silencing overflows in MDCT and FFT

6 files changed, 59 insertions, 44 deletions

diff --git a/celt/_kiss_fft_guts.h b/celt/_kiss_fft_guts.h
index 5e3d58fd..17392b3e 100644
--- a/celt/_kiss_fft_guts.h
+++ b/celt/_kiss_fft_guts.h
@@ -58,12 +58,12 @@
 #   define S_MUL(a,b) MULT16_32_Q15(b, a)
 
 #   define C_MUL(m,a,b) \
-      do{ (m).r = SUB32(S_MUL((a).r,(b).r) , S_MUL((a).i,(b).i)); \
-          (m).i = ADD32(S_MUL((a).r,(b).i) , S_MUL((a).i,(b).r)); }while(0)
+      do{ (m).r = SUB32_ovflw(S_MUL((a).r,(b).r) , S_MUL((a).i,(b).i)); \
+          (m).i = ADD32_ovflw(S_MUL((a).r,(b).i) , S_MUL((a).i,(b).r)); }while(0)
 
 #   define C_MULC(m,a,b) \
-      do{ (m).r = ADD32(S_MUL((a).r,(b).r) , S_MUL((a).i,(b).i)); \
-          (m).i = SUB32(S_MUL((a).i,(b).r) , S_MUL((a).r,(b).i)); }while(0)
+      do{ (m).r = ADD32_ovflw(S_MUL((a).r,(b).r) , S_MUL((a).i,(b).i)); \
+          (m).i = SUB32_ovflw(S_MUL((a).i,(b).r) , S_MUL((a).r,(b).i)); }while(0)
 
 #   define C_MULBYSCALAR( c, s ) \
       do{ (c).r =  S_MUL( (c).r , s ) ;\
@@ -77,17 +77,17 @@
                 DIVSCALAR( (c).i  , div); }while (0)
 
 #define  C_ADD( res, a,b)\
-    do {(res).r=ADD32((a).r,(b).r);  (res).i=ADD32((a).i,(b).i); \
+    do {(res).r=ADD32_ovflw((a).r,(b).r);  (res).i=ADD32_ovflw((a).i,(b).i); \
     }while(0)
 #define  C_SUB( res, a,b)\
-    do {(res).r=SUB32((a).r,(b).r);  (res).i=SUB32((a).i,(b).i); \
+    do {(res).r=SUB32_ovflw((a).r,(b).r);  (res).i=SUB32_ovflw((a).i,(b).i); \
     }while(0)
 #define C_ADDTO( res , a)\
-    do {(res).r = ADD32((res).r, (a).r);  (res).i = ADD32((res).i,(a).i);\
+    do {(res).r = ADD32_ovflw((res).r, (a).r);  (res).i = ADD32_ovflw((res).i,(a).i);\
     }while(0)
 
 #define C_SUBFROM( res , a)\
-    do {(res).r = ADD32((res).r,(a).r);  (res).i = SUB32((res).i,(a).i); \
+    do {(res).r = ADD32_ovflw((res).r,(a).r);  (res).i = SUB32_ovflw((res).i,(a).i); \
     }while(0)
 
 #if defined(OPUS_ARM_INLINE_ASM)
diff --git a/celt/arch.h b/celt/arch.h
index 8ceab5fe..05e434b9 100644
--- a/celt/arch.h
+++ b/celt/arch.h
@@ -186,6 +186,7 @@ static OPUS_INLINE int celt_isnan(float x)
 
 #define NEG16(x) (-(x))
 #define NEG32(x) (-(x))
+#define NEG32_ovflw(x) (-(x))
 #define EXTRACT16(x) (x)
 #define EXTEND32(x) (x)
 #define SHR16(a,shift) (a)
@@ -209,6 +210,8 @@ static OPUS_INLINE int celt_isnan(float x)
 #define SUB16(a,b) ((a)-(b))
 #define ADD32(a,b) ((a)+(b))
 #define SUB32(a,b) ((a)-(b))
+#define ADD32_ovflw(a,b) ((a)+(b))
+#define SUB32_ovflw(a,b) ((a)-(b))
 #define MULT16_16_16(a,b)     ((a)*(b))
 #define MULT16_16(a,b)     ((opus_val32)(a)*(opus_val32)(b))
 #define MAC16_16(c,a,b)     ((c)+(opus_val32)(a)*(opus_val32)(b))
diff --git a/celt/fixed_debug.h b/celt/fixed_debug.h
index d28227f5..f55dbf92 100644
--- a/celt/fixed_debug.h
+++ b/celt/fixed_debug.h
@@ -59,6 +59,12 @@ extern opus_int64 celt_mips;
 #define SHR(a,b) SHR32(a,b)
 #define PSHR(a,b) PSHR32(a,b)
 
