refactor(verify): extract the shared goobj link-parity harness

Assisted-by: GLM 5.3 Flash

verify/goobj_link_test.go

@@ -34,6 +34,20 @@ import (
 // repack, so a build-layout change that silently skipped the substitution
 // fails the test instead of passing it vacuously.
 
+// buildLinkParityGasm builds the gasm binary from the tree under test, one
+// level above this package, so every link-parity test exercises the shipped
+// CLI path rather than the library.
+func buildLinkParityGasm(t *testing.T, goBin string) string {
+	t.Helper()
+	gasmBin := filepath.Join(t.TempDir(), "gasm")
+	build := exec.Command(goBin, "build", "-o", gasmBin, "./cmd/gasm")
+	build.Dir = ".."
+	if out, err := build.CombinedOutput(); err != nil {
+		t.Fatalf("build gasm: %v\n%s", err, out)
+	}
+	return gasmBin
+}
+
 // goobjLinkModule is the Go side of the regression module.  The assembly
 // declares the five functions; main verifies their semantics and prints a
 // deterministic line the linked binaries must agree on.
@@ -130,28 +144,29 @@ func TestGOOBJLinkRegression(t *testing.T) {
 
 	// One gasm binary for every architecture, built from the tree under
 	// test: the regression exercises the shipped CLI path, not the library.
-	// The build runs from the module root, one level above this package.
+	gasmBin := buildLinkParityGasm(t, goBin)
-	gasmBin := filepath.Join(t.TempDir(), "gasm")
-	gasmBuild := exec.Command(goBin, "build", "-o", gasmBin, "./cmd/gasm")
-	gasmBuild.Dir = ".."
-	if out, err := gasmBuild.CombinedOutput(); err != nil {
-		t.Fatalf("build gasm: %v\n%s", err, out)
-	}
 
 	for _, goarch := range []string{"amd64", "arm64", "riscv64", "loong64"} {
 		t.Run(goarch, func(t *testing.T) {
-			testGOOBJLinkArch(t, goBin, gasmBin, goarch)
+			goobjLinkKernel(t, goBin, gasmBin, goarch, "linkreg_"+goarch+".s", goobjLinkMainSrc)
 		})
 	}
 }
 
-func testGOOBJLinkArch(t *testing.T, goBin, gasmBin, goarch string) {
+// goobjLinkKernel runs the whole regression for one architecture against
+// one kernel: the kernel is assembled by the toolchain for the baseline,
+// re-assembled by the gasm CLI, substituted into the real build's package
+// archive and the program relinked.  The Go side (mainSrc) carries the
+// semantics and prints the deterministic line the two binaries must share.
+// The standing linkreg kernels and the newer family kernels all go through
+// this one path, so a change here moves every link-parity claim at once.
+func goobjLinkKernel(t *testing.T, goBin, gasmBin, goarch, kernelFile, mainSrc string) {
 	t.Helper()
 	dir := t.TempDir()
 
 	// The module: main.go, go.mod and the kernel as main_<goarch>.s, the
 	// name the build system selects the assembly by.
-	kernel, err := os.ReadFile(filepath.Join("testdata", "linkreg_"+goarch+".s"))
+	kernel, err := os.ReadFile(filepath.Join("testdata", kernelFile))
 	if err != nil {
 		t.Fatalf("read kernel: %v", err)
 	}
@@ -159,7 +174,7 @@ func testGOOBJLinkArch(t *testing.T, goBin, gasmBin, goarch string) {
 	if err := os.WriteFile(asmPath, kernel, 0o644); err != nil {
 		t.Fatal(err)
 	}
-	if err := os.WriteFile(filepath.Join(dir, "main.go"), []byte(goobjLinkMainSrc), 0o644); err != nil {
+	if err := os.WriteFile(filepath.Join(dir, "main.go"), []byte(mainSrc), 0o644); err != nil {
 		t.Fatal(err)
 	}
 	if err := os.WriteFile(filepath.Join(dir, "go.mod"), []byte("module linkreg\n\ngo 1.27\n"), 0o644); err != nil {