Add preliminary support for cosmocc -mclang

C++ code compiles very slowly with cosmocc, possibly because we're using
LLVM LIBCXX with GCC, and LLVM doesn't work as hard to make GCC go fast.
Therefore, it should be possible, to ask cosmocc to favor Clang over GCC
under the hood. On llamafile, my intention's to use this to make certain
files, e.g. llama.cpp/common.cpp, go from taking 17 seconds to 5 seconds

This new -mclang flag isn't ready for production yet since there's still
the question of how to get Clang to generate SJLJ exception code. If you
use this, then it's recommended you also pass -fno-exceptions.

The tradeoff is we're adding a 121mb binary to the cosmocc distribution.
There are no plans as of yet to fully migrate to Clang since GCC is very
good and has always treated us well.

libc/runtime/runtime.h

@@ -119,7 +119,7 @@ void __morph_begin(void) libcesque;
 void __morph_end(void) libcesque;
 void __jit_begin(void) libcesque;
 void __jit_end(void) libcesque;
-void __clear_cache(void *, void *) libcesque;
+void __clear_cache(void *, void *);
 /* portability */
 bool32 IsGenuineBlink(void) libcesque;
 bool32 IsCygwin(void) libcesque;

libc/str/BUILD.mk

@@ -44,9 +44,6 @@ $(LIBC_STR_A).pkg:						\
 		$(LIBC_STR_A_OBJS)				\
 		$(foreach x,$(LIBC_STR_A_DIRECTDEPS),$($(x)_A).pkg)
 
-o/$(MODE)/libc/str/wow.o: private				\
-		CC = gcc
-
 o/$(MODE)/libc/str/wmemset.o					\
 o/$(MODE)/libc/str/memset16.o					\
 o/$(MODE)/libc/str/dosdatetimetounix.o: private			\

tool/cosmocc/README.md

@@ -417,7 +417,7 @@ statements instead, so that Cosmopolitan Libc's system constants will
 work as expected. Our modifications to GNU GCC are published under the
 ISC license at <https://github.com/ahgamut/gcc/tree/portcosmo-14.1>. The
 binaries you see here were first published at
-<https://github.com/ahgamut/superconfigure/releases/tag/z0.0.52> which
+<https://github.com/ahgamut/superconfigure/releases/tag/z0.0.53> which
 is regularly updated.
 
 ## Legal

tool/cosmocc/bin/cosmocc

@@ -75,6 +75,15 @@ elif [ ! -d "$TMPDIR" ]; then
   fi
 fi
 
+CLANG=0
+CC_X86_64="$BIN/x86_64-linux-cosmo-gcc"
+CC_AARCH64="$BIN/aarch64-linux-cosmo-gcc"
+CXX_X86_64="$BIN/x86_64-linux-cosmo-g++"
+CXX_AARCH64="$BIN/aarch64-linux-cosmo-g++"
+FPORTCOSMO="-fportcosmo"
+TARGET_X86_64=
+TARGET_AARCH64=
+
 X=
 OPT=
 ARGS=
@@ -93,6 +102,7 @@ FLAGS_AARCH64=
 INPUT_FILE_COUNT=0
 DEPENDENCY_OUTPUT=
 NEED_DEPENDENCY_OUTPUT=
+
 for x; do
   if [ x"$x" != x"${x#* }" ]; then
     fatal_error "arguments containing spaces unsupported: $x"
@@ -185,6 +195,16 @@ EOF
   elif [ x"$x" = x"-moptlinux" ]; then
     MODE=optlinux
     continue
+  elif [ x"$x" = x"-mclang" ]; then
+    CLANG=1
+    CC_X86_64="$BIN/cosmo-clang"
+    CC_AARCH64="$BIN/cosmo-clang"
+    CXX_X86_64="$BIN/cosmo-clang++"
+    CXX_AARCH64="$BIN/cosmo-clang++"
+    TARGET_X86_64="--target=x86_64"
+    TARGET_AARCH64="--target=aarch64"
+    FPORTCOSMO=
+    continue
   elif [ x"$x" = x"-m64" ]; then
     continue
   elif [ x"$x" = x"-fomit-frame-pointer" ]; then
@@ -298,7 +318,7 @@ fi
 PLATFORM="-D__COSMOPOLITAN__ -D__COSMOCC__ -D__FATCOSMOCC__"
 PREDEF="-include libc/integral/normalize.inc"
 CPPFLAGS="-fno-pie -nostdinc -isystem $BIN/../include"
-CFLAGS="-fportcosmo -fno-dwarf2-cfi-asm -fno-unwind-tables -fno-asynchronous-unwind-tables -fno-semantic-interposition"
+CFLAGS="$FPORTCOSMO -fno-dwarf2-cfi-asm -fno-unwind-tables -fno-asynchronous-unwind-tables -fno-semantic-interposition"
 LDFLAGS="-static -nostdlib -no-pie -fuse-ld=bfd -Wl,-z,noexecstack -Wl,-z,norelro -Wl,--gc-sections"
 PRECIOUS="-fno-omit-frame-pointer"
 
