Hi,
when re-testing the new STRING_CST semantic patch here:
https://gcc.gnu.org/ml/gcc-patches/2018-08/msg01569.html
I noticed that the (my) fix for PR 87053 does still use
semantic properties of the STRING_CST that is not compatible
with the new proposed STRING_CST semantics.
That means that c_strlen needs to handle the case
where strings are not zero terminated.
When this is fixed, fortran.dg/pr45636.f90 starts to regress,
because the check in gimple_fold_builtin_memory_op here:
if (tree_fits_uhwi_p (len)
&& compare_tree_int (len, MOVE_MAX) <= 0
/* ??? Don't transform copies from strings with known length this
confuses the tree-ssa-strlen.c. This doesn't handle
the case in gcc.dg/strlenopt-8.c which is XFAILed for that
reason. */
&& !c_strlen (src, 2))
does now return NULL_TREE, because the fortran string is not null terminated.
However that allows the folding which makes the fortran test case fail.
I fixed that by pulling in the c_getstr patch again, and use
it to make another exception for string constants without any embedded NUL.
That is what tree-ssa-forwprop.c can handle, and should make this work in
fortran again.
Bootstrapped and reg-tested on x86_64-pc-linux-gnu.
Is it OK for trunk?
Thanks
Bernd.
2018-08-30 Bernd Edlinger <bernd.edlin...@hotmail.de>
* builtins.c (c_strlen): Handle not zero terminated STRING_CSTs
correctly.
* fold-const.c (c_getstr): Fix function comment. Remove unused third
argument. Fix range checks.
* fold-const.h (c_getstr): Adjust protoype.
* gimple-fold.c (gimple_fold_builtin_memory_op): Avoid folding when
string is constant but contains no NUL byte.
diff -Npur gcc/builtins.c gcc/builtins.c
--- gcc/builtins.c 2018-08-30 08:21:13.000000000 +0200
+++ gcc/builtins.c 2018-08-30 21:46:11.155211333 +0200
@@ -604,12 +604,12 @@ c_strlen (tree src, int only_value, unsi
In that case, the elements of the array after the terminating NUL are
all NUL. */
HOST_WIDE_INT strelts = TREE_STRING_LENGTH (src);
- strelts = strelts / eltsize - 1;
+ strelts = strelts / eltsize;
if (!tree_fits_uhwi_p (memsize))
return NULL_TREE;
- HOST_WIDE_INT maxelts = tree_to_uhwi (memsize) / eltsize - 1;
+ HOST_WIDE_INT maxelts = tree_to_uhwi (memsize) / eltsize;
/* PTR can point to the byte representation of any string type, including
char* and wchar_t*. */
@@ -617,10 +617,6 @@ c_strlen (tree src, int only_value, unsi
if (byteoff && TREE_CODE (byteoff) != INTEGER_CST)
{
- /* For empty strings the result should be zero. */
- if (maxelts == 0)
- return ssize_int (0);
-
/* The code below works only for single byte character types. */
if (eltsize != 1)
return NULL_TREE;
@@ -632,9 +628,13 @@ c_strlen (tree src, int only_value, unsi
unsigned len = string_length (ptr, eltsize, strelts);
/* Return when an embedded null character is found or none at all. */
- if (len < strelts || len > maxelts)
+ if (len + 1 < strelts || len >= maxelts)
return NULL_TREE;
+ /* For empty strings the result should be zero. */
+ if (len == 0)
+ return ssize_int (0);
+
/* We don't know the starting offset, but we do know that the string
has no internal zero bytes. If the offset falls within the bounds
of the string subtract the offset from the length of the string,
@@ -644,7 +644,7 @@ c_strlen (tree src, int only_value, unsi
offsave = fold_convert (ssizetype, offsave);
tree condexp = fold_build2_loc (loc, LE_EXPR, boolean_type_node, offsave,
build_int_cst (ssizetype, len));
- tree lenexp = size_diffop_loc (loc, ssize_int (strelts), offsave);
+ tree lenexp = size_diffop_loc (loc, ssize_int (len), offsave);
return fold_build3_loc (loc, COND_EXPR, ssizetype, condexp, lenexp,
build_zero_cst (ssizetype));
}
@@ -663,7 +663,7 @@ c_strlen (tree src, int only_value, unsi
/* If the offset is known to be out of bounds, warn, and call strlen at
runtime. */
- if (eltoff < 0 || eltoff > maxelts)
+ if (eltoff < 0 || eltoff >= maxelts)
{
/* Suppress multiple warnings for propagated constant strings. */
if (only_value != 2
@@ -691,9 +691,9 @@ c_strlen (tree src, int only_value, unsi
unsigned len = string_length (ptr + eltoff * eltsize, eltsize,
strelts - eltoff);
- /* Don't know what to return if there was no zero termination.
+ /* Don't know what to return if there was no zero termination.
Ideally this would turn into a gcc_checking_assert over time. */
- if (len > maxelts - eltoff)
+ if (len >= maxelts - eltoff)
return NULL_TREE;
return ssize_int (len);
diff -Npur gcc/fold-const.c gcc/fold-const.c
--- gcc/fold-const.c 2018-08-30 08:21:13.000000000 +0200
+++ gcc/fold-const.c 2018-08-30 21:03:12.612460165 +0200
@@ -14576,23 +14576,20 @@ fold_build_pointer_plus_hwi_loc (locatio
/* Return a pointer P to a NUL-terminated string representing the sequence
of constant characters referred to by SRC (or a subsequence of such
characters within it if SRC is a reference to a string plus some
- constant offset). If STRLEN is non-null, store stgrlen(P) in *STRLEN.
