ppc: dsputil: comment formatting and wording/grammar improvements

libavcodec/ppc/dsputil_altivec.c

@@ -47,27 +47,27 @@ static int sad16_x2_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size
     sad = (vector unsigned int)vec_splat_u32(0);
     for (i = 0; i < h; i++) {
         /* Read unaligned pixels into our vectors. The vectors are as follows:
-           pix1v: pix1[0]-pix1[15]
-           pix2v: pix2[0]-pix2[15]      pix2iv: pix2[1]-pix2[16] */
+         * pix1v: pix1[0] - pix1[15]
+         * pix2v: pix2[0] - pix2[15]      pix2iv: pix2[1] - pix2[16] */
         pix1v  = vec_ld( 0, pix1);
         pix2l  = vec_ld( 0, pix2);
         pix2r  = vec_ld(16, pix2);
         pix2v  = vec_perm(pix2l, pix2r, perm1);
         pix2iv = vec_perm(pix2l, pix2r, perm2);
 
-        /* Calculate the average vector */
+        /* Calculate the average vector. */
         avgv = vec_avg(pix2v, pix2iv);
 
-        /* Calculate a sum of abs differences vector */
+        /* Calculate a sum of abs differences vector. */
         t5 = vec_sub(vec_max(pix1v, avgv), vec_min(pix1v, avgv));
 
-        /* Add each 4 pixel group together and put 4 results into sad */
+        /* Add each 4 pixel group together and put 4 results into sad. */
         sad = vec_sum4s(t5, sad);
 
         pix1 += line_size;
         pix2 += line_size;
     }
-    /* Sum up the four partial sums, and put the result into s */
+    /* Sum up the four partial sums, and put the result into s. */
     sumdiffs = vec_sums((vector signed int) sad, (vector signed int) zero);
     sumdiffs = vec_splat(sumdiffs, 3);
     vec_ste(sumdiffs, 0, &s);
@@ -91,33 +91,33 @@ static int sad16_y2_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size
     sad = (vector unsigned int)vec_splat_u32(0);
 
     /* Due to the fact that pix3 = pix2 + line_size, the pix3 of one
-       iteration becomes pix2 in the next iteration. We can use this
-       fact to avoid a potentially expensive unaligned read, each
-       time around the loop.
-       Read unaligned pixels into our vectors. The vectors are as follows:
-       pix2v: pix2[0]-pix2[15]
-       Split the pixel vectors into shorts */
+     * iteration becomes pix2 in the next iteration. We can use this
+     * fact to avoid a potentially expensive unaligned read, each
+     * time around the loop.
+     * Read unaligned pixels into our vectors. The vectors are as follows:
+     * pix2v: pix2[0] - pix2[15]
+     * Split the pixel vectors into shorts. */
     pix2l = vec_ld( 0, pix2);
     pix2r = vec_ld(15, pix2);
     pix2v = vec_perm(pix2l, pix2r, perm);
 
     for (i = 0; i < h; i++) {
         /* Read unaligned pixels into our vectors. The vectors are as follows:
-           pix1v: pix1[0]-pix1[15]
-           pix3v: pix3[0]-pix3[15] */
+         * pix1v: pix1[0] - pix1[15]
+         * pix3v: pix3[0] - pix3[15] */
         pix1v = vec_ld(0, pix1);
 
         pix2l = vec_ld( 0, pix3);
         pix2r = vec_ld(15, pix3);
         pix3v = vec_perm(pix2l, pix2r, perm);
 
-        /* Calculate the average vector */
+        /* Calculate the average vector. */
         avgv = vec_avg(pix2v, pix3v);
 
-        /* Calculate a sum of abs differences vector */
+        /* Calculate a sum of abs differences vector. */
         t5 = vec_sub(vec_max(pix1v, avgv), vec_min(pix1v, avgv));
 
-        /* Add each 4 pixel group together and put 4 results into sad */
+        /* Add each 4 pixel group together and put 4 results into sad. */
         sad = vec_sum4s(t5, sad);
 
         pix1 += line_size;
@@ -126,7 +126,7 @@ static int sad16_y2_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size
 
     }
 
-    /* Sum up the four partial sums, and put the result into s */
+    /* Sum up the four partial sums, and put the result into s. */
     sumdiffs = vec_sums((vector signed int) sad, (vector signed int) zero);
     sumdiffs = vec_splat(sumdiffs, 3);
     vec_ste(sumdiffs, 0, &s);
@@ -157,12 +157,12 @@ static int sad16_xy2_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_siz
     s = 0;
 
