The existing implementation of f_c_string is quite inefficient, doing
either 2 or 3 allocations and copies of the input string prefix. This
rewrite adds folding for constant string arguments and handles other
cases with a single allocation and copy.
This patch also adds the missing documentation for this intrinsic to the
gfortran manual.
gcc/fortran/ChangeLog
* intrinsic.texi (F_C_STRING): New section.
* trans-intrinsic.cc (conv_trim): Delete.
(conv_isocbinding_function): Rewrite the F_C_STRING case.
gcc/testsuite/ChangeLog
* gfortran.dg/f_c_string3.f90: New.
* gfortran.dg/f_c_string4.f90: New.
* gfortran.dg/f_c_string5.f90: New.
---
gcc/fortran/intrinsic.texi | 57 ++++
gcc/fortran/trans-intrinsic.cc | 328 ++++++++++++----------
gcc/testsuite/gfortran.dg/f_c_string3.f90 | 53 ++++
gcc/testsuite/gfortran.dg/f_c_string4.f90 | 26 ++
gcc/testsuite/gfortran.dg/f_c_string5.f90 | 20 ++
5 files changed, 328 insertions(+), 156 deletions(-)
create mode 100644 gcc/testsuite/gfortran.dg/f_c_string3.f90
create mode 100644 gcc/testsuite/gfortran.dg/f_c_string4.f90
create mode 100644 gcc/testsuite/gfortran.dg/f_c_string5.f90
diff --git a/gcc/fortran/intrinsic.texi b/gcc/fortran/intrinsic.texi
index 8a33fff68f9..699b38e157c 100644
--- a/gcc/fortran/intrinsic.texi
+++ b/gcc/fortran/intrinsic.texi
@@ -159,6 +159,7 @@ Some basic guidelines for editing this document:
* @code{EXP}: EXP, Exponential function
* @code{EXPONENT}: EXPONENT, Exponent function
* @code{EXTENDS_TYPE_OF}: EXTENDS_TYPE_OF, Query dynamic type for extension
+* @code{F_C_STRING}: F_C_STRING, Convert character scalar to C string
* @code{FDATE}: FDATE, Subroutine (or function) to get the current
time as a string
* @code{FGET}: FGET, Read a single character in stream mode from
stdin
* @code{FGETC}: FGETC, Read a single character in stream mode
@@ -3558,6 +3559,7 @@ Fortran 2023 and later.
@ref{C_LOC}, @*
@ref{C_F_POINTER}
@ref{C_F_PROCPOINTER}
+@ref{F_C_STRING}
@end table
@@ -6394,6 +6396,61 @@ Fortran 2003 and later
+@node F_C_STRING
+@section @code{F_C_STRING} --- Convert Fortran character scalar to C string
+@fnindex F_C_STRING
+@cindex string, convert Fortran to C
+
+@table @asis
+@item @emph{Synopsis}:
+@code{RESULT = F_C_STRING(STRING[, ASIS])}
+
+@item @emph{Description}:
+The @code{F_C_STRING} intrinsic is equivalent to @code{STRING//C_NULL_CHAR}
+if the @code{ASIS} argument is present and true, and to
+@code{TRIM(STRING)//C_NULL_CHAR} otherwise.
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STRING} @tab A character scalar of kind @code{C_CHAR}.
+@item @var{ASIS} @tab An optional logical scalar.
+@end multitable
+
+@item @emph{Return value}:
+The result is a null-terminated character scalar of the same type and kind
+as @code{STRING}, suitable for passing to a C function that accepts a
+@code{char *} argument.
+
+@item @emph{Example}:
+@smallexample
+program main
+ use iso_c_binding, only: f_c_string, c_char
+ implicit none (external, type)
+ character(:, c_char), allocatable :: s1, s2, s3
+
+ ! s1 is null-terminated "hello, world! "
+ s1 = f_c_string ("hello, world! ", .true.)
+
+ ! s2 is null-terminated "hello, world!"
+ s2 = f_c_string ("hello, world! ", .false.)
