libgo: support x32 as GOARCH=amd64p32 GOOS=linux

This is enough to let libgo build when configured using
    --with-multilib-list=m64,m32,mx32.  I don't have an x32-enabled kernel
    so I haven't tested whether it executes correctly.
    
    For https://gcc.gnu.org/PR87470
    
    Reviewed-on: https://go-review.googlesource.com/138817

From-SVN: r264772

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-013a9e68c9a31f888733d46182d19f9e5d956f27
+2f56d51c6b3104242613c74b02fa6c63a2fe16c5
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/configure

@@ -13685,7 +13685,19 @@ _ACEOF
 if ac_fn_c_try_compile "$LINENO"; then :
   GOARCH=386
 else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#ifdef __ILP32__
+#error x32
+#endif
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
   GOARCH=amd64
+else
+  GOARCH=amd64p32
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 fi
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
     ;;

libgo/configure.ac

@@ -252,8 +252,13 @@ changequote([,])dnl
 #ifdef __x86_64__
 #error 64-bit
 #endif],
-[GOARCH=386],
-[GOARCH=amd64])
+	[GOARCH=386],
+	AC_COMPILE_IFELSE([
+#ifdef __ILP32__
+#error x32
+#endif],
+	[GOARCH=amd64],
+	[GOARCH=amd64p32]))
     ;;
   ia64-*-*)
     GOARCH=ia64

libgo/go/hash/crc32/crc32_amd64p32.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build ignore
+
 package crc32
 
 import "internal/cpu"

libgo/go/internal/syscall/unix/getrandom_linux_amd64p32.go

@@ -0,0 +1,9 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package unix
+
+// Linux getrandom system call number.
+// See GetRandom in getrandom_linux.go.
+const randomTrap uintptr = 0x40000000 + 318

libgo/go/runtime/lfstack_32bit.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build 386 arm nacl armbe m68k mips mipsle mips64p32 mips64p32le nios2 ppc s390 sh shbe sparc
+// +build 386 amd64p32 arm nacl armbe m68k mips mipsle mips64p32 mips64p32le nios2 ppc s390 sh shbe sparc
 
 package runtime
 

libgo/goarch.sh

@@ -57,10 +57,15 @@ case $goarch in
 	defaultphyspagesize=8192
 	pcquantum=4
 	;;
-    amd64 | amd64p32)
+    amd64)
 	family=AMD64
 	hugepagesize="1 << 21"
 	;;
+    amd64p32)
+	family=AMD64
+	hugepagesize="1 << 21"
+	ptrsize=4
+	;;
     arm | armbe)
 	family=ARM
 	cachelinesize=32