MIPS: make mipsisa32 and mipsisa64 link more systematic

Introduce `static const struct mips_mach_extension mips_mach_32_64[]`
and `mips_mach_extends_32_64 (unsigned long base, unsigned long extension)`,
to make mipsisa32 and mipsisa64 interlink more systemtic.

Normally, the ISA mipsisa64rN has two subset: mipsisa64r(N-1) and
mipsisa32rN. `mips_mach_extensions` can hold only mipsisa64r(N-1),
so we need to introduce a new instruction `mips_mach_32_64`, which holds the pair 32vs64.

Note: R6 is not compatible with pre-R6.

bfd/ChangeLog:

	* elfxx-mips.c (mips_mach_extends_p): make mipsisa32 and
	  mipsisa64 interlink more systematic.
	  (mips_mach_32_64): new struct added.
	  (mips_mach_extends_32_64): new function added.

1 files changed, 26 insertions, 8 deletions

diff --git a/bfd/elfxx-mips.c b/bfd/elfxx-mips.c
index 751deed..13a8995 100644
--- a/bfd/elfxx-mips.c
+++ b/bfd/elfxx-mips.c
@@ -14524,6 +14524,16 @@ struct mips_mach_extension
   unsigned long extension, base;
 };
 
+/* An array that maps 64-bit architectures to the corresponding 32-bit
+   architectures.  */
+static const struct mips_mach_extension mips_mach_32_64[] =
+{
+  { bfd_mach_mipsisa64r6, bfd_mach_mipsisa32r6 },
+  { bfd_mach_mipsisa64r5, bfd_mach_mipsisa32r5 },
+  { bfd_mach_mipsisa64r3, bfd_mach_mipsisa32r3 },
+  { bfd_mach_mipsisa64r2, bfd_mach_mipsisa32r2 },
+  { bfd_mach_mipsisa64,   bfd_mach_mipsisa32 }
+};
 
 /* An array describing how BFD machines relate to one another.  The entries
    are ordered topologically with MIPS I extensions listed last.  */
@@ -14601,29 +14611,37 @@ static const struct mips_mach_extension mips_mach_extensions[] =
   { bfd_mach_mips3900, bfd_mach_mips3000 }
 };
 
-/* Return true if bfd machine EXTENSION is an extension of machine BASE.  */
+/* Return true if bfd machine EXTENSION is the same as BASE, or if
+   EXTENSION is the 64-bit equivalent of a 32-bit BASE.  */
 
 static bool
-mips_mach_extends_p (unsigned long base, unsigned long extension)
+mips_mach_extends_32_64 (unsigned long base, unsigned long extension)
 {
   size_t i;
 
   if (extension == base)
     return true;
 
-  if (base == bfd_mach_mipsisa32
-      && mips_mach_extends_p (bfd_mach_mipsisa64, extension))
-    return true;
+  for (i = 0; i < ARRAY_SIZE (mips_mach_32_64); i++)
+    if (extension == mips_mach_32_64[i].extension)
+      return base == mips_mach_32_64[i].base;
+
+  return false;
+}
+
+static bool
+mips_mach_extends_p (unsigned long base, unsigned long extension)
+{
+  size_t i;
 
-  if (base == bfd_mach_mipsisa32r2
-      && mips_mach_extends_p (bfd_mach_mipsisa64r2, extension))
+  if (mips_mach_extends_32_64 (base, extension))
     return true;
 
   for (i = 0; i < ARRAY_SIZE (mips_mach_extensions); i++)
     if (extension == mips_mach_extensions[i].extension)
       {
 	extension = mips_mach_extensions[i].base;
-	if (extension == base)
+	if (mips_mach_extends_32_64 (base, extension))
 	  return true;
       }