wasm: remove -wasm-abi= flag

This flag controls whether to convert external i64 parameters for use in
a browser-like environment.

This flag was needed in the past because back then we only supported
wasm on browsers but no WASI. Now, I can't think of a reason why anybody
would want to change the default. For `-target=wasm` (used for
browser-like environments), the wasm_exec.js file expects this
i64-via-stack ABI. For WASI, there is no limitation on i64 values and
`-wasm-abi=generic` is the default.

builder/build.go

@@ -1077,7 +1077,6 @@ func optimizeProgram(mod llvm.Module, config *compileopts.Config) error {
 	// cannot be represented exactly in JavaScript (JS only has doubles). To
 	// keep functions interoperable, pass int64 types as pointers to
 	// stack-allocated values.
-	// Use -wasm-abi=generic to disable this behaviour.
 	if config.WasmAbi() == "js" {
 		err := transform.ExternalInt64AsPtr(mod, config)
 		if err != nil {

compileopts/config.go

@@ -511,12 +511,8 @@ func (c *Config) RelocationModel() string {
 	return "static"
 }
 
-// WasmAbi returns the WASM ABI which is specified in the target JSON file, and
-// the value is overridden by `-wasm-abi` flag if it is provided
+// WasmAbi returns the WASM ABI which is specified in the target JSON file.
 func (c *Config) WasmAbi() string {
-	if c.Options.WasmAbi != "" {
-		return c.Options.WasmAbi
-	}
 	return c.Target.WasmAbi
 }
 

compileopts/options.go

@@ -42,7 +42,6 @@ type Options struct {
 	PrintAllocs     *regexp.Regexp // regexp string
 	PrintStacks     bool
 	Tags            []string
-	WasmAbi         string
 	GlobalValues    map[string]map[string]string // map[pkgpath]map[varname]value
 	TestConfig      TestConfig
 	Programmer      string

main.go

@@ -1392,7 +1392,6 @@ func main() {
 	port := flag.String("port", "", "flash port (can specify multiple candidates separated by commas)")
 	programmer := flag.String("programmer", "", "which hardware programmer to use")
 	ldflags := flag.String("ldflags", "", "Go link tool compatible ldflags")
-	wasmAbi := flag.String("wasm-abi", "", "WebAssembly ABI conventions: js (no i64 params) or generic")
 	llvmFeatures := flag.String("llvm-features", "", "comma separated LLVM features to enable")
 	cpuprofile := flag.String("cpuprofile", "", "cpuprofile output")
 	monitor := flag.Bool("monitor", false, "enable serial monitor")
@@ -1481,7 +1480,6 @@ func main() {
 		PrintAllocs:     printAllocs,
 		Tags:            []string(tags),
 		GlobalValues:    globalVarValues,
-		WasmAbi:         *wasmAbi,
 		Programmer:      *programmer,
 		OpenOCDCommands: ocdCommands,
 		LLVMFeatures:    *llvmFeatures,

transform/wasm-abi.go

@@ -14,8 +14,7 @@ import (
 // resolved, this pass may be avoided. For more details:
 // https://github.com/WebAssembly/design/issues/1172
 //
-// This pass can be enabled/disabled with the -wasm-abi flag, and is enabled by
-// default as of december 2019.
+// This pass is enabled via the wasm-abi JSON target key.
 func ExternalInt64AsPtr(mod llvm.Module, config *compileopts.Config) error {
 	ctx := mod.Context()
 	builder := ctx.NewBuilder()
@@ -145,7 +144,7 @@ func ExternalInt64AsPtr(mod llvm.Module, config *compileopts.Config) error {
 			builder.SetInsertPointAtEnd(entryBlock)
 			var callParams []llvm.Value
 			if fnType.ReturnType() == int64Type {
-				return errors.New("not yet implemented: exported function returns i64 with -wasm-abi=js; " +
+				return errors.New("not yet implemented: exported function returns i64 with the JS wasm-abi; " +
 					"see https://tinygo.org/compiler-internals/calling-convention/")
 			}
 			for i, origParam := range fn.Params() {