Avoid an unsigned overflow in invert_quant

Change-Id: I16a570b2af66b6580d1cd6f8345a25f079009bf4

vp10/encoder/quantize.c

@@ -219,12 +219,12 @@ void vp10_regular_quantize_b_4x4(MACROBLOCK *x, int plane, int block,
 
 static void invert_quant(int16_t *quant, int16_t *shift, int d) {
   unsigned t;
-  int l;
+  int l, m;
   t = d;
   for (l = 0; t > 1; l++)
     t >>= 1;
-  t = 1 + (1 << (16 + l)) / d;
-  *quant = (int16_t)(t - (1 << 16));
+  m = 1 + (1 << (16 + l)) / d;
+  *quant = (int16_t)(m - (1 << 16));
   *shift = 1 << (16 - l);
 }
 

vp8/encoder/vp8_quantize.c

@@ -227,12 +227,12 @@ static void invert_quant(int improved_quant, short *quant,
     if(improved_quant)
     {
         unsigned t;
-        int l;
+        int l, m;
         t = d;
         for(l = 0; t > 1; l++)
             t>>=1;
-        t = 1 + (1<<(16+l))/d;
-        *quant = (short)(t - (1<<16));
+        m = 1 + (1<<(16+l))/d;
+        *quant = (short)(m - (1<<16));
         *shift = l;
         /* use multiplication and constant shift by 16 */
         *shift = 1 << (16 - *shift);

vp9/encoder/vp9_quantize.c

@@ -219,12 +219,12 @@ void vp9_regular_quantize_b_4x4(MACROBLOCK *x, int plane, int block,
 
 static void invert_quant(int16_t *quant, int16_t *shift, int d) {
   unsigned t;
-  int l;
+  int l, m;
   t = d;
   for (l = 0; t > 1; l++)
     t >>= 1;
-  t = 1 + (1 << (16 + l)) / d;
-  *quant = (int16_t)(t - (1 << 16));
+  m = 1 + (1 << (16 + l)) / d;
+  *quant = (int16_t)(m - (1 << 16));
   *shift = 1 << (16 - l);
 }