cmd/link/internal/ld: move more of mustLinkExternal into internal/platform

internal/platform.MustLinkExternal is used in various places to
determine whether external linking is required. It should always
match what the linker actually requires, but today does not match
because the linker imposes additional constraints.

Updates #31544.

Change-Id: I0cc6ad587e95c607329dea5d60d29a5fb2a9e722
Reviewed-on: https://go-review.googlesource.com/c/go/+/472515
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>

4 files changed, 10 insertions, 44 deletions

diff --git a/src/cmd/link/internal/ld/config.go b/src/cmd/link/internal/ld/config.go
index f2dfa1c1cd..7cce28dac5 100644
--- a/src/cmd/link/internal/ld/config.go
+++ b/src/cmd/link/internal/ld/config.go
@@ -5,7 +5,6 @@
 package ld
 
 import (
-	"cmd/internal/sys"
 	"fmt"
 	"internal/buildcfg"
 	"internal/platform"
@@ -125,7 +124,7 @@ func mustLinkExternal(ctxt *Link) (res bool, reason string) {
 		}()
 	}
 
-	if platform.MustLinkExternal(buildcfg.GOOS, buildcfg.GOARCH) {
+	if platform.MustLinkExternal(buildcfg.GOOS, buildcfg.GOARCH, false) {
 		return true, fmt.Sprintf("%s/%s requires external linking", buildcfg.GOOS, buildcfg.GOARCH)
 	}
 
@@ -137,25 +136,9 @@ func mustLinkExternal(ctxt *Link) (res bool, reason string) {
 		return true, "asan"
 	}
 
-	// Internally linking cgo is incomplete on some architectures.
-	// https://golang.org/issue/14449
-	if iscgo && ctxt.Arch.InFamily(sys.Loong64, sys.MIPS64, sys.MIPS, sys.RISCV64) {
+	if iscgo && platform.MustLinkExternal(buildcfg.GOOS, buildcfg.GOARCH, true) {
 		return true, buildcfg.GOARCH + " does not support internal cgo"
 	}
-	if iscgo && (buildcfg.GOOS == "android" || buildcfg.GOOS == "dragonfly") {
-		// It seems that on Dragonfly thread local storage is
-		// set up by the dynamic linker, so internal cgo linking
-		// doesn't work. Test case is "go test runtime/cgo".
-		return true, buildcfg.GOOS + " does not support internal cgo"
-	}
-	if iscgo && buildcfg.GOOS == "windows" && buildcfg.GOARCH == "arm64" {
-		// windows/arm64 internal linking is not implemented.
-		return true, buildcfg.GOOS + "/" + buildcfg.GOARCH + " does not support internal cgo"
-	}
-	if iscgo && ctxt.Arch == sys.ArchPPC64 {
-		// Big Endian PPC64 cgo internal linking is not implemented for aix or linux.
-		return true, buildcfg.GOOS + " does not support internal cgo"
-	}
 
 	// Some build modes require work the internal linker cannot do (yet).
 	switch ctxt.BuildMode {
@@ -164,12 +147,7 @@ func mustLinkExternal(ctxt *Link) (res bool, reason string) {
 	case BuildModeCShared:
 		return true, "buildmode=c-shared"
 	case BuildModePIE:
-		switch buildcfg.GOOS + "/" + buildcfg.GOARCH {
-		case "android/arm64":
-		case "linux/amd64", "linux/arm64", "linux/ppc64le":
-		case "windows/386", "windows/amd64", "windows/arm", "windows/arm64":
-		case "darwin/amd64", "darwin/arm64":
-		default:
+		if !platform.InternalLinkPIESupported(buildcfg.GOOS, buildcfg.GOARCH) {
 			// Internal linking does not support TLS_IE.
 			return true, "buildmode=pie"
 		}
diff --git a/src/cmd/link/internal/ld/dwarf_test.go b/src/cmd/link/internal/ld/dwarf_test.go
index 6fac85a01d..ee3ea9d175 100644
--- a/src/cmd/link/internal/ld/dwarf_test.go
+++ b/src/cmd/link/internal/ld/dwarf_test.go
@@ -274,7 +274,7 @@ func TestSizes(t *testing.T) {
 	}
 
