all: Replace if (ARCH_FOO) checks by #if ARCH_FOO

This is more spec-compliant because it does not rely
on dead-code elimination by the compiler. Especially
MSVC has problems with this, as can be seen in
https://ffmpeg.org/pipermail/ffmpeg-devel/2022-May/296373.html
or
https://ffmpeg.org/pipermail/ffmpeg-devel/2022-May/297022.html

This commit does not eliminate every instance where we rely
on dead code elimination: It only tackles branching to
the initialization of arch-specific dsp code, not e.g. all
uses of CONFIG_ and HAVE_ checks. But maybe it is already
enough to compile FFmpeg with MSVC with whole-programm-optimizations
enabled (if one does not disable too many components).

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavcodec/aacdec_template.c

@@ -3550,8 +3550,9 @@ static void aacdec_init(AACContext *c)
 #endif
 
 #if !USE_FIXED
-    if(ARCH_MIPS)
-        ff_aacdec_init_mips(c);
+#if ARCH_MIPS
+    ff_aacdec_init_mips(c);
+#endif
 #endif /* !USE_FIXED */
 }
 /**

libavcodec/aacenc.c

@@ -1096,11 +1096,13 @@ static av_cold int aac_encode_init(AVCodecContext *avctx)
     s->abs_pow34   = abs_pow34_v;
     s->quant_bands = quantize_bands;
 
-    if (ARCH_X86)
-        ff_aac_dsp_init_x86(s);
+#if ARCH_X86
+    ff_aac_dsp_init_x86(s);
+#endif
 
-    if (HAVE_MIPSDSP)
-        ff_aac_coder_init_mips(s);
+#if HAVE_MIPSDSP
+    ff_aac_coder_init_mips(s);
+#endif
 
     ff_af_queue_init(avctx, &s->afq);
     ff_aac_tableinit();

libavcodec/aacpsdsp_template.c

@@ -221,13 +221,14 @@ av_cold void AAC_RENAME(ff_psdsp_init)(PSDSPContext *s)
     s->stereo_interpolate[1]  = ps_stereo_interpolate_ipdopd_c;
 
 #if !USE_FIXED
-    if (ARCH_ARM)
-        ff_psdsp_init_arm(s);
-    if (ARCH_AARCH64)
-        ff_psdsp_init_aarch64(s);
-    if (ARCH_MIPS)
-        ff_psdsp_init_mips(s);
-    if (ARCH_X86)
-        ff_psdsp_init_x86(s);
+#if ARCH_ARM
+    ff_psdsp_init_arm(s);
+#elif ARCH_AARCH64
+    ff_psdsp_init_aarch64(s);
+#elif ARCH_MIPS
+    ff_psdsp_init_mips(s);
+#elif ARCH_X86
+    ff_psdsp_init_x86(s);
+#endif
 #endif /* !USE_FIXED */
 }

libavcodec/aacsbr_template.c

@@ -1573,7 +1573,8 @@ static void aacsbr_func_ptr_init(AACSBRContext *c)
     c->sbr_hf_inverse_filter = sbr_hf_inverse_filter;
 
 #if !USE_FIXED
-    if(ARCH_MIPS)
-        ff_aacsbr_func_ptr_init_mips(c);
+#if ARCH_MIPS
+    ff_aacsbr_func_ptr_init_mips(c);
+#endif
 #endif
 }

libavcodec/ac3dsp.c

@@ -363,8 +363,9 @@ void ff_ac3dsp_downmix(AC3DSPContext *c, float **samples, float **matrix,
             c->downmix = ac3_downmix_5_to_1_symmetric_c;
         }
 
-        if (ARCH_X86)
-            ff_ac3dsp_set_downmix_x86(c);
+#if ARCH_X86
+        ff_ac3dsp_set_downmix_x86(c);
+#endif
     }
 
     if (c->downmix)
@@ -388,10 +389,11 @@ av_cold void ff_ac3dsp_init(AC3DSPContext *c, int bit_exact)
     c->downmix               = NULL;
     c->downmix_fixed         = NULL;
 
-    if (ARCH_ARM)
-        ff_ac3dsp_init_arm(c, bit_exact);
-    if (ARCH_X86)
-        ff_ac3dsp_init_x86(c, bit_exact);
-    if (ARCH_MIPS)
-        ff_ac3dsp_init_mips(c, bit_exact);
+#if ARCH_ARM
+    ff_ac3dsp_init_arm(c, bit_exact);
+#elif ARCH_X86
+    ff_ac3dsp_init_x86(c, bit_exact);
+#elif ARCH_MIPS
+    ff_ac3dsp_init_mips(c, bit_exact);
+#endif
 }

libavcodec/acelp_filters.c

@@ -152,6 +152,7 @@ void ff_acelp_filter_init(ACELPFContext *c)
     c->acelp_interpolatef                      = ff_acelp_interpolatef;
     c->acelp_apply_order_2_transfer_function   = ff_acelp_apply_order_2_transfer_function;
 
-    if(HAVE_MIPSFPU)
-        ff_acelp_filter_init_mips(c);
+#if HAVE_MIPSFPU
+    ff_acelp_filter_init_mips(c);
+#endif
 }

libavcodec/acelp_vectors.c

@@ -259,6 +259,7 @@ void ff_acelp_vectors_init(ACELPVContext *c)
 {
     c->weighted_vector_sumf   = ff_weighted_vector_sumf;
 
-    if(HAVE_MIPSFPU)
-        ff_acelp_vectors_init_mips(c);
+#if HAVE_MIPSFPU
+    ff_acelp_vectors_init_mips(c);
+#endif
 }

libavcodec/alacdsp.c

@@ -58,6 +58,7 @@ av_cold void ff_alacdsp_init(ALACDSPContext *c)
     c->append_extra_bits[0] =
     c->append_extra_bits[1] = append_extra_bits;
 
-    if (ARCH_X86)
-        ff_alacdsp_init_x86(c);
+#if ARCH_X86
+    ff_alacdsp_init_x86(c);
+#endif
 }

libavcodec/audiodsp.c

@@ -109,10 +109,11 @@ av_cold void ff_audiodsp_init(AudioDSPContext *c)
     c->vector_clip_int32   = vector_clip_int32_c;
     c->vector_clipf        = vector_clipf_c;
 
-    if (ARCH_ARM)
-        ff_audiodsp_init_arm(c);
-    if (ARCH_PPC)
-        ff_audiodsp_init_ppc(c);
-    if (ARCH_X86)
-        ff_audiodsp_init_x86(c);
+#if ARCH_ARM
+    ff_audiodsp_init_arm(c);
+#elif ARCH_PPC
+    ff_audiodsp_init_ppc(c);
+#elif ARCH_X86
+    ff_audiodsp_init_x86(c);
+#endif
 }

libavcodec/blockdsp.c

@@ -64,14 +64,15 @@ av_cold void ff_blockdsp_init(BlockDSPContext *c, AVCodecContext *avctx)
     c->fill_block_tab[0] = fill_block16_c;
     c->fill_block_tab[1] = fill_block8_c;
 
-    if (ARCH_ALPHA)
-        ff_blockdsp_init_alpha(c);
-    if (ARCH_ARM)
-        ff_blockdsp_init_arm(c);
-    if (ARCH_PPC)
-        ff_blockdsp_init_ppc(c);
-    if (ARCH_X86)
-        ff_blockdsp_init_x86(c, avctx);
-    if (ARCH_MIPS)
-        ff_blockdsp_init_mips(c);
+#if ARCH_ALPHA
+    ff_blockdsp_init_alpha(c);
+#elif ARCH_ARM
+    ff_blockdsp_init_arm(c);
+#elif ARCH_PPC
+    ff_blockdsp_init_ppc(c);
+#elif ARCH_X86
+    ff_blockdsp_init_x86(c, avctx);
+#elif ARCH_MIPS
+    ff_blockdsp_init_mips(c);
+#endif
 }