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Commit 9f3dcd14 by Janne Blomqvist
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PR 78534 Reinstate better string copy algorithm 

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.

gcc/fortran/ChangeLog:

2018-01-31  Janne Blomqvist  <jb@gcc.gnu.org>

	PR fortran/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:

2018-01-31  Janne Blomqvist  <jb@gcc.gnu.org>

	PR fortran/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.

From-SVN: r257233
parent 957a25ab
Showing with 51 additions and 27 deletions
gcc/fortran/ChangeLog
2018-01-31 Janne Blomqvist <jb@gcc.gnu.org>
PR fortran/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.
2018-01-30 Jakub Jelinek <jakub@redhat.com>
PR debug/84131
......
gcc/fortran/trans-expr.c
......@@ -6411,8 +6411,6 @@ 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),
......@@ -6420,7 +6418,6 @@ 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))
......@@ -6526,11 +6523,20 @@ 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. */
......@@ -6559,21 +6565,16 @@ 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
......@@ -6588,14 +6589,19 @@ 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);
......
gcc/testsuite/ChangeLog
2018-01-31 Janne Blomqvist <jb@gcc.gnu.org>
PR fortran/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.
2018-01-31 Richard Biener <rguenther@suse.de>
PR tree-optimization/84132
......
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=]" }
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" } }
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" } }
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