[PATCH 00/35] wasm: Add Wasm TCG backend based on wasm64

[Kohei Tokunaga <ktokunaga.mail@gmail.com>]

This patch series adds a TCG backend for WebAssembly. Unlike eariler
attempts [1], it is implemented using Emscripten's wasm64 target to support
64bit guests.

The first four commits are temporarily imported from a separated patch
series which enables 64bit guests using wasm64 [2]. These commits are under
review in that series and are included here only to allow subsequent patches
to build. Please ignore them when reviewing this series.

# New TCG Backend for Browsers

A new TCG backend translates IR instructions into Wasm instructions and runs
them using the browser's WebAssembly APIs (WebAssembly.Module and
WebAssembly.instantiate). To minimize compilation overhead and avoid hitting
the browser's limitation of the number of instances, this backend integrates
a forked TCI. TBs run on TCI by default, with frequently executed TBs
compiled into WebAssembly.

# 64bit guests support by wasm64

Support for 64bit guests is being reviewed in a separated patch series [2],
which enables QEMU to use 64bit pointers by compiling with the --cpu=wasm64
flag. The Wasm TCG backend is based on this feature and also requires
--cpu=wasm64.

QEMU compiled with --cpu=wasm64 runs on wasm64-capable engines. To support
engines which don't support wasm64 (e.g. Safari), the Wasm backend can use
the compatibility flag "--enable-wasm64-32bit-address-limit" also introduced
in [2]. This flag enables 64bit pointers in the C code while Emscripten
lowers the output binary to wasm32 and limits the maximum memory size to
4GB. As a result, the Wasm backend can run on wasm32 engiens while
supporting 64bit guests.

Note: The flag was originally named --wasm64-32bit-address-limit but this
patch series moved it from the configure script into meson_options.txt. To
follow Meson's naming conventions, it was renamed to
--enable-wasm64-32bit-address-limit.

# Overview of build process

To compile QEMU with Emscripten, the following dependencies are required.
The emsdk-wasm-cross.docker environment includes all necessary components
and can be used as the build environment:

- Emscripten SDK (emsdk) v4.0.10
- Libraries cross-compiled with Emscripten (please see also
  emsdk-wasm-cross.docker for build steps)
  - GLib v2.84.0
  - zlib v1.3.1
  - libffi v3.5.2
  - Pixman v0.44.2

The configure script supports --cpu=wasm64 flag to compile QEMU with 64bit
pointer support.

emconfigure ./configure --cpu=wasm64 \
                        --static --disable-tools \
                        --target-list=x86_64-softmmu
emmake make -j$(nproc)

If the output needs to run on wasm32 engines, use
"--enable-wasm64-32bit-address-limit" flag.

emconfigure ./configure --cpu=wasm64 --enable-wasm64-32bit-address-limit \
                        --static --disable-tools \
                        --target-list=x86_64-softmmu
emmake make -j$(nproc)

Either of the above commands generates the following files:

- qemu-system-x86_64.js
- qemu-system-x86_64.wasm

Guest images can be packaged using Emscripten's file_packager.py tool.
For example, if the images are stored in a directory named "pack", the
following command packages them, allowing QEMU to access them through
Emscripten's virtual filesystem:

/path/to/file_packager.py qemu-system-x86_64.data --preload pack > load.js

This process generates the following files:

- qemu-system-x86_64.data
- load.js

Emscripten allows passing arguments to the QEMU command via the Module
object in JavaScript:

Module['arguments'] = [
    '-nographic', '-m', '512M',
    '-L', 'pack/',
    '-drive', 'if=virtio,format=raw,file=pack/rootfs.bin',
    '-kernel', 'pack/bzImage',
    '-append', 'earlyprintk=ttyS0 console=ttyS0 root=/dev/vda loglevel=7',
];

The sample repository [3] (tcgdev64 branch) provides a complete setup,
including an HTML file that implements a terminal UI.

[1] https://patchew.org/QEMU/cover.1747744132.git.ktokunaga.mail@gmail.com/
[2] https://patchew.org/QEMU/cover.1754534225.git.ktokunaga.mail@gmail.com/
[3] https://github.com/ktock/qemu-wasm-sample/tree/tcgdev64