     /* Due to the fact that pix3 = pix2 + line_size, the pix3 of one
-       iteration becomes pix2 in the next iteration. We can use this
-       fact to avoid a potentially expensive unaligned read, as well
-       as some splitting, and vector addition each time around the loop.
-       Read unaligned pixels into our vectors. The vectors are as follows:
-       pix2v: pix2[0]-pix2[15]  pix2iv: pix2[1]-pix2[16]
-       Split the pixel vectors into shorts */
+     * iteration becomes pix2 in the next iteration. We can use this
+     * fact to avoid a potentially expensive unaligned read, as well
+     * as some splitting, and vector addition each time around the loop.
+     * Read unaligned pixels into our vectors. The vectors are as follows:
+     * pix2v: pix2[0] - pix2[15]  pix2iv: pix2[1] - pix2[16]
+     * Split the pixel vectors into shorts. */
     pix2l  = vec_ld( 0, pix2);
     pix2r  = vec_ld(16, pix2);
     pix2v  = vec_perm(pix2l, pix2r, perm1);
@@ -177,8 +177,8 @@ static int sad16_xy2_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_siz
 
     for (i = 0; i < h; i++) {
         /* Read unaligned pixels into our vectors. The vectors are as follows:
-           pix1v: pix1[0]-pix1[15]
-           pix3v: pix3[0]-pix3[15]      pix3iv: pix3[1]-pix3[16] */
+         * pix1v: pix1[0] - pix1[15]
+         * pix3v: pix3[0] - pix3[15]      pix3iv: pix3[1] - pix3[16] */
         pix1v = vec_ld(0, pix1);
 
         pix2l  = vec_ld( 0, pix3);
@@ -187,40 +187,40 @@ static int sad16_xy2_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_siz
         pix3iv = vec_perm(pix2l, pix2r, perm2);
 
         /* Note that AltiVec does have vec_avg, but this works on vector pairs
-           and rounds up. We could do avg(avg(a,b),avg(c,d)), but the rounding
-           would mean that, for example, avg(3,0,0,1) = 2, when it should be 1.
-           Instead, we have to split the pixel vectors into vectors of shorts,
-           and do the averaging by hand. */
+         * and rounds up. We could do avg(avg(a, b), avg(c, d)), but the
+         * rounding would mean that, for example, avg(3, 0, 0, 1) = 2, when
+         * it should be 1. Instead, we have to split the pixel vectors into
+         * vectors of shorts and do the averaging by hand. */
 
-        /* Split the pixel vectors into shorts */
+        /* Split the pixel vectors into shorts. */
         pix3hv  = (vector unsigned short) vec_mergeh(zero, pix3v);
         pix3lv  = (vector unsigned short) vec_mergel(zero, pix3v);
         pix3ihv = (vector unsigned short) vec_mergeh(zero, pix3iv);
         pix3ilv = (vector unsigned short) vec_mergel(zero, pix3iv);
 
-        /* Do the averaging on them */
+        /* Do the averaging on them. */
         t3 = vec_add(pix3hv, pix3ihv);
         t4 = vec_add(pix3lv, pix3ilv);
 
         avghv = vec_sr(vec_add(vec_add(t1, t3), two), two);
         avglv = vec_sr(vec_add(vec_add(t2, t4), two), two);
 
-        /* Pack the shorts back into a result */
+        /* Pack the shorts back into a result. */
         avgv = vec_pack(avghv, avglv);
 
-        /* Calculate a sum of abs differences vector */
+        /* Calculate a sum of abs differences vector. */
         t5 = vec_sub(vec_max(pix1v, avgv), vec_min(pix1v, avgv));
 
-        /* Add each 4 pixel group together and put 4 results into sad */
+        /* Add each 4 pixel group together and put 4 results into sad. */
         sad = vec_sum4s(t5, sad);
 
         pix1 += line_size;
         pix3 += line_size;
-        /* Transfer the calculated values for pix3 into pix2 */
+        /* Transfer the calculated values for pix3 into pix2. */
         t1 = t3;
         t2 = t4;
     }
-    /* Sum up the four partial sums, and put the result into s */
+    /* Sum up the four partial sums, and put the result into s. */
     sumdiffs = vec_sums((vector signed int) sad, (vector signed int) zero);
     sumdiffs = vec_splat(sumdiffs, 3);
     vec_ste(sumdiffs, 0, &s);
@@ -242,25 +242,25 @@ static int sad16_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size, i
 
 
     for (i = 0; i < h; i++) {
-        /* Read potentially unaligned pixels into t1 and t2 */
+        /* Read potentially unaligned pixels into t1 and t2. */
         vector unsigned char pix2l = vec_ld( 0, pix2);
         vector unsigned char pix2r = vec_ld(15, pix2);
         t1 = vec_ld(0, pix1);
         t2 = vec_perm(pix2l, pix2r, perm);
 
-        /* Calculate a sum of abs differences vector */
+        /* Calculate a sum of abs differences vector. */
         t3 = vec_max(t1, t2);
         t4 = vec_min(t1, t2);
         t5 = vec_sub(t3, t4);
 