+
+ ! s3 is null-terminated "hello, world!" (same as s2 example)
+ s3 = f_c_string ("hello, world! ")
+end program main
+
+@end smallexample
+
+@item @emph{Standard}:
+Fortran 2023 and later.
+
+@item @emph{See also}:
+@ref{C_F_STRPOINTER}
+@end table
+
+
@node FDATE
@section @code{FDATE} --- Get the current time as a string
@fnindex FDATE
diff --git a/gcc/fortran/trans-intrinsic.cc b/gcc/fortran/trans-intrinsic.cc
index a18a6436062..fdb9ddb52ea 100644
--- a/gcc/fortran/trans-intrinsic.cc
+++ b/gcc/fortran/trans-intrinsic.cc
@@ -9840,37 +9840,6 @@ gfc_conv_intrinsic_loc (gfc_se * se, gfc_expr * expr)
se->expr = temp_var;
}
-
-/* Specialized trim for f_c_string. */
-
-static void
-conv_trim (gfc_se *tse, gfc_se *str)
-{
- tree cond, plen, pvar, tlen, ttmp, tvar;
-
- tlen = gfc_create_var (gfc_charlen_type_node, "tlen");
- plen = gfc_build_addr_expr (NULL_TREE, tlen);
-
- tvar = gfc_create_var (pchar_type_node, "tstr");
- pvar = gfc_build_addr_expr (ppvoid_type_node, tvar);
-
- ttmp = build_call_expr_loc (input_location, gfor_fndecl_string_trim, 4,
- plen, pvar, str->string_length, str->expr);
-
- gfc_add_expr_to_block (&tse->pre, ttmp);
-
- /* Free the temporary afterwards, if necessary. */
- cond = fold_build2_loc (input_location, GT_EXPR, logical_type_node,
- tlen, build_int_cst (TREE_TYPE (tlen), 0));
- ttmp = gfc_call_free (tvar);
- ttmp = build3_v (COND_EXPR, cond, ttmp, build_empty_stmt (input_location));
- gfc_add_expr_to_block (&tse->post, ttmp);
-
- tse->expr = tvar;
- tse->string_length = tlen;
-}
-
-
/* The following routine generates code for the intrinsic functions from
the ISO_C_BINDING module: C_LOC, C_FUNLOC, C_ASSOCIATED, and
F_C_STRING. */
@@ -9965,141 +9934,188 @@ conv_isocbinding_function (gfc_se *se, gfc_expr *expr)
f_c_string(string, .false.) -> trim(string) // c_null_char
f_c_string(string, .true.) -> string // c_null_char */
- gfc_se lse, rse, tse;
- tree len, tmp, var;
gfc_expr *string = arg->expr;
gfc_expr *asis = arg->next->expr;
- gfc_expr *cnc;
+ bool need_asis = false, need_trim = false;
+ gfc_se asis_se;
- /* Convert string. */
- gfc_init_se (&lse, se);
- gfc_conv_expr (&lse, string);
- gfc_conv_string_parameter (&lse);
-
- /* Create a string for C_NULL_CHAR and convert it. */
- cnc = gfc_get_character_expr (gfc_default_character_kind,
- &string->where, "\0", 1);
- gfc_init_se (&rse, se);
- gfc_conv_expr (&rse, cnc);
- gfc_conv_string_parameter (&rse);
- gfc_free_expr (cnc);
-
-#ifdef cnode
-#undef cnode
-#endif
-#define cnode gfc_charlen_type_node
- if (asis)
+ if (!asis)
{
- stmtblock_t block;
- gfc_se asis_se, vse;
- tree elen, evar, tlen, tvar;
- tree else_branch, then_branch;
-
- elen = evar = tlen = tvar = NULL_TREE;
-
- /* f_c_string(string, .true.) -> string // c_null_char */
-
- gfc_init_block (&block);
-
- gfc_add_block_to_block (&block, &lse.pre);
- gfc_add_block_to_block (&block, &rse.pre);
-
- tlen = fold_build2_loc (input_location, PLUS_EXPR, cnode,
- fold_convert (cnode, lse.string_length),
- fold_convert (cnode, rse.string_length));
-
- gfc_init_se (&vse, se);
- tvar = gfc_conv_string_tmp (&vse, pchar_type_node, tlen);
- gfc_add_block_to_block (&block, &vse.pre);
