Avoid interger overflow in aom_blend_*_c()

BUG=b/69445855,b/69441422

Change-Id: Iaf5aba78dc39f01c87fb726611e674d34af6bffe

aom_dsp/blend_a64_mask.c

diff --git a/aom_dsp/blend_a64_mask.c b/aom_dsp/blend_a64_mask.c
index c35fa19..2abf098 100644
--- a/aom_dsp/blend_a64_mask.c
+++ b/aom_dsp/blend_a64_mask.c
@@ -41,40 +41,44 @@
   if (subw == 0 && subh == 0) {
     for (i = 0; i < h; ++i) {
       for (j = 0; j < w; ++j) {
-        const int m = mask[i * mask_stride + j];
-        dst[i * dst_stride + j] = AOM_BLEND_A64(m, src0[i * src0_stride + j],
-                                                src1[i * src1_stride + j]);
+        const int64_t m = mask[i * mask_stride + j];
+        dst[i * dst_stride + j] =
+            (int32_t)AOM_BLEND_A64(m, src0[i * src0_stride + j],
+                                   src1[i * src1_stride + j]);
       }
     }
   } else if (subw == 1 && subh == 1) {
     for (i = 0; i < h; ++i) {
       for (j = 0; j < w; ++j) {
-        const int m = ROUND_POWER_OF_TWO(
+        const int64_t m = ROUND_POWER_OF_TWO(
             mask[(2 * i) * mask_stride + (2 * j)] +
                 mask[(2 * i + 1) * mask_stride + (2 * j)] +
                 mask[(2 * i) * mask_stride + (2 * j + 1)] +
                 mask[(2 * i + 1) * mask_stride + (2 * j + 1)],
             2);
-        dst[i * dst_stride + j] = AOM_BLEND_A64(m, src0[i * src0_stride + j],
-                                                src1[i * src1_stride + j]);
+        dst[i * dst_stride + j] =
+            (int32_t)AOM_BLEND_A64(m, src0[i * src0_stride + j],
+                                   src1[i * src1_stride + j]);
       }
     }
   } else if (subw == 1 && subh == 0) {
     for (i = 0; i < h; ++i) {
       for (j = 0; j < w; ++j) {
-        const int m = AOM_BLEND_AVG(mask[i * mask_stride + (2 * j)],
-                                    mask[i * mask_stride + (2 * j + 1)]);
-        dst[i * dst_stride + j] = AOM_BLEND_A64(m, src0[i * src0_stride + j],
-                                                src1[i * src1_stride + j]);
+        const int64_t m = AOM_BLEND_AVG(mask[i * mask_stride + (2 * j)],
+                                        mask[i * mask_stride + (2 * j + 1)]);
+        dst[i * dst_stride + j] =
+            (int32_t)AOM_BLEND_A64(m, src0[i * src0_stride + j],
+                                   src1[i * src1_stride + j]);
       }
     }
   } else {
     for (i = 0; i < h; ++i) {
       for (j = 0; j < w; ++j) {
-        const int m = AOM_BLEND_AVG(mask[(2 * i) * mask_stride + j],
-                                    mask[(2 * i + 1) * mask_stride + j]);
-        dst[i * dst_stride + j] = AOM_BLEND_A64(m, src0[i * src0_stride + j],
-                                                src1[i * src1_stride + j]);
+        const int64_t m = AOM_BLEND_AVG(mask[(2 * i) * mask_stride + j],
+                                        mask[(2 * i + 1) * mask_stride + j]);
+        dst[i * dst_stride + j] =
+            (int32_t)AOM_BLEND_A64(m, src0[i * src0_stride + j],
+                                   src1[i * src1_stride + j]);
       }
     }
   }