wasm: remove i64 workaround, use BigInt instead

Browsers previously didn't support the WebAssembly i64 type, so we had
to work around that limitation by converting the LLVM i64 type to
something else. Some people used a pair of i32 values, but we used a
pointer to a stack allocated i64.

Now however, all major browsers and Node.js do support WebAssembly
BigInt integration so that i64 values can be passed back and forth
between WebAssembly and JavaScript easily. Therefore, I think the time
has come to drop support for this workaround.

For more information: https://v8.dev/features/wasm-bigint (note that
TinyGo has used a slightly different way of passing i64 values between
JS and Wasm).

For information on browser support: https://webassembly.org/roadmap/

compileopts/config.go

@@ -492,11 +492,6 @@ func (c *Config) RelocationModel() string {
 	return "static"
 }
 
-// WasmAbi returns the WASM ABI which is specified in the target JSON file.
-func (c *Config) WasmAbi() string {
-	return c.Target.WasmAbi
-}
-
 // EmulatorName is a shorthand to get the command for this emulator, something
 // like qemu-system-arm or simavr.
 func (c *Config) EmulatorName() string {

compileopts/target.go

@@ -62,7 +62,6 @@ type TargetSpec struct {
 	JLinkDevice      string   `json:"jlink-device"`
 	CodeModel        string   `json:"code-model"`
 	RelocationModel  string   `json:"relocation-model"`
-	WasmAbi          string   `json:"wasm-abi"`
 }
 
 // overrideProperties overrides all properties that are set in child into itself using reflection.