-
- tmp = build_call_expr_loc (input_location, gfor_fndecl_concat_string,
- 6, tlen, tvar,
- lse.string_length, lse.expr,
- rse.string_length, rse.expr);
- gfc_add_expr_to_block (&block, tmp);
-
- then_branch = gfc_finish_block (&block);
-
- /* f_c_string(string, .false.) = trim(string) // c_null_char */
-
- gfc_init_block (&block);
-
- gfc_init_se (&tse, se);
- conv_trim (&tse, &lse);
- gfc_add_block_to_block (&block, &tse.pre);
- gfc_add_block_to_block (&block, &rse.pre);
-
- elen = fold_build2_loc (input_location, PLUS_EXPR, cnode,
- fold_convert (cnode, tse.string_length),
- fold_convert (cnode, rse.string_length));
-
- gfc_init_se (&vse, se);
- evar = gfc_conv_string_tmp (&vse, pchar_type_node, elen);
- gfc_add_block_to_block (&block, &vse.pre);
-
- tmp = build_call_expr_loc (input_location, gfor_fndecl_concat_string,
- 6, elen, evar,
- tse.string_length, tse.expr,
- rse.string_length, rse.expr);
- gfc_add_expr_to_block (&block, tmp);
-
- else_branch = gfc_finish_block (&block);
-
- gfc_init_se (&asis_se, se);
- gfc_conv_expr (&asis_se, asis);
- if (asis->expr_type == EXPR_VARIABLE
- && asis->symtree->n.sym->attr.dummy
- && asis->symtree->n.sym->attr.optional)
- {
- tree present = gfc_conv_expr_present (asis->symtree->n.sym);
- asis_se.expr = build3_loc (input_location, COND_EXPR,
- logical_type_node, present,
- asis_se.expr,
- build_int_cst (logical_type_node, 0));
- }
- gfc_add_block_to_block (&se->pre, &asis_se.pre);
- tmp = fold_build3_loc (input_location, COND_EXPR, void_type_node,
- asis_se.expr, then_branch, else_branch);
-
- gfc_add_expr_to_block (&se->pre, tmp);
-
- var = fold_build3_loc (input_location, COND_EXPR, pchar_type_node,
- asis_se.expr, tvar, evar);
- gfc_add_expr_to_block (&se->pre, var);
-
- len = fold_build3_loc (input_location, COND_EXPR, cnode,
- asis_se.expr, tlen, elen);
- gfc_add_expr_to_block (&se->pre, len);
+ need_trim = true;
+ need_asis = false;
+ }
+ else if (asis->expr_type == EXPR_CONSTANT)
+ {
+ need_asis = asis->value.logical;
+ need_trim = !need_asis;
}
else
{
- /* f_c_string(string) = trim(string) // c_null_char */
-
- gfc_add_block_to_block (&se->pre, &lse.pre);
- gfc_add_block_to_block (&se->pre, &rse.pre);
-
- gfc_init_se (&tse, se);
- conv_trim (&tse, &lse);
- gfc_add_block_to_block (&se->pre, &tse.pre);
- gfc_add_block_to_block (&se->post, &tse.post);
-
- len = fold_build2_loc (input_location, PLUS_EXPR, cnode,
- fold_convert (cnode, tse.string_length),
- fold_convert (cnode, rse.string_length));
-
- var = gfc_conv_string_tmp (se, pchar_type_node, len);
-
- tmp = build_call_expr_loc (input_location, gfor_fndecl_concat_string,
- 6, len, var,
- tse.string_length, tse.expr,
- rse.string_length, rse.expr);
- gfc_add_expr_to_block (&se->pre, tmp);
+ /* A conditional expression is needed. */
+ need_asis = true;
+ need_trim = true;
+ gfc_init_se (&asis_se, se);
+ gfc_conv_expr (&asis_se, asis);
+ if (asis->expr_type == EXPR_VARIABLE
+ && asis->symtree->n.sym->attr.dummy
+ && asis->symtree->n.sym->attr.optional)
+ {
+ tree present = gfc_conv_expr_present (asis->symtree->n.sym);
+ asis_se.expr
+ = build3_loc (input_location, COND_EXPR,
