build: Add explanatory comments to (optimization) blocks in the Makefiles

libavcodec/Makefile

@@ -26,7 +26,7 @@ OBJS = allcodecs.o                                                      \
        raw.o                                                            \
        utils.o                                                          \
 
-# parts needed for many different codecs
+# subsystems
 OBJS-$(CONFIG_AANDCTTABLES)            += aandcttab.o
 OBJS-$(CONFIG_AC3DSP)                  += ac3dsp.o
 OBJS-$(CONFIG_AUDIO_FRAME_QUEUE)       += audio_frame_queue.o

libavcodec/arm/Makefile

@@ -2,6 +2,7 @@ ARCH_HEADERS = mathops.h
 
 OBJS                                   += arm/fmtconvert_init_arm.o
 
+# subsystems
 OBJS-$(CONFIG_AC3DSP)                  += arm/ac3dsp_init_arm.o         \
                                           arm/ac3dsp_arm.o
 OBJS-$(CONFIG_AUDIODSP)                += arm/audiodsp_init_arm.o
@@ -27,6 +28,7 @@ OBJS-$(CONFIG_PIXBLOCKDSP)             += arm/pixblockdsp_init_arm.o
 OBJS-$(CONFIG_VIDEODSP)                += arm/videodsp_init_arm.o
 OBJS-$(CONFIG_VP3DSP)                  += arm/vp3dsp_init_arm.o
 
+# decoders/encoders
 OBJS-$(CONFIG_AAC_DECODER)             += arm/aacpsdsp_init_arm.o       \
                                           arm/sbrdsp_init_arm.o
 OBJS-$(CONFIG_APE_DECODER)             += arm/apedsp_init_arm.o
@@ -43,6 +45,9 @@ OBJS-$(CONFIG_RV30_DECODER)            += arm/rv34dsp_init_arm.o
 OBJS-$(CONFIG_RV40_DECODER)            += arm/rv34dsp_init_arm.o        \
                                           arm/rv40dsp_init_arm.o
 
+
+# ARMv5 optimizations
+# subsystems
 ARMV5TE-OBJS-$(CONFIG_IDCTDSP)         += arm/idctdsp_init_armv5te.o    \
                                           arm/simple_idct_armv5te.o
 ARMV5TE-OBJS-$(CONFIG_MPEGVIDEO)       += arm/mpegvideo_armv5te.o       \
@@ -50,8 +55,12 @@ ARMV5TE-OBJS-$(CONFIG_MPEGVIDEO)       += arm/mpegvideo_armv5te.o       \
 ARMV5TE-OBJS-$(CONFIG_VIDEODSP)        += arm/videodsp_init_armv5te.o   \
                                           arm/videodsp_armv5te.o
 
+# decoders/encoders
 ARMV5TE-OBJS-$(CONFIG_MLP_DECODER)     += arm/mlpdsp_armv5te.o
 
+
+# ARMv6 optimizations
+# subsystems
 ARMV6-OBJS-$(CONFIG_AC3DSP)            += arm/ac3dsp_armv6.o
 ARMV6-OBJS-$(CONFIG_HPELDSP)           += arm/hpeldsp_init_armv6.o      \
                                           arm/hpeldsp_armv6.o
@@ -63,6 +72,7 @@ ARMV6-OBJS-$(CONFIG_MPEGAUDIODSP)      += arm/mpegaudiodsp_fixed_armv6.o
 ARMV6-OBJS-$(CONFIG_MPEGVIDEOENC)      += arm/mpegvideoencdsp_armv6.o
 ARMV6-OBJS-$(CONFIG_PIXBLOCKDSP)       += arm/pixblockdsp_armv6.o
 
+# decoders/encoders
 ARMV6-OBJS-$(CONFIG_MLP_DECODER)       += arm/mlpdsp_armv6.o
 ARMV6-OBJS-$(CONFIG_STARTCODE)         += arm/startcode_armv6.o
 ARMV6-OBJS-$(CONFIG_VP7_DECODER)       += arm/vp8_armv6.o               \
@@ -72,17 +82,24 @@ ARMV6-OBJS-$(CONFIG_VP8_DECODER)       += arm/vp8_armv6.o               \
                                           arm/vp8dsp_init_armv6.o       \
                                           arm/vp8dsp_armv6.o
 
+
+# VFP optimizations
 VFP-OBJS                               += arm/fmtconvert_vfp.o
 
+# subsystems
 VFP-OBJS-$(CONFIG_FFT)                 += arm/fft_vfp.o
 VFP-OBJS-$(CONFIG_MDCT)                += arm/mdct_vfp.o
 VFP-OBJS-$(HAVE_ARMV6)                 += arm/fmtconvert_vfp_armv6.o
 
+# decoders/encoders
 VFP-OBJS-$(CONFIG_DCA_DECODER)         += arm/dcadsp_vfp.o              \
                                           arm/synth_filter_vfp.o
 
+
+# NEON optimizations
 NEON-OBJS                              += arm/fmtconvert_neon.o
 
