swscale/x86/uops: generate NASM macros using uops_macros.h

Rather than hard-coding a separate set of NASM macros, or generating them
with a separate function, we can just leverage the C preprocessor to generate
a NASM source file *from* the existing ops macros.

This is maybe a bit unorthodox, but it avoids unnecessary overhead from
re-generating the macros twice, avoids manual updating of the NASM macros,
and generally does not come with any real downside except being a bit ugly.

The main source of ugliness is the fact that the C preprocessor expands
everything into a single line, whereas NASM expects separate statements to
be on separate lines. Very fortunately, we can work around this by writing a
another NASM macro to take its arguments and dump them onto multiple lines.

It may seem premature, but I went ahead and defined all the macros, since
it was easy enough to do.

I added the %include in this commit to trigger build errors that occur only
as a result of introducing this file in the same commit that introduces it.

Signed-off-by: Niklas Haas <git@haasn.dev>

.gitignore

@@ -26,6 +26,7 @@
 *.spv
 *.spv.c
 *.spv.gz
+*.gen.asm
 *.gen.c
 *.gen.S
 *.ptx

ffbuild/common.mak

@@ -254,7 +254,7 @@ $(TOOLOBJS): | tools
 
 OUTDIRS := $(OUTDIRS) $(dir $(OBJS) $(HOBJS) $(HOSTOBJS) $(SHLIBOBJS) $(STLIBOBJS) $(TESTOBJS))
 
-CLEANSUFFIXES     = *.d *.gcda *.gcno *.h.c *.ho *.map *.o *.objs *.pc *.ptx *.ptx.gz *.ptx.c *.spv *.spv.gz *.spv.c *.gen.c *.gen.S *.ver *.version *.html.gz *.html.c *.css.min.gz *.css.min *.css.c *~ *.ilk *.pdb
+CLEANSUFFIXES     = *.d *.gcda *.gcno *.h.c *.ho *.map *.o *.objs *.pc *.ptx *.ptx.gz *.ptx.c *.spv *.spv.gz *.spv.c *.gen.asm *.gen.c *.gen.S *.ver *.version *.html.gz *.html.c *.css.min.gz *.css.min *.css.c *~ *.ilk *.pdb
 LIBSUFFIXES       = *.a *.lib *.so *.so.* *.dylib *.dll *.def *.dll.a
 
 define RULES

libswscale/x86/Makefile

@@ -15,9 +15,18 @@ X86ASM-OBJS                     += x86/input.o                          \
                                    x86/yuv_2_rgb.o                      \
                                    x86/yuv2yuvX.o                       \
 
+SKIPHEADERS                     += x86/uops_macros.asm.h
+
 ifdef ARCH_X86_64
 X86ASM-OBJS-$(CONFIG_UNSTABLE)  += x86/ops_common.o                     \
                                    x86/ops_int.o                        \
                                    x86/ops_float.o                      \
                                    x86/ops.o
+
+$(SUBDIR)x86/ops_common.o: $(SUBDIR)x86/uops_macros.gen.asm
+$(SUBDIR)x86/ops_int.o: $(SUBDIR)x86/uops_macros.gen.asm
+$(SUBDIR)x86/ops_float.o: $(SUBDIR)x86/uops_macros.gen.asm
+$(SUBDIR)x86/uops_macros.gen.asm: $(SRC_PATH)/libswscale/x86/uops_macros.asm.h \
+                                  $(SRC_PATH)/libswscale/uops_macros.h
+	$(HOSTCC) $(CC_E) $(CPPFLAGS) $<
 endif

libswscale/x86/ops_include.asm

@@ -19,6 +19,7 @@
 ;******************************************************************************
 
 %include "libavutil/x86/x86util.asm"
+%include "libswscale/x86/uops_macros.gen.asm"
 
