x86: Don't use asm statement for trunc/truncf

Compiler inlines trunc and truncf with SSE4.1.  But older versions of GCC
doesn't inline them with -Os:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121861

Don't use asm statement for trunc and truncf if compiler can inline them
with -Os.  It removes one register move with GCC 16:

__modff_sse41:                        __modff_sse41:
.LFB23:                               .LFB23:
   .cfi_startproc                        .cfi_startproc
   endbr64                               endbr64
   subq  $24, %rsp                       subq  $24, %rsp
   .cfi_def_cfa_offset 32                .cfi_def_cfa_offset 32
   movq  %fs:40, %rax                    movq  %fs:40, %rax
   movq  %rax, 8(%rsp)                   movq  %rax, 8(%rsp)
   xorl  %eax, %eax                      xorl  %eax, %eax
   movd  %xmm0, %eax                     movd  %xmm0, %eax
   addl  %eax, %eax                      addl  %eax, %eax
   cmpl  $-16777216, %eax                cmpl  $-16777216, %eax
   je .L7                                je .L7
                                   >     movaps   %xmm0, %xmm3
   movaps   %xmm0, %xmm4                 movaps   %xmm0, %xmm4
   movss .LC0(%rip), %xmm2         |     movss .LC0(%rip), %xmm1
   movaps   %xmm2, %xmm3           |     movaps   %xmm1, %xmm2
   andps %xmm0, %xmm2              |     roundss  $11, %xmm3, %xmm3
   roundss $11, %xmm0, %xmm1       |     subss %xmm3, %xmm4
   subss %xmm1, %xmm4              |     andps %xmm0, %xmm1
   andnps   %xmm4, %xmm3           |     andnps   %xmm4, %xmm2
   orps  %xmm3, %xmm2              |     orps  %xmm2, %xmm1
.L3:                                  .L3:
   movss %xmm1, (%rdi)             |     movss %xmm3, (%rdi)
   movq  8(%rsp), %rax                   movq  8(%rsp), %rax
   subq  %fs:40, %rax                    subq  %fs:40, %rax
   jne   .L8                             jne   .L8
   movaps   %xmm2, %xmm0           |     movaps   %xmm1, %xmm0
   addq  $24, %rsp                       addq  $24, %rsp
   .cfi_remember_state                   .cfi_remember_state
   .cfi_def_cfa_offset 8                 .cfi_def_cfa_offset 8
   ret                                   ret

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Uros Bizjak <ubizjak@gmail.com>

diff --git a/config.h.in b/config.h.in
index 8b4077f578d57e11ff454930c732d2f129f9533f..9fb369c64048616116e919679a04279d5c36470c 100644 (file)
--- a/config.h.in
+++ b/config.h.in
@@ -308,4 +308,7 @@
 /* Define if -mapxf is enabled by default on x86.  */
 #undef HAVE_X86_APX
 
+/* Define if trunc is inlined on x86.  */
+#undef HAVE_X86_INLINE_TRUNC
+
 #endif

diff --git a/sysdeps/x86/configure b/sysdeps/x86/configure
index a021cdbcf500b5994eb25c7de1dee5ae9ce466fc..2e95277f29efb71e76bb9b13124d8e9c7896a54b 100644 (file)
--- a/sysdeps/x86/configure
+++ b/sysdeps/x86/configure
@@ -340,6 +340,58 @@ fi
 config_vars="$config_vars
 test-cc-cflags-no-direct-extern-access = $libc_cv_test_cc_cflags_no_direct_extern_access"
 
