Merge tag 'for-upstream' of https://gitlab.com/bonzini/qemu into staging

* configure: use a native non-cross compiler for linux-user
* meson: cleanups
* target/i386: miscellaneous cleanups and optim

Merge tag 'for-upstream' of https://gitlab.com/bonzini/qemu into staging

* configure: use a native non-cross compiler for linux-user
* meson: cleanups
* target/i386: miscellaneous cleanups and optimizations
* target/i386: implement CMPccXADD
* target/i386: the sgx_epc_get_section stub is reachable
* esp: check for NULL result from scsi_device_find()

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* tag 'for-upstream' of https://gitlab.com/bonzini/qemu: (46 commits)
meson.build: report graphics backends separately
configure, meson: rename targetos to host_os
meson: rename config_all
meson: remove CONFIG_ALL
meson: remove config_targetos
meson: remove CONFIG_POSIX and CONFIG_WIN32 from config_targetos
meson: remove OS definitions from config_targetos
meson: always probe u2f and canokey if the option is enabled
meson: move subdirs to "Collect sources" section
meson: move config-host.h definitions together
meson: move CFI detection code with other compiler flags
meson: keep subprojects together
meson: move accelerator dependency checks together
meson: move option validation together
meson: move program checks together
meson: add more sections to main meson.build
configure: unify again the case arms in probe_target_compiler
configure: remove unnecessary subshell
Makefile: clean qemu-iotests output
meson: use version_compare() to compare version
...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

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target/i386: introduce flags writeback mechanism

ALU instructions can write to both memory and flags. If the CC_SRC*
and CC_DST locations have been written already when a memory access
causes a fau

target/i386: introduce flags writeback mechanism

ALU instructions can write to both memory and flags. If the CC_SRC*
and CC_DST locations have been written already when a memory access
causes a fault, the value in CC_SRC* and CC_DST might be interpreted
with the wrong CC_OP (the one that is in effect before the instruction.

Besides just using the wrong result for the flags, something like
subtracting -1 can have disastrous effects if the current CC_OP is
CC_OP_EFLAGS: this is because QEMU does not expect bits outside the ALU
flags to be set in CC_SRC, and env->eflags can end up set to all-ones.
In the case of the attached testcase, this sets IOPL to 3 and would
cause an assertion failure if SUB is moved to the new decoder.

This mechanism is not really needed for BMI instructions, which can
only write to a register, but put it to use anyway for cleanliness.
In the case of BZHI, the code has to be modified slightly to ensure
that decode->cc_src is written, otherwise the new assertions trigger.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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