On Wed, Oct 26, 2011 at 10:22:21PM -0700, Ian Lance Taylor wrote:
> I don't think it is possible to trigger this using C because I don't
> think it is possible to have a zero-length STRING_CST in C.
Ugh.
I think the following should work, after all it will be tiny more efficient,
I chose to use c_strlen just to avoid some code duplication.
c_strlen will return even variable lengths etc. and we are only interested
in constant string lengths, etc. If c_strlen is only called in places which
expect zero-terminated strings, it will be fine.
2011-10-27 Jakub Jelinek <ja...@redhat.com>
* tree-ssa-strlen.c: Include expr.h.
(get_stridx): Don't use c_strlen, instead use string_constant
and compute string length from it.
* Makefile.in (tree-ssa-strlen.o): Depend on $(EXPR_H).
--- gcc/tree-ssa-strlen.c.jj 2011-10-26 14:19:11.000000000 +0200
+++ gcc/tree-ssa-strlen.c 2011-10-27 08:55:39.000000000 +0200
@@ -28,6 +28,7 @@ along with GCC; see the file COPYING3.
#include "tree-ssa-propagate.h"
#include "gimple-pretty-print.h"
#include "params.h"
+#include "expr.h"
/* A vector indexed by SSA_NAME_VERSION. 0 means unknown, positive value
is an index into strinfo vector, negative value stands for
@@ -176,7 +177,7 @@ get_addr_stridx (tree exp)
static int
get_stridx (tree exp)
{
- tree l;
+ tree s, o;
if (TREE_CODE (exp) == SSA_NAME)
return VEC_index (int, ssa_ver_to_stridx, SSA_NAME_VERSION (exp));
@@ -188,14 +189,17 @@ get_stridx (tree exp)
return idx;
}
- l = c_strlen (exp, 0);
- if (l != NULL_TREE
- && host_integerp (l, 1))
- {
- unsigned HOST_WIDE_INT len = tree_low_cst (l, 1);
- if (len == (unsigned int) len
- && (int) len >= 0)
- return ~(int) len;
+ s = string_constant (exp, &o);
+ if (s != NULL_TREE
+ && (o == NULL_TREE || host_integerp (o, 0))
+ && TREE_STRING_LENGTH (s) > 0)
+ {
+ HOST_WIDE_INT offset = o ? tree_low_cst (o, 0) : 0;
+ const char *p = TREE_STRING_POINTER (s);
+ int max = TREE_STRING_LENGTH (s) - 1;
+
+ if (p[max] == '\0' && offset >= 0 && offset <= max)
+ return ~(int) strlen (p + offset);
}
return 0;
}
--- gcc/Makefile.in.jj 2011-10-26 14:19:11.000000000 +0200
+++ gcc/Makefile.in 2011-10-27 08:54:10.000000000 +0200
@@ -3173,7 +3173,7 @@ tree-ssa-ccp.o : tree-ssa-ccp.c $(TREE_F
$(DBGCNT_H) tree-pretty-print.h gimple-pretty-print.h gimple-fold.h
tree-ssa-strlen.o : tree-ssa-strlen.c $(CONFIG_H) $(SYSTEM_H) coretypes.h \
$(TREE_FLOW_H) $(TREE_PASS_H) domwalk.h alloc-pool.h tree-ssa-propagate.h \
- gimple-pretty-print.h $(PARAMS_H)
+ gimple-pretty-print.h $(PARAMS_H) $(EXPR_H)
tree-sra.o : tree-sra.c $(CONFIG_H) $(SYSTEM_H) coretypes.h alloc-pool.h \
$(TM_H) $(TREE_H) $(GIMPLE_H) $(CGRAPH_H) $(TREE_FLOW_H) \
$(IPA_PROP_H) $(DIAGNOSTIC_H) statistics.h $(TREE_DUMP_H) $(TIMEVAR_H) \
Jakub
