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>

4 files changed, 43 insertions, 38 deletions

diff --git a/libavutil/cpu.c b/libavutil/cpu.c
index 24b99d2554..0035e927a5 100644
--- a/libavutil/cpu.c
+++ b/libavutil/cpu.c
@@ -54,18 +54,19 @@ static atomic_int cpu_count = ATOMIC_VAR_INIT(-1);
 
 static int get_cpu_flags(void)
 {
-    if (ARCH_MIPS)
-        return ff_get_cpu_flags_mips();
-    if (ARCH_AARCH64)
-        return ff_get_cpu_flags_aarch64();
-    if (ARCH_ARM)
-        return ff_get_cpu_flags_arm();
-    if (ARCH_PPC)
-        return ff_get_cpu_flags_ppc();
-    if (ARCH_X86)
-        return ff_get_cpu_flags_x86();
-    if (ARCH_LOONGARCH)
-        return ff_get_cpu_flags_loongarch();
+#if ARCH_MIPS
+    return ff_get_cpu_flags_mips();
+#elif ARCH_AARCH64
+    return ff_get_cpu_flags_aarch64();
+#elif ARCH_ARM
+    return ff_get_cpu_flags_arm();
+#elif ARCH_PPC
+    return ff_get_cpu_flags_ppc();
+#elif ARCH_X86
+    return ff_get_cpu_flags_x86();
+#elif ARCH_LOONGARCH
+    return ff_get_cpu_flags_loongarch();
+#endif
     return 0;
 }
 
@@ -252,18 +253,19 @@ void av_cpu_force_count(int count)
 
 size_t av_cpu_max_align(void)
 {
-    if (ARCH_MIPS)
-        return ff_get_cpu_max_align_mips();
-    if (ARCH_AARCH64)
-        return ff_get_cpu_max_align_aarch64();
-    if (ARCH_ARM)
-        return ff_get_cpu_max_align_arm();
-    if (ARCH_PPC)
-        return ff_get_cpu_max_align_ppc();
-    if (ARCH_X86)
-        return ff_get_cpu_max_align_x86();
-    if (ARCH_LOONGARCH)
-        return ff_get_cpu_max_align_loongarch();
+#if ARCH_MIPS
+    return ff_get_cpu_max_align_mips();
+#elif ARCH_AARCH64
+    return ff_get_cpu_max_align_aarch64();
+#elif ARCH_ARM
+    return ff_get_cpu_max_align_arm();
+#elif ARCH_PPC
+    return ff_get_cpu_max_align_ppc();
+#elif ARCH_X86
+    return ff_get_cpu_max_align_x86();
+#elif ARCH_LOONGARCH
+    return ff_get_cpu_max_align_loongarch();
+#endif
 
     return 8;
 }
diff --git a/libavutil/fixed_dsp.c b/libavutil/fixed_dsp.c
index 098ef9c061..154f3bc2d3 100644
--- a/libavutil/fixed_dsp.c
+++ b/libavutil/fixed_dsp.c
@@ -162,8 +162,9 @@ AVFixedDSPContext * avpriv_alloc_fixed_dsp(int bit_exact)
     fdsp->butterflies_fixed = butterflies_fixed_c;
     fdsp->scalarproduct_fixed = scalarproduct_fixed_c;
 
-    if (ARCH_X86)
-        ff_fixed_dsp_init_x86(fdsp);
+#if ARCH_X86
+    ff_fixed_dsp_init_x86(fdsp);
+#endif
 
     return fdsp;
 }
diff --git a/libavutil/float_dsp.c b/libavutil/float_dsp.c
index 6e28d71b57..8676c8b0f8 100644
--- a/libavutil/float_dsp.c
+++ b/libavutil/float_dsp.c
@@ -150,15 +150,16 @@ av_cold AVFloatDSPContext *avpriv_float_dsp_alloc(int bit_exact)
     fdsp->butterflies_float = butterflies_float_c;
     fdsp->scalarproduct_float = avpriv_scalarproduct_float_c;
 
-    if (ARCH_AARCH64)
-        ff_float_dsp_init_aarch64(fdsp);
-    if (ARCH_ARM)
-        ff_float_dsp_init_arm(fdsp);
-    if (ARCH_PPC)
-        ff_float_dsp_init_ppc(fdsp, bit_exact);
-    if (ARCH_X86)
-        ff_float_dsp_init_x86(fdsp);
-    if (ARCH_MIPS)
-        ff_float_dsp_init_mips(fdsp);
+#if ARCH_AARCH64
+    ff_float_dsp_init_aarch64(fdsp);
+#elif ARCH_ARM
+    ff_float_dsp_init_arm(fdsp);
+#elif ARCH_PPC
+    ff_float_dsp_init_ppc(fdsp, bit_exact);
+#elif ARCH_X86
+    ff_float_dsp_init_x86(fdsp);
+#elif ARCH_MIPS
+    ff_float_dsp_init_mips(fdsp);
+#endif
     return fdsp;
 }
diff --git a/libavutil/lls.c b/libavutil/lls.c
index ea2d80e662..c1e038daf1 100644
--- a/libavutil/lls.c
+++ b/libavutil/lls.c
@@ -117,6 +117,7 @@ av_cold void avpriv_init_lls(LLSModel *m, int indep_count)
     m->indep_count = indep_count;
     m->update_lls = update_lls;
     m->evaluate_lls = evaluate_lls;
-    if (ARCH_X86)
-        ff_init_lls_x86(m);
+#if ARCH_X86
+    ff_init_lls_x86(m);
+#endif
 }