-        /* Add each 4 pixel group together and put 4 results into sad */
+        /* Add each 4 pixel group together and put 4 results into sad. */
         sad = vec_sum4s(t5, sad);
 
         pix1 += line_size;
         pix2 += line_size;
     }
 
-    /* Sum up the four partial sums, and put the result into s */
+    /* Sum up the four partial sums, and put the result into s. */
     sumdiffs = vec_sums((vector signed int) sad, (vector signed int) zero);
     sumdiffs = vec_splat(sumdiffs, 3);
     vec_ste(sumdiffs, 0, &s);
@@ -283,9 +283,9 @@ static int sad8_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size, in
     sad = (vector unsigned int)vec_splat_u32(0);
 
     for (i = 0; i < h; i++) {
-        /* Read potentially unaligned pixels into t1 and t2
-           Since we're reading 16 pixels, and actually only want 8,
-           mask out the last 8 pixels. The 0s don't change the sum. */
+        /* Read potentially unaligned pixels into t1 and t2.
+         * Since we're reading 16 pixels, and actually only want 8,
+         * mask out the last 8 pixels. The 0s don't change the sum. */
         vector unsigned char pix1l = vec_ld(0, pix1);
         vector unsigned char pix1r = vec_ld(7, pix1);
         vector unsigned char pix2l = vec_ld(0, pix2);
@@ -293,19 +293,19 @@ static int sad8_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size, in
         t1 = vec_and(vec_perm(pix1l, pix1r, perm1), permclear);
         t2 = vec_and(vec_perm(pix2l, pix2r, perm2), permclear);
 
-        /* Calculate a sum of abs differences vector */
+        /* Calculate a sum of abs differences vector. */
         t3 = vec_max(t1, t2);
         t4 = vec_min(t1, t2);
         t5 = vec_sub(t3, t4);
 
-        /* Add each 4 pixel group together and put 4 results into sad */
+        /* Add each 4 pixel group together and put 4 results into sad. */
         sad = vec_sum4s(t5, sad);
 
         pix1 += line_size;
         pix2 += line_size;
     }
 
-    /* Sum up the four partial sums, and put the result into s */
+    /* Sum up the four partial sums, and put the result into s. */
     sumdiffs = vec_sums((vector signed int) sad, (vector signed int) zero);
     sumdiffs = vec_splat(sumdiffs, 3);
     vec_ste(sumdiffs, 0, &s);
@@ -327,17 +327,17 @@ static int pix_norm1_altivec(uint8_t *pix, int line_size)
 
     s = 0;
     for (i = 0; i < 16; i++) {
-        /* Read in the potentially unaligned pixels */
+        /* Read the potentially unaligned pixels. */
         vector unsigned char pixl = vec_ld( 0, pix);
         vector unsigned char pixr = vec_ld(15, pix);
         pixv = vec_perm(pixl, pixr, perm);
 
-        /* Square the values, and add them to our sum */
+        /* Square the values, and add them to our sum. */
         sv = vec_msum(pixv, pixv, sv);
 
         pix += line_size;
     }
-    /* Sum up the four partial sums, and put the result into s */
+    /* Sum up the four partial sums, and put the result into s. */
     sum = vec_sums((vector signed int) sv, (vector signed int) zero);
     sum = vec_splat(sum, 3);
     vec_ste(sum, 0, &s);
@@ -345,11 +345,8 @@ static int pix_norm1_altivec(uint8_t *pix, int line_size)
     return s;
 }
 
-/**
- * Sum of Squared Errors for a 8x8 block.
- * AltiVec-enhanced.
- * It's the sad8_altivec code above w/ squaring added.
- */
+/* Sum of Squared Errors for an 8x8 block, AltiVec-enhanced.
+ * It's the sad8_altivec code above w/ squaring added. */
 static int sse8_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size, int h)
 {
     int i;
@@ -365,9 +362,9 @@ static int sse8_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size, in
     sum = (vector unsigned int)vec_splat_u32(0);
 
     for (i = 0; i < h; i++) {
-        /* Read potentially unaligned pixels into t1 and t2
-           Since we're reading 16 pixels, and actually only want 8,
-           mask out the last 8 pixels. The 0s don't change the sum. */
+        /* Read potentially unaligned pixels into t1 and t2.
+         * Since we're reading 16 pixels, and actually only want 8,
+         * mask out the last 8 pixels. The 0s don't change the sum. */
         vector unsigned char pix1l = vec_ld(0, pix1);
         vector unsigned char pix1r = vec_ld(7, pix1);
         vector unsigned char pix2l = vec_ld(0, pix2);
@@ -376,21 +373,21 @@ static int sse8_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size, in
         t2 = vec_and(vec_perm(pix2l, pix2r, perm2), permclear);
 
         /* Since we want to use unsigned chars, we can take advantage
-           of the fact that abs(a-b)^2 = (a-b)^2. */
+         * of the fact that abs(a - b) ^ 2 = (a - b) ^ 2. */
 
-        /* Calculate abs differences vector */
+        /* Calculate abs differences vector. */
         t3 = vec_max(t1, t2);
         t4 = vec_min(t1, t2);
         t5 = vec_sub(t3, t4);
 
-        /* Square the values and add them to our sum */
+        /* Square the values and add them to our sum. */
         sum = vec_msum(t5, t5, sum);
 
         pix1 += line_size;
         pix2 += line_size;
     }
 
-    /* Sum up the four partial sums, and put the result into s */
+    /* Sum up the four partial sums, and put the result into s. */
     sumsqr = vec_sums((vector signed int) sum, (vector signed int) zero);
     sumsqr = vec_splat(sumsqr, 3);
     vec_ste(sumsqr, 0, &s);
@@ -398,11 +395,8 @@ static int sse8_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size, in
     return s;
 }
 