@@ -307,7 +327,9 @@ if [ x"$OPT" != x"-Os" ] && [ x"$MODE" != x"tiny" ] && [ x"$MODE" != x"optlinux"
   CFLAGS="$CFLAGS -fno-optimize-sibling-calls -mno-omit-leaf-frame-pointer"
 fi
 if [ x"$OPT" != x"-O3" ] && [ x"$MODE" != x"optlinux" ]; then
+  if [ $CLANG -eq 0 ]; then
     CFLAGS="$CFLAGS -fno-schedule-insns2"
+  fi
 fi
 
 if [ x"$X" = x"c" ] || [ x"$X" = x"c-header" ]; then
@@ -320,11 +342,9 @@ else
   CPLUSPLUS=0
 fi
 
-CC_X86_64="$BIN/x86_64-linux-cosmo-gcc"
-CC_AARCH64="$BIN/aarch64-linux-cosmo-gcc"
 if [ $CPLUSPLUS -eq 1 ]; then
-  CC_X86_64="$BIN/x86_64-linux-cosmo-g++"
-  CC_AARCH64="$BIN/aarch64-linux-cosmo-g++"
+  CC_X86_64=$CXX_X86_64
+  CC_AARCH64=$CXX_AARCH64
   if [ $INTENT != cpp ]; then
     CFLAGS="$CFLAGS -fno-rtti -fno-exceptions -fuse-cxa-atexit"
   fi
@@ -461,6 +481,7 @@ build_object() {
   (
     set -- \
         "$CC_X86_64" \
+        $TARGET_X86_64 \
         -o"$OUTPUT_X86_64" \
         $PLATFORM \
         $PREDEF \
@@ -482,6 +503,7 @@ build_object() {
   (
     set -- \
         "$CC_AARCH64" \
+        $TARGET_AARCH64 \
         -o"$OUTPUT_AARCH64" \
         $PLATFORM \
         $PREDEF \
@@ -588,6 +610,7 @@ TEMP_FILES="${TEMP_FILES} $out2"
 (
   set -- \
       "$CC_X86_64" \
+      $TARGET_X86_64 \
       -o"$OUTPUT_X86_64"\
       $CRT_X86_64 \
       $LDFLAGS_X86_64 \
@@ -605,6 +628,7 @@ pid1=$!
 (
   set -- \
       "$CC_AARCH64" \
+      $TARGET_AARCH64 \
       -o"$OUTPUT_AARCH64"\
       $CRT_AARCH64 \
       $LDFLAGS_AARCH64 \

tool/cosmocc/package.sh

@@ -182,12 +182,17 @@ fetch() {
 OLD=$PWD
 cd "$OUTDIR/"
 if [ ! -x bin/x86_64-linux-cosmo-gcc ]; then
-  fetch https://github.com/ahgamut/superconfigure/releases/download/z0.0.52/aarch64-gcc.zip
-  unzip aarch64-gcc.zip
+  fetch https://github.com/ahgamut/superconfigure/releases/download/z0.0.53/aarch64-gcc.zip &
+  fetch https://github.com/ahgamut/superconfigure/releases/download/z0.0.53/x86_64-gcc.zip &
+  fetch https://github.com/ahgamut/superconfigure/releases/download/z0.0.53/llvm.zip &
+  wait
+  unzip aarch64-gcc.zip &
+  unzip x86_64-gcc.zip &
+  unzip llvm.zip bin/clang-18 &
+  wait
   rm -f aarch64-gcc.zip
-  fetch https://github.com/ahgamut/superconfigure/releases/download/z0.0.52/x86_64-gcc.zip
-  unzip x86_64-gcc.zip
   rm -f x86_64-gcc.zip
+  mv bin/clang-18 bin/cosmo-clang
 fi
 rm -f bin/*-cpp
 rm -f bin/*-gcc-*