openmp: Map holds clause to IFN_ASSUME for Fortran

Same as r13-3107-g847f5addc4d07a2f3b95f5daa50ab4a64dfd957d did for C/C++.
Convert '!$omp assume holds(cond)' to IFN_ASSUME (cond).
    
gcc/fortran/
	* trans-openmp.cc (gfc_trans_omp_assume): New.
	(gfc_trans_omp_directive): Call it.

gcc/teststuite/
	* gfortran.dg/gomp/assume-3.f90: New test.
	* gfortran.dg/gomp/assume-4.f90: New test.

 gcc/fortran/trans-openmp.cc                 | 37 +++++++++++++++++++++-
 gcc/testsuite/gfortran.dg/gomp/assume-3.f90 | 46 +++++++++++++++++++++++++++
 gcc/testsuite/gfortran.dg/gomp/assume-4.f90 | 48 +++++++++++++++++++++++++++++
 3 files changed, 130 insertions(+), 1 deletion(-)

diff --git a/gcc/fortran/trans-openmp.cc b/gcc/fortran/trans-openmp.cc
index 21053694f81..8ea573f7d02 100644
--- a/gcc/fortran/trans-openmp.cc
+++ b/gcc/fortran/trans-openmp.cc
@@ -4570,6 +4570,41 @@ gfc_trans_oacc_wait_directive (gfc_code *code)
 static tree gfc_trans_omp_sections (gfc_code *, gfc_omp_clauses *);
 static tree gfc_trans_omp_workshare (gfc_code *, gfc_omp_clauses *);
 
+static tree
+gfc_trans_omp_assume (gfc_code *code)
+{
+  stmtblock_t block;
+  gfc_init_block (&block);
+  gfc_omp_assumptions *assume = code->ext.omp_clauses->assume;
+  if (assume)
+    for (gfc_expr_list *el = assume->holds; el; el = el->next)
+      {
+	location_t loc = gfc_get_location (&el->expr->where);
+	gfc_se se;
+	gfc_init_se (&se, NULL);
+	gfc_conv_expr (&se, el->expr);
+	tree t;
+	if (se.pre.head == NULL_TREE && se.post.head == NULL_TREE)
+	  t = se.expr;
+	else
+	  {
+	    tree var = gfc_create_var (TREE_TYPE (se.expr), NULL);
+	    stmtblock_t block2;
+	    gfc_init_block (&block2);
+	    gfc_add_block_to_block (&block2, &se.pre);
+	    gfc_add_modify_loc (loc, &block2, var, se.expr);
+	    gfc_add_block_to_block (&block2, &se.post);
+	    t = gfc_finish_block (&block2);
+	    t = build4 (TARGET_EXPR, boolean_type_node, var, t, NULL, NULL);
+	  }
+	t = build_call_expr_internal_loc (loc, IFN_ASSUME,
+					  void_type_node, 1, t);
+	gfc_add_expr_to_block (&block, t);
+      }
+  gfc_add_expr_to_block (&block, gfc_trans_omp_code (code->block->next, true));
+  return gfc_finish_block (&block);
+}
+
 static tree
 gfc_trans_omp_atomic (gfc_code *code)
 {
@@ -7488,7 +7523,7 @@ gfc_trans_omp_directive (gfc_code *code)
   switch (code->op)
     {
     case EXEC_OMP_ASSUME:
-      return gfc_trans_omp_code (code->block->next, true);
+      return gfc_trans_omp_assume (code);
     case EXEC_OMP_ATOMIC:
       return gfc_trans_omp_atomic (code);
     case EXEC_OMP_BARRIER:
diff --git a/gcc/testsuite/gfortran.dg/gomp/assume-3.f90 b/gcc/testsuite/gfortran.dg/gomp/assume-3.f90
new file mode 100644
index 00000000000..e5deace306e
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/gomp/assume-3.f90
@@ -0,0 +1,46 @@
+! { dg-do compile }
+! { dg-options "-fopenmp -O2 -fdump-tree-optimized -fdump-tree-original" }
+
+! { dg-final { scan-tree-dump-times ".ASSUME \\(x == 42\\);" 1 "original" } }
+! { dg-final { scan-tree-dump-times ".ASSUME \\(x <= 41\\);" 1 "original" } }
+! { dg-final { scan-tree-dump-times ".ASSUME \\(y <= 6\\);" 1 "original" } }
+! { dg-final { scan-tree-dump-times ".ASSUME \\(y > 5\\);" 1 "original" } }
+
+! { dg-final { scan-tree-dump-times "return 42;" 3 "optimized" } }
+! { dg-final { scan-tree-dump-not "return -1;" "optimized" } }
+
+integer function foo (x)
+  implicit none
+  integer, value :: x
+  integer :: y
+  !$omp assume holds (x == 42)
+    y = x;
+  !$omp end assume
+  foo = y
+end
+
+integer function bar (x)
+  implicit none
+  integer, value :: x
+  !$omp assume holds (x < 42)
+  block
+  end block
+  if (x == 42) then
+    bar = -1
+    return
+  end if
+  bar = 42
+end
+
+integer function foobar (y)
+  implicit none
+  integer, value :: y
+  !$omp assume holds(y > 5) holds (y < 7)
+  block
+    if (y == 6) then
+      foobar = 42
+      return
+    end if
+  end block
+  foobar = -1
+end
diff --git a/gcc/testsuite/gfortran.dg/gomp/assume-4.f90 b/gcc/testsuite/gfortran.dg/gomp/assume-4.f90
new file mode 100644
index 00000000000..f1f91924cea
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/gomp/assume-4.f90
@@ -0,0 +1,48 @@
+! { dg-do compile }
+! { dg-options "-fopenmp -O2 -fdump-tree-original -fdump-tree-optimized" }
+! { dg-final { scan-tree-dump-times ".ASSUME \\(i_lower_bound \\(\\) < i\\);" 1 "original" }
+! { dg-final { scan-tree-dump-times ".ASSUME \\(TARGET_EXPR <D.\[0-9\]+, D.\[0-9\]+ = j_upper_bound \\(\\);" 1 "original" }
+! { dg-final { scan-tree-dump-times "__builtin_free" 1 "original" }
+
+! { dg-final { scan-tree-dump-not "i_lower_bound" "optimized" }
+! { dg-final { scan-tree-dump-not "j_upper_bound" "optimized" }
+! { dg-final { scan-tree-dump-not "__builtin_free" "optimized" }
+
+! Note: Currently, the assumption does not help with optimization in either variant.
+
+  implicit none
+  integer, value :: i
+
+  !$omp assume holds(i > i_lower_bound ())
+  block
+    if (i > 4) then
+      f = 42
+    else
+      f = -1
+    end if
+  end block
+contains
+  function i_lower_bound ()
+    integer :: i_lower_bound
+    i_lower_bound = 5
+  end function
+end
+
+integer function g(j)
+  implicit none
+  integer, value :: j
+
+  !$omp assume holds(j < j_upper_bound ())
+  block
+    if (j < 10) then
+      g = 42
+    else
+      g = -1
+    end if
+  end block
+contains
+  function j_upper_bound ()
+    integer, allocatable :: j_upper_bound
+    j_upper_bound = 10
+  end function
+end