MIPS: microMIPS: Add instruction utility macros.

Add two new macros for microMIPS. One checks if an exception was
taken in either microMIPS or classic MIPS mode. The other checks
if a microMIPS instruction is 16-bit or 32-bit in length.

[ralf@linux-mips.org: Removed unnecessary parenthesis as noted by
Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>]

Signed-off-by: Steven J. Hill <sjhill@mips.com>
Cc: linux-mips@linux-mips.org
Cc: cernekee@gmail.com
Cc: kevink@paralogos.com
Cc: ddaney.cavm@gmail.com
Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Patchwork: https://patchwork.linux-mips.org/patch/4924/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
(cherry picked from commit 49df26472338b935fd5781bf94a77a88b148a716)

arch/mips/include/asm/mipsregs.h

@@ -622,6 +622,24 @@
 
 #ifndef __ASSEMBLY__
 
+/*
+ * Macros for handling the ISA mode bit for microMIPS.
+ */
+#define get_isa16_mode(x)		((x) & 0x1)
+#define msk_isa16_mode(x)		((x) & ~0x1)
+#define set_isa16_mode(x)		do { (x) |= 0x1; } while(0)
+
+/*
+ * microMIPS instructions can be 16-bit or 32-bit in length. This
+ * returns a 1 if the instruction is 16-bit and a 0 if 32-bit.
+ */
+static inline int mm_insn_16bit(u16 insn)
+{
+	u16 opcode = (insn >> 10) & 0x7;
+
+	return (opcode >= 1 && opcode <= 3) ? 1 : 0;
+}
+
 /*
  * Functions to access the R10000 performance counters.	 These are basically
  * mfc0 and mtc0 instructions from and to coprocessor register with a 5-bit