x86: Set minimum x86-64 level marker [BZ #27318]

Since the full ISA set used in an ELF binary is unknown to compiler,
an x86-64 ISA level marker indicates the minimum, not maximum, ISA set
required to run such an ELF binary.  We never guarantee a library with
an x86-64 ISA level v3 marker doesn't contain other ISAs beyond x86-64
ISA level v3, like AVX VNNI.  We check the x86-64 ISA level marker for
the minimum ISA set.  Since -march=sandybridge enables only some ISAs
in x86-64 ISA level v3, we should set the needed ISA marker to v2.
Otherwise, libc is compiled with -march=sandybridge will fail to run on
Sandy Bridge:

$ ./elf/ld.so ./libc.so
./libc.so: (p) CPU ISA level is lower than required: needed: 7; got: 3

Set the minimum, instead of maximum, x86-64 ISA level marker should have
no impact on the glibc-hwcaps directory assignment logic in ldconfig nor
ld.so.

config.h.in

@@ -275,4 +275,10 @@
 /* Define if x86 ISA level should be included in shared libraries.  */
 #undef INCLUDE_X86_ISA_LEVEL
 
+/* Define if -msahf is enabled by default on x86.  */
+#undef HAVE_X86_LAHF_SAHF
+
+/* Define if -mmovbe is enabled by default on x86.  */
+#undef HAVE_X86_MOVBE
+
 #endif

sysdeps/x86/configure

@@ -126,6 +126,8 @@ cat > conftest2.S <<EOF
 4:
 EOF
 libc_cv_include_x86_isa_level=no
+libc_cv_have_x86_lahf_sahf=no
+libc_cv_have_x86_movbe=no
 if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -nostartfiles -nostdlib -r -o conftest conftest1.S conftest2.S'
   { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
   (eval $ac_try) 2>&5
@@ -135,6 +137,24 @@ if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -nostartfiles -nostdlib -r -o conftest c
   count=`LC_ALL=C $READELF -n conftest | grep NT_GNU_PROPERTY_TYPE_0 | wc -l`
   if test "$count" = 1; then
     libc_cv_include_x86_isa_level=yes
+    cat > conftest.c <<EOF
+EOF
+    if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -fverbose-asm -S -o - conftest.c'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; } | grep -q "\-msahf"; then
+      libc_cv_have_x86_lahf_sahf=yes
+    fi
+    if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -fverbose-asm -S -o - conftest.c'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; } | grep -q "\-mmovbe"; then
+      libc_cv_have_x86_movbe=yes
+    fi
   fi
 fi
 rm -f conftest*
@@ -144,6 +164,14 @@ $as_echo "$libc_cv_include_x86_isa_level" >&6; }
 if test $libc_cv_include_x86_isa_level = yes; then
   $as_echo "#define INCLUDE_X86_ISA_LEVEL 1" >>confdefs.h
 
+fi
+if test $libc_cv_have_x86_lahf_sahf = yes; then
+  $as_echo "#define HAVE_X86_LAHF_SAHF 1" >>confdefs.h
+
+fi
+if test $libc_cv_have_x86_movbe = yes; then
+  $as_echo "#define HAVE_X86_MOVBE 1" >>confdefs.h
+
 fi
 config_vars="$config_vars
 enable-x86-isa-level = $libc_cv_include_x86_isa_level"