+ logical_type_node, present,
+ asis_se.expr, logical_false_node);
+ }
+ gfc_make_safe_expr (&asis_se);
}
- se->expr = var;
- se->string_length = len;
+ /* Handle the case of a constant string argument first. */
+ if (string->expr_type == EXPR_CONSTANT)
+ {
+ /* Output for the asis "then" case goes tlen/tstr, and the
+ trimmed case in elen/estr. */
+ tree elen, estr, tlen, tstr;
+ elen = estr = tlen = tstr = NULL_TREE;
-#undef cnode
+ gfc_char_t *orig_string = string->value.character.string;
+ gfc_charlen_t orig_len = string->value.character.length;
+ gfc_charlen_t n;
+ gfc_char_t *buf
+ = (gfc_char_t *) alloca ((orig_len + 1) * sizeof (gfc_char_t));
+ memcpy (buf, orig_string, orig_len * sizeof (gfc_char_t));
+ buf[orig_len] = '\0';
+ int kind = gfc_default_character_kind;
+ gcc_assert (string->ts.kind == kind);
+
+ /* Build the new string constant(s). */
+ if (need_asis)
+ {
+ tstr = gfc_build_wide_string_const (kind, orig_len + 1, buf);
+ tlen = TYPE_MAX_VALUE (TYPE_DOMAIN (TREE_TYPE (tstr)));
+ if (!need_trim)
+ {
+ se->expr = tstr;
+ se->string_length = tlen;
+ return;
+ }
+ }
+ if (need_trim)
+ {
+ for (n = orig_len; n; n--)
+ if (buf[n - 1] != ' ')
+ break;
+ buf[n] = '\0';
+ if (need_asis && n == orig_len)
+ {
+ /* Special case; trimming is a no-op. Add side-effects
+ from the condition and then just return the string
+ without a conditional. */
+ gfc_add_block_to_block (&se->pre, &asis_se.pre);
+ se->expr = tstr;
+ se->string_length = tlen;
+ return;
+ }
+ else
+ {
+ estr = gfc_build_wide_string_const (kind, n + 1, buf);
+ elen = TYPE_MAX_VALUE (TYPE_DOMAIN (TREE_TYPE (estr)));
+ }
+ if (!need_asis)
+ {
+ se->expr = estr;
+ se->string_length = elen;
+ return;
+ }
+ }
+ gcc_assert (need_asis && need_trim);
+ gfc_add_block_to_block (&se->pre, &asis_se.pre);
+ se->expr
+ = fold_build3_loc (input_location, COND_EXPR,
+ pchar_type_node, asis_se.expr,
+ tstr, estr);
+ se->string_length
+ = fold_build3_loc (input_location, COND_EXPR,
+ gfc_charlen_type_node, asis_se.expr,
+ tlen, elen);
+ return;
+ }
+ else
+ /* We have to generate code to do the string transformation(s) at
+ runtime. */
+ {
+ tree tmp;
+
+ /* Convert input string. */
+ gfc_se sse;
+ gfc_init_se (&sse, se);
+ gfc_conv_expr (&sse, string);
+ gfc_conv_string_parameter (&sse);
+ gfc_make_safe_expr (&sse);
+ gfc_add_block_to_block (&se->pre, &sse.pre);
+
+ /* Use a temporary for the (possibly trimmed) string length. */
+ tree lenvar = gfc_create_var (gfc_charlen_type_node, NULL);
+ gfc_add_modify (&se->pre, lenvar, sse.string_length);
+
+ /* Build the expression for a call to LEN_TRIM if we may need
+ to trim the string. If it's conditional, handle that too. */
+ if (need_trim)
+ {
+ tree trimlen
+ = build_call_expr_loc (input_location,
+ gfor_fndecl_string_len_trim, 2,
+ lenvar, sse.expr);
+ if (need_asis)
+ {
+ gfc_add_block_to_block (&se->pre, &asis_se.pre);
+ tmp = fold_build3_loc (input_location, COND_EXPR,
+ gfc_charlen_type_node, asis_se.expr,
+ lenvar, trimlen);
+ gfc_add_modify (&se->pre, lenvar, tmp);
+ }
+ else
+ gfc_add_modify (&se->pre, lenvar, trimlen);
+ }
+
+ /* Allocate a new string newvar that is lenvar+1 bytes long.
