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
This commit is contained in:
Janne Blomqvist
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6 changed files with 51 additions and 27 deletions
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@ -1,3 +1,11 @@
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2018-01-31 Janne Blomqvist <jb@gcc.gnu.org>
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PR fortran/78534
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* trans-expr.c (fill_with_spaces): Use memset instead of
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generating loop.
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(gfc_trans_string_copy): Improve opportunity to use builtins with
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constant lengths.
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2018-01-30 Jakub Jelinek <jakub@redhat.com>
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PR debug/84131
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@ -6411,8 +6411,6 @@ fill_with_spaces (tree start, tree type, tree size)
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tree i, el, exit_label, cond, tmp;
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/* For a simple char type, we can call memset(). */
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/* TODO: This code does work and is potentially more efficient, but
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causes spurious -Wstringop-overflow warnings.
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if (compare_tree_int (TYPE_SIZE_UNIT (type), 1) == 0)
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return build_call_expr_loc (input_location,
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builtin_decl_explicit (BUILT_IN_MEMSET),
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@ -6420,7 +6418,6 @@ fill_with_spaces (tree start, tree type, tree size)
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build_int_cst (gfc_get_int_type (gfc_c_int_kind),
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lang_hooks.to_target_charset (' ')),
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fold_convert (size_type_node, size));
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*/
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/* Otherwise, we use a loop:
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for (el = start, i = size; i > 0; el--, i+= TYPE_SIZE_UNIT (type))
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@ -6526,11 +6523,20 @@ gfc_trans_string_copy (stmtblock_t * block, tree dlength, tree dest,
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/* The string copy algorithm below generates code like
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if (dlen > 0) {
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memmove (dest, src, min(dlen, slen));
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if (slen < dlen)
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memset(&dest[slen], ' ', dlen - slen);
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}
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if (destlen > 0)
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{
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if (srclen < destlen)
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{
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memmove (dest, src, srclen);
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// Pad with spaces.
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memset (&dest[srclen], ' ', destlen - srclen);
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}
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else
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{
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// Truncate if too long.
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memmove (dest, src, destlen);
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}
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}
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*/
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/* Do nothing if the destination length is zero. */
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@ -6559,21 +6565,16 @@ gfc_trans_string_copy (stmtblock_t * block, tree dlength, tree dest,
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else
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src = gfc_build_addr_expr (pvoid_type_node, src);
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/* First do the memmove. */
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tmp2 = fold_build2_loc (input_location, MIN_EXPR, TREE_TYPE (dlen), dlen,
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slen);
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tmp2 = build_call_expr_loc (input_location,
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builtin_decl_explicit (BUILT_IN_MEMMOVE),
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3, dest, src,
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fold_convert (size_type_node, tmp2));
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stmtblock_t tmpblock2;
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gfc_init_block (&tmpblock2);
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gfc_add_expr_to_block (&tmpblock2, tmp2);
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/* If the destination is longer, fill the end with spaces. */
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/* Truncate string if source is too long. */
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cond2 = fold_build2_loc (input_location, LT_EXPR, logical_type_node, slen,
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dlen);
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/* Copy and pad with spaces. */
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tmp3 = build_call_expr_loc (input_location,
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builtin_decl_explicit (BUILT_IN_MEMMOVE),
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3, dest, src,
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fold_convert (size_type_node, slen));
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/* Wstringop-overflow appears at -O3 even though this warning is not
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explicitly available in fortran nor can it be switched off. If the
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source length is a constant, its negative appears as a very large
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@ -6588,14 +6589,19 @@ gfc_trans_string_copy (stmtblock_t * block, tree dlength, tree dest,
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tmp4 = fill_with_spaces (tmp4, chartype, tmp);
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gfc_init_block (&tempblock);
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gfc_add_expr_to_block (&tempblock, tmp3);
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gfc_add_expr_to_block (&tempblock, tmp4);
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tmp3 = gfc_finish_block (&tempblock);
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/* The truncated memmove if the slen >= dlen. */
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tmp2 = build_call_expr_loc (input_location,
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builtin_decl_explicit (BUILT_IN_MEMMOVE),
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3, dest, src,
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fold_convert (size_type_node, dlen));
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/* The whole copy_string function is there. */
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tmp = fold_build3_loc (input_location, COND_EXPR, void_type_node, cond2,
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tmp3, build_empty_stmt (input_location));
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gfc_add_expr_to_block (&tmpblock2, tmp);
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tmp = gfc_finish_block (&tmpblock2);
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tmp3, tmp2);
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tmp = fold_build3_loc (input_location, COND_EXPR, void_type_node, cond, tmp,
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build_empty_stmt (input_location));
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gfc_add_expr_to_block (block, tmp);
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@ -1,3 +1,11 @@
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2018-01-31 Janne Blomqvist <jb@gcc.gnu.org>
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PR fortran/78534
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* gfortran.dg/allocate_deferred_char_scalar_1.f03: Prune
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-Wstringop-overflow warnings due to spurious warning with -O1.
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* gfortran.dg/char_cast_1.f90: Update dump scan pattern.
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* gfortran.dg/transfer_intrinsic_1.f90: Likewise.
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2018-01-31 Richard Biener <rguenther@suse.de>
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PR tree-optimization/84132
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@ -265,3 +265,5 @@ contains
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if(len(p4) /= 3) call abort()
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end subroutine source3
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end program test
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! Spurious -Wstringop-overflow warning with -O1
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! { dg-prune-output "\\\[-Wstringop-overflow=]" }
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@ -25,6 +25,6 @@
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return
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end function Upper
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end
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! The sign that all is well is that [S.10][1] appears twice.
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! Platform dependent variations are [S$10][1], [__S_10][1], [S___10][1]
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! { dg-final { scan-tree-dump-times "10\\\]\\\[1\\\]" 2 "original" } }
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! The sign that all is well is that [S.6][1] appears twice.
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! Platform dependent variations are [S$6][1], [__S_6][1], [S___6][1]
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! { dg-final { scan-tree-dump-times "6\\\]\\\[1\\\]" 2 "original" } }
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@ -14,4 +14,4 @@ subroutine BytesToString(bytes, string)
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character(len=*) :: string
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string = transfer(bytes, string)
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end subroutine
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! { dg-final { scan-tree-dump-times "MIN_EXPR" 2 "original" } }
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! { dg-final { scan-tree-dump-times "MIN_EXPR" 1 "original" } }
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