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wasm: fix functions exported through //export #3845

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Jul 28, 2023
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wasm: fix functions exported through //export #3845

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45 changes: 13 additions & 32 deletions compiler/symbol.go
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Original file line number Diff line number Diff line change
Expand Up @@ -23,9 +23,9 @@ import (
// The linkName value contains a valid link name, even if //go:linkname is not
// present.
type functionInfo struct {
module string // go:wasm-module
importName string // go:linkname, go:export - The name the developer assigns
linkName string // go:linkname, go:export - The name that we map for the particular module -> importName
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
Expand Down Expand Up @@ -194,20 +194,14 @@ func (c *compilerContext) getFunction(fn *ssa.Function) (llvm.Type, llvm.Value)
// External/exported functions may not retain pointer values.
// https://golang.org/cmd/cgo/#hdr-Passing_pointers
if info.exported {
if c.archFamily() == "wasm32" {
if c.archFamily() == "wasm32" && len(fn.Blocks) == 0 {
// We need to add the wasm-import-module and the wasm-import-name
// attributes.
module := info.module
if module == "" {
module = "env"
if info.wasmModule != "" {
llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("wasm-import-module", info.wasmModule))
}
llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("wasm-import-module", module))

name := info.importName
if name == "" {
name = info.linkName
}
llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("wasm-import-name", name))
llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("wasm-import-name", info.wasmName))
}
nocaptureKind := llvm.AttributeKindID("nocapture")
nocapture := c.ctx.CreateEnumAttribute(nocaptureKind, 0)
Expand Down Expand Up @@ -260,10 +254,6 @@ func (c *compilerContext) parsePragmas(info *functionInfo, f *ssa.Function) {
return
}
if decl, ok := f.Syntax().(*ast.FuncDecl); ok && decl.Doc != nil {

// Our importName for a wasm module (if we are compiling to wasm), or llvm link name
var importName string

for _, comment := range decl.Doc.List {
text := comment.Text
if strings.HasPrefix(text, "//export ") {
Expand All @@ -281,18 +271,20 @@ func (c *compilerContext) parsePragmas(info *functionInfo, f *ssa.Function) {
continue
}

importName = parts[1]
info.linkName = parts[1]
info.wasmName = info.linkName
info.exported = true
case "//go:interrupt":
if hasUnsafeImport(f.Pkg.Pkg) {
info.interrupt = true
}
case "//go:wasm-module":
// Alternative comment for setting the import module.
// This is deprecated, use //go:wasmimport instead.
if len(parts) != 2 {
continue
}
info.module = parts[1]
info.wasmModule = parts[1]
case "//go:wasmimport":
// Import a WebAssembly function, for example a WASI function.
// Original proposal: https://github.com/golang/go/issues/38248
Expand All @@ -302,8 +294,8 @@ func (c *compilerContext) parsePragmas(info *functionInfo, f *ssa.Function) {
}
c.checkWasmImport(f, comment.Text)
info.exported = true
info.module = parts[1]
info.importName = parts[2]
info.wasmModule = parts[1]
info.wasmName = parts[2]
case "//go:inline":
info.inline = inlineHint
case "//go:noinline":
Expand Down Expand Up @@ -347,17 +339,6 @@ func (c *compilerContext) parsePragmas(info *functionInfo, f *ssa.Function) {
}
}
}

// Set the importName for our exported function if we have one
if importName != "" {
if info.module == "" {
info.linkName = importName
} else {
// WebAssembly import
info.importName = importName
}
}

}
}

Expand Down
13 changes: 13 additions & 0 deletions compiler/testdata/pragma.go
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,19 @@ func exportedFunctionInSection() {
//go:wasmimport modulename import1
func declaredImport()

// Legacy way of importing a function.
//
//go:wasm-module foobar
//export imported
func foobarImport()

// The wasm-module pragma is not functional here, but it should be safe.
//
//go:wasm-module foobar
//export exported
func foobarExportModule() {
}

// This function should not: it's only a declaration and not a definition.
//
//go:section .special_function_section
Expand Down
16 changes: 13 additions & 3 deletions compiler/testdata/pragma.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ target triple = "wasm32-unknown-wasi"
@extern_global = external global [0 x i8], align 1
@main.alignedGlobal = hidden global [4 x i32] zeroinitializer, align 32
@main.alignedGlobal16 = hidden global [4 x i32] zeroinitializer, align 16
@llvm.used = appending global [2 x ptr] [ptr @extern_func, ptr @exportedFunctionInSection]
@llvm.used = appending global [3 x ptr] [ptr @extern_func, ptr @exportedFunctionInSection, ptr @exported]
@main.globalInSection = hidden global i32 0, section ".special_global_section", align 4
@undefinedGlobalNotInSection = external global i32, align 4
@main.multipleGlobalPragmas = hidden global i32 0, section ".global_section", align 1024
Expand Down Expand Up @@ -62,13 +62,23 @@ entry:

declare void @main.declaredImport() #7

declare void @imported() #8

; Function Attrs: nounwind
define void @exported() #9 {
entry:
ret void
}

declare void @main.undefinedFunctionNotInSection(ptr) #1

attributes #0 = { allockind("alloc,zeroed") allocsize(0) "alloc-family"="runtime.alloc" "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" }
attributes #1 = { "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" }
attributes #2 = { nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" }
attributes #3 = { nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" "wasm-export-name"="extern_func" "wasm-import-module"="env" "wasm-import-name"="extern_func" }
attributes #3 = { nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" "wasm-export-name"="extern_func" }
attributes #4 = { inlinehint nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" }
attributes #5 = { noinline nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" }
attributes #6 = { noinline nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" "wasm-export-name"="exportedFunctionInSection" "wasm-import-module"="env" "wasm-import-name"="exportedFunctionInSection" }
attributes #6 = { noinline nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" "wasm-export-name"="exportedFunctionInSection" }
attributes #7 = { "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" "wasm-import-module"="modulename" "wasm-import-name"="import1" }
attributes #8 = { "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" "wasm-import-module"="foobar" "wasm-import-name"="imported" }
attributes #9 = { nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" "wasm-export-name"="exported" }
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