+ memcpy the first lenvar bytes from the input string, and
+ add a null character. Note that lenvar, the length of
+ the (trimmed) original string, has type gfc_charlen_type_node,
+ but newlen is size_type_node. */
+ tree string_type_node = build_pointer_type (char_type_node);
+ tree newvar = gfc_create_var (string_type_node, NULL);
+ tree newlen = fold_build2_loc (input_location, PLUS_EXPR,
+ size_type_node,
+ fold_convert (size_type_node,
+ lenvar),
+ size_one_node);
+ gfc_add_modify (&se->pre, newvar,
+ gfc_call_malloc (&se->pre, string_type_node,
+ newlen));
+ tmp = build_call_expr_loc (input_location,
+ builtin_decl_explicit (BUILT_IN_MEMCPY),
+ 3,
+ fold_convert (pvoid_type_node, newvar),
+ fold_convert (pvoid_type_node, sse.expr),
+ fold_convert (size_type_node, lenvar));
+ gfc_add_expr_to_block (&se->pre, tmp);
+ tmp = fold_build2_loc (input_location, POINTER_PLUS_EXPR,
+ string_type_node, newvar,
+ fold_convert (size_type_node, lenvar));
+ tmp = fold_build1_loc (input_location, INDIRECT_REF,
+ char_type_node, tmp);
+ gfc_add_modify (&se->pre, tmp,
+ fold_convert (char_type_node, integer_zero_node));
+
+ /* Remember to free the string later. */
+ tmp = gfc_call_free (newvar);
+ gfc_add_expr_to_block (&se->post, tmp);
+
+ /* Return the result. */
+ se->expr = newvar;
+ se->string_length = fold_convert (gfc_charlen_type_node, newlen);
+ return;
+ }
}
else
gcc_unreachable ();
diff --git a/gcc/testsuite/gfortran.dg/f_c_string3.f90
b/gcc/testsuite/gfortran.dg/f_c_string3.f90
new file mode 100644
index 00000000000..3e9d4a79d3b
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/f_c_string3.f90
@@ -0,0 +1,53 @@
+! Test f_c_string cases that can be fully constant-folded
+! { dg-do compile }
+! { dg-additional-options "-fdump-tree-original" }
+
+use iso_c_binding, only: f_c_string, c_char
+implicit none (external, type)
+character(*, c_char), parameter :: str1 = "blah1"
+character(*, c_char), parameter :: str2 = "blah2"
+character(*, c_char), parameter :: str3 = "blah3"
+character(*, c_char), parameter :: str4 = "blah4 "
+character(*, c_char), parameter :: str5 = "blah5 "
+character(*, c_char), parameter :: str6 = "blah6 "
+external foo
+
+call foo(f_c_string("hello world1", asis=.true.))
+! { dg-final { scan-tree-dump-times "hello world1.\[^\\n\\r\]*, 13" 1
"original" } }
+
+call foo(f_c_string("hello world2", asis=.false.))
+! { dg-final { scan-tree-dump-times "hello world2.\[^\\n\\r\]*, 13" 1
"original" } }
+
+call foo(f_c_string("hello world3"))
+! { dg-final { scan-tree-dump-times "hello world3.\[^\\n\\r\]*, 13" 1
"original" } }
+
+call foo(f_c_string("hello1 ", asis=.true.))