+/** Add two 32-bit values, ignore any overflows */
+#define ADD32_ovflw(a,b) (celt_mips+=2,(opus_val32)((opus_uint32)(a)+(opus_uint32)(b)))
+/** Subtract two 32-bit values, ignore any overflows  */
+#define SUB32_ovflw(a,b) (celt_mips+=2,(opus_val32)((opus_uint32)(a)-(opus_uint32)(b)))
+#define NEG32_ovflw(a) (celt_mips+=2,(opus_val32)(-(opus_uint32)(a)))
+
 static OPUS_INLINE short NEG16(int x)
 {
    int res;
diff --git a/celt/fixed_generic.h b/celt/fixed_generic.h
index 1cfd6d69..32e38ff0 100644
--- a/celt/fixed_generic.h
+++ b/celt/fixed_generic.h
@@ -117,6 +117,12 @@
 /** Subtract two 32-bit values */
 #define SUB32(a,b) ((opus_val32)(a)-(opus_val32)(b))
 
+/** Add two 32-bit values, ignore any overflows */
+#define ADD32_ovflw(a,b) ((opus_val32)((opus_uint32)(a)+(opus_uint32)(b)))
+/** Subtract two 32-bit values, ignore any overflows  */
+#define SUB32_ovflw(a,b) ((opus_val32)((opus_uint32)(a)-(opus_uint32)(b)))
+#define NEG32_ovflw(a) ((opus_val32)(-(opus_uint32)(a)))
+
 /** 16x16 multiplication where the result fits in 16 bits */
 #define MULT16_16_16(a,b)     ((((opus_val16)(a))*((opus_val16)(b))))
 
diff --git a/celt/kiss_fft.c b/celt/kiss_fft.c
index 1f8fd053..83775165 100644
--- a/celt/kiss_fft.c
+++ b/celt/kiss_fft.c
@@ -82,8 +82,8 @@ static void kf_bfly2(
          C_SUB( Fout2[0] ,  Fout[0] , t );
          C_ADDTO( Fout[0] ,  t );
 
-         t.r = S_MUL(Fout2[1].r+Fout2[1].i, tw);
-         t.i = S_MUL(Fout2[1].i-Fout2[1].r, tw);
+         t.r = S_MUL(ADD32_ovflw(Fout2[1].r, Fout2[1].i), tw);
+         t.i = S_MUL(SUB32_ovflw(Fout2[1].i, Fout2[1].r), tw);
          C_SUB( Fout2[1] ,  Fout[1] , t );
          C_ADDTO( Fout[1] ,  t );
 
@@ -92,8 +92,8 @@ static void kf_bfly2(
          C_SUB( Fout2[2] ,  Fout[2] , t );
          C_ADDTO( Fout[2] ,  t );
 
-         t.r = S_MUL(Fout2[3].i-Fout2[3].r, tw);
-         t.i = S_MUL(-Fout2[3].i-Fout2[3].r, tw);
+         t.r = S_MUL(SUB32_ovflw(Fout2[3].i, Fout2[3].r), tw);
+         t.i = S_MUL(NEG32_ovflw(ADD32_ovflw(Fout2[3].i, Fout2[3].r)), tw);
          C_SUB( Fout2[3] ,  Fout[3] , t );
          C_ADDTO( Fout[3] ,  t );
          Fout += 8;
@@ -126,10 +126,10 @@ static void kf_bfly4(
          C_ADDTO( *Fout , scratch1 );
          C_SUB( scratch1 , Fout[1] , Fout[3] );
 
-         Fout[1].r = scratch0.r + scratch1.i;
-         Fout[1].i = scratch0.i - scratch1.r;
-         Fout[3].r = scratch0.r - scratch1.i;
-         Fout[3].i = scratch0.i + scratch1.r;
+         Fout[1].r = ADD32_ovflw(scratch0.r, scratch1.i);
+         Fout[1].i = SUB32_ovflw(scratch0.i, scratch1.r);
+         Fout[3].r = SUB32_ovflw(scratch0.r, scratch1.i);
+         Fout[3].i = ADD32_ovflw(scratch0.i, scratch1.r);
          Fout+=4;
       }
    } else {
@@ -160,10 +160,10 @@ static void kf_bfly4(
             tw3 += fstride*3;
             C_ADDTO( *Fout , scratch[3] );
 
