Fixed converters and added comments for better readability

2 files changed, 48 insertions, 20 deletions

diff --git a/host/lib/convert/sse2_fc32_to_sc16.cpp b/host/lib/convert/sse2_fc32_to_sc16.cpp
index f5a2b7610..a83e9b46c 100644
--- a/host/lib/convert/sse2_fc32_to_sc16.cpp
+++ b/host/lib/convert/sse2_fc32_to_sc16.cpp
@@ -27,6 +27,7 @@ DECLARE_CONVERTER(fc32, 1, sc16_item32_le, 1, PRIORITY_SIMD){
 
     const __m128 scalar = _mm_set_ps1(float(scale_factor));
 
+    // this macro converts values faster by using SSE intrinsics to convert 4 values at a time
     #define convert_fc32_1_to_item32_1_nswap_guts(_al_)                 \
     for (; i+3 < nsamps; i+=4){                                         \
         /* load from input */                                           \
@@ -48,19 +49,25 @@ DECLARE_CONVERTER(fc32, 1, sc16_item32_le, 1, PRIORITY_SIMD){
 
     size_t i = 0;
 
-    //dispatch according to alignment
+    // need to dispatch according to alignment for fastest conversion
     switch (size_t(input) & 0xf){
+    case 0x0:
+        // the data is 16-byte aligned, so do the fast processing of the bulk of the samples
+        convert_fc32_1_to_item32_1_nswap_guts(_)
+        break;
     case 0x8:
+        // the first sample is 8-byte aligned - process it to align the remainder of the samples to 16-bytes
         xx_to_item32_sc16<uhd::htowx>(input, output, 1, scale_factor);
         i++;
-        break;
-    case 0x0:
+        // do faster processing of the bulk of the samples now that we are 16-byte aligned
         convert_fc32_1_to_item32_1_nswap_guts(_)
         break;
-    default: convert_fc32_1_to_item32_1_nswap_guts(u_)
+    default:
+        // we are not 8 or 16-byte aligned, so do fast processing with the unaligned load
+        convert_fc32_1_to_item32_1_nswap_guts(u_)
     }
 
-    //convert remainder
+    // convert any remaining samples
     xx_to_item32_sc16<uhd::htowx>(input+i, output+i, nsamps-i, scale_factor);
 }
 
@@ -70,6 +77,7 @@ DECLARE_CONVERTER(fc32, 1, sc16_item32_be, 1, PRIORITY_SIMD){
 
     const __m128 scalar = _mm_set_ps1(float(scale_factor));
 
+    // this macro converts values faster by using SSE intrinsics to convert 4 values at a time
     #define convert_fc32_1_to_item32_1_bswap_guts(_al_)                 \
     for (; i+3 < nsamps; i+=4){                                         \
         /* load from input */                                           \
@@ -90,18 +98,24 @@ DECLARE_CONVERTER(fc32, 1, sc16_item32_be, 1, PRIORITY_SIMD){
 
     size_t i = 0;
 
-    //dispatch according to alignment
+    // need to dispatch according to alignment for fastest conversion
     switch (size_t(input) & 0xf){
+    case 0x0:
+        // the data is 16-byte aligned, so do the fast processing of the bulk of the samples
+        convert_fc32_1_to_item32_1_bswap_guts(_)
     case 0x8:
+        // the first value is 8-byte aligned - process it and prepare the bulk of the data for fast conversion
         xx_to_item32_sc16<uhd::htonx>(input, output, 1, scale_factor);
         i++;
-        break;
-    case 0x0:
+        // do faster processing of the remaining samples now that we are 16-byte aligned
         convert_fc32_1_to_item32_1_bswap_guts(_)
         break;
-    default: convert_fc32_1_to_item32_1_bswap_guts(u_)
+        break;
+    default:
+        // we are not 8 or 16-byte aligned, so do fast processing with the unaligned load
+        convert_fc32_1_to_item32_1_bswap_guts(u_)
     }
 
