to:
[evaluate loop bounds and step]
- count = (to + step - from) / step;
+ empty = (step > 0 ? to < from : to > from);
+ countm1 = (to - from) / step;
dovar = from;
+ if (empty) goto exit_label;
for (;;)
{
body;
cycle_label:
dovar += step
- count--;
- if (count <=0) goto exit_label;
+ countm1--;
+ if (countm1 ==0) goto exit_label;
}
exit_label:
- TODO: Large loop counts
- The code above assumes the loop count fits into a signed integer kind,
- i.e. Does not work for loop counts > 2^31 for integer(kind=4) variables
- We must support the full range. */
+ countm1 is an unsigned integer. It is equal to the loop count minus one,
+ because the loop count itself can overflow. */
tree
gfc_trans_do (gfc_code * code)
tree from;
tree to;
tree step;
- tree count;
- tree count_one;
+ tree empty;
+ tree countm1;
tree type;
+ tree utype;
tree cond;
tree cycle_label;
tree exit_label;
tree tmp;
+ tree pos_step;
stmtblock_t block;
stmtblock_t body;
|| tree_int_cst_equal (step, integer_minus_one_node)))
return gfc_trans_simple_do (code, &block, dovar, from, to, step);
- /* Initialize loop count. This code is executed before we enter the
- loop body. We generate: count = (to + step - from) / step. */
+ /* We need a special check for empty loops:
+ empty = (step > 0 ? to < from : to > from); */
+ pos_step = fold_build2 (GT_EXPR, boolean_type_node, step,
+ fold_convert (type, integer_zero_node));
+ empty = fold_build3 (COND_EXPR, boolean_type_node, pos_step,
+ fold_build2 (LT_EXPR, boolean_type_node, to, from),
+ fold_build2 (GT_EXPR, boolean_type_node, to, from));
- tmp = fold_build2 (MINUS_EXPR, type, step, from);
- tmp = fold_build2 (PLUS_EXPR, type, to, tmp);
+ /* Initialize loop count. This code is executed before we enter the
+ loop body. We generate: countm1 = abs(to - from) / abs(step). */
if (TREE_CODE (type) == INTEGER_TYPE)
{
- tmp = fold_build2 (TRUNC_DIV_EXPR, type, tmp, step);
- count = gfc_create_var (type, "count");
+ tree ustep;
+
+ utype = gfc_unsigned_type (type);
+
+ /* tmp = abs(to - from) / abs(step) */
+ ustep = fold_convert (utype, fold_build1 (ABS_EXPR, type, step));
+ tmp = fold_build3 (COND_EXPR, type, pos_step,
+ fold_build2 (MINUS_EXPR, type, to, from),
+ fold_build2 (MINUS_EXPR, type, from, to));
+ tmp = fold_build2 (TRUNC_DIV_EXPR, utype, fold_convert (utype, tmp),
+ ustep);
}
else
{
/* TODO: We could use the same width as the real type.
