01:00
Aurelien Jarno 7aab08aa78 tcg/arm: fix cross-endian qemu_st16
The bswap16 TCG opcode assumes that the high bytes of the temp equal
to 0 before calling it. The ARM backend implementation takes this
assumption to slightly optimize the generated code.

The same implementation is called for implementing the cross-endian
qemu_st16 opcode, where this assumption is not true anymore. One way to
fix that would be to zero the high bytes before calling it. Given the
store instruction just ignore them, it is possible to provide a slightly
more optimized version. With ARMv6+ the rev16 instruction does the work
correctly. For lower ARM versions the patch provides a version which
behaves correctly with non-zero high bytes, but fill them with junk.

Cc: Andrzej Zaborowski <balrogg@gmail.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-stable@nongnu.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
2012-11-24 13:19:53 +01:00
Aurelien Jarno d17bd1d8cc tcg/arm: fix TLB access in qemu-ld/st ops
The TCG arm backend considers likely that the offset to the TLB
entries does not exceed 12 bits for mem_index = 0. In practice this is
not true for at least the MIPS target.

The current patch fixes that by loading the bits 23-12 with a separate
instruction, and using loads with address writeback, independently of
the value of mem_idx. In total this allow a 24-bit offset, which is a
lot more than needed.

Cc: Andrzej Zaborowski <balrogg@gmail.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-stable@nongnu.org
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
2012-11-24 13:19:53 +01:00
malc ecf51c9abe tcg/ppc: Fix !softmmu case
Signed-off-by: malc <av1474@comtv.ru>
2012-11-21 10:56:22 +04:00
malc ecdffbccd7 tcg/ppc: Remove unused s_bits variable
Thanks to Alexander Graf for heads up.

Signed-off-by: malc <av1474@comtv.ru>
2012-11-19 22:22:24 +04:00
Stefan Weil e24dc9feb0 tci: Support deposit operations
The operations for INDEX_op_deposit_i32 and INDEX_op_deposit_i64
are now supported and enabled by default.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2012-11-18 20:40:08 +00:00
Evgeny Voevodin 83eeb39669 TCG: Remove unused global variables
Signed-off-by: Evgeny Voevodin <e.voevodin@samsung.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2012-11-17 13:53:38 +00:00
Evgeny Voevodin 1ff0a2c594 TCG: Use gen_opparam_buf from context instead of global variable.
Signed-off-by: Evgeny Voevodin <e.voevodin@samsung.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2012-11-17 13:53:37 +00:00
Evgeny Voevodin 92414b31e7 TCG: Use gen_opc_buf from context instead of global variable.
Signed-off-by: Evgeny Voevodin <e.voevodin@samsung.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2012-11-17 13:53:36 +00:00
Evgeny Voevodin c4afe5c4d3 TCG: Use gen_opparam_ptr from context instead of global variable.
Signed-off-by: Evgeny Voevodin <e.voevodin@samsung.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2012-11-17 13:53:34 +00:00
Evgeny Voevodin efd7f48600 TCG: Use gen_opc_ptr from context instead of global variable.
Signed-off-by: Evgeny Voevodin <e.voevodin@samsung.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2012-11-17 13:53:27 +00:00
Evgeny Voevodin 8232a46a16 tcg/tcg.h: Duplicate global TCG variables in TCGContext
Signed-off-by: Evgeny Voevodin <e.voevodin@samsung.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2012-11-17 13:53:26 +00:00
Kirill Batuzov 3c5645fab3 tcg: properly check that op's output needs to be synced to memory
Fix typo introduced in b3a1be87ba.

Reported-by: Ruslan Savchenko <ruslan.savchenko@gmail.com>
Signed-off-by: Kirill Batuzov <batuzovk@ispras.ru>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
2012-11-11 16:06:46 +01:00
malc c878da3b27 tcg/ppc32: Use trampolines to trim the code size for mmu slow path accessors
mmu access looks something like:

<check tlb>
if miss goto slow_path
<fast path>
done:
...

; end of the TB
slow_path:
 <pre process>
 mr r3, r27         ; move areg0 to r3
                    ; (r3 holds the first argument for all the PPC32 ABIs)
 <call mmu_helper>
 b $+8
 .long done
 <post process>
 b done

On ppc32 <call mmu_helper> is:

(SysV and Darwin)

mmu_helper is most likely not within direct branching distance from
the call site, necessitating

a. moving 32 bit offset of mmu_helper into a GPR ; 8 bytes
b. moving GPR to CTR/LR                          ; 4 bytes
c. (finally) branching to CTR/LR                 ; 4 bytes

r3 setting              - 4 bytes
call                    - 16 bytes
dummy jump over retaddr - 4 bytes
embedded retaddr        - 4 bytes
         Total overhead - 28 bytes

(PowerOpen (AIX))
a. moving 32 bit offset of mmu_helper's TOC into a GPR1 ; 8 bytes
b. loading 32 bit function pointer into GPR2            ; 4 bytes
c. moving GPR2 to CTR/LR                                ; 4 bytes
d. loading 32 bit small area pointer into R2            ; 4 bytes
e. (finally) branching to CTR/LR                        ; 4 bytes

r3 setting              - 4 bytes
call                    - 24 bytes
dummy jump over retaddr - 4 bytes
embedded retaddr        - 4 bytes
         Total overhead - 36 bytes

Following is done to trim the code size of slow path sections:

In tcg_target_qemu_prologue trampolines are emitted that look like this:

trampoline:
mfspr r3, LR
addi  r3, 4
mtspr LR, r3      ; fixup LR to point over embedded retaddr
mr    r3, r27
<jump mmu_helper> ; tail call of sorts

And slow path becomes:

slow_path:
 <pre process>
 <call trampoline>
 .long done
 <post process>
 b done

call                    - 4 bytes (trampoline is within code gen buffer
                                   and most likely accessible via
                                   direct branch)
embedded retaddr        - 4 bytes
         Total overhead - 8 bytes

In the end the icache pressure is decreased by 20/28 bytes at the cost
of an extra jump to trampoline and adjusting LR (to skip over embedded
retaddr) once inside.

Signed-off-by: malc <av1474@comtv.ru>
2012-11-06 04:37:57 +04:00
malc ed224a56b3 tcg/ppc: ld/st optimization
Signed-off-by: malc <av1474@comtv.ru>
2012-11-03 20:17:54 +04:00