cmd/go: pass in overlaid paths for .s files

This change adds support for adding overlays on assembly files.

For #39958

Change-Id: I1a328656199cc836f48e16de1ffd944fdd07fb39
Reviewed-on: https://go-review.googlesource.com/c/go/+/266417
Trust: Michael Matloob <matloob@golang.org>
Run-TryBot: Michael Matloob <matloob@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>

src/cmd/go/internal/work/gc.go

@@ -370,9 +370,10 @@ func (gcToolchain) asm(b *Builder, a *Action, sfiles []string) ([]string, error)
 
 	var ofiles []string
 	for _, sfile := range sfiles {
+		overlayPath, _ := fsys.OverlayPath(mkAbs(p.Dir, sfile))
 		ofile := a.Objdir + sfile[:len(sfile)-len(".s")] + ".o"
 		ofiles = append(ofiles, ofile)
-		args1 := append(args, "-o", ofile, mkAbs(p.Dir, sfile))
+		args1 := append(args, "-o", ofile, overlayPath)
 		if err := b.run(a, p.Dir, p.ImportPath, nil, args1...); err != nil {
 			return nil, err
 		}
@@ -388,7 +389,8 @@ func (gcToolchain) symabis(b *Builder, a *Action, sfiles []string) (string, erro
 			if p.ImportPath == "runtime/cgo" && strings.HasPrefix(sfile, "gcc_") {
 				continue
 			}
-			args = append(args, mkAbs(p.Dir, sfile))
+			op, _ := fsys.OverlayPath(mkAbs(p.Dir, sfile))
+			args = append(args, op)
 		}
 
 		// Supply an empty go_asm.h as if the compiler had been run.

src/cmd/go/internal/work/gccgo.go

@@ -199,7 +199,7 @@ func (tools gccgoToolchain) asm(b *Builder, a *Action, sfiles []string) ([]strin
 		base := filepath.Base(sfile)
 		ofile := a.Objdir + base[:len(base)-len(".s")] + ".o"
 		ofiles = append(ofiles, ofile)
-		sfile = mkAbs(p.Dir, sfile)
+		sfile, _ = fsys.OverlayPath(mkAbs(p.Dir, sfile))
 		defs := []string{"-D", "GOOS_" + cfg.Goos, "-D", "GOARCH_" + cfg.Goarch}
 		if pkgpath := tools.gccgoCleanPkgpath(b, p); pkgpath != "" {
 			defs = append(defs, `-D`, `GOPKGPATH=`+pkgpath)

src/cmd/go/testdata/script/build_overlay.txt

@@ -43,6 +43,10 @@ go build -overlay overlay.json -o main_cgo_angle$GOEXE ./cgo_hello_angle
 exec ./main_cgo_angle$GOEXE
 stdout '^hello cgo\r?\n'
 
+go build -overlay overlay.json -o main_call_asm$GOEXE ./call_asm
+exec ./main_call_asm$GOEXE
+! stdout .
+
 go list -compiled -overlay overlay.json -f '{{range .CompiledGoFiles}}{{. | printf "%s\n"}}{{end}}' ./cgo_hello_replace
 cp stdout compiled_cgo_sources.txt
 go run ../print_line_comments.go compiled_cgo_sources.txt
@@ -79,6 +83,10 @@ go build -compiler=gccgo  -overlay overlay.json -o main_cgo_angle_gccgo$GOEXE ./
 exec ./main_cgo_angle_gccgo$GOEXE
 stdout '^hello cgo\r?\n'
 
+go build -compiler=gccgo -overlay overlay.json -o main_call_asm_gccgo$GOEXE ./call_asm
+exec ./main_call_asm_gccgo$GOEXE
+! stdout .
+
 -- m/go.mod --
 // TODO(matloob): how do overlays work with go.mod (especially if mod=readonly)
 module m
@@ -105,6 +113,7 @@ the actual code is in the overlay
 		"dir2/i.go": "overlay/dir2_i.go",
 		"printpath/main.go": "overlay/printpath.go",
 		"printpath/other.go": "overlay2/printpath2.go",
+		"call_asm/asm.s": "overlay/asm_file.s",
 		"cgo_hello_replace/cgo_header.h": "overlay/cgo_head.h",
 		"cgo_hello_replace/hello.c": "overlay/hello.c",
 		"cgo_hello_quote/cgo_hello.go": "overlay/cgo_hello_quote.go",
@@ -139,6 +148,14 @@ import "m/dir2"
 func main() {
 	dir2.PrintMessage()
 }
+-- m/call_asm/main.go --
+package main
+
+func foo() // There will be a "missing function body" error if the assembly file isn't found.
+
+func main() {
+	foo()
+}
 -- m/overlay/dir_g.go --
 package dir