+conftest_code="
+extern float truncf (float __x) __attribute__ ((__nothrow__,__const__));
+
+float
+tf (float x)
+{
+  return truncf (x);
+}
+"
+
+cat > conftest.c <<EOF
+$conftest_code
+EOF
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking if -Os inlines trunc" >&5
+printf %s "checking if -Os inlines trunc... " >&6; }
+if test ${libc_cv_cc_x86_inline_trunc+y}
+then :
+  printf %s "(cached) " >&6
+else case e in #(
+  e)   if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -S -Os -msse4.1 conftest.c -o conftest 1>&5'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }
+  then
+
+libc_cv_cc_x86_inline_trunc=no
+if grep -E -q "roundss" conftest; then
+  libc_cv_cc_x86_inline_trunc=yes
+fi
+
+  else
+
+echo "failed to check if -Os inlines trunc."
+rm -f conftest*
+exit 1
+
+  fi ;;
+esac
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_cv_cc_x86_inline_trunc" >&5
+printf "%s\n" "$libc_cv_cc_x86_inline_trunc" >&6; }
+rm -f conftest*
+if test "$libc_cv_cc_x86_inline_trunc" = yes; then
+  printf "%s\n" "#define HAVE_X86_INLINE_TRUNC 1" >>confdefs.h
+
+else
+  printf "%s\n" "#define HAVE_X86_INLINE_TRUNC 0" >>confdefs.h
+
+fi
+
 if test "${libc_cv_cc_no_direct_extern_access}${libc_cv_test_cc_cflags_no_direct_extern_access}" = yes; then
   libc_cv_protected_data=no
 fi

diff --git a/sysdeps/x86/configure.ac b/sysdeps/x86/configure.ac
index a87e2f6c41048c4753a713e41dc38eb508697073..f3888e6618b60d7a89d8c351a3b182aaedc737b0 100644 (file)
--- a/sysdeps/x86/configure.ac
+++ b/sysdeps/x86/configure.ac
@@ -192,6 +192,37 @@ fi
 LIBC_CONFIG_VAR(test-cc-cflags-no-direct-extern-access,
                $libc_cv_test_cc_cflags_no_direct_extern_access)
 
+conftest_code="
+extern float truncf (float __x) __attribute__ ((__nothrow__,__const__));
+
+float
+tf (float x)
+{
+  return truncf (x);
+}
+"
+dnl Check if CC inlines trunc with -Os.
+LIBC_TRY_CC_COMMAND([if -Os inlines trunc],
+  [$conftest_code],
+  [-S -Os -msse4.1],
+  libc_cv_cc_x86_inline_trunc,
+  [
+libc_cv_cc_x86_inline_trunc=no
+if grep -E -q "roundss" conftest; then
+  libc_cv_cc_x86_inline_trunc=yes
+fi
+],
+[
+echo "failed to check if -Os inlines trunc."
+rm -f conftest*
+exit 1
+])
+if test "$libc_cv_cc_x86_inline_trunc" = yes; then
+  AC_DEFINE(HAVE_X86_INLINE_TRUNC, 1)
+else
+  AC_DEFINE(HAVE_X86_INLINE_TRUNC, 0)
+fi
+
 dnl If the building compiler enables no direct external data access by
 dnl default, access to protected data in shared libraries from executables
 dnl must be compiled with no direct external data access.  If the testing

diff --git a/sysdeps/x86/fpu/math_private.h b/sysdeps/x86/fpu/math_private.h
index d30d580ceac44e65ee04069aa39f32ada4ad898a..bba085a5788b020765d8684a2aaf353351a8fa5b 100644 (file)
--- a/sysdeps/x86/fpu/math_private.h
+++ b/sysdeps/x86/fpu/math_private.h
@@ -33,27 +33,23 @@ __NTH (__ieee754_atan2l (long double y, long double x))
 __extern_always_inline double
 __trunc (double x)
 {
-#ifdef __AVX__
-  asm ("vroundsd $11, %1, %1, %0" : "=v" (x) : "v" (x));
-#elif defined __SSE4_1__
-  asm ("roundsd $11, %1, %0" : "=x" (x) : "x" (x));
+#if HAVE_X86_INLINE_TRUNC || !defined __SSE4_1__
+  return trunc (x);
 #else
-  x = trunc (x);
-#endif
+  asm ("%vroundsd $11, %d1, %0" : "=v" (x) : "v" (x));
   return x;
+#endif
 }
 
 __extern_always_inline float
 __truncf (float x)
 {
-#ifdef __AVX__
-  asm ("vroundss $11, %1, %1, %0" : "=v" (x) : "v" (x));
-#elif defined __SSE4_1__
-  asm ("roundss $11, %1, %0" : "=x" (x) : "x" (x));
+#if HAVE_X86_INLINE_TRUNC || !defined __SSE4_1__
+  return truncf (x);
 #else
-  x = truncf (x);
-#endif
+  asm ("%vroundss $11, %d1, %0" : "=v" (x) : "v" (x));
   return x;
+#endif
 }
 
 #endif