-/**
- * Sum of Squared Errors for a 16x16 block.
- * AltiVec-enhanced.
- * It's the sad16_altivec code above w/ squaring added.
- */
+/* Sum of Squared Errors for a 16x16 block, AltiVec-enhanced.
+ * It's the sad16_altivec code above w/ squaring added. */
 static int sse16_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size, int h)
 {
     int i;
@@ -416,28 +410,28 @@ static int sse16_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size, i
     sum = (vector unsigned int)vec_splat_u32(0);
 
     for (i = 0; i < h; i++) {
-        /* Read potentially unaligned pixels into t1 and t2 */
+        /* Read potentially unaligned pixels into t1 and t2. */
         vector unsigned char pix2l = vec_ld( 0, pix2);
         vector unsigned char pix2r = vec_ld(15, pix2);
         t1 = vec_ld(0, pix1);
         t2 = vec_perm(pix2l, pix2r, perm);
 
         /* Since we want to use unsigned chars, we can take advantage
-           of the fact that abs(a-b)^2 = (a-b)^2. */
+         * of the fact that abs(a - b) ^ 2 = (a - b) ^ 2. */
 
-        /* Calculate abs differences vector */
+        /* Calculate abs differences vector. */
         t3 = vec_max(t1, t2);
         t4 = vec_min(t1, t2);
         t5 = vec_sub(t3, t4);
 
-        /* Square the values and add them to our sum */
+        /* Square the values and add them to our sum. */
         sum = vec_msum(t5, t5, sum);
 
         pix1 += line_size;
         pix2 += line_size;
     }
 
-    /* Sum up the four partial sums, and put the result into s */
+    /* Sum up the four partial sums, and put the result into s. */
     sumsqr = vec_sums((vector signed int) sum, (vector signed int) zero);
     sumsqr = vec_splat(sumsqr, 3);
     vec_ste(sumsqr, 0, &s);
@@ -459,18 +453,18 @@ static int pix_sum_altivec(uint8_t * pix, int line_size)
     sad = (vector unsigned int)vec_splat_u32(0);
 
     for (i = 0; i < 16; i++) {
-        /* Read the potentially unaligned 16 pixels into t1 */
+        /* Read the potentially unaligned 16 pixels into t1. */
         vector unsigned char pixl = vec_ld( 0, pix);
         vector unsigned char pixr = vec_ld(15, pix);
         t1 = vec_perm(pixl, pixr, perm);
 
-        /* Add each 4 pixel group together and put 4 results into sad */
+        /* Add each 4 pixel group together and put 4 results into sad. */
         sad = vec_sum4s(t1, sad);
 
         pix += line_size;
     }
 
-    /* Sum up the four partial sums, and put the result into s */
+    /* Sum up the four partial sums, and put the result into s. */
     sumdiffs = vec_sums((vector signed int) sad, (vector signed int) zero);
     sumdiffs = vec_splat(sumdiffs, 3);
     vec_ste(sumdiffs, 0, &s);
@@ -487,6 +481,9 @@ static void get_pixels_altivec(int16_t *restrict block, const uint8_t *pixels, i
     vector signed short shorts;
 
     for (i = 0; i < 8; i++) {
+        /* Read potentially unaligned pixels.
+         * We're reading 16 pixels, and actually only want 8,
+         * but we simply ignore the extras. */
         // Read potentially unaligned pixels.
         // We're reading 16 pixels, and actually only want 8,
         // but we simply ignore the extras.
@@ -494,10 +491,10 @@ static void get_pixels_altivec(int16_t *restrict block, const uint8_t *pixels, i
         vector unsigned char pixr = vec_ld(7, pixels);
         bytes = vec_perm(pixl, pixr, perm);
 
-        // convert the bytes into shorts
+        // Convert the bytes into shorts.
         shorts = (vector signed short)vec_mergeh(zero, bytes);
 
-        // save the data to the block, we assume the block is 16-byte aligned
+        // Save the data to the block, we assume the block is 16-byte aligned.
         vec_st(shorts, i*16, (vector signed short*)block);
 
         pixels += line_size;
@@ -515,60 +512,59 @@ static void diff_pixels_altivec(int16_t *restrict block, const uint8_t *s1,
     vector signed short shorts1, shorts2;
 
     for (i = 0; i < 4; i++) {
-        // Read potentially unaligned pixels
-        // We're reading 16 pixels, and actually only want 8,
-        // but we simply ignore the extras.
+        /* Read potentially unaligned pixels.
+         * We're reading 16 pixels, and actually only want 8,
+         * but we simply ignore the extras. */
         pixl = vec_ld( 0, s1);
         pixr = vec_ld(15, s1);
         bytes = vec_perm(pixl, pixr, perm1);
 
-        // convert the bytes into shorts
+        // Convert the bytes into shorts.
         shorts1 = (vector signed short)vec_mergeh(zero, bytes);
 
