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wasm: add //go:wasmexport support (#4451)

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This adds support for the `//go:wasmexport` pragma as proposed here:
https://github.com/golang/go/issues/65199

It is currently implemented only for wasip1 and wasm-unknown, but it is
certainly possible to extend it to other targets like GOOS=js and
wasip2.
This commit is contained in:
Ayke
2024-10-05 00:33:47 +02:00
committed by GitHub
parent 407889864f
commit 9da8b5c786
22 changed files with 765 additions and 67 deletions
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compiler/symbol.go
+58 -18
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@@ -23,15 +23,17 @@ import (
// The linkName value contains a valid link name, even if //go:linkname is not
// present.
type functionInfo struct {
wasmModule string // go:wasm-module
wasmName string // wasm-export-name or wasm-import-name in the IR
linkName string // go:linkname, go:export - the IR function name
section string // go:section - object file section name
exported bool // go:export, CGo
interrupt bool // go:interrupt
nobounds bool // go:nobounds
variadic bool // go:variadic (CGo only)
inline inlineType // go:inline
wasmModule string // go:wasm-module
wasmName string // wasm-export-name or wasm-import-name in the IR
wasmExport string // go:wasmexport is defined (export is unset, this adds an exported wrapper)
wasmExportPos token.Pos // position of //go:wasmexport comment
linkName string // go:linkname, go:export - the IR function name
section string // go:section - object file section name
exported bool // go:export, CGo
interrupt bool // go:interrupt
nobounds bool // go:nobounds
variadic bool // go:variadic (CGo only)
inline inlineType // go:inline
}
type inlineType int
@@ -241,8 +243,22 @@ func (c *compilerContext) getFunctionInfo(f *ssa.Function) functionInfo {
// Pick the default linkName.
linkName: f.RelString(nil),
}
// Check for a few runtime functions that are treated specially.
if info.linkName == "runtime.wasmEntryReactor" && c.BuildMode == "c-shared" {
info.linkName = "_initialize"
info.wasmName = "_initialize"
info.exported = true
}
if info.linkName == "runtime.wasmEntryCommand" && c.BuildMode == "default" {
info.linkName = "_start"
info.wasmName = "_start"
info.exported = true
}
// Check for //go: pragmas, which may change the link name (among others).
c.parsePragmas(&info, f)
c.functionInfos[f] = info
return info
}
@@ -296,10 +312,39 @@ func (c *compilerContext) parsePragmas(info *functionInfo, f *ssa.Function) {
if len(parts) != 3 {
continue
}
c.checkWasmImport(f, comment.Text)
if f.Blocks != nil {
// Defined functions cannot be exported.
c.addError(f.Pos(), "can only use //go:wasmimport on declarations")
continue
}
c.checkWasmImportExport(f, comment.Text)
info.exported = true
info.wasmModule = parts[1]
info.wasmName = parts[2]
case "//go:wasmexport":
if f.Blocks == nil {
c.addError(f.Pos(), "can only use //go:wasmexport on definitions")
continue
}
if len(parts) != 2 {
c.addError(f.Pos(), fmt.Sprintf("expected one parameter to //go:wasmimport, not %d", len(parts)-1))
continue
}
name := parts[1]
if name == "_start" || name == "_initialize" {
c.addError(f.Pos(), fmt.Sprintf("//go:wasmexport does not allow %#v", name))
continue
}
if c.BuildMode != "c-shared" && f.RelString(nil) == "main.main" {
c.addError(f.Pos(), fmt.Sprintf("//go:wasmexport does not allow main.main to be exported with -buildmode=%s", c.BuildMode))
continue
}
if c.archFamily() != "wasm32" {
c.addError(f.Pos(), "//go:wasmexport is only supported on wasm")
}
c.checkWasmImportExport(f, comment.Text)
info.wasmExport = name
info.wasmExportPos = comment.Slash
case "//go:inline":
info.inline = inlineHint
case "//go:noinline":
@@ -346,22 +391,17 @@ func (c *compilerContext) parsePragmas(info *functionInfo, f *ssa.Function) {
}
}
// Check whether this function cannot be used in //go:wasmimport. It will add an
// error if this is the case.
// Check whether this function can be used in //go:wasmimport or
// //go:wasmexport. It will add an error if this is not the case.
//
// The list of allowed types is based on this proposal:
// https://github.com/golang/go/issues/59149
func (c *compilerContext) checkWasmImport(f *ssa.Function, pragma string) {
func (c *compilerContext) checkWasmImportExport(f *ssa.Function, pragma string) {
if c.pkg.Path() == "runtime" || c.pkg.Path() == "syscall/js" || c.pkg.Path() == "syscall" {
// The runtime is a special case. Allow all kinds of parameters
// (importantly, including pointers).
return
}
if f.Blocks != nil {
// Defined functions cannot be exported.
c.addError(f.Pos(), "can only use //go:wasmimport on declarations")
return
}
if f.Signature.Results().Len() > 1 {
c.addError(f.Signature.Results().At(1).Pos(), fmt.Sprintf("%s: too many return values", pragma))
} else if f.Signature.Results().Len() == 1 {