https://gcc.gnu.org/g:efd0ef174b7fdf08b18c5efbd141ef81d73de407

commit efd0ef174b7fdf08b18c5efbd141ef81d73de407
Author: Mikael Morin <[email protected]>
Date:   Sat Nov 18 20:54:20 2023 +0100

    fortran: Check for empty MINLOC/MAXLOC ARRAY along DIM only
    
    Bootstrapped and regression-tested on x86_64-pc-linux-gnu.
    OK for master?
    
    -- >8 --
    
    In the function generating inline code to implement MINLOC and MAXLOC, only
    check for ARRAY size along DIM if DIM is present.
    
    The check for ARRAY emptyness had been checking the size of the full array,
    which is correct for MINLOC and MAXLOC without DIM.  But if DIM is
    present, the reduction is along DIM only so the check for emptyness
    should consider that dimension only as well.
    
    This sounds like a correctness issue, but fortunately the cases where it
    makes a difference are cases where ARRAY is empty, so even if the value
    calculated for MINLOC or MAXLOC is wrong, it's wrapped in a zero iteration
    loop, and the wrong values are not actually used.  In the end this just
    avoids unnecessary calculations.
    
    A previous version of this patch regressed on non-constant DIM with rank 1
    ARRAY.  The new testcase checks that that case is supported.
    
    gcc/fortran/ChangeLog:
    
            * trans-intrinsic.cc (gfc_conv_intrinsic_minmaxloc): Only get the 
size
            along DIM instead of the full size if DIM is present.
    
    gcc/testsuite/ChangeLog:
    
            * gfortran.dg/minmaxloc_22.f90: New test.

Diff:
---
 gcc/fortran/trans-intrinsic.cc             | 19 ++++++++++++++++++-
 gcc/testsuite/gfortran.dg/minmaxloc_22.f90 | 26 ++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/gcc/fortran/trans-intrinsic.cc b/gcc/fortran/trans-intrinsic.cc
index 12bda2108bf4..8b4fd8e23312 100644
--- a/gcc/fortran/trans-intrinsic.cc
+++ b/gcc/fortran/trans-intrinsic.cc
@@ -5642,7 +5642,24 @@ gfc_conv_intrinsic_minmaxloc (gfc_se * se, gfc_expr * 
expr, enum tree_code op)
   if (!(maskexpr && maskexpr->rank > 0))
     {
       mpz_t asize;
-      if (gfc_array_size (arrayexpr, &asize))
+      bool reduction_size_known;
+
+      if (dim_present)
+       {
+         int reduction_dim;
+         if (dim_arg->expr->expr_type == EXPR_CONSTANT)
+           reduction_dim = mpz_get_si (dim_arg->expr->value.integer) - 1;
+         else if (arrayexpr->rank == 1)
+           reduction_dim = 0;
+         else
+           gcc_unreachable ();
+         reduction_size_known = gfc_array_dimen_size (arrayexpr, reduction_dim,
+                                                      &asize);
+       }
+      else
+       reduction_size_known = gfc_array_size (arrayexpr, &asize);
+
+      if (reduction_size_known)
        {
          nonempty = gfc_conv_mpz_to_tree (asize, gfc_index_integer_kind);
          mpz_clear (asize);
diff --git a/gcc/testsuite/gfortran.dg/minmaxloc_22.f90 
b/gcc/testsuite/gfortran.dg/minmaxloc_22.f90
new file mode 100644
index 000000000000..ec97d1435af8
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/minmaxloc_22.f90
@@ -0,0 +1,26 @@
+! { dg-do compile }
+! { dg-additional-options "-O" }
+!
+! Check that the inline code generated for MINLOC and MAXLOC supports
+! a non-constant DIM argument if ARRAY has rank 1.
+
+program p
+  implicit none
+  integer, parameter :: n = 5
+  integer :: a(n), i
+  a = (/ (i**2, i=1,n) /)
+  print *, f(a, 1), g(a, 1)
+contains
+  function f(a, d)
+    integer :: a(n)
+    integer :: d
+    integer :: f
+    f = minloc(a, dim=d) 
+  end function
+  function g(a, d)
+    integer :: a(n)
+    integer :: d
+    integer :: g
+    g = maxloc(a, dim=d) 
+  end function
+end program p

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