Kohei Tokunaga (35):
  meson: Add wasm64 support to the --cpu flag
  configure: Enable to propagate -sMEMORY64 flag to Emscripten
  dockerfiles: Add support for wasm64 to the wasm Dockerfile
  .gitlab-ci.d: Add build tests for wasm64
  tcg: Fork TCI for wasm backend
  tcg/wasm: Do not use TCI disassembler in Wasm backend
  tcg/wasm: Set TCG_TARGET_REG_BITS to 64
  meson: Enable to build wasm backend
  tcg/wasm: Set TCG_TARGET_INSN_UNIT_SIZE to 1
  tcg/wasm: Add and/or/xor instructions
  tcg/wasm: Add add/sub/mul instructions
  tcg/wasm: Add shl/shr/sar instructions
  tcg/wasm: Add setcond/negsetcond/movcond instructions
  tcg/wasm: Add deposit/sextract/extract instrcutions
  tcg/wasm: Add load and store instructions
  tcg/wasm: Add mov/movi instructions
  tcg/wasm: Add ext instructions
  tcg/wasm: Add bswap instructions
  tcg/wasm: Add rem/div instructions
  tcg/wasm: Add andc/orc/eqv/nand/nor instructions
  tcg/wasm: Add neg/not/ctpop instructions
  tcg/wasm: Add rot/clz/ctz instructions
  tcg/wasm: Add br/brcond instructions
  tcg/wasm: Add exit_tb/goto_tb/goto_ptr instructions
  tcg/wasm: Add call instruction
  tcg/wasm: Add qemu_ld/qemu_st instructions
  tcg/wasm: Mark unimplemented instructions as C_NotImplemented
  tcg/wasm: Add initialization of fundamental registers
  tcg/wasm: Write wasm binary to TB
  tcg/wasm: Implement instantiation of Wasm binary
  tcg/wasm: Allow switching coroutine from a helper
  tcg/wasm: Enable instantiation of TBs executed many times
  tcg/wasm: Enable TLB lookup
  meson: Propagate optimization flag for linking on Emscripten
  .gitlab-ci.d: build wasm backend in CI

 .gitlab-ci.d/buildtest.yml                    |   26 +-
 .gitlab-ci.d/container-cross.yml              |   20 +-
 .gitlab-ci.d/container-template.yml           |    4 +-
 MAINTAINERS                                   |    9 +-
 configure                                     |   14 +-
 include/accel/tcg/getpc.h                     |    2 +-
 include/tcg/helper-info.h                     |    4 +-
 include/tcg/tcg.h                             |    2 +-
 meson.build                                   |   14 +-
 meson_options.txt                             |    3 +
 scripts/meson-buildoptions.sh                 |    5 +
 tcg/aarch64/tcg-target.c.inc                  |   11 +
 tcg/arm/tcg-target.c.inc                      |   11 +
 tcg/i386/tcg-target.c.inc                     |   11 +
 tcg/loongarch64/tcg-target.c.inc              |   11 +
 tcg/meson.build                               |    5 +
 tcg/mips/tcg-target.c.inc                     |   11 +
 tcg/ppc/tcg-target.c.inc                      |   11 +
 tcg/region.c                                  |   10 +-
 tcg/riscv/tcg-target.c.inc                    |   11 +
 tcg/s390x/tcg-target.c.inc                    |   11 +
 tcg/sparc64/tcg-target.c.inc                  |   11 +
 tcg/tcg.c                                     |   23 +-
 tcg/tci/tcg-target.c.inc                      |   11 +
 tcg/wasm.c                                    | 1112 ++++++
 tcg/wasm.h                                    |  119 +
 tcg/wasm/tcg-target-con-set.h                 |   21 +
 tcg/wasm/tcg-target-con-str.h                 |   11 +
 tcg/wasm/tcg-target-has.h                     |   22 +
 tcg/wasm/tcg-target-mo.h                      |   17 +
 tcg/wasm/tcg-target-opc.h.inc                 |   15 +
 tcg/wasm/tcg-target-reg-bits.h                |   15 +
 tcg/wasm/tcg-target.c.inc                     | 3167 +++++++++++++++++
 tcg/wasm/tcg-target.h                         |   77 +
 ...2-cross.docker => emsdk-wasm-cross.docker} |   29 +-
 35 files changed, 4822 insertions(+), 34 deletions(-)
 create mode 100644 tcg/wasm.c
 create mode 100644 tcg/wasm.h
 create mode 100644 tcg/wasm/tcg-target-con-set.h
 create mode 100644 tcg/wasm/tcg-target-con-str.h
 create mode 100644 tcg/wasm/tcg-target-has.h
 create mode 100644 tcg/wasm/tcg-target-mo.h
 create mode 100644 tcg/wasm/tcg-target-opc.h.inc
 create mode 100644 tcg/wasm/tcg-target-reg-bits.h
 create mode 100644 tcg/wasm/tcg-target.c.inc
 create mode 100644 tcg/wasm/tcg-target.h
 rename tests/docker/dockerfiles/{emsdk-wasm32-cross.docker => emsdk-wasm-cross.docker} (85%)

-- 
2.43.0