[gcc r13-2758] Fortran: handle RADIX kind in IEEE_SET_ROUNDING_MODE

["Franथईois-Xavier Coudert" <fxcoudert@gcc.gnu.org>]

https://gcc.gnu.org/g:519196a27cf534e94f158733b25a4f9d10737031

commit r13-2758-g519196a27cf534e94f158733b25a4f9d10737031
Author: Francois-Xavier Coudert <fxcoudert@gcc.gnu.org>
Date:   Wed Sep 21 11:06:19 2022 +0200

    Fortran: handle RADIX kind in IEEE_SET_ROUNDING_MODE
    
    Make sure that calling IEEE_SET_ROUNDING_MODE with RADIX=10 does not
    affect the binary rounding mode.
    
    2022-09-21  Francois-Xavier Coudert  <fxcoudert@gcc.gnu.org>
    
    libgfortran/
    
            * ieee/ieee_arithmetic.F90 (IEEE_SET_ROUNDING_MODE): Handle
            RADIX argument better.
    
    gcc/testsuite/
    
            * gfortran.dg/ieee/rounding_3.f90: New test.

Diff:
---
 gcc/testsuite/gfortran.dg/ieee/rounding_3.f90 | 27 +++++++++++++++++++++++++++
 libgfortran/ieee/ieee_arithmetic.F90          | 12 +++++++++---
 2 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/gcc/testsuite/gfortran.dg/ieee/rounding_3.f90 b/gcc/testsuite/gfortran.dg/ieee/rounding_3.f90
new file mode 100644
index 00000000000..ff4e834a042
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/ieee/rounding_3.f90
@@ -0,0 +1,27 @@
+! { dg-do run }
+
+  ! Test IEEE_GET_ROUNDING_MODE and IEEE_SET_ROUNDING_MODE
+  ! with a RADIX argument
+  use, intrinsic :: ieee_arithmetic
+  implicit none
+
+  real :: sx1
+  type(ieee_round_type) :: r
+
+  if (ieee_support_rounding(ieee_up, sx1) .and. &
+      ieee_support_rounding(ieee_down, sx1)) then
+
+    call ieee_set_rounding_mode(ieee_up)
+    call ieee_get_rounding_mode(r)
+    if (r /= ieee_up) stop 1
+
+    call ieee_set_rounding_mode(ieee_down, radix=2)
+    call ieee_get_rounding_mode(r, radix=2)
+    if (r /= ieee_down) stop 2
+
+    call ieee_set_rounding_mode(ieee_up, radix=10)
+    call ieee_get_rounding_mode(r, radix=2)
+    if (r /= ieee_down) stop 3
+  end if
+
+end
diff --git a/libgfortran/ieee/ieee_arithmetic.F90 b/libgfortran/ieee/ieee_arithmetic.F90
index ce30e4afca3..4c8e3bb5e64 100644
--- a/libgfortran/ieee/ieee_arithmetic.F90
+++ b/libgfortran/ieee/ieee_arithmetic.F90
@@ -816,7 +816,7 @@ REM_MACRO(4,4,4)
                      IEEE_SUPPORT_ROUNDING_NOARG
   end interface
   public :: IEEE_SUPPORT_ROUNDING
-  
+
   ! Interface to the FPU-specific function
   interface
     pure integer function support_rounding_helper(flag) &
@@ -839,7 +839,7 @@ REM_MACRO(4,4,4)
                      IEEE_SUPPORT_UNDERFLOW_CONTROL_NOARG
   end interface
   public :: IEEE_SUPPORT_UNDERFLOW_CONTROL
-  
+
   ! Interface to the FPU-specific function
   interface
     pure integer function support_underflow_control_helper(kind) &
@@ -1074,7 +1074,13 @@ contains
         integer, value :: val
       end subroutine
     end interface
-    
+
+    ! We do not support RADIX = 10, and such calls should not
+    ! modify the binary rounding mode.
+    if (present(RADIX)) then
+      if (RADIX == 10) return
+    end if
+
     call helper(ROUND_VALUE%hidden)
   end subroutine