-        // Do the same for the second block of pixels
+        // Do the same for the second block of pixels.
         pixl = vec_ld( 0, s2);
         pixr = vec_ld(15, s2);
         bytes = vec_perm(pixl, pixr, perm2);
 
-        // convert the bytes into shorts
+        // Convert the bytes into shorts.
         shorts2 = (vector signed short)vec_mergeh(zero, bytes);
 
-        // Do the subtraction
+        // Do the subtraction.
         shorts1 = vec_sub(shorts1, shorts2);
 
-        // save the data to the block, we assume the block is 16-byte aligned
+        // Save the data to the block, we assume the block is 16-byte aligned.
         vec_st(shorts1, 0, (vector signed short*)block);
 
         s1 += stride;
         s2 += stride;
         block += 8;
 
+        /* The code below is a copy of the code above...
+         * This is a manual unroll. */
 
-        // The code below is a copy of the code above... This is a manual
-        // unroll.
-
-        // Read potentially unaligned pixels
-        // We're reading 16 pixels, and actually only want 8,
-        // but we simply ignore the extras.
+        /* Read potentially unaligned pixels.
+         * We're reading 16 pixels, and actually only want 8,
+         * but we simply ignore the extras. */
         pixl = vec_ld( 0, s1);
         pixr = vec_ld(15, s1);
         bytes = vec_perm(pixl, pixr, perm1);
 
-        // convert the bytes into shorts
+        // Convert the bytes into shorts.
         shorts1 = (vector signed short)vec_mergeh(zero, bytes);
 
-        // Do the same for the second block of pixels
+        // Do the same for the second block of pixels.
         pixl = vec_ld( 0, s2);
         pixr = vec_ld(15, s2);
         bytes = vec_perm(pixl, pixr, perm2);
 
-        // convert the bytes into shorts
+        // Convert the bytes into shorts.
         shorts2 = (vector signed short)vec_mergeh(zero, bytes);
 
-        // Do the subtraction
+        // Do the subtraction.
         shorts1 = vec_sub(shorts1, shorts2);
 
-        // save the data to the block, we assume the block is 16-byte aligned
+        // Save the data to the block, we assume the block is 16-byte aligned.
         vec_st(shorts1, 0, (vector signed short*)block);
 
         s1 += stride;
@@ -595,14 +591,14 @@ static void add_bytes_altivec(uint8_t *dst, uint8_t *src, int w) {
     register int i;
     register vector unsigned char vdst, vsrc;
 
-    /* dst and src are 16 bytes-aligned (guaranteed) */
+    /* dst and src are 16 bytes-aligned (guaranteed). */
     for (i = 0 ; (i + 15) < w ; i+=16) {
         vdst = vec_ld(i, (unsigned char*)dst);
         vsrc = vec_ld(i, (unsigned char*)src);
         vdst = vec_add(vsrc, vdst);
         vec_st(vdst, i, (unsigned char*)dst);
     }
-    /* if w is not a multiple of 16 */
+    /* If w is not a multiple of 16. */
     for (; (i < w) ; i++) {
         dst[i] = src[i];
     }
@@ -643,8 +639,8 @@ static int hadamard8_diff8x8_altivec(/*MpegEncContext*/ void *s, uint8_t *dst, u
     dst1 = vec_ld(stride * i, dst);                                   \
     dst2 = vec_ld((stride * i) + 15, dst);                            \
     dstO = vec_perm(dst1, dst2, vec_lvsl(stride * i, dst));           \
-    /* promote the unsigned chars to signed shorts */                 \
-    /* we're in the 8x8 function, we only care for the first 8 */     \
+    /* Promote the unsigned chars to signed shorts. */                \
+    /* We're in the 8x8 function, we only care for the first 8. */    \
     srcV = (vector signed short)vec_mergeh((vector signed char)vzero, \
            (vector signed char)srcO);                                 \
     dstV = (vector signed short)vec_mergeh((vector signed char)vzero, \
@@ -713,24 +709,23 @@ static int hadamard8_diff8x8_altivec(/*MpegEncContext*/ void *s, uint8_t *dst, u
 }
 