This would probably cause more problems that it solves
when we implement "long double" types. */
+ utype = gfc_unsigned_type (gfc_array_index_type);
+ tmp = fold_build2 (MINUS_EXPR, type, to, from);
tmp = fold_build2 (RDIV_EXPR, type, tmp, step);
- tmp = fold_build1 (FIX_TRUNC_EXPR, gfc_array_index_type, tmp);
- count = gfc_create_var (gfc_array_index_type, "count");
+ tmp = fold_build1 (FIX_TRUNC_EXPR, utype, tmp);
}
- gfc_add_modify_expr (&block, count, tmp);
+ countm1 = gfc_create_var (utype, "countm1");
+ gfc_add_modify_expr (&block, countm1, tmp);
- count_one = build_int_cst (TREE_TYPE (count), 1);
+ /* Cycle and exit statements are implemented with gotos. */
+ cycle_label = gfc_build_label_decl (NULL_TREE);
+ exit_label = gfc_build_label_decl (NULL_TREE);
+ TREE_USED (exit_label) = 1;
/* Initialize the DO variable: dovar = from. */
gfc_add_modify_expr (&block, dovar, from);
+ /* If the loop is empty, go directly to the exit label. */
+ tmp = fold_build3 (COND_EXPR, void_type_node, empty,
+ build1_v (GOTO_EXPR, exit_label), build_empty_stmt ());
+ gfc_add_expr_to_block (&block, tmp);
+
/* Loop body. */
gfc_start_block (&body);
- /* Cycle and exit statements are implemented with gotos. */
- cycle_label = gfc_build_label_decl (NULL_TREE);
- exit_label = gfc_build_label_decl (NULL_TREE);
-
- /* Start with the loop condition. Loop until count <= 0. */
- cond = fold_build2 (LE_EXPR, boolean_type_node, count,
- build_int_cst (TREE_TYPE (count), 0));
- tmp = build1_v (GOTO_EXPR, exit_label);
- TREE_USED (exit_label) = 1;
- tmp = fold_build3 (COND_EXPR, void_type_node,
- cond, tmp, build_empty_stmt ());
- gfc_add_expr_to_block (&body, tmp);
-
/* Put these labels where they can be found later. We put the
labels in a TREE_LIST node (because TREE_CHAIN is already
used). cycle_label goes in TREE_PURPOSE (backend_decl), exit
gfc_add_expr_to_block (&body, tmp);
}
+ /* End with the loop condition. Loop until countm1 == 0. */
+ cond = fold_build2 (EQ_EXPR, boolean_type_node, countm1,
+ build_int_cst (utype, 0));
+ tmp = build1_v (GOTO_EXPR, exit_label);
+ tmp = fold_build3 (COND_EXPR, void_type_node,
+ cond, tmp, build_empty_stmt ());
+ gfc_add_expr_to_block (&body, tmp);
+
/* Increment the loop variable. */
tmp = build2 (PLUS_EXPR, type, dovar, step);
gfc_add_modify_expr (&body, dovar, tmp);
/* Decrement the loop count. */
- tmp = build2 (MINUS_EXPR, TREE_TYPE (count), count, count_one);
- gfc_add_modify_expr (&body, count, tmp);
+ tmp = build2 (MINUS_EXPR, utype, countm1, build_int_cst (utype, 1));
+ gfc_add_modify_expr (&body, countm1, tmp);
/* End of loop body. */
tmp = gfc_finish_block (&body);
--- /dev/null
+! { dg-do run }
+! { dg-options "-std=legacy -ffree-line-length-none" }
+program test
+ integer :: count
+ integer :: i
+ integer(kind=1) :: i1
+ real :: r
+
+#define TEST_LOOP(var,from,to,step,total,test) \
+ count = 0 ; do var = from, to, step ; count = count + 1 ; end do ; \
+ if (count /= total) call abort ; \
