LJpegDecompressor: make 'trailing pixels' workaround less special

Looks like not specializing all of the loops but just peeling it from the innermost loop is good-enough. ``` Comparing /home/lebedevri/rawspeed/build-Clang18-release/src/utilities/rsbench/rsbench-old to /home/lebedevri/rawspeed/build-Clang18-release/src/utilities/rsbench/rsbench Benchmark Time CPU Time Old Time New CPU Old CPU New -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ./Adobe DNG Converter/Canon EOS 5D Mark III/5G4A9394-compressed-lossless.DNG/threads:32/process_time/real_time_pvalue 0.0806 0.0776 U Test, Repetitions: 27 vs 27 ./Adobe DNG Converter/Canon EOS 5D Mark III/5G4A9394-compressed-lossless.DNG/threads:32/process_time/real_time_mean -0.0149 -0.0146 12 11 367 362 ./Adobe DNG Converter/Canon EOS 5D Mark III/5G4A9394-compressed-lossless.DNG/threads:32/process_time/real_time_median -0.0134 -0.0125 12 11 364 360 ./Adobe DNG Converter/Canon EOS 5D Mark III/5G4A9394-compressed-lossless.DNG/threads:32/process_time/real_time_stddev -0.1154 -0.1142 0 0 12 11 ./Adobe DNG Converter/Canon EOS 5D Mark III/5G4A9394-compressed-lossless.DNG/threads:32/process_time/real_time_cv -0.1020 -0.1011 0 0 0 0 ./Adobe DNG Converter/Canon EOS 5D Mark III/5G4A9395-compressed-lossless.DNG/threads:32/process_time/real_time_pvalue 0.4675 0.4999 U Test, Repetitions: 27 vs 27 ./Adobe DNG Converter/Canon EOS 5D Mark III/5G4A9395-compressed-lossless.DNG/threads:32/process_time/real_time_mean -0.0061 -0.0052 15 15 484 481 ./Adobe DNG Converter/Canon EOS 5D Mark III/5G4A9395-compressed-lossless.DNG/threads:32/process_time/real_time_median -0.0127 -0.0130 15 15 483 477 ./Adobe DNG Converter/Canon EOS 5D Mark III/5G4A9395-compressed-lossless.DNG/threads:32/process_time/real_time_stddev -0.3251 -0.3283 1 0 20 14 ./Adobe DNG Converter/Canon EOS 5D Mark III/5G4A9395-compressed-lossless.DNG/threads:32/process_time/real_time_cv -0.3210 -0.3248 0 0 0 0 ./Adobe DNG Converter/Canon EOS 5D Mark IV/B13A0729.dng/threads:32/process_time/real_time_pvalue 0.4363 0.3776 U Test, Repetitions: 27 vs 27 ./Adobe DNG Converter/Canon EOS 5D Mark IV/B13A0729.dng/threads:32/process_time/real_time_mean -0.0021 -0.0021 30 30 946 945 ./Adobe DNG Converter/Canon EOS 5D Mark IV/B13A0729.dng/threads:32/process_time/real_time_median -0.0049 -0.0061 30 30 944 938 ./Adobe DNG Converter/Canon EOS 5D Mark IV/B13A0729.dng/threads:32/process_time/real_time_stddev +0.2897 +0.3269 1 1 17 23 ./Adobe DNG Converter/Canon EOS 5D Mark IV/B13A0729.dng/threads:32/process_time/real_time_cv +0.2925 +0.3296 0 0 0 0 ./Fujifilm/X100S/fujifilm-x100s-daylight-DSCF9505.dng/threads:32/process_time/real_time_pvalue 0.0002 0.0001 U Test, Repetitions: 27 vs 27 ./Fujifilm/X100S/fujifilm-x100s-daylight-DSCF9505.dng/threads:32/process_time/real_time_mean +0.0377 +0.0377 4 4 127 131 ./Fujifilm/X100S/fujifilm-x100s-daylight-DSCF9505.dng/threads:32/process_time/real_time_median +0.0351 +0.0366 4 4 125 129 ./Fujifilm/X100S/fujifilm-x100s-daylight-DSCF9505.dng/threads:32/process_time/real_time_stddev +0.2754 +0.2903 0 0 3 4 ./Fujifilm/X100S/fujifilm-x100s-daylight-DSCF9505.dng/threads:32/process_time/real_time_cv +0.2292 +0.2435 0 0 0 0 ./Samsung/Galaxy S21 Ultra/20230712_115041.dng/threads:32/process_time/real_time_pvalue 0.0000 0.0002 U Test, Repetitions: 27 vs 27 ./Samsung/Galaxy S21 Ultra/20230712_115041.dng/threads:32/process_time/real_time_mean -0.0016 -0.0011 150 150 150 150 ./Samsung/Galaxy S21 Ultra/20230712_115041.dng/threads:32/process_time/real_time_median -0.0013 -0.0010 150 150 150 150 ./Samsung/Galaxy S21 Ultra/20230712_115041.dng/threads:32/process_time/real_time_stddev +0.2080 -0.0552 0 0 0 0 ./Samsung/Galaxy S21 Ultra/20230712_115041.dng/threads:32/process_time/real_time_cv +0.2099 -0.0542 0 0 0 0 ./Samsung/Galaxy S23 Ultra/20231214_130645.dng/threads:32/process_time/real_time_pvalue 0.0448 0.8763 U Test, Repetitions: 27 vs 27 ./Samsung/Galaxy S23 Ultra/20231214_130645.dng/threads:32/process_time/real_time_mean -0.0020 +0.0015 583 582 6974 6985 ./Samsung/Galaxy S23 Ultra/20231214_130645.dng/threads:32/process_time/real_time_median -0.0022 -0.0018 582 581 7190 7177 ./Samsung/Galaxy S23 Ultra/20231214_130645.dng/threads:32/process_time/real_time_stddev +0.2048 -0.0249 3 4 1162 1133 ./Samsung/Galaxy S23 Ultra/20231214_130645.dng/threads:32/process_time/real_time_cv +0.2073 -0.0264 0 0 0 0 ./Sony/ILCE-7RM5/7RM5-S35-LosslessCompressedMedium.ARW/threads:32/process_time/real_time_pvalue 0.0234 0.0280 U Test, Repetitions: 27 vs 27 ./Sony/ILCE-7RM5/7RM5-S35-LosslessCompressedMedium.ARW/threads:32/process_time/real_time_mean -0.0142 -0.0145 29 29 920 907 ./Sony/ILCE-7RM5/7RM5-S35-LosslessCompressedMedium.ARW/threads:32/process_time/real_time_median -0.0237 -0.0215 29 29 914 895 ./Sony/ILCE-7RM5/7RM5-S35-LosslessCompressedMedium.ARW/threads:32/process_time/real_time_stddev +0.0196 -0.0155 1 1 26 26 ./Sony/ILCE-7RM5/7RM5-S35-LosslessCompressedMedium.ARW/threads:32/process_time/real_time_cv +0.0342 -0.0010 0 0 0 0 OVERALL_GEOMEAN -0.0006 +0.0007 0 0 1 1 ```
darktable-org · Mar 25, 2024 · 2a3a9e9 · 2a3a9e9
1 parent 55fbd20
commit 2a3a9e9
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Showing 2 changed files with 17 additions and 39 deletions.
diff --git a/src/librawspeed/decompressors/LJpegDecompressor.cpp b/src/librawspeed/decompressors/LJpegDecompressor.cpp
@@ -167,7 +167,7 @@ std::array<uint16_t, N_COMP> LJpegDecompressor::getInitialPreds() const {
   return preds;
 }
 
