target/sh4: Merge mach and macl into a union

Allow host access to the entire 64-bit accumulator.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

target/sh4/cpu.h

@@ -155,12 +155,22 @@ typedef struct CPUArchState {
     uint32_t pc;                /* program counter */
     uint32_t delayed_pc;        /* target of delayed branch */
     uint32_t delayed_cond;      /* condition of delayed branch */
-    uint32_t mach;              /* multiply and accumulate high */
-    uint32_t macl;              /* multiply and accumulate low */
     uint32_t pr;                /* procedure register */
     uint32_t fpscr;             /* floating point status/control register */
     uint32_t fpul;              /* floating point communication register */
 
+    /* multiply and accumulate: high, low and combined. */
+    union {
+        uint64_t mac;
+        struct {
+#if HOST_BIG_ENDIAN
+            uint32_t mach, macl;
+#else
+            uint32_t macl, mach;
+#endif
+        };
+    };
+
     /* float point status register */
     float_status fp_status;