On 7/4/25 16:45, Kohei Tokunaga wrote:
A TB consists of a wasmTBHeader followed by the data listed below. The wasmTBHeader contains pointers for each element:- TCI code - Wasm code - Array of function indices imported into the Wasm instance - Counter tracking the number of TB executions - Pointer to the Wasm instance information The Wasm backend (tcg/wasm32.c) and Wasm instances running on the same thread share information, such as CPUArchState, through a wasmContext structure. The Wasm backend defines tcg_qemu_tb_exec as a common entry point for TBs, similar to the TCI backend. tcg_qemu_tb_exec runs TBs on a forked TCI interpreter by default, while compiles and executes frequently executed TBs as Wasm. The code generator (tcg/wasm32) receives TCG IR and generates both Wasm and TCI instructions. Since Wasm cannot directly jump to specific addresses, labels are implemented using Wasm control flow instructions. As shown in the pseudo-code below, a TB wraps instructions in a large loop, where codes are placed within if blocks separated by labels. Branching is handled by breaking from the current block and entering the target block. loop if ... code after label1 end if ... code after label2 end ... end Additionally, the Wasm backend differs from other backends in several ways: - goto_tb and goto_ptr return control to tcg_qemu_tb_exec which runs the target TB - Helper function pointers are stored in an array in TB and imported into the Wasm instance on execution - Wasm TBs lack prologue and epilogue. TBs are executed via tcg_qemu_tb_exec Browsers cause out of memory error if too many Wasm instances are created. To prevent this, the Wasm backend tracks active instances using an array. When instantiating a new instance risks exceeding the limit, the backend removes older instances to avoid browser errors. These removed instances are re-instantiated when needed. Signed-off-by: Kohei Tokunaga <[email protected]> --- include/accel/tcg/getpc.h | 2 +- include/tcg/helper-info.h | 4 +- include/tcg/tcg.h | 2 +- meson.build | 2 + tcg/meson.build | 5 + tcg/tcg.c | 26 +- tcg/wasm32.c | 1260 +++++++++ tcg/wasm32.h | 39 + tcg/wasm32/tcg-target-con-set.h | 18 + tcg/wasm32/tcg-target-con-str.h | 8 + tcg/wasm32/tcg-target-has.h | 102 + tcg/wasm32/tcg-target-mo.h | 12 + tcg/wasm32/tcg-target-opc.h.inc | 4 + tcg/wasm32/tcg-target-reg-bits.h | 12 + tcg/wasm32/tcg-target.c.inc | 4484 ++++++++++++++++++++++++++++++ tcg/wasm32/tcg-target.h | 65 + 16 files changed, 6035 insertions(+), 10 deletions(-)
Eh TBH this is too much to review as a single patch. Do you already have an idea how different the wasm64 implementation can be?
