Convert some undefined 1<<31 shifts into 1U<<31.

According to ISO 9899:1999 S 6.5.7/4:

The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits
are filled with zeros. If E1 has an unsigned type, the value of the
result is E1× 2^E2, reduced modulo one more than the maximum value
representable in the result type. If E1 has a signed type and
nonnegative value, and E1× 2^E2 is representable in the result type, then
that is the resulting value; otherwise, the behavior is undefined.

libavcodec/aacdec.c

@@ -964,19 +964,19 @@ static inline float *VMUL4S(float *dst, const float *v, unsigned idx,
     union float754 s = { .f = *scale };
     union float754 t;
 
-    t.i = s.i ^ (sign & 1<<31);
+    t.i = s.i ^ (sign & 1U<<31);
     *dst++ = v[idx    & 3] * t.f;
 
     sign <<= nz & 1; nz >>= 1;
-    t.i = s.i ^ (sign & 1<<31);
+    t.i = s.i ^ (sign & 1U<<31);
     *dst++ = v[idx>>2 & 3] * t.f;
 
     sign <<= nz & 1; nz >>= 1;
-    t.i = s.i ^ (sign & 1<<31);
+    t.i = s.i ^ (sign & 1U<<31);
     *dst++ = v[idx>>4 & 3] * t.f;
 
     sign <<= nz & 1; nz >>= 1;
-    t.i = s.i ^ (sign & 1<<31);
+    t.i = s.i ^ (sign & 1U<<31);
     *dst++ = v[idx>>6 & 3] * t.f;
 
     return dst;
@@ -1169,11 +1169,11 @@ static int decode_spectrum_and_dequant(AACContext *ac, float coef[1024],
                                     b += 4;
                                     n = (1 << b) + SHOW_UBITS(re, gb, b);
                                     LAST_SKIP_BITS(re, gb, b);
-                                    *icf++ = cbrt_tab[n] | (bits & 1<<31);
+                                    *icf++ = cbrt_tab[n] | (bits & 1U<<31);
                                     bits <<= 1;
                                 } else {
                                     unsigned v = ((const uint32_t*)vq)[cb_idx & 15];
-                                    *icf++ = (bits & 1<<31) | v;
+                                    *icf++ = (bits & 1U<<31) | v;
                                     bits <<= !!v;
                                 }
                                 cb_idx >>= 4;

libavcodec/dsputil.c

@@ -3827,7 +3827,7 @@ static inline uint32_t clipf_c_one(uint32_t a, uint32_t mini,
 {
 
     if(a > mini) return mini;
-    else if((a^(1<<31)) > maxisign) return maxi;
+    else if((a^(1U<<31)) > maxisign) return maxi;
     else return a;
 }
 
@@ -3835,7 +3835,7 @@ static void vector_clipf_c_opposite_sign(float *dst, const float *src, float *mi
     int i;
     uint32_t mini = *(uint32_t*)min;
     uint32_t maxi = *(uint32_t*)max;
-    uint32_t maxisign = maxi ^ (1<<31);
+    uint32_t maxisign = maxi ^ (1U<<31);
     uint32_t *dsti = (uint32_t*)dst;
     const uint32_t *srci = (const uint32_t*)src;
     for(i=0; i<len; i+=8) {

libavcodec/fraps.c

@@ -180,7 +180,7 @@ static int decode_frame(AVCodecContext *avctx,
             return -1;
         }
         /* bit 31 means same as previous pic */
-        f->pict_type = (header & (1<<31))? FF_P_TYPE : FF_I_TYPE;
+        f->pict_type = (header & (1U<<31))? FF_P_TYPE : FF_I_TYPE;
         f->key_frame = f->pict_type == FF_I_TYPE;
 
         if (f->pict_type == FF_I_TYPE) {
@@ -223,7 +223,7 @@ static int decode_frame(AVCodecContext *avctx,
             return -1;
         }
         /* bit 31 means same as previous pic */
-        f->pict_type = (header & (1<<31))? FF_P_TYPE : FF_I_TYPE;
+        f->pict_type = (header & (1U<<31))? FF_P_TYPE : FF_I_TYPE;
         f->key_frame = f->pict_type == FF_I_TYPE;
 
         if (f->pict_type == FF_I_TYPE) {

libavcodec/ppc/fft_altivec.c

@@ -122,7 +122,7 @@ static void ff_imdct_calc_altivec(FFTContext *s, FFTSample *output, const FFTSam
     int n = 1 << s->mdct_bits;
     int n4 = n >> 2;
     int n16 = n >> 4;
-    vec_u32 sign = {1<<31,1<<31,1<<31,1<<31};
+    vec_u32 sign = {1U<<31,1U<<31,1U<<31,1U<<31};
     vec_u32 *p0 = (vec_u32*)(output+n4);
     vec_u32 *p1 = (vec_u32*)(output+n4*3);
 

libavcodec/vorbis_enc.c

@@ -394,7 +394,7 @@ static void put_float(PutBitContext *pb, float f)
     mant = (int)ldexp(frexp(f, &exp), 20);
     exp += 788 - 20;
     if (mant < 0) {
-        res |= (1 << 31);
+        res |= (1U << 31);
         mant = -mant;
     }
     res |= mant | (exp << 21);