+# subsystems
 NEON-OBJS-$(CONFIG_AC3DSP)             += arm/ac3dsp_neon.o
 NEON-OBJS-$(CONFIG_AUDIODSP)           += arm/audiodsp_init_neon.o      \
                                           arm/audiodsp_neon.o           \
@@ -108,6 +125,7 @@ NEON-OBJS-$(CONFIG_MPEGVIDEO)          += arm/mpegvideo_neon.o
 NEON-OBJS-$(CONFIG_RDFT)               += arm/rdft_neon.o
 NEON-OBJS-$(CONFIG_VP3DSP)             += arm/vp3dsp_neon.o
 
+# decoders/encoders
 NEON-OBJS-$(CONFIG_AAC_DECODER)        += arm/aacpsdsp_neon.o           \
                                           arm/sbrdsp_neon.o
 NEON-OBJS-$(CONFIG_APE_DECODER)        += arm/apedsp_neon.o

libavcodec/ppc/Makefile

@@ -1,5 +1,6 @@
 OBJS                                   += ppc/fmtconvert_altivec.o      \
 
+# subsystems
 OBJS-$(CONFIG_AUDIODSP)                += ppc/audiodsp.o
 OBJS-$(CONFIG_BLOCKDSP)                += ppc/blockdsp.o
 OBJS-$(CONFIG_FFT)                     += ppc/fft_init.o                \
@@ -20,6 +21,7 @@ OBJS-$(CONFIG_PIXBLOCKDSP)             += ppc/pixblockdsp.o
 OBJS-$(CONFIG_VIDEODSP)                += ppc/videodsp_ppc.o
 OBJS-$(CONFIG_VP3DSP)                  += ppc/vp3dsp_altivec.o
 
+# decoders/encoders
 OBJS-$(CONFIG_APE_DECODER)             += ppc/apedsp_altivec.o
 OBJS-$(CONFIG_SVQ1_ENCODER)            += ppc/svq1enc_altivec.o
 OBJS-$(CONFIG_VC1_DECODER)             += ppc/vc1dsp_altivec.o

libavcodec/x86/Makefile

@@ -1,6 +1,7 @@
 OBJS                                   += x86/constants.o               \
                                           x86/fmtconvert_init.o         \
 
+# subsystems
 OBJS-$(CONFIG_AC3DSP)                  += x86/ac3dsp_init.o
 OBJS-$(CONFIG_AUDIODSP)                += x86/audiodsp_init.o
 OBJS-$(CONFIG_BLOCKDSP)                += x86/blockdsp.o
@@ -30,6 +31,7 @@ OBJS-$(CONFIG_VIDEODSP)                += x86/videodsp_init.o
 OBJS-$(CONFIG_VP3DSP)                  += x86/vp3dsp_init.o
 OBJS-$(CONFIG_XMM_CLOBBER_TEST)        += x86/w64xmmtest.o
 
+# decoders/encoders
 OBJS-$(CONFIG_AAC_DECODER)             += x86/sbrdsp_init.o
 OBJS-$(CONFIG_APE_DECODER)             += x86/apedsp_init.o
 OBJS-$(CONFIG_CAVS_DECODER)            += x86/cavsdsp.o
@@ -52,6 +54,9 @@ OBJS-$(CONFIG_VP7_DECODER)             += x86/vp8dsp_init.o
 OBJS-$(CONFIG_VP8_DECODER)             += x86/vp8dsp_init.o
 OBJS-$(CONFIG_VP9_DECODER)             += x86/vp9dsp_init.o
 
+
+# GCC inline assembly optimizations
+# subsystems
 MMX-OBJS-$(CONFIG_AUDIODSP)            += x86/audiodsp_mmx.o
 MMX-OBJS-$(CONFIG_HPELDSP)             += x86/fpel_mmx.o                \
                                           x86/hpeldsp_mmx.o
@@ -60,13 +65,17 @@ MMX-OBJS-$(CONFIG_IDCTDSP)             += x86/idctdsp_mmx.o             \
                                           x86/simple_idct.o
 MMX-OBJS-$(CONFIG_QPELDSP)             += x86/fpel_mmx.o
 
+# decoders/encoders
 MMX-OBJS-$(CONFIG_MPEG4_DECODER)       += x86/idct_mmx_xvid.o           \
                                           x86/idct_sse2_xvid.o
 MMX-OBJS-$(CONFIG_VC1_DECODER)         += x86/vc1dsp_mmx.o
 
+
+# YASM optimizations
 YASM-OBJS                              += x86/deinterlace.o             \
                                           x86/fmtconvert.o              \
 
+# subsystems
 YASM-OBJS-$(CONFIG_AC3DSP)             += x86/ac3dsp.o
 YASM-OBJS-$(CONFIG_AUDIODSP)           += x86/audiodsp.o
 YASM-OBJS-$(CONFIG_BSWAPDSP)           += x86/bswapdsp.o
@@ -101,6 +110,7 @@ YASM-OBJS-$(CONFIG_QPELDSP)            += x86/qpeldsp.o                 \
 YASM-OBJS-$(CONFIG_VIDEODSP)           += x86/videodsp.o
 YASM-OBJS-$(CONFIG_VP3DSP)             += x86/vp3dsp.o
 
+# decoders/encoders
 YASM-OBJS-$(CONFIG_AAC_DECODER)        += x86/sbrdsp.o
 YASM-OBJS-$(CONFIG_APE_DECODER)        += x86/apedsp.o
 YASM-OBJS-$(CONFIG_DCA_DECODER)        += x86/dcadsp.o