 /*
-16x8 works with 16 elements; it allows to avoid replicating loads, and
-give the compiler more rooms for scheduling.  It's only used from
-inside hadamard8_diff16_altivec.
-
-Unfortunately, it seems gcc-3.3 is a bit dumb, and the compiled code has a LOT
-of spill code, it seems gcc (unlike xlc) cannot keep everything in registers
-by itself. The following code include hand-made registers allocation. It's not
-clean, but on a 7450 the resulting code is much faster (best case fall from
-700+ cycles to 550).
-
-xlc doesn't add spill code, but it doesn't know how to schedule for the 7450,
-and its code isn't much faster than gcc-3.3 on the 7450 (but uses 25% less
-instructions...)
-
-On the 970, the hand-made RA is still a win (around 690 vs. around 780), but
-xlc goes to around 660 on the regular C code...
-*/
-
+ * 16x8 works with 16 elements; it allows to avoid replicating loads, and
+ * gives the compiler more room for scheduling. It's only used from
+ * inside hadamard8_diff16_altivec.
+ *
+ * Unfortunately, it seems gcc-3.3 is a bit dumb, and the compiled code has
+ * a LOT of spill code, it seems gcc (unlike xlc) cannot keep everything in
+ * registers by itself. The following code includes hand-made register
+ * allocation. It's not clean, but on a 7450 the resulting code is much faster
+ * (best case falls from 700+ cycles to 550).
+ *
+ * xlc doesn't add spill code, but it doesn't know how to schedule for the
+ * 7450, and its code isn't much faster than gcc-3.3 on the 7450 (but uses
+ * 25% fewer instructions...)
+ *
+ * On the 970, the hand-made RA is still a win (around 690 vs. around 780),
+ * but xlc goes to around 660 on the regular C code...
+ */
 static int hadamard8_diff16x8_altivec(/*MpegEncContext*/ void *s, uint8_t *dst, uint8_t *src, int stride, int h) {
     int sum;
     register vector signed short
@@ -805,7 +800,7 @@ static int hadamard8_diff16x8_altivec(/*MpegEncContext*/ void *s, uint8_t *dst,
     dst1 = vec_ld(stride * i, dst);                                   \
     dst2 = vec_ld((stride * i) + 16, dst);                            \
     dstO = vec_perm(dst1, dst2, vec_lvsl(stride * i, dst));           \
-    /* promote the unsigned chars to signed shorts */                 \
+    /* Promote the unsigned chars to signed shorts. */                \
     srcV = (vector signed short)vec_mergeh((vector signed char)vzero, \
            (vector signed char)srcO);                                 \
     dstV = (vector signed short)vec_mergeh((vector signed char)vzero, \

libavcodec/ppc/dsputil_ppc.c

@@ -32,24 +32,23 @@
 
 /* ***** WARNING ***** WARNING ***** WARNING ***** */
 /*
-clear_blocks_dcbz32_ppc will not work properly on PowerPC processors with a
-cache line size not equal to 32 bytes.
-Fortunately all processor used by Apple up to at least the 7450 (aka second
-generation G4) use 32 bytes cache line.
-This is due to the use of the 'dcbz' instruction. It simply clear to zero a
-single cache line, so you need to know the cache line size to use it !
-It's absurd, but it's fast...
-
-update 24/06/2003 : Apple released yesterday the G5, with a PPC970. cache line
-size: 128 bytes. Oups.
-The semantic of dcbz was changed, it always clear 32 bytes. so the function
-below will work, but will be slow. So I fixed check_dcbz_effect to use dcbzl,
-which is defined to clear a cache line (as dcbz before). So we still can
-distinguish, and use dcbz (32 bytes) or dcbzl (one cache line) as required.
-
-see <http://developer.apple.com/technotes/tn/tn2087.html>
-and <http://developer.apple.com/technotes/tn/tn2086.html>
-*/
+ * clear_blocks_dcbz32_ppc will not work properly on PowerPC processors with
+ * a cache line size not equal to 32 bytes. Fortunately all processors used
+ * by Apple up to at least the 7450 (AKA second generation G4) use 32-byte
+ * cache lines. This is due to the use of the 'dcbz' instruction. It simply
+ * clears a single cache line to zero, so you need to know the cache line
+ * size to use it! It's absurd, but it's fast...
+ *
+ * update 24/06/2003: Apple released the G5 yesterday, with a PPC970.
+ * cache line size: 128 bytes. Oups.
+ * The semantics of dcbz was changed, it always clears 32 bytes. So the function
+ * below will work, but will be slow. So I fixed check_dcbz_effect to use dcbzl,
+ * which is defined to clear a cache line (as dcbz before). So we can still
+ * distinguish, and use dcbz (32 bytes) or dcbzl (one cache line) as required.
+ *
+ * see <http://developer.apple.com/technotes/tn/tn2087.html>
+ * and <http://developer.apple.com/technotes/tn/tn2086.html>
+ */
 static void clear_blocks_dcbz32_ppc(int16_t *blocks)
 {
     register int misal = ((unsigned long)blocks & 0x00000010);
@@ -73,17 +72,17 @@ static void clear_blocks_dcbz32_ppc(int16_t *blocks)
     }
 }
 
-/* same as above, when dcbzl clear a whole 128B cache line
-   i.e. the PPC970 aka G5 */
+/* Same as above, when dcbzl clears a whole 128 bytes cache line
+ * i.e. the PPC970 AKA G5. */
 #if HAVE_DCBZL
 static void clear_blocks_dcbz128_ppc(int16_t *blocks)
 {
     register int misal = ((unsigned long)blocks & 0x0000007f);
     register int i = 0;
     if (misal) {
-        // we could probably also optimize this case,
-        // but there's not much point as the machines
-        // aren't available yet (2003-06-26)
+        /* We could probably also optimize this case,
+         * but there's not much point as the machines
+         * aren't available yet (2003-06-26). */
         memset(blocks, 0, sizeof(int16_t)*6*64);
     }
     else
@@ -99,11 +98,10 @@ static void clear_blocks_dcbz128_ppc(int16_t *blocks)
 #endif
 
