commit 0835c0f0bad351117154b815f34f8af19ea7e325

Author: Matt Whitlock <sourceware@mattwhitlock.name>

Date:   Wed Jun 16 23:40:47 2021 -0400

    x86: fix Autoconf caching of instruction support checks [BZ #27991]

    The Autoconf documentation for the AC_CACHE_CHECK macro states:

      The commands-to-set-it must have no side effects except for setting

      the variable cache-id, see below.

    However, the tests for support of -msahf and -mmovbe were embedded in

    the commands-to-set-it for lib_cv_include_x86_isa_level. This had the

    consequence that libc_cv_have_x86_lahf_sahf and libc_cv_have_x86_movbe

    were not defined whenever lib_cv_include_x86_isa_level was read from

    cache. These variables' being undefined meant that their unquoted use

    in later test expressions led to the 'test' built-in's misparsing its

    arguments and emitting errors like "test: =: unexpected operator" or

    "test: =: unary operator expected", depending on the particular shell.

    This commit refactors the tests for LAHF/SAHF and MOVBE instruction

    support into their own AC_CACHE_CHECK macro invocations to obey the

    rule that the commands-to-set-it must have no side effects other than

    setting the variable named by cache-id.

    Signed-off-by: Matt Whitlock <sourceware@mattwhitlock.name>

    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

diff --git a/sysdeps/x86/configure b/sysdeps/x86/configure

index ead1295c38cf5f4e..62676bb686850938 100644

--- a/sysdeps/x86/configure

+++ b/sysdeps/x86/configure

@@ -126,8 +126,6 @@ cat > conftest2.S <

 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

@@ -137,9 +135,22 @@ 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

-    if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -fverbose-asm -S -o - conftest.c'

+  fi

+fi

+rm -f conftest*

+fi

+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_include_x86_isa_level" >&5

+$as_echo "$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

+

+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for LAHF/SAHF instruction support" >&5

+$as_echo_n "checking for LAHF/SAHF instruction support... " >&6; }

+if ${libc_cv_have_x86_lahf_sahf+:} false; then :

+  $as_echo_n "(cached) " >&6

+else

+      libc_cv_have_x86_lahf_sahf=no

+    if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -fverbose-asm -S -o - -x c /dev/null'

   { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5

   (eval $ac_try) 2>&5

   ac_status=$?

@@ -147,7 +158,20 @@ EOF

   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'

+fi

+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_have_x86_lahf_sahf" >&5

+$as_echo "$libc_cv_have_x86_lahf_sahf" >&6; }

+  if test $libc_cv_have_x86_lahf_sahf = yes; then

+    $as_echo "#define HAVE_X86_LAHF_SAHF 1" >>confdefs.h

+

+  fi

+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for MOVBE instruction support" >&5

+$as_echo_n "checking for MOVBE instruction support... " >&6; }

+if ${libc_cv_have_x86_movbe+:} false; then :

+  $as_echo_n "(cached) " >&6

+else

+      libc_cv_have_x86_movbe=no

+    if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -fverbose-asm -S -o - -x c /dev/null'

   { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5

   (eval $ac_try) 2>&5

   ac_status=$?

@@ -155,23 +179,13 @@ EOF

   test $ac_status = 0; }; } | grep -q "\-mmovbe"; then

       libc_cv_have_x86_movbe=yes

     fi

-  fi

-fi

-rm -f conftest*

-fi

-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_include_x86_isa_level" >&5

-$as_echo "$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

+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_have_x86_movbe" >&5

+$as_echo "$libc_cv_have_x86_movbe" >&6; }

+  if test $libc_cv_have_x86_movbe = yes; then

+    $as_echo "#define HAVE_X86_MOVBE 1" >>confdefs.h

+  fi

 fi

 config_vars="$config_vars

 enable-x86-isa-level = $libc_cv_include_x86_isa_level"

diff --git a/sysdeps/x86/configure.ac b/sysdeps/x86/configure.ac

index bca97fdc2f1ac1a7..04a12ab68048cd66 100644

--- a/sysdeps/x86/configure.ac

+++ b/sysdeps/x86/configure.ac

@@ -98,30 +98,32 @@ cat > conftest2.S <

 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

-    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)

+  AC_CACHE_CHECK([for LAHF/SAHF instruction support],

+		 libc_cv_have_x86_lahf_sahf, [dnl

+    libc_cv_have_x86_lahf_sahf=no

+    if AC_TRY_COMMAND(${CC-cc} $CFLAGS $CPPFLAGS -fverbose-asm -S -o - -x c /dev/null) | grep -q "\-msahf"; then

+      libc_cv_have_x86_lahf_sahf=yes

+    fi])

+  if test $libc_cv_have_x86_lahf_sahf = yes; then

+    AC_DEFINE(HAVE_X86_LAHF_SAHF)

+  fi

+  AC_CACHE_CHECK([for MOVBE instruction support],

+		 libc_cv_have_x86_movbe, [dnl

+    libc_cv_have_x86_movbe=no

+    if AC_TRY_COMMAND(${CC-cc} $CFLAGS $CPPFLAGS -fverbose-asm -S -o - -x c /dev/null) | grep -q "\-mmovbe"; then

+      libc_cv_have_x86_movbe=yes

+    fi])

+  if test $libc_cv_have_x86_movbe = yes; then

+    AC_DEFINE(HAVE_X86_MOVBE)

+  fi

 fi

 LIBC_CONFIG_VAR([enable-x86-isa-level], [$libc_cv_include_x86_isa_level])