 ; High-level explanation of how the x86 backend works:
 ;

libswscale/x86/uops_macros.asm.h

@@ -0,0 +1,89 @@
+/**
+ * Copyright (C) 2025 Niklas Haas
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * WARNING: This file is preprocessed by the C compiler to generate the NASM
+ * source file uops_macros.gen.asm. It must *NOT* include any headers that
+ * may inadvertently declare any C syntax. The following header only declares
+ * further macros, and is therefore safe.
+ */
+#include "../uops_macros.h"
+
+/**
+ * NASM expects one statement per source line, but the C preprocessor expands
+ * multi-line macros into a single line. This NASM macro allows us to work
+ * around that by expanding its arguments into multiple lines.
+ */
+%macro MULTILINE 0-*
+ %rep %0
+    %1
+  %rotate 1
+ %endrep
+%endmacro
+
+/* Used to suppress "trailing empty parameter" warnings */
+%macro dummy 0
+%endmacro
+
+#define DECL_OP_MACRO(...) {DECL_OP MACRO __VA_ARGS__},
+#define DEF_MACRO(UOP, TYPE)                            \
+    %define DECL_##TYPE##_##UOP(MACRO)                  \
+    MULTILINE SWS_FOR_##TYPE##_##UOP(DECL_OP_MACRO)     \
+    dummy
+
+#define DEF_ALL_MACROS(TYPE)                \
+    MULTILINE                               \
+    {DEF_MACRO(READ_BIT,            TYPE)}, \
+    {DEF_MACRO(READ_NIBBLE,         TYPE)}, \
+    {DEF_MACRO(READ_PACKED,         TYPE)}, \
+    {DEF_MACRO(READ_PLANAR,         TYPE)}, \
+    {DEF_MACRO(READ_PLANAR_FH,      TYPE)}, \
+    {DEF_MACRO(READ_PLANAR_FV,      TYPE)}, \
+    {DEF_MACRO(READ_PLANAR_FV_FMA,  TYPE)}, \
+    {DEF_MACRO(WRITE_BIT,           TYPE)}, \
+    {DEF_MACRO(WRITE_NIBBLE,        TYPE)}, \
+    {DEF_MACRO(WRITE_PACKED,        TYPE)}, \
+    {DEF_MACRO(WRITE_PLANAR,        TYPE)}, \
+    {DEF_MACRO(PERMUTE,             TYPE)}, \
+    {DEF_MACRO(COPY,                TYPE)}, \
+    {DEF_MACRO(SWAP_BYTES,          TYPE)}, \
+    {DEF_MACRO(EXPAND_BIT,          TYPE)}, \
+    {DEF_MACRO(EXPAND_PAIR,         TYPE)}, \
+    {DEF_MACRO(EXPAND_QUAD,         TYPE)}, \
+    {DEF_MACRO(TO_U8,               TYPE)}, \
+    {DEF_MACRO(TO_U16,              TYPE)}, \
+    {DEF_MACRO(TO_U32,              TYPE)}, \
+    {DEF_MACRO(TO_F32,              TYPE)}, \
+    {DEF_MACRO(SCALE,               TYPE)}, \
+    {DEF_MACRO(LINEAR_FMA,          TYPE)}, \
+    {DEF_MACRO(ADD,                 TYPE)}, \
+    {DEF_MACRO(MIN,                 TYPE)}, \
+    {DEF_MACRO(MAX,                 TYPE)}, \
+    {DEF_MACRO(UNPACK,              TYPE)}, \
+    {DEF_MACRO(PACK,                TYPE)}, \
+    {DEF_MACRO(LSHIFT,              TYPE)}, \
+    {DEF_MACRO(RSHIFT,              TYPE)}, \
+    {DEF_MACRO(CLEAR,               TYPE)}, \
+    {DEF_MACRO(DITHER,              TYPE)}
+
+DEF_ALL_MACROS(U8)
+DEF_ALL_MACROS(U16)
+DEF_ALL_MACROS(U32)
+DEF_ALL_MACROS(F32)

tests/ref/fate/source

@@ -28,6 +28,7 @@ compat/float/float.h
 compat/float/limits.h
 compat/stdbit/stdbit.h
 libavcodec/bitstream_template.h
+libswscale/x86/uops_macros.asm.h
 tools/decode_simple.h
 Use of av_clip() where av_clip_uintp2() could be used:
 Use of av_clip() where av_clip_intp2() could be used: