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>

5 files changed, 30 insertions, 25 deletions

diff --git a/libswscale/rgb2rgb.c b/libswscale/rgb2rgb.c
index a7300f3ba4..b8be76913b 100644
--- a/libswscale/rgb2rgb.c
+++ b/libswscale/rgb2rgb.c
@@ -137,10 +137,11 @@ void (*yuyvtoyuv422)(uint8_t *ydst, uint8_t *udst, uint8_t *vdst,
 av_cold void ff_sws_rgb2rgb_init(void)
 {
     rgb2rgb_init_c();
-    if (ARCH_AARCH64)
-        rgb2rgb_init_aarch64();
-    if (ARCH_X86)
-        rgb2rgb_init_x86();
+#if ARCH_AARCH64
+    rgb2rgb_init_aarch64();
+#elif ARCH_X86
+    rgb2rgb_init_x86();
+#endif
 }
 
 void rgb32to24(const uint8_t *src, uint8_t *dst, int src_size)
diff --git a/libswscale/swscale.c b/libswscale/swscale.c
index 3ed547d526..7b40f49da4 100644
--- a/libswscale/swscale.c
+++ b/libswscale/swscale.c
@@ -590,14 +590,15 @@ void ff_sws_init_scale(SwsContext *c)
 {
     sws_init_swscale(c);
 
-    if (ARCH_PPC)
-        ff_sws_init_swscale_ppc(c);
-    if (ARCH_X86)
-        ff_sws_init_swscale_x86(c);
-    if (ARCH_AARCH64)
-        ff_sws_init_swscale_aarch64(c);
-    if (ARCH_ARM)
-        ff_sws_init_swscale_arm(c);
+#if ARCH_PPC
+    ff_sws_init_swscale_ppc(c);
+#elif ARCH_X86
+    ff_sws_init_swscale_x86(c);
+#elif ARCH_AARCH64
+    ff_sws_init_swscale_aarch64(c);
+#elif ARCH_ARM
+    ff_sws_init_swscale_arm(c);
+#endif
 }
 
 static void reset_ptr(const uint8_t *src[], enum AVPixelFormat format)
diff --git a/libswscale/swscale_unscaled.c b/libswscale/swscale_unscaled.c
index 7cb2a62f07..8838cc8b53 100644
--- a/libswscale/swscale_unscaled.c
+++ b/libswscale/swscale_unscaled.c
@@ -2222,12 +2222,13 @@ void ff_get_unscaled_swscale(SwsContext *c)
             c->convert_unscaled = planarCopyWrapper;
     }
 
-    if (ARCH_PPC)
-        ff_get_unscaled_swscale_ppc(c);
-     if (ARCH_ARM)
-         ff_get_unscaled_swscale_arm(c);
-    if (ARCH_AARCH64)
-        ff_get_unscaled_swscale_aarch64(c);
+#if ARCH_PPC
+    ff_get_unscaled_swscale_ppc(c);
+#elif ARCH_ARM
+    ff_get_unscaled_swscale_arm(c);
+#elif ARCH_AARCH64
+    ff_get_unscaled_swscale_aarch64(c);
+#endif
 }
 
 /* Convert the palette to the same packed 32-bit format as the palette */
diff --git a/libswscale/utils.c b/libswscale/utils.c
index 105781c4f4..cb4f5b521c 100644
--- a/libswscale/utils.c
+++ b/libswscale/utils.c
@@ -1044,9 +1044,10 @@ int sws_setColorspaceDetails(struct SwsContext *c, const int inv_table[4],
                                  contrast, saturation);
         // FIXME factorize
 
-        if (ARCH_PPC)
-            ff_yuv2rgb_init_tables_ppc(c, inv_table, brightness,
-                                       contrast, saturation);
+#if ARCH_PPC
+        ff_yuv2rgb_init_tables_ppc(c, inv_table, brightness,
+                                   contrast, saturation);
+#endif
     }
 
     fill_rgb2yuv_table(c, table, dstRange);
diff --git a/libswscale/yuv2rgb.c b/libswscale/yuv2rgb.c
index 76232cb364..6ee483d12a 100644
--- a/libswscale/yuv2rgb.c
+++ b/libswscale/yuv2rgb.c
@@ -679,10 +679,11 @@ SwsFunc ff_yuv2rgb_get_func_ptr(SwsContext *c)
 {
     SwsFunc t = NULL;
 
-    if (ARCH_PPC)
-        t = ff_yuv2rgb_init_ppc(c);
-    if (ARCH_X86)
-        t = ff_yuv2rgb_init_x86(c);
+#if ARCH_PPC
+    t = ff_yuv2rgb_init_ppc(c);
+#elif ARCH_X86
+    t = ff_yuv2rgb_init_x86(c);
+#endif
 
     if (t)
         return t;