-    //convert remainder
+    // convert any remaining samples
     xx_to_item32_sc16<uhd::htonx>(input+i, output+i, nsamps-i, scale_factor);
 }
diff --git a/host/lib/convert/sse2_sc16_to_fc32.cpp b/host/lib/convert/sse2_sc16_to_fc32.cpp
index 7a9860970..0ac7f1798 100644
--- a/host/lib/convert/sse2_sc16_to_fc32.cpp
+++ b/host/lib/convert/sse2_sc16_to_fc32.cpp
@@ -28,6 +28,7 @@ DECLARE_CONVERTER(sc16_item32_le, 1, fc32, 1, PRIORITY_SIMD){
     const __m128 scalar = _mm_set_ps1(float(scale_factor)/(1 << 16));
     const __m128i zeroi = _mm_setzero_si128();
 
+    // this macro converts values faster by using SSE intrinsics to convert 4 values at a time
     #define convert_item32_1_to_fc32_1_nswap_guts(_al_)                 \
     for (; i+3 < nsamps; i+=4){                                         \
         /* load from input */                                           \
@@ -50,19 +51,25 @@ DECLARE_CONVERTER(sc16_item32_le, 1, fc32, 1, PRIORITY_SIMD){
 
     size_t i = 0;
 
-    //dispatch according to alignment
+    // need to dispatch according to alignment for fastest conversion
     switch (size_t(output) & 0xf){
+    case 0x0:
+        // the data is 16-byte aligned, so do the fast processing of the bulk of the samples
+        convert_item32_1_to_fc32_1_nswap_guts(_)
+        break;
     case 0x8:
+        // the first sample is 8-byte aligned - process it to align the remainder of the samples to 16-bytes
         item32_sc16_to_xx<uhd::htowx>(input, output, 1, scale_factor);
         i++;
-        break;
-    case 0x0:
+        // do faster processing of the bulk of the samples now that we are 16-byte aligned
         convert_item32_1_to_fc32_1_nswap_guts(_)
         break;
-    default: convert_item32_1_to_fc32_1_nswap_guts(u_)
+    default:
+        // we are not 8 or 16-byte aligned, so do fast processing with the unaligned load and store
+        convert_item32_1_to_fc32_1_nswap_guts(u_)
     }
 
-    //convert remainder
+    // convert any remaining samples
     item32_sc16_to_xx<uhd::htowx>(input+i, output+i, nsamps-i, scale_factor);
 }
 
@@ -73,6 +80,7 @@ DECLARE_CONVERTER(sc16_item32_be, 1, fc32, 1, PRIORITY_SIMD){
     const __m128 scalar = _mm_set_ps1(float(scale_factor)/(1 << 16));
     const __m128i zeroi = _mm_setzero_si128();
 
+    // this macro converts values faster by using SSE intrinsics to convert 4 values at a time
     #define convert_item32_1_to_fc32_1_bswap_guts(_al_)                 \
     for (; i+3 < nsamps; i+=4){                                         \
         /* load from input */                                           \
@@ -94,18 +102,24 @@ DECLARE_CONVERTER(sc16_item32_be, 1, fc32, 1, PRIORITY_SIMD){
 
     size_t i = 0;
 
-    //dispatch according to alignment
+    // need to dispatch according to alignment for fastest conversion
     switch (size_t(output) & 0xf){
+    case 0x0:
+        // the data is 16-byte aligned, so do the fast processing of the bulk of the samples
+        convert_item32_1_to_fc32_1_bswap_guts(_)
+        break;
     case 0x8:
+        // the first sample is 8-byte aligned - process it to align the remainder of the samples to 16-bytes
         item32_sc16_to_xx<uhd::htonx>(input, output, 1, scale_factor);
         i++;
-        break;
-    case 0x0:
+        // do faster processing of the bulk of the samples now that we are 16-byte aligned
         convert_item32_1_to_fc32_1_bswap_guts(_)
         break;
-    default: convert_item32_1_to_fc32_1_bswap_guts(u_)
+    default:
+        // we are not 8 or 16-byte aligned, so do fast processing with the unaligned load and store
+        convert_item32_1_to_fc32_1_bswap_guts(u_)
     }
 
-    //convert remainder
+    // convert any remaining samples
     item32_sc16_to_xx<uhd::htonx>(input+i, output+i, nsamps-i, scale_factor);
 }