- If STRSIZE is non-null, store in *STRSIZE the size of the array
- the string is stored in; in that case, even though P points to a NUL
- terminated string, SRC need not refer to one. This can happen when
- SRC refers to a constant character array initialized to all non-NUL
- values, as in the C declaration: char a[4] = "1234"; */
+ constant offset). If STRLEN is non-null, store the number of bytes
+ in the string constant including the terminating NUL char. *STRLEN is
+ typically strlen(P) + 1 in the absence of embedded NUL characters. */
const char *
-c_getstr (tree src, unsigned HOST_WIDE_INT *strlen /* = NULL */,
- unsigned HOST_WIDE_INT *strsize /* = NULL */)
+c_getstr (tree src, unsigned HOST_WIDE_INT *strlen /* = NULL */)
{
tree offset_node;
+ tree mem_size;
if (strlen)
*strlen = 0;
- src = string_constant (src, &offset_node, NULL, NULL);
+ src = string_constant (src, &offset_node, &mem_size, NULL);
if (src == 0)
return NULL;
@@ -14605,25 +14602,14 @@ c_getstr (tree src, unsigned HOST_WIDE_I
offset = tree_to_uhwi (offset_node);
}
+ if (!tree_fits_uhwi_p (mem_size))
+ return NULL;
+
/* STRING_LENGTH is the size of the string literal, including any
embedded NULs. STRING_SIZE is the size of the array the string
literal is stored in. */
unsigned HOST_WIDE_INT string_length = TREE_STRING_LENGTH (src);
- unsigned HOST_WIDE_INT string_size = string_length;
- tree type = TREE_TYPE (src);
- if (tree size = TYPE_SIZE_UNIT (type))
- if (tree_fits_shwi_p (size))
- string_size = tree_to_uhwi (size);
-
- if (strlen)
- {
- /* Compute and store the length of the substring at OFFSET.
- All offsets past the initial length refer to null strings. */
- if (offset <= string_length)
- *strlen = string_length - offset;
- else
- *strlen = 0;
- }
+ unsigned HOST_WIDE_INT string_size = tree_to_uhwi (mem_size);
const char *string = TREE_STRING_POINTER (src);
@@ -14631,21 +14617,26 @@ c_getstr (tree src, unsigned HOST_WIDE_I
|| offset >= string_size)
return NULL;
- if (strsize)
+ if (strlen)
{
- /* Support even constant character arrays that aren't proper
- NUL-terminated strings. */
- *strsize = string_size;
+ /* Compute and store the length of the substring at OFFSET.
+ All offsets past the initial length refer to null strings. */
+ if (offset < string_length)
+ *strlen = string_length - offset;
+ else
+ *strlen = 1;
}
- else if (string[string_length - 1] != '\0')
+ else
{
- /* Support only properly NUL-terminated strings but handle
- consecutive strings within the same array, such as the six
- substrings in "1\0002\0003". */
- return NULL;
+ tree eltype = TREE_TYPE (TREE_TYPE (src));
+ /* Support only properly NUL-terminated single byte strings. */
+ if (tree_to_uhwi (TYPE_SIZE_UNIT (eltype)) != 1)
+ return NULL;
+ if (string[string_length - 1] != '\0')
+ return NULL;
}
- return offset <= string_length ? string + offset : "";
+ return offset < string_length ? string + offset : "";
}
/* Given a tree T, compute which bits in T may be nonzero. */
diff -Npur gcc/fold-const.h gcc/fold-const.h
--- gcc/fold-const.h 2018-08-30 08:20:44.000000000 +0200
+++ gcc/fold-const.h 2018-08-30 20:58:54.154101370 +0200
@@ -187,8 +187,7 @@ extern bool expr_not_equal_to (tree t, c
extern tree const_unop (enum tree_code, tree, tree);
extern tree const_binop (enum tree_code, tree, tree, tree);
extern bool negate_mathfn_p (combined_fn);
-extern const char *c_getstr (tree, unsigned HOST_WIDE_INT * = NULL,
- unsigned HOST_WIDE_INT * = NULL);
+extern const char *c_getstr (tree, unsigned HOST_WIDE_INT * = NULL);
extern wide_int tree_nonzero_bits (const_tree);
/* Return OFF converted to a pointer offset type suitable as offset for
diff -Npur gcc/gimple-fold.c gcc/gimple-fold.c
--- gcc/gimple-fold.c 2018-08-28 15:44:49.000000000 +0200
+++ gcc/gimple-fold.c 2018-08-31 00:57:50.947845988 +0200
@@ -725,6 +725,8 @@ gimple_fold_builtin_memory_op (gimple_st
tree srctype, desttype;
unsigned int src_align, dest_align;
tree off0;
+ const char *tmp_str;
+ unsigned HOST_WIDE_INT tmp_len;
/* Build accesses at offset zero with a ref-all character type. */
off0 = build_int_cst (build_pointer_type_for_mode (char_type_node,
@@ -742,7 +744,9 @@ gimple_fold_builtin_memory_op (gimple_st
confuses the tree-ssa-strlen.c. This doesn't handle
the case in gcc.dg/strlenopt-8.c which is XFAILed for that
reason. */
- && !c_strlen (src, 2))
+ && !c_strlen (src, 2)
+ && !((tmp_str = c_getstr (src, &tmp_len)) != NULL
+ && memchr (tmp_str, 0, tmp_len) == NULL))
{
unsigned ilen = tree_to_uhwi (len);
if (pow2p_hwi (ilen))
