Fix SVM interpreter's decoding of doubles.

They are encoded as 64-bit significand and 16-bit exponent, not as
machine (IEEE 754) doubles.

diff --git a/src/microcode/svm1-interp.c b/src/microcode/svm1-interp.c
index db8ac4cca5f5ee6bbd676a9f0d14ea5eef6f2746..d1aa86d068930e0a79abff9d676a8d49ba00b54a 100644 (file)
--- a/src/microcode/svm1-interp.c
+++ b/src/microcode/svm1-interp.c
@@ -318,6 +318,16 @@ decode_unsigned_32 (void)
   return ((b3 << 24) | (b2 << 16) | (b1 << 8) | b0);
 }
 
+static uint64_t
+decode_unsigned_64 (void)
+{
+  uint64_t b0, b1, b2, b3, b4, b5, b6, b7;
+  b0 = NEXT_BYTE; b1 = NEXT_BYTE; b2 = NEXT_BYTE; b3 = NEXT_BYTE;
+  b4 = NEXT_BYTE; b5 = NEXT_BYTE; b6 = NEXT_BYTE; b7 = NEXT_BYTE;
+  return ((b7 << 56) | (b6 << 48) | (b5 << 40) | (b4 << 32)
+         | (b3 << 24) | (b2 << 16) | (b1 << 8) | b0);
+}
+\f
 static long
 decode_signed_8 (void)
 {
@@ -351,30 +361,27 @@ decode_signed_32 (void)
 #endif
 }
 
+static int64_t
+decode_signed_64 (void)
+{
+  uint64_t n = (decode_unsigned_64 ());
+  if (n < ((uint64_t) 0x8000000000000000))
+    return ((int64_t) n);
+  n -= ((uint64_t) 0x8000000000000000);
+  {
+    int64_t r = ((int64_t) n);
+    r -= ((int64_t) 0x4000000000000000);
+    r -= ((int64_t) 0x4000000000000000);
+    return (r);
+  }
+}
+
 static double
 decode_float (void)
 {
-  union { double f; byte_t b [(sizeof (double))]; } x;
-
-  if (little_endian_p)
-    {
-      unsigned int i = 0;
-      while (i < (sizeof (double)))
-       {
-         ((x.b) [i]) = NEXT_BYTE;
-         i += 1;
-       }
-    }
-  else
-    {
-      unsigned int i = (sizeof (double));
-      while (i > 0)
-       {
-         i -= 1;
-         ((x.b) [i]) = NEXT_BYTE;
-       }
-    }
-  return (x.f);
+  int64_t significand = (decode_signed_64 ());
+  int exponent = (decode_signed_16 ());
+  return (ldexp (((double) significand), exponent));
 }
 \f
 /* Instruction definitions */