[Bug fortran/107424] [13 Regression] ICE in gfc_trans_omp_do, at fortran/trans-openmp.cc:5397 - and wrong code - with non-rectangular loops

["burnus at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107424

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |burnus at gcc dot gnu.org
           Keywords|                            |ice-on-valid-code,
                   |                            |wrong-code
            Summary|[13 Regression] ICE in      |[13 Regression] ICE in
                   |gfc_trans_omp_do, at        |gfc_trans_omp_do, at
                   |fortran/trans-openmp.cc:539 |fortran/trans-openmp.cc:539
                   |7                           |7 - and wrong code - with
                   |                            |non-rectangular loops

--- Comment #2 from Tobias Burnus <burnus at gcc dot gnu.org> ---
The following program does not ICE but it shows with -Wall:
  Warning: ‘i’ is used uninitialized
the code is as above (comment 0) except for:

   do i = 1, 9, 1   !  <<< only change: Stride == 1; ICE has stride == 2.
      do j = 1, i

Looking at the dump:

    integer(kind=4) D.4264;

    D.4264 = i;  // BAD: Uninitialized variable
    #pragma omp for collapse(2)
      {
        {
          #pragma omp simd collapse(2)
          for (i = 1; i <= 9; i = i + 1)
            for (j = 1; j <= D.4264; j = j + 1)  // Wrong: use loop war 'i' not
'D.4264'!
              {
                L.1:;
              }

--------------

Draft patch for this issue – but not for the original issue (the ICE):

--- a/gcc/fortran/trans-openmp.cc
+++ b/gcc/fortran/trans-openmp.cc
@@ -5224 +5224 @@ gfc_trans_omp_do (gfc_code *code, gfc_exec_op op, stmtblock_t
*pblock,
-      from = gfc_evaluate_now (se.expr, pblock);
+      from = DECL_P (se.expr) ? se.expr : gfc_evaluate_now (se.expr, pblock);
@@ -5229 +5229 @@ gfc_trans_omp_do (gfc_code *code, gfc_exec_op op, stmtblock_t
*pblock,
-      to = gfc_evaluate_now (se.expr, pblock);
+      to = DECL_P (se.expr) ? se.expr : gfc_evaluate_now (se.expr, pblock);
@@ -5234 +5234 @@ gfc_trans_omp_do (gfc_code *code, gfc_exec_op op, stmtblock_t
*pblock,
-      step = gfc_evaluate_now (se.expr, pblock);
+      step = DECL_P (se.expr) ? se.expr : gfc_evaluate_now (se.expr, pblock);