 	// External linking may bring in C symbols with unknown size. Skip.
-	testenv.MustInternalLink(t)
+	testenv.MustInternalLink(t, false)
 
 	t.Parallel()
 
@@ -882,7 +882,7 @@ func TestAbstractOriginSanityIssue26237(t *testing.T) {
 
 func TestRuntimeTypeAttrInternal(t *testing.T) {
 	testenv.MustHaveGoBuild(t)
-	testenv.MustInternalLink(t)
+	testenv.MustInternalLink(t, false)
 
 	if runtime.GOOS == "plan9" {
 		t.Skip("skipping on plan9; no DWARF symbol table in executables")
@@ -1165,7 +1165,7 @@ func main() {
 	// TODO: maybe there is some way to tell the external linker not to put
 	// those symbols in the executable's symbol table? Prefix the symbol name
 	// with "." or "L" to pretend it is a label?
-	if !testenv.CanInternalLink() {
+	if !testenv.CanInternalLink(false) {
 		return
 	}
 
diff --git a/src/cmd/link/internal/ld/ld_test.go b/src/cmd/link/internal/ld/ld_test.go
index 314dab7d7d..22bc11eff3 100644
--- a/src/cmd/link/internal/ld/ld_test.go
+++ b/src/cmd/link/internal/ld/ld_test.go
@@ -21,7 +21,7 @@ func TestUndefinedRelocErrors(t *testing.T) {
 
 	// When external linking, symbols may be defined externally, so we allow
 	// undefined symbols and let external linker resolve. Skip the test.
-	testenv.MustInternalLink(t)
+	testenv.MustInternalLink(t, false)
 
 	t.Parallel()
 
diff --git a/src/cmd/link/link_test.go b/src/cmd/link/link_test.go
index b4ef9ada17..121ef95853 100644
--- a/src/cmd/link/link_test.go
+++ b/src/cmd/link/link_test.go
@@ -176,19 +176,7 @@ main.x: relocation target main.zero not defined
 func TestIssue33979(t *testing.T) {
 	testenv.MustHaveGoBuild(t)
 	testenv.MustHaveCGO(t)
-	testenv.MustInternalLink(t)
-
-	// Skip test on platforms that do not support cgo internal linking.
-	switch runtime.GOARCH {
-	case "loong64":
-		t.Skipf("Skipping on %s/%s", runtime.GOOS, runtime.GOARCH)
-	case "mips", "mipsle", "mips64", "mips64le":
-		t.Skipf("Skipping on %s/%s", runtime.GOOS, runtime.GOARCH)
-	}
-	if runtime.GOOS == "aix" ||
-		runtime.GOOS == "windows" && runtime.GOARCH == "arm64" {
-		t.Skipf("Skipping on %s/%s", runtime.GOOS, runtime.GOARCH)
-	}
+	testenv.MustInternalLink(t, true)
 
 	t.Parallel()
 
@@ -751,8 +739,8 @@ func TestTrampolineCgo(t *testing.T) {
 
 		// Test internal linking mode.
 
-		if runtime.GOARCH == "ppc64" || (runtime.GOARCH == "arm64" && runtime.GOOS == "windows") || !testenv.CanInternalLink() {
-			return // internal linking cgo is not supported
+		if !testenv.CanInternalLink(true) {
+			continue
 		}
 		cmd = testenv.Command(t, testenv.GoToolPath(t), "build", "-buildmode="+mode, "-ldflags=-debugtramp=2 -linkmode=internal", "-o", exe, src)
 		out, err = cmd.CombinedOutput()