sysdeps/x86/configure.ac

@@ -98,14 +98,30 @@ cat > conftest2.S <<EOF
 4:
 EOF
 libc_cv_include_x86_isa_level=no
+libc_cv_have_x86_lahf_sahf=no
+libc_cv_have_x86_movbe=no
 if AC_TRY_COMMAND(${CC-cc} $CFLAGS $CPPFLAGS -nostartfiles -nostdlib -r -o conftest conftest1.S conftest2.S); then
   count=`LC_ALL=C $READELF -n conftest | grep NT_GNU_PROPERTY_TYPE_0 | wc -l`
   if test "$count" = 1; then
     libc_cv_include_x86_isa_level=yes
+    cat > conftest.c <<EOF
+EOF
+    if AC_TRY_COMMAND(${CC-cc} $CFLAGS $CPPFLAGS -fverbose-asm -S -o - conftest.c) | grep -q "\-msahf"; then
+      libc_cv_have_x86_lahf_sahf=yes
+    fi
+    if AC_TRY_COMMAND(${CC-cc} $CFLAGS $CPPFLAGS -fverbose-asm -S -o - conftest.c) | grep -q "\-mmovbe"; then
+      libc_cv_have_x86_movbe=yes
+    fi
   fi
 fi
 rm -f conftest*])
 if test $libc_cv_include_x86_isa_level = yes; then
   AC_DEFINE(INCLUDE_X86_ISA_LEVEL)
 fi
+if test $libc_cv_have_x86_lahf_sahf = yes; then
+  AC_DEFINE(HAVE_X86_LAHF_SAHF)
+fi
+if test $libc_cv_have_x86_movbe = yes; then
+  AC_DEFINE(HAVE_X86_MOVBE)
+fi
 LIBC_CONFIG_VAR([enable-x86-isa-level], [$libc_cv_include_x86_isa_level])

sysdeps/x86/isa-level.c

@@ -29,32 +29,35 @@
 
 /* ELF program property for x86 ISA level.  */
 #ifdef INCLUDE_X86_ISA_LEVEL
-# if defined __x86_64__ || defined __FXSR__ || !defined _SOFT_FLOAT \
+# if defined __SSE__ && defined __SSE2__
-     || defined  __MMX__ || defined __SSE__ || defined __SSE2__
+/* NB: ISAs, excluding MMX, in x86-64 ISA level baseline are used.  */
 #  define ISA_BASELINE	GNU_PROPERTY_X86_ISA_1_BASELINE
 # else
 #  define ISA_BASELINE	0
 # endif
 
-# if defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16 \
+# if ISA_BASELINE && defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16 \
-     || (defined __x86_64__ && defined __LAHF_SAHF__) \
+     && defined HAVE_X86_LAHF_SAHF && defined __POPCNT__ \
-     || defined __POPCNT__ || defined __SSE3__ \
+     && defined __SSE3__ && defined __SSSE3__ && defined __SSE4_1__ \
-     || defined __SSSE3__ || defined __SSE4_1__ || defined __SSE4_2__
+     && defined __SSE4_2__
+/* NB: ISAs in x86-64 ISA level v2 are used.  */
 #  define ISA_V2	GNU_PROPERTY_X86_ISA_1_V2
 # else
 #  define ISA_V2	0
 # endif
 
-# if defined __AVX__ || defined __AVX2__ || defined __F16C__ \
+# if ISA_V2 && defined __AVX__ && defined __AVX2__ && defined __F16C__ \
-     || defined __FMA__ || defined __LZCNT__ || defined __MOVBE__ \
+     && defined __FMA__ && defined __LZCNT__ && defined HAVE_X86_MOVBE
-     || defined __XSAVE__
+/* NB: ISAs in x86-64 ISA level v3 are used.  */
 #  define ISA_V3	GNU_PROPERTY_X86_ISA_1_V3
 # else
 #  define ISA_V3	0
 # endif
 
-# if defined __AVX512F__ || defined __AVX512BW__ || defined __AVX512CD__ \
+# if ISA_V3 && defined __AVX512F__ && defined __AVX512BW__ \
-     || defined __AVX512DQ__ || defined __AVX512VL__
+     && defined __AVX512CD__ && defined __AVX512DQ__ \
+     && defined __AVX512VL__
+/* NB: ISAs in x86-64 ISA level v4 are used.  */
 #  define ISA_V4	GNU_PROPERTY_X86_ISA_1_V4
 # else
 #  define ISA_V4	0