-            Fout[m].r = scratch[5].r + scratch[4].i;
-            Fout[m].i = scratch[5].i - scratch[4].r;
-            Fout[m3].r = scratch[5].r - scratch[4].i;
-            Fout[m3].i = scratch[5].i + scratch[4].r;
+            Fout[m].r = ADD32_ovflw(scratch[5].r, scratch[4].i);
+            Fout[m].i = SUB32_ovflw(scratch[5].i, scratch[4].r);
+            Fout[m3].r = SUB32_ovflw(scratch[5].r, scratch[4].i);
+            Fout[m3].i = ADD32_ovflw(scratch[5].i, scratch[4].r);
             ++Fout;
          }
       }
@@ -212,18 +212,18 @@ static void kf_bfly3(
          tw1 += fstride;
          tw2 += fstride*2;
 
-         Fout[m].r = Fout->r - HALF_OF(scratch[3].r);
-         Fout[m].i = Fout->i - HALF_OF(scratch[3].i);
+         Fout[m].r = SUB32_ovflw(Fout->r, HALF_OF(scratch[3].r));
+         Fout[m].i = SUB32_ovflw(Fout->i, HALF_OF(scratch[3].i));
 
          C_MULBYSCALAR( scratch[0] , epi3.i );
 
          C_ADDTO(*Fout,scratch[3]);
 
-         Fout[m2].r = Fout[m].r + scratch[0].i;
-         Fout[m2].i = Fout[m].i - scratch[0].r;
+         Fout[m2].r = ADD32_ovflw(Fout[m].r, scratch[0].i);
+         Fout[m2].i = SUB32_ovflw(Fout[m].i, scratch[0].r);
 
-         Fout[m].r -= scratch[0].i;
-         Fout[m].i += scratch[0].r;
+         Fout[m].r = SUB32_ovflw(Fout[m].r, scratch[0].i);
+         Fout[m].i = ADD32_ovflw(Fout[m].i, scratch[0].r);
 
          ++Fout;
       } while(--k);
@@ -282,22 +282,22 @@ static void kf_bfly5(
          C_ADD( scratch[8],scratch[2],scratch[3]);
          C_SUB( scratch[9],scratch[2],scratch[3]);
 
-         Fout0->r += scratch[7].r + scratch[8].r;
-         Fout0->i += scratch[7].i + scratch[8].i;
+         Fout0->r = ADD32_ovflw(Fout0->r, ADD32_ovflw(scratch[7].r, scratch[8].r));
+         Fout0->i = ADD32_ovflw(Fout0->i, ADD32_ovflw(scratch[7].i, scratch[8].i));
 
-         scratch[5].r = scratch[0].r + S_MUL(scratch[7].r,ya.r) + S_MUL(scratch[8].r,yb.r);
-         scratch[5].i = scratch[0].i + S_MUL(scratch[7].i,ya.r) + S_MUL(scratch[8].i,yb.r);
+         scratch[5].r = ADD32_ovflw(scratch[0].r, ADD32_ovflw(S_MUL(scratch[7].r,ya.r), S_MUL(scratch[8].r,yb.r)));
+         scratch[5].i = ADD32_ovflw(scratch[0].i, ADD32_ovflw(S_MUL(scratch[7].i,ya.r), S_MUL(scratch[8].i,yb.r)));
 
-         scratch[6].r =  S_MUL(scratch[10].i,ya.i) + S_MUL(scratch[9].i,yb.i);
-         scratch[6].i = -S_MUL(scratch[10].r,ya.i) - S_MUL(scratch[9].r,yb.i);
+         scratch[6].r =  ADD32_ovflw(S_MUL(scratch[10].i,ya.i), S_MUL(scratch[9].i,yb.i));
+         scratch[6].i = NEG32_ovflw(ADD32_ovflw(S_MUL(scratch[10].r,ya.i), S_MUL(scratch[9].r,yb.i)));
 
          C_SUB(*Fout1,scratch[5],scratch[6]);
          C_ADD(*Fout4,scratch[5],scratch[6]);
 
