As part of the change to larger character lengths, the string copy
algorithm was temporarily pessimized to get around some spurious
-Wstringop-overflow warnings. Having tried a number of variations of
this algorithm I have managed to get it down to one spurious warning,
only with -O1 optimization, in the testsuite. This patch reinstates
the optimized variant and modifies this one testcase to ignore the
warning.
Regtested on x86_64-pc-linux-gnu, Ok for trunk?
gcc/fortran/ChangeLog:
2018-01-23 Janne Blomqvist <j...@gcc.gnu.org>
PR 78534
* trans-expr.c (fill_with_spaces): Use memset instead of
generating loop.
(gfc_trans_string_copy): Improve opportunity to use builtins with
constant lengths.
gcc/testsuite/ChangeLog:
2018-01-23 Janne Blomqvist <j...@gcc.gnu.org>
PR 78534
* gfortran.dg/allocate_deferred_char_scalar_1.f03: Prune
-Wstringop-overflow warnings due to spurious warning with -O1.
* gfortran.dg/char_cast_1.f90: Update dump scan pattern.
* gfortran.dg/transfer_intrinsic_1.f90: Likewise.
---
gcc/fortran/trans-expr.c | 52 ++++++++++++----------
.../allocate_deferred_char_scalar_1.f03 | 2 +
gcc/testsuite/gfortran.dg/char_cast_1.f90 | 6 +--
gcc/testsuite/gfortran.dg/transfer_intrinsic_1.f90 | 2 +-
4 files changed, 35 insertions(+), 27 deletions(-)
diff --git a/gcc/fortran/trans-expr.c b/gcc/fortran/trans-expr.c
index e90036f..4da6cee 100644
--- a/gcc/fortran/trans-expr.c
+++ b/gcc/fortran/trans-expr.c
@@ -6407,8 +6407,6 @@ fill_with_spaces (tree start, tree type, tree size)
tree i, el, exit_label, cond, tmp;
/* For a simple char type, we can call memset(). */
- /* TODO: This code does work and is potentially more efficient, but
- causes spurious -Wstringop-overflow warnings.
if (compare_tree_int (TYPE_SIZE_UNIT (type), 1) == 0)
return build_call_expr_loc (input_location,
builtin_decl_explicit (BUILT_IN_MEMSET),
@@ -6416,7 +6414,6 @@ fill_with_spaces (tree start, tree type, tree size)
build_int_cst (gfc_get_int_type (gfc_c_int_kind),
lang_hooks.to_target_charset (' ')),
fold_convert (size_type_node, size));
- */
/* Otherwise, we use a loop:
for (el = start, i = size; i > 0; el--, i+= TYPE_SIZE_UNIT (type))
@@ -6522,11 +6519,20 @@ gfc_trans_string_copy (stmtblock_t * block, tree
dlength, tree dest,
/* The string copy algorithm below generates code like
- if (dlen > 0) {
- memmove (dest, src, min(dlen, slen));
- if (slen < dlen)
- memset(&dest[slen], ' ', dlen - slen);
- }
+ if (destlen > 0)
+ {
+ if (srclen < destlen)
+ {
+ memmove (dest, src, srclen);
+ // Pad with spaces.
+ memset (&dest[srclen], ' ', destlen - srclen);
+ }
+ else
+ {
+ // Truncate if too long.