+! { dg-final { scan-tree-dump-times "hello1 .\[^\\n\\r\]*, 8" 1 "original" } }
+
+call foo(f_c_string("hello2 ", asis=.false.))
+! { dg-final { scan-tree-dump-times "hello2.\[^\\n\\r\]*, 7" 1 "original" } }
+
+call foo(f_c_string("hello3 "))
+! { dg-final { scan-tree-dump-times "hello3.\[^\\n\\r\]*, 7" 1 "original" } }
+
+call foo(f_c_string(str1, asis=.true.))
+! { dg-final { scan-tree-dump-times "blah1.\[^\\n\\r\]*, 6" 1 "original" } }
+
+call foo(f_c_string(str2, asis=.false.))
+! { dg-final { scan-tree-dump-times "blah2.\[^\\n\\r\]*, 6" 1 "original" } }
+
+call foo(f_c_string(str3))
+! { dg-final { scan-tree-dump-times "blah3.\[^\\n\\r\]*, 6" 1 "original" } }
+
+call foo(f_c_string(str4, asis=.true.))
+! { dg-final { scan-tree-dump-times "blah4 .\[^\\n\\r\]*, 9" 1 "original" } }
+
+call foo(f_c_string(str5, asis=.false.))
+! { dg-final { scan-tree-dump-times "blah5.\[^\\n\\r\]*, 6" 1 "original" } }
+
+call foo(f_c_string(str6))
+! { dg-final { scan-tree-dump-times "blah6.\[^\\n\\r\]*, 6" 1 "original" } }
+
+end
+
+
diff --git a/gcc/testsuite/gfortran.dg/f_c_string4.f90
b/gcc/testsuite/gfortran.dg/f_c_string4.f90
new file mode 100644
index 00000000000..d38e16f0268
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/f_c_string4.f90
@@ -0,0 +1,26 @@
+! Test f_c_string cases with constant strings but that need a conditional.
+! { dg-do compile }
+! { dg-additional-options "-fdump-tree-original" }
+
+subroutine doit (x)
+
+use iso_c_binding, only: f_c_string, c_char
+implicit none (external, type)
+logical :: x
+character(*, c_char), parameter :: str1 = "blah1"
+character(*, c_char), parameter :: str2 = "blah2 "
+external foo
+
+call foo(f_c_string("hello world1", asis=x))
+! { dg-final { scan-tree-dump-times "hello world1.\[^\\n\\r\]*, 13" 1
"original" } }
+
+call foo(f_c_string("hello1 ", asis=x))
+! { dg-final { scan-tree-dump-times "hello1 .\[^\\n\\r\]* 8 : 7" 1 "original"
} }
+
+call foo(f_c_string(str1, asis=x))
+! { dg-final { scan-tree-dump-times "blah1.\[^\\n\\r\]*, 6" 1 "original" } }
+
+call foo(f_c_string(str2, asis=x))
+! { dg-final { scan-tree-dump-times "blah2 .\[^\\n\\r\]* 9 : 6" 1 "original"
} }
+
+end subroutine
diff --git a/gcc/testsuite/gfortran.dg/f_c_string5.f90
b/gcc/testsuite/gfortran.dg/f_c_string5.f90
new file mode 100644
index 00000000000..25c5115f214
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/f_c_string5.f90
@@ -0,0 +1,20 @@
+! { dg-do run }
+! This is the example from the manual.
+
+program main
+ use iso_c_binding, only: f_c_string, c_char
+ implicit none (external, type)
+ character(:, c_char), allocatable :: s1, s2, s3
+
+ ! s1 is null-terminated "hello, world! "
+ s1 = f_c_string ("hello, world! ", .true.)
+ if (len(s1) .ne. 17) stop 100
+
+ ! s2 is null-terminated "hello, world!"
+ s2 = f_c_string ("hello, world! ", .false.)
+ if (len(s2) .ne. 14) stop 200
+
+ ! s3 is null-terminated "hello, world!" (same as s2 example)
+ s3 = f_c_string ("hello, world! ")
+ if (len(s3) .ne. 14) stop 200
+end program main
--
2.39.5