 #if HAVE_DCBZL
-/* check dcbz report how many bytes are set to 0 by dcbz */
-/* update 24/06/2003 : replace dcbz by dcbzl to get
-   the intended effect (Apple "fixed" dcbz)
-   unfortunately this cannot be used unless the assembler
-   knows about dcbzl ... */
+/* Check dcbz report how many bytes are set to 0 by dcbz. */
+/* update 24/06/2003: Replace dcbz by dcbzl to get the intended effect
+ * (Apple "fixed" dcbz). Unfortunately this cannot be used unless the
+ * assembler knows about dcbzl ... */
 static long check_dcbzl_effect(void)
 {
     register char *fakedata = av_malloc(1024);
@@ -120,8 +118,8 @@ static long check_dcbzl_effect(void)
 
     memset(fakedata, 0xFF, 1024);
 
-    /* below the constraint "b" seems to mean "Address base register"
-       in gcc-3.3 / RS/6000 speaks. seems to avoid using r0, so.... */
+    /* Below the constraint "b" seems to mean "address base register"
+     * in gcc-3.3 / RS/6000 speaks. Seems to avoid using r0, so.... */
     __asm__ volatile("dcbzl %0, %1" : : "b" (fakedata_middle), "r" (zero));
 
     for (i = 0; i < 1024 ; i ++) {
@@ -144,7 +142,7 @@ av_cold void ff_dsputil_init_ppc(DSPContext *c, AVCodecContext *avctx)
 {
     const int high_bit_depth = avctx->bits_per_raw_sample > 8;
 
-    // Common optimizations whether AltiVec is available or not
+    // common optimizations whether AltiVec is available or not
     if (!high_bit_depth) {
     switch (check_dcbzl_effect()) {
         case 32:

libavcodec/ppc/fdct_altivec.c

@@ -259,11 +259,10 @@ void ff_fdct_altivec(int16_t *block)
 #undef MERGE_S16
     /* }}} */
 
+    /* Some of the initial calculations can be done as vector short
+     * before conversion to vector float.  The following code section
+     * takes advantage of this. */
 
-/* Some of the initial calculations can be done as vector short before
- * conversion to vector float.  The following code section takes advantage
- * of this.
- */
     /* fdct rows {{{ */
     x0 = ((vector float)vec_add(vs16(b00), vs16(b70)));
     x7 = ((vector float)vec_sub(vs16(b00), vs16(b70)));

libavcodec/ppc/fft_altivec.c

@@ -27,12 +27,12 @@
 #include "libavcodec/fft.h"
 
 /**
- * Do a complex FFT with the parameters defined in ff_fft_init(). The
- * input data must be permuted before with s->revtab table. No
- * 1.0/sqrt(n) normalization is done.
- * AltiVec-enabled
- * This code assumes that the 'z' pointer is 16 bytes-aligned
- * It also assumes all FFTComplex are 8 bytes-aligned pair of float
+ * Do a complex FFT with the parameters defined in ff_fft_init().
+ * The input data must be permuted before with s->revtab table.
+ * No 1.0 / sqrt(n) normalization is done.
+ * AltiVec-enabled:
+ * This code assumes that the 'z' pointer is 16 bytes-aligned.
+ * It also assumes all FFTComplex are 8 bytes-aligned pairs of floats.
  */
 
 void ff_fft_calc_altivec(FFTContext *s, FFTComplex *z);

libavcodec/ppc/gmc_altivec.c

 /*
- * GMC (Global Motion Compensation)
- * AltiVec-enabled
+ * GMC (Global Motion Compensation), AltiVec-enabled
+ *
  * Copyright (c) 2003 Romain Dolbeau <romain@dolbeau.org>
  *
  * This file is part of Libav.
@@ -25,10 +25,8 @@
 #include "libavutil/ppc/util_altivec.h"
 #include "dsputil_altivec.h"
 
-/*
-  altivec-enhanced gmc1. ATM this code assume stride is a multiple of 8,
-  to preserve proper dst alignment.
-*/
+/* AltiVec-enhanced gmc1. ATM this code assumes stride is a multiple of 8
+ * to preserve proper dst alignment. */
 void ff_gmc1_altivec(uint8_t *dst /* align 8 */, uint8_t *src /* align1 */, int stride, int h, int x16, int y16, int rounder)
 {
     const DECLARE_ALIGNED(16, unsigned short, rounder_a) = rounder;
@@ -56,18 +54,16 @@ void ff_gmc1_altivec(uint8_t *dst /* align 8 */, uint8_t *src /* align1 */, int
 
     rounderV = vec_splat((vec_u16)vec_lde(0, &rounder_a), 0);
 