-template <int N_COMP, bool WeirdWidth>
+template <int N_COMP>
 void LJpegDecompressor::decodeRowN(
     Array1DRef<uint16_t> outRow, std::array<uint16_t, N_COMP> pred,
     std::array<std::reference_wrapper<const PrefixCodeDecoder<>>, N_COMP> ht,
@@ -187,10 +187,7 @@ void LJpegDecompressor::decodeRowN(
   }
 
   // Sometimes we also need to consume one more block, and produce part of it.
-  if /*constexpr*/ (WeirdWidth) {
-    // FIXME: evaluate i-cache implications due to this being compile-time.
-    static_assert(N_COMP > 1 || !WeirdWidth,
-                  "can't want part of 1-pixel-wide block");
+  if (trailingPixels != 0) {
     // Some rather esoteric DNG's have odd dimensions, e.g. width % 2 = 1.
     // We may end up needing just part of last N_COMP pixels.
     invariant(trailingPixels > 0);
@@ -218,8 +215,7 @@ void LJpegDecompressor::decodeRowN(
 }
 
 // N_COMP == number of components (2, 3 or 4)
-template <int N_COMP, bool WeirdWidth>
-ByteStream::size_type LJpegDecompressor::decodeN() const {
+template <int N_COMP> ByteStream::size_type LJpegDecompressor::decodeN() const {
   invariant(mRaw->getCpp() > 0);
   invariant(N_COMP > 0);
 
@@ -292,7 +288,7 @@ ByteStream::size_type LJpegDecompressor::decodeN() const {
                                /*index=*/0)
                      .getAsArray1DRef();
 
-      decodeRowN<N_COMP, WeirdWidth>(outRow, pred, ht, bs);
+      decodeRowN<N_COMP>(outRow, pred, ht, bs);
     }
 
     inputStream.skipBytes(bs.getStreamPosition());
@@ -302,34 +298,17 @@ ByteStream::size_type LJpegDecompressor::decodeN() const {
 }
 
 ByteStream::size_type LJpegDecompressor::decode() const {
-  if (trailingPixels == 0) {
-    switch (frame.cps) {
-    case 1:
-      return decodeN<1>();
-    case 2:
-      return decodeN<2>();
-    case 3:
-      return decodeN<3>();
-    case 4:
-      return decodeN<4>();
-    default:
-      __builtin_unreachable();
-    }
-  } else /* trailingPixels != 0 */ {
-    // FIXME: using different function just for one tile likely causes
-    // i-cache misses and whatnot. Need to check how not splitting it into
-    // two different functions affects performance of the normal case.
-    switch (frame.cps) {
-    // Naturally can't happen for CPS=1.
-    case 2:
-      return decodeN<2, /*WeirdWidth=*/true>();
-    case 3:
-      return decodeN<3, /*WeirdWidth=*/true>();
-    case 4:
-      return decodeN<4, /*WeirdWidth=*/true>();
-    default:
-      __builtin_unreachable();
-    }
+  switch (frame.cps) {
+  case 1:
+    return decodeN<1>();
+  case 2:
+    return decodeN<2>();
+  case 3:
+    return decodeN<3>();
+  case 4:
+    return decodeN<4>();
+  default:
+    __builtin_unreachable();
   }
 }
 

diff --git a/src/librawspeed/decompressors/LJpegDecompressor.h b/src/librawspeed/decompressors/LJpegDecompressor.h
@@ -75,14 +75,13 @@ class LJpegDecompressor final {
   template <int N_COMP>
   [[nodiscard]] std::array<uint16_t, N_COMP> getInitialPreds() const;
 
-  template <int N_COMP, bool WeirdWidth>
+  template <int N_COMP>
   __attribute__((always_inline)) inline void decodeRowN(
       Array1DRef<uint16_t> outRow, std::array<uint16_t, N_COMP> pred,
       std::array<std::reference_wrapper<const PrefixCodeDecoder<>>, N_COMP> ht,
       BitStreamerJPEG& bs) const;
 
-  template <int N_COMP, bool WeirdWidth = false>
-  [[nodiscard]] ByteStream::size_type decodeN() const;
+  template <int N_COMP> [[nodiscard]] ByteStream::size_type decodeN() const;
 
 public:
   LJpegDecompressor(RawImage img, iRectangle2D imgFrame, Frame frame,