+ if (test (from, to, step) /= total) call abort
+
+ ! Integer loops
+ TEST_LOOP(i, 0, 0, 1, 1, test_i)
+ TEST_LOOP(i, 0, 0, 2, 1, test_i)
+ TEST_LOOP(i, 0, 0, -1, 1, test_i)
+ TEST_LOOP(i, 0, 0, -2, 1, test_i)
+
+ TEST_LOOP(i, 0, 1, 1, 2, test_i)
+ TEST_LOOP(i, 0, 1, 2, 1, test_i)
+ TEST_LOOP(i, 0, 1, 3, 1, test_i)
+ TEST_LOOP(i, 0, 1, huge(0), 1, test_i)
+ TEST_LOOP(i, 0, 1, -1, 0, test_i)
+ TEST_LOOP(i, 0, 1, -2, 0, test_i)
+ TEST_LOOP(i, 0, 1, -3, 0, test_i)
+ TEST_LOOP(i, 0, 1, -huge(0), 0, test_i)
+ TEST_LOOP(i, 0, 1, -huge(0)-1, 0, test_i)
+
+ TEST_LOOP(i, 1, 0, 1, 0, test_i)
+ TEST_LOOP(i, 1, 0, 2, 0, test_i)
+ TEST_LOOP(i, 1, 0, 3, 0, test_i)
+ TEST_LOOP(i, 1, 0, huge(0), 0, test_i)
+ TEST_LOOP(i, 1, 0, -1, 2, test_i)
+ TEST_LOOP(i, 1, 0, -2, 1, test_i)
+ TEST_LOOP(i, 1, 0, -3, 1, test_i)
+ TEST_LOOP(i, 1, 0, -huge(0), 1, test_i)
+ TEST_LOOP(i, 1, 0, -huge(0)-1, 1, test_i)
+
+ TEST_LOOP(i, 0, 17, 1, 18, test_i)
+ TEST_LOOP(i, 0, 17, 2, 9, test_i)
+ TEST_LOOP(i, 0, 17, 3, 6, test_i)
+ TEST_LOOP(i, 0, 17, 4, 5, test_i)
+ TEST_LOOP(i, 0, 17, 5, 4, test_i)
+ TEST_LOOP(i, 17, 0, -1, 18, test_i)
+ TEST_LOOP(i, 17, 0, -2, 9, test_i)
+ TEST_LOOP(i, 17, 0, -3, 6, test_i)
+ TEST_LOOP(i, 17, 0, -4, 5, test_i)
+ TEST_LOOP(i, 17, 0, -5, 4, test_i)
+
+ TEST_LOOP(i1, -huge(i1)-1_1, huge(i1), 1_1, int(huge(i1))*2+2, test_i1)
+ TEST_LOOP(i1, -huge(i1)-1_1, huge(i1), 2_1, int(huge(i1))+1, test_i1)
+ TEST_LOOP(i1, -huge(i1)-1_1, huge(i1), huge(i1), 3, test_i1)
+
+ TEST_LOOP(i1, huge(i1), -huge(i1)-1_1, -1_1, int(huge(i1))*2+2, test_i1)
+ TEST_LOOP(i1, huge(i1), -huge(i1)-1_1, -2_1, int(huge(i1))+1, test_i1)
+ TEST_LOOP(i1, huge(i1), -huge(i1)-1_1, -huge(i1), 3, test_i1)
+ TEST_LOOP(i1, huge(i1), -huge(i1)-1_1, -huge(i1)-1_1, 2, test_i1)
+
+ TEST_LOOP(i1, -2_1, 3_1, huge(i1), 1, test_i1)
+ TEST_LOOP(i1, -2_1, 3_1, -huge(i1), 0, test_i1)
+ TEST_LOOP(i1, 2_1, -3_1, -huge(i1), 1, test_i1)
+ TEST_LOOP(i1, 2_1, -3_1, huge(i1), 0, test_i1)
+
+ ! Real loops
+ TEST_LOOP(r, 0.0, 1.0, 0.11, 1 + int(1.0/0.11), test_r)
+ TEST_LOOP(r, 0.0, 1.0, -0.11, 0, test_r)
+ TEST_LOOP(r, 0.0, -1.0, 0.11, 0, test_r)
+ TEST_LOOP(r, 0.0, -1.0, -0.11, 1 + int(1.0/0.11), test_r)
+ TEST_LOOP(r, 0.0, 0.0, 0.11, 1, test_r)
+ TEST_LOOP(r, 0.0, 0.0, -0.11, 1, test_r)
+
+#undef TEST_LOOP
+
+contains
+
+ function test_i1 (from, to, step) result(res)
+ integer(kind=1), intent(in) :: from, to, step
+ integer(kind=1) :: i
+ integer :: res
+
+ res = 0
+ do i = from, to, step
+ res = res + 1
+ end do
+ end function test_i1
+
+ function test_i (from, to, step) result(res)
+ integer, intent(in) :: from, to, step
+ integer :: i
+ integer :: res
+
+ res = 0
+ do i = from, to, step
+ res = res + 1
+ end do
+ end function test_i
+
+ function test_r (from, to, step) result(res)
+ real, intent(in) :: from, to, step
+ real :: i
+ integer :: res
+
+ res = 0
+ do i = from, to, step
+ res = res + 1
+ end do
+ end function test_r
+
+end program test