MIPS: Set r6 as default arch if vendor is img

This behavior is used by downstream toolchain since 2014,
and has been in GCC since the same year.

We don't support mips64*-img* due to GCC doesn't support it,
and we believe that the multilib should be used for this case.

bfd/config.bfd

@@ -1550,7 +1550,7 @@ case "${targ_defvec} ${targ_selvecs}" in
 esac
 
 case "${targ}" in
-  mipsisa32r6* | mipsisa64r6*)
+  mipsisa32r6* | mipsisa64r6* | mips*-img-*)
     targ_cflags="$targ_cflags -DMIPS_DEFAULT_R6=1"
     ;;
 esac

gas/configure

@@ -12264,6 +12264,12 @@ _ACEOF
 	    use_ef_mips_abi_o32=1
 	    ;;
 	esac
+	# If Vendor is IMG, then MIPSr6 is used
+	case ${target} in
+	  mips*-img-*)
+	    mips_cpu=mips32r6
+	    ;;
+	esac
 	# Decide whether to generate 32-bit or 64-bit code by default.
 	# Used to resolve -march=from-abi when an embedded ABI is selected.
 	case ${target} in

gas/configure.ac

@@ -382,6 +382,12 @@ changequote([,])dnl
 	    use_ef_mips_abi_o32=1
 	    ;;
 	esac
+	# If Vendor is IMG, then MIPSr6 is used
+	case ${target} in
+	  mips*-img-*)
+	    mips_cpu=mips32r6
+	    ;;
+	esac
 	# Decide whether to generate 32-bit or 64-bit code by default.
 	# Used to resolve -march=from-abi when an embedded ABI is selected.
 	case ${target} in

gas/testsuite/gas/mips/mips.exp

@@ -473,7 +473,7 @@ mips_arch_create mips32r5 32	mips32r3 { fpisa3 fpisa4 fpisa5 ror } \
 mips_arch_create mips32r6 32	mips32r5 { fpisa3 fpisa4 fpisa5 ror } \
 			{ -march=mips32r6 -mtune=mips32r6 --defsym r6=} \
 			{ -mmips:isa32r6 } \
-			{ mipsisa32r6-*-* mipsisa32r6el-*-* }
+			{ mipsisa32r6-*-* mipsisa32r6el-*-* mips*-img-* }
 mips_arch_create mips64	64	mips5	{ mips32 } \
 			{ -march=mips64 -mtune=mips64 } { -mmips:isa64 } \
 			{ mipsisa64-*-* mipsisa64el-*-* }

gas/testsuite/gas/mips/module-defer-warn2.d

@@ -1,5 +1,5 @@
 #name: .module deferred warnings 2 (pre-R2)
 #source: module-defer-warn2.s
 #as: -32
-#skip: mipsisa32r?* mipsisa64r?*
+#skip: mipsisa32r?* mipsisa64r?* mips*-img-*
 #error_output: module-defer-warn2.l