target-ppc: Define Endian-Correct Accessors for VSR Field Access

This change defines accessors for VSR doubleword and word fields that
are correct from a host Endian perspective.  This allows code to
use the Power ISA indexing numbers in code.

For example, the xscvdpsxws instruction has a target VSR that looks
like this:

  0           32       64                    127
  +-----------+--------+-----------+-----------+
  | undefined | SW     | undefined | undefined |
  +-----------+--------+-----------+-----------+

VSX helper code will use VsrW(1) to access this field.

Signed-off-by: Tom Musta <tommusta@gmail.com>
Tested-by: Tom Musta <tommusta@gmail.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

target-ppc/fpu_helper.c

@@ -1782,6 +1782,14 @@ typedef union _ppc_vsr_t {
     float64 f64[2];
 } ppc_vsr_t;
 
+#if defined(HOST_WORDS_BIGENDIAN)
+#define VsrW(i) u32[i]
+#define VsrD(i) u64[i]
+#else
+#define VsrW(i) u32[3-(i)]
+#define VsrD(i) u64[1-(i)]
+#endif
+
 static void getVSR(int n, ppc_vsr_t *vsr, CPUPPCState *env)
 {
     if (n < 32) {