+ memmove (dest, src, destlen);
+ }
+ }
*/
/* Do nothing if the destination length is zero. */
@@ -6555,21 +6561,16 @@ gfc_trans_string_copy (stmtblock_t * block, tree
dlength, tree dest,
else
src = gfc_build_addr_expr (pvoid_type_node, src);
- /* First do the memmove. */
- tmp2 = fold_build2_loc (input_location, MIN_EXPR, TREE_TYPE (dlen), dlen,
- slen);
- tmp2 = build_call_expr_loc (input_location,
- builtin_decl_explicit (BUILT_IN_MEMMOVE),
- 3, dest, src,
- fold_convert (size_type_node, tmp2));
- stmtblock_t tmpblock2;
- gfc_init_block (&tmpblock2);
- gfc_add_expr_to_block (&tmpblock2, tmp2);
-
- /* If the destination is longer, fill the end with spaces. */
+ /* Truncate string if source is too long. */
cond2 = fold_build2_loc (input_location, LT_EXPR, logical_type_node, slen,
dlen);
+ /* Copy and pad with spaces. */
+ tmp3 = build_call_expr_loc (input_location,
+ builtin_decl_explicit (BUILT_IN_MEMMOVE),
+ 3, dest, src,
+ fold_convert (size_type_node, slen));
+
/* Wstringop-overflow appears at -O3 even though this warning is not
explicitly available in fortran nor can it be switched off. If the
source length is a constant, its negative appears as a very large
@@ -6584,14 +6585,19 @@ gfc_trans_string_copy (stmtblock_t * block, tree
dlength, tree dest,
tmp4 = fill_with_spaces (tmp4, chartype, tmp);
gfc_init_block (&tempblock);
+ gfc_add_expr_to_block (&tempblock, tmp3);
gfc_add_expr_to_block (&tempblock, tmp4);
tmp3 = gfc_finish_block (&tempblock);
+ /* The truncated memmove if the slen >= dlen. */
+ tmp2 = build_call_expr_loc (input_location,
+ builtin_decl_explicit (BUILT_IN_MEMMOVE),
+ 3, dest, src,
+ fold_convert (size_type_node, dlen));
+
/* The whole copy_string function is there. */
tmp = fold_build3_loc (input_location, COND_EXPR, void_type_node, cond2,
- tmp3, build_empty_stmt (input_location));
- gfc_add_expr_to_block (&tmpblock2, tmp);
- tmp = gfc_finish_block (&tmpblock2);
+ tmp3, tmp2);
tmp = fold_build3_loc (input_location, COND_EXPR, void_type_node, cond, tmp,
build_empty_stmt (input_location));
gfc_add_expr_to_block (block, tmp);
diff --git a/gcc/testsuite/gfortran.dg/allocate_deferred_char_scalar_1.f03
b/gcc/testsuite/gfortran.dg/allocate_deferred_char_scalar_1.f03
index b9b7040..d5ca573 100644
--- a/gcc/testsuite/gfortran.dg/allocate_deferred_char_scalar_1.f03
+++ b/gcc/testsuite/gfortran.dg/allocate_deferred_char_scalar_1.f03
@@ -265,3 +265,5 @@ contains
if(len(p4) /= 3) call abort()
end subroutine source3
end program test
+! Spurious -Wstringop-overflow warning with -O1
+! { dg-prune-output "\\\[-Wstringop-overflow=]" }
diff --git a/gcc/testsuite/gfortran.dg/char_cast_1.f90
b/gcc/testsuite/gfortran.dg/char_cast_1.f90
index 70963bb..02e695d 100644
--- a/gcc/testsuite/gfortran.dg/char_cast_1.f90
+++ b/gcc/testsuite/gfortran.dg/char_cast_1.f90
@@ -25,6 +25,6 @@
return
end function Upper
end
-! The sign that all is well is that [S.10][1] appears twice.
-! Platform dependent variations are [S$10][1], [__S_10][1], [S___10][1]
-! { dg-final { scan-tree-dump-times "10\\\]\\\[1\\\]" 2 "original" } }
+! The sign that all is well is that [S.6][1] appears twice.
+! Platform dependent variations are [S$6][1], [__S_6][1], [S___6][1]
+! { dg-final { scan-tree-dump-times "6\\\]\\\[1\\\]" 2 "original" } }
diff --git a/gcc/testsuite/gfortran.dg/transfer_intrinsic_1.f90
b/gcc/testsuite/gfortran.dg/transfer_intrinsic_1.f90
index 73a7e77..5f46cd0 100644
--- a/gcc/testsuite/gfortran.dg/transfer_intrinsic_1.f90
+++ b/gcc/testsuite/gfortran.dg/transfer_intrinsic_1.f90
@@ -14,4 +14,4 @@ subroutine BytesToString(bytes, string)
character(len=*) :: string
string = transfer(bytes, string)
end subroutine
-! { dg-final { scan-tree-dump-times "MIN_EXPR" 2 "original" } }
+! { dg-final { scan-tree-dump-times "MIN_EXPR" 1 "original" } }
--
2.7.4