-         scratch[11].r = scratch[0].r + S_MUL(scratch[7].r,yb.r) + S_MUL(scratch[8].r,ya.r);
-         scratch[11].i = scratch[0].i + S_MUL(scratch[7].i,yb.r) + S_MUL(scratch[8].i,ya.r);
-         scratch[12].r = - S_MUL(scratch[10].i,yb.i) + S_MUL(scratch[9].i,ya.i);
-         scratch[12].i = S_MUL(scratch[10].r,yb.i) - S_MUL(scratch[9].r,ya.i);
+         scratch[11].r = ADD32_ovflw(scratch[0].r, ADD32_ovflw(S_MUL(scratch[7].r,yb.r), S_MUL(scratch[8].r,ya.r)));
+         scratch[11].i = ADD32_ovflw(scratch[0].i, ADD32_ovflw(S_MUL(scratch[7].i,yb.r), S_MUL(scratch[8].i,ya.r)));
+         scratch[12].r = SUB32_ovflw(S_MUL(scratch[9].i,ya.i), S_MUL(scratch[10].i,yb.i));
+         scratch[12].i = SUB32_ovflw(S_MUL(scratch[10].r,yb.i), S_MUL(scratch[9].r,ya.i));
 
          C_ADD(*Fout2,scratch[11],scratch[12]);
          C_SUB(*Fout3,scratch[11],scratch[12]);
diff --git a/celt/mdct.c b/celt/mdct.c
index 5315ad11..5c6dab5b 100644
--- a/celt/mdct.c
+++ b/celt/mdct.c
@@ -270,8 +270,8 @@ void clt_mdct_backward_c(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_sca
          int rev;
          kiss_fft_scalar yr, yi;
          rev = *bitrev++;
-         yr = S_MUL(*xp2, t[i]) + S_MUL(*xp1, t[N4+i]);
-         yi = S_MUL(*xp1, t[i]) - S_MUL(*xp2, t[N4+i]);
+         yr = ADD32_ovflw(S_MUL(*xp2, t[i]), S_MUL(*xp1, t[N4+i]));
+         yi = SUB32_ovflw(S_MUL(*xp1, t[i]), S_MUL(*xp2, t[N4+i]));
          /* We swap real and imag because we use an FFT instead of an IFFT. */
          yp[2*rev+1] = yr;
          yp[2*rev] = yi;
@@ -301,8 +301,8 @@ void clt_mdct_backward_c(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_sca
          t0 = t[i];
          t1 = t[N4+i];
          /* We'd scale up by 2 here, but instead it's done when mixing the windows */
-         yr = S_MUL(re,t0) + S_MUL(im,t1);
-         yi = S_MUL(re,t1) - S_MUL(im,t0);
+         yr = ADD32_ovflw(S_MUL(re,t0), S_MUL(im,t1));
+         yi = SUB32_ovflw(S_MUL(re,t1), S_MUL(im,t0));
          /* We swap real and imag because we're using an FFT instead of an IFFT. */
          re = yp1[1];
          im = yp1[0];
@@ -312,8 +312,8 @@ void clt_mdct_backward_c(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_sca
          t0 = t[(N4-i-1)];
          t1 = t[(N2-i-1)];
          /* We'd scale up by 2 here, but instead it's done when mixing the windows */
-         yr = S_MUL(re,t0) + S_MUL(im,t1);
-         yi = S_MUL(re,t1) - S_MUL(im,t0);
+         yr = ADD32_ovflw(S_MUL(re,t0), S_MUL(im,t1));
+         yi = SUB32_ovflw(S_MUL(re,t1), S_MUL(im,t0));
          yp1[0] = yr;
          yp0[1] = yi;
          yp0 += 2;
@@ -333,8 +333,8 @@ void clt_mdct_backward_c(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_sca
          kiss_fft_scalar x1, x2;
          x1 = *xp1;
          x2 = *yp1;
-         *yp1++ = MULT16_32_Q15(*wp2, x2) - MULT16_32_Q15(*wp1, x1);
-         *xp1-- = MULT16_32_Q15(*wp1, x2) + MULT16_32_Q15(*wp2, x1);
+         *yp1++ = SUB32_ovflw(MULT16_32_Q15(*wp2, x2), MULT16_32_Q15(*wp1, x1));
+         *xp1-- = ADD32_ovflw(MULT16_32_Q15(*wp1, x2), MULT16_32_Q15(*wp2, x1));
          wp1++;
          wp2--;
       }