WIP: replace register-alloc with purely stack-based translation

[Robbepop]

Closes #1484.

ToDo

• Implement translation of Wasm operators.
  • {i32,i64,f32,f64}.const
  • return, br_if, br, unreachable, nop
  • local.{get,set,tee}
  • i{32,64}.{popcnt,clz,ctz}
  • i{32,64}.{add,sub,mul,div_s,div_u,rem_s,rem_u,shl,shr_s,shr_u,rotl,rotr}
  • conversion instructions
  • f{32,64}.{abs,neg,ceil,floor,nearest,trunc,sqrt}
  • f{32,64}.{add,sub,mul,div,min,max,copysign}
  • global.{get,set}
  • memory.{size,grow,init,copy,fill} & data.drop
  • table.{size,grow,init,copy,fill} & elem.drop
  • memory.load
  • memory.store
  • call
  • call_indirect
  • return_call
  • return_call_indirect
  • select
  • ref.{func,null,is_null}
  • br_table
  • simd
  • wide-arithmetic
• Implement optimizations
  • fuse_local_set/tee
  • fuse_eqz
  • fuse_nez
  • fuse_cmp_branch
  • fuse_cmp_select
• Add support to the translation stack to overwrite types of local operands.
  • Optimize (reinterpret (local $n)) instruction translation by not requiring a copy instruction.
  • Optimize (ref.is_null (local $n)) instruction translation by not requiring a copy instruction.
• Fix known translation bugs:
  • attempt to subtract with overflow
    • Failing: wasm_br_if
  • attempt to subtract with overflow (2)
    • Failing: wasm_br_if, wasm_return_call, wasm_return_call_indirect
  • tried to pop operand from empty stack
    • Failing: wasm_stack, wasm_return_call_indirect
  • assertion failed: self.range.start <= self.range.end
    • Failing: wasm_names, wasm_return_call, wasm_return_call_indirect, wasm_float_exprs, wasm_imports
  • infinite loop during execution
    • Affected: wasm_return_call, wasm_return_call_indirect
  • compiled functions must have at least one instruction
    • Failing: wasm_loop, wasm_block
  • failed directive on: call stack exhausted
    • Failing: wasm_forward:17:1, wasm_fac:102:1
  • encountered mismatch in evaluation. expected I64(7034535277573963776) but found I64(0)
    • Failing: wasm_fac:102:1
  • encountered mismatch in evaluation. expected I32(1) but found I32(0)
    • Failing: wasm_forward:18:1
  • assertion failed: matches!(condition.ty(), ValType::I32, | ValType::I64)
    • Failing: wasm_call_indirect
  • failed directive on: encountered mismatch in evaluation. expected I64(0) but found I64(4607182418800017408)
    • Failing: wasm_func:260:1
  • failed directive: encountered mismatch in evaluation. expected I64(-1) but found I64(0)
    • Failing: wasm_endianness:148:1

[codecov]

Codecov Report

Attention: Patch coverage is 3.75361% with 1000 lines in your changes missing coverage. Please review.

Project coverage is 67.72%. Comparing base (57b28e7) to head (8cea35b).

Files with missing lines	Patch %	Lines
...es/wasmi/src/engine/translator/func2/simd/visit.rs	0.00%	256 Missing ⚠️
crates/wasmi/src/engine/translator/func2/visit.rs	0.00%	213 Missing ⚠️
...wasmi/src/engine/translator/func2/stack/control.rs	0.00%	115 Missing ⚠️
...asmi/src/engine/translator/func2/stack/operands.rs	0.00%	115 Missing ⚠️
...tes/wasmi/src/engine/translator/func2/stack/mod.rs	0.00%	87 Missing ⚠️
crates/wasmi/src/engine/translator/func2/mod.rs	0.00%	62 Missing ⚠️
...wasmi/src/engine/translator/func2/stack/operand.rs	0.00%	46 Missing ⚠️
...es/wasmi/src/engine/translator/func2/layout/mod.rs	0.00%	37 Missing ⚠️
...wasmi/src/engine/translator/func2/layout/consts.rs	0.00%	32 Missing ⚠️
crates/wasmi/src/engine/translator/func2/instrs.rs	0.00%	17 Missing ⚠️
... and 3 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1512      +/-   ##
==========================================
- Coverage   71.75%   67.72%   -4.03%     
==========================================
  Files         179      191      +12     
  Lines       16524    17563    +1039     
==========================================
+ Hits        11856    11895      +39     
- Misses       4668     5668    +1000     

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