-    // we'll be able to pick-up our 9 char elements
-    // at src from those 32 bytes
-    // we load the first batch here, as inside the loop
-    // we can re-use 'src+stride' from one iteration
-    // as the 'src' of the next.
+    /* we'll be able to pick-up our 9 char elements at src from those
+     * 32 bytes we load the first batch here, as inside the loop we can
+     * reuse 'src + stride' from one iteration as the 'src' of the next. */
     src_0 = vec_ld(0, src);
     src_1 = vec_ld(16, src);
     srcvA = vec_perm(src_0, src_1, vec_lvsl(0, src));
 
     if (src_really_odd != 0x0000000F) {
-        // if src & 0xF == 0xF, then (src+1) is properly aligned
-        // on the second vector.
+        /* If src & 0xF == 0xF, then (src + 1) is properly aligned
+         * on the second vector. */
         srcvB = vec_perm(src_0, src_1, vec_lvsl(1, src));
     } else {
         srcvB = src_1;
@@ -81,17 +77,16 @@ void ff_gmc1_altivec(uint8_t *dst /* align 8 */, uint8_t *src /* align1 */, int
 
         dstv = vec_ld(0, dst);
 
-        // we we'll be able to pick-up our 9 char elements
-        // at src + stride from those 32 bytes
-        // then reuse the resulting 2 vectors srvcC and srcvD
-        // as the next srcvA and srcvB
+        /* We'll be able to pick-up our 9 char elements at src + stride from
+         * those 32 bytes then reuse the resulting 2 vectors srvcC and srcvD
+         * as the next srcvA and srcvB. */
         src_0 = vec_ld(stride + 0, src);
         src_1 = vec_ld(stride + 16, src);
         srcvC = vec_perm(src_0, src_1, vec_lvsl(stride + 0, src));
 
         if (src_really_odd != 0x0000000F) {
-            // if src & 0xF == 0xF, then (src+1) is properly aligned
-            // on the second vector.
+            /* If src & 0xF == 0xF, then (src + 1) is properly aligned
+             * on the second vector. */
             srcvD = vec_perm(src_0, src_1, vec_lvsl(stride + 1, src));
         } else {
             srcvD = src_1;
@@ -100,10 +95,9 @@ void ff_gmc1_altivec(uint8_t *dst /* align 8 */, uint8_t *src /* align1 */, int
         srcvC = vec_mergeh(vczero, srcvC);
         srcvD = vec_mergeh(vczero, srcvD);
 
-
-        // OK, now we (finally) do the math :-)
-        // those four instructions replaces 32 int muls & 32 int adds.
-        // isn't AltiVec nice ?
+        /* OK, now we (finally) do the math :-)
+         * Those four instructions replace 32 int muls & 32 int adds.
+         * Isn't AltiVec nice? */
         tempA = vec_mladd((vector unsigned short)srcvA, Av, rounderV);
         tempB = vec_mladd((vector unsigned short)srcvB, Bv, tempA);
         tempC = vec_mladd((vector unsigned short)srcvC, Cv, tempB);

libavcodec/ppc/idct_altivec.c

@@ -18,24 +18,19 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-/*
- * NOTE: This code is based on GPL code from the libmpeg2 project.  The
+/* NOTE: This code is based on GPL code from the libmpeg2 project.  The
  * author, Michel Lespinasses, has given explicit permission to release
  * under LGPL as part of Libav.
- */
-
-/*
+ *
  * Libav integration by Dieter Shirley
  *
  * This file is a direct copy of the AltiVec IDCT module from the libmpeg2
  * project.  I've deleted all of the libmpeg2-specific code, renamed the
  * functions and reordered the function parameters.  The only change to the
  * IDCT function itself was to factor out the partial transposition, and to
- * perform a full transpose at the end of the function.
- */
-
+ * perform a full transpose at the end of the function. */
 
-#include <stdlib.h>                                      /* malloc(), free() */
+#include <stdlib.h>
 #include <string.h>
 #include "config.h"
 #if HAVE_ALTIVEC_H

libavcodec/ppc/int_altivec.c

@@ -19,9 +19,9 @@
  */
 
 /**
- ** @file
- ** integer misc ops.
- **/
+ * @file
+ * miscellaneous integer operations
+ */
 
 #include "config.h"
 #if HAVE_ALTIVEC_H
@@ -43,8 +43,8 @@ static int ssd_int8_vs_int16_altivec(const int8_t *pix1, const int16_t *pix2,
             int32_t score[4];
           } u;
     u.vscore = vec_splat_s32(0);
-//
-//XXX lazy way, fix it later
+
+// XXX lazy way, fix it later
 
 #define vec_unaligned_load(b) \
     vec_perm(vec_ld(0,b),vec_ld(15,b),vec_lvsl(0, b));
@@ -52,12 +52,12 @@ static int ssd_int8_vs_int16_altivec(const int8_t *pix1, const int16_t *pix2,
     size16 = size >> 4;
     while(size16) {
 //        score += (pix1[i]-pix2[i])*(pix1[i]-pix2[i]);
-        //load pix1 and the first batch of pix2
+        // load pix1 and the first batch of pix2
 
         vpix1 = vec_unaligned_load(pix1);
         vpix2 = vec_unaligned_load(pix2);
         pix2 += 8;
-        //unpack
+        // unpack
         vpix1h = vec_unpackh(vpix1);
         vdiff  = vec_sub(vpix1h, vpix2);
         vpix1l = vec_unpackl(vpix1);