winch(x64): Call indirect (#7100)

* winch(x64): Call indirect

This change adds support for the `call_indirect` instruction to Winch.

Libcalls are a pre-requisite for supporting `call_indirect` in order to
lazily initialy funcrefs. This change adds support for libcalls to
Winch by introducing a `BuiltinFunctions` struct similar to Cranelift's
`BuiltinFunctionSignatures` struct.

In general, libcalls are handled like any other function call, with the
only difference that given that not all the information to fulfill the
function call might be known up-front, control is given to the caller
for finalizing the call.

The introduction of function references also involves dealing with
pointer-sized loads and stores, so this change also adds the required
functionality to `FuncEnv` and `MacroAssembler` to be pointer aware,
making it straight forward to derive an `OperandSize` or `WasmType` from
the target's pointer size.

Finally, given the complexity of the call_indirect instrunction, this
change bundles an improvement to the register allocator, allowing it to
track the allocatable vs non-allocatable registers, this is done to
avoid any mistakes when allocating/de-allocating registers that are not
alloctable.

--
prtest:full

* Address review comments

* Fix typos
* Better documentation for `new_unchecked`
* Introduce `max` for `BitSet`
* Make allocatable property `u64`

* winch(calls): Overhaul `FnCall`

This commit simplifies `FnCall`'s interface making its usage more
uniform throughout the compiler. In summary, this change:

* Avoids side effects in the `FnCall::new` constructor, and also makes
  it the only constructor.
* Exposes `FnCall::save_live_registers` and
  `FnCall::calculate_call_stack_space` to calculate the stack space
  consumed by the call and so that the caller can decide which one to
  use at callsites depending on their use-case.

* tests: Fix regset tests

build.rs

@@ -205,11 +205,17 @@ fn ignore(testsuite: &str, testname: &str, strategy: &str) -> bool {
     // We ignore tests that assert for traps on windows, given
     // that Winch doesn't encode unwind information for Windows, yet.
     if strategy == "Winch" {
+        if testsuite == "misc_testsuite" {
+            // The misc/call_indirect is fully supported by Winch.
+            if testname == "call_indirect" {
+                return false;
+            }
+        }
         if testsuite != "winch" {
             return true;
         }
 
-        let assert_trap = ["i32", "i64"].contains(&testname);
+        let assert_trap = ["i32", "i64", "call_indirect"].contains(&testname);
 
         if assert_trap && env::var("CARGO_CFG_TARGET_OS").unwrap().as_str() == "windows" {
             return true;

crates/winch/src/compiler.rs

@@ -68,7 +68,7 @@ impl wasmtime_environ::Compiler for Compiler {
         let mut validator = validator.into_validator(self.take_allocations());
         let buffer = self
             .isa
-            .compile_function(ty, &body, &translation, &mut validator)
+            .compile_function(ty, types, &body, &translation, &mut validator)
             .map_err(|e| CompileError::Codegen(format!("{e:?}")));
         self.save_allocations(validator.into_allocations());
         let buffer = buffer?;

fuzz/fuzz_targets/differential.rs

@@ -374,7 +374,8 @@ fn winch_supports_module(module: &[u8]) -> bool {
                         | F32Abs { .. }
                         | F64Abs { .. }
                         | F32Neg { .. }
-                        | F64Neg { .. } => {}
+                        | F64Neg { .. }
+                        | CallIndirect { .. } => {}
                         _ => {
                             supported = false;
                             break 'main;