all: implement wasmimport directive

Go programs can now use the //go:wasmimport module_name function_name
directive to import functions from the WebAssembly runtime.

For now, the directive is restricted to the runtime and syscall/js
packages.

* Derived from CL 350737
* Original work modified to work with changes to the IR conversion code.
* Modification of CL 350737 changes to fully exist in Unified IR path (emp)
* Original work modified to work with changes to the ABI configuration code.
* Fixes #38248

Co-authored-by: Vedant Roy <vroy101@gmail.com>
Co-authored-by: Richard Musiol <mail@richard-musiol.de>
Co-authored-by: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
Change-Id: I740719735d91c306ac718a435a78e1ee9686bc16
Reviewed-on: https://go-review.googlesource.com/c/go/+/463018
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
Reviewed-by: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>

1 files changed, 14 insertions, 3 deletions

diff --git a/src/cmd/internal/obj/objfile.go b/src/cmd/internal/obj/objfile.go
index 73c29d9686..78fa4c1076 100644
--- a/src/cmd/internal/obj/objfile.go
+++ b/src/cmd/internal/obj/objfile.go
@@ -605,7 +605,12 @@ func (w *writer) Aux(s *LSym) {
 		for _, pcSym := range fn.Pcln.Pcdata {
 			w.aux1(goobj.AuxPcdata, pcSym)
 		}
-
+		if fn.WasmImportSym != nil {
+			if fn.WasmImportSym.Size == 0 {
+				panic("wasmimport aux sym must have non-zero size")
+			}
+			w.aux1(goobj.AuxWasmImport, fn.WasmImportSym)
+		}
 	}
 }
 
@@ -703,6 +708,12 @@ func nAuxSym(s *LSym) int {
 			n++
 		}
 		n += len(fn.Pcln.Pcdata)
+		if fn.WasmImport != nil {
+			if fn.WasmImportSym == nil || fn.WasmImportSym.Size == 0 {
+				panic("wasmimport aux sym must exist and have non-zero size")
+			}
+			n++
+		}
 	}
 	return n
 }
@@ -759,8 +770,8 @@ func genFuncInfoSyms(ctxt *Link) {
 		fn.FuncInfoSym = isym
 		b.Reset()
 
-		dwsyms := []*LSym{fn.dwarfRangesSym, fn.dwarfLocSym, fn.dwarfDebugLinesSym, fn.dwarfInfoSym}
-		for _, s := range dwsyms {
+		auxsyms := []*LSym{fn.dwarfRangesSym, fn.dwarfLocSym, fn.dwarfDebugLinesSym, fn.dwarfInfoSym, fn.WasmImportSym}
+		for _, s := range auxsyms {
 			if s == nil || s.Size == 0 {
 				continue
 			}