target/mips: Define R5900 ISA, MMI ASE, and R5900 CPU preprocessor constants

The R5900 implements the 64-bit MIPS III instruction set except
DMULT, DMULTU, DDIV, DDIVU, LL, SC, LLD and SCD. The MIPS IV
instructions MOVN, MOVZ and PREF are implemented. It has the
R5900-specific three-operand instructions MADD, MADDU, MULT and
MULTU as well as pipeline 1 versions MULT1, MULTU1, DIV1, DIVU1,
MADD1, MADDU1, MFHI1, MFLO1, MTHI1 and MTLO1. A set of 93 128-bit
multimedia instructions specific to the R5900 is also implemented.

The Toshiba TX System RISC TX79 Core Architecture manual:

https://wiki.qemu.org/File:C790.pdf

describes the C790 processor that is a follow-up to the R5900. There
are a few notable differences in that the R5900 FPU

- is not IEEE 754-1985 compliant,
- does not implement double format, and
- its machine code is nonstandard.
Reviewed-by: NAleksandar Markovic <amarkovic@wavecomp.com>
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: NFredrik Noring <noring@nocrew.org>
Signed-off-by: NAleksandar Markovic <amarkovic@wavecomp.com>

target/mips/mips-defs.h

@@ -64,9 +64,11 @@
 #define INSN_LOONGSON2E   0x0001000000000000ULL
 #define INSN_LOONGSON2F   0x0002000000000000ULL
 #define INSN_VR54XX       0x0004000000000000ULL
+#define INSN_R5900        0x0008000000000000ULL
 /*
  *   bits 56-63: vendor-specific ASEs
  */
+#define ASE_MMI           0x0100000000000000ULL
 
 /* MIPS CPU defines. */
 #define		CPU_MIPS1	(ISA_MIPS1)
@@ -74,6 +76,7 @@
 #define		CPU_MIPS3	(CPU_MIPS2 | ISA_MIPS3)
 #define		CPU_MIPS4	(CPU_MIPS3 | ISA_MIPS4)
 #define		CPU_VR54XX	(CPU_MIPS4 | INSN_VR54XX)
+#define         CPU_R5900       (CPU_MIPS3 | INSN_R5900)
 #define		CPU_LOONGSON2E  (CPU_MIPS3 | INSN_LOONGSON2E)
 #define		CPU_LOONGSON2F  (CPU_MIPS3 | INSN_LOONGSON2F)