Hi!
As mentioned in PR78901, the current -fprintf-return-value optimization
will remove (replace with constant) calls like:
int
foo (void)
{
return snprintf (0, 0, "%s%d", "abcde", 5);
}
but not
void
bar (void)
{
snprintf (0, 0, "%s%d", "abcde", 5);
}
which doesn't have any side-effect either (and there we even don't care that
much about whether the return value is constant or not, just that there
are no other side-effects like %n directive).
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2017-01-02 Jakub Jelinek <ja...@redhat.com>
* gimple-ssa-sprintf.c (try_substitute_return_value): Remove
info.nowrite calls with no lhs that can't throw. Return bool
whether gsi_remove has been called or not.
(pass_sprintf_length::handle_gimple_call): Return bool whether
try_substitute_return_value called gsi_remove. Formatting fix.
(pass_sprintf_length::execute): Don't use gsi_remove if
handle_gimple_call returned true.
* gcc.dg/tree-ssa/builtin-snprintf-1.c: New test.
--- gcc/gimple-ssa-sprintf.c.jj 2017-01-02 13:05:08.400755201 +0100
+++ gcc/gimple-ssa-sprintf.c 2017-01-02 13:20:20.684895563 +0100
@@ -128,7 +128,7 @@ public:
fold_return_value = param;
}
- void handle_gimple_call (gimple_stmt_iterator*);
+ bool handle_gimple_call (gimple_stmt_iterator *);
struct call_info;
bool compute_format_length (call_info &, format_result *);
@@ -2686,7 +2686,7 @@ get_destination_size (tree dest)
is known and exact. A result that isn't suitable for substitution may
have its range set to the range of return values, if that is known. */
-static void
+static bool
try_substitute_return_value (gimple_stmt_iterator *gsi,
const pass_sprintf_length::call_info &info,
const format_result &res)
@@ -2746,6 +2746,23 @@ try_substitute_return_value (gimple_stmt
res.constant ? "constant" : "variable");
}
}
+ else if (lhs == NULL_TREE
+ && info.nowrite
+ && !stmt_ends_bb_p (info.callstmt))
+ {
+ /* Remove the call to the bounded function with a zero size
+ (e.g., snprintf(0, 0, "%i", 123)) if there is no lhs. */
+ unlink_stmt_vdef (info.callstmt);
+ gsi_remove (gsi, true);
+ if (dump_file)
+ {
+ location_t callloc = gimple_location (info.callstmt);
+ fprintf (dump_file, "On line %i removing ",
+ LOCATION_LINE (callloc));
+ print_generic_expr (dump_file, info.func, dump_flags);
+ fprintf (dump_file, " call.\n");
+ }
+ }
else
{
unsigned HOST_WIDE_INT maxbytes;
@@ -2801,19 +2818,22 @@ try_substitute_return_value (gimple_stmt
inbounds, (unsigned long)res.number_chars, ign);
}
}
+
+ return false;
}
/* Determine if a GIMPLE CALL is to one of the sprintf-like built-in
- functions and if so, handle it. */
+ functions and if so, handle it. Return true if the call is removed
+ and gsi_next should not be performed in the caller. */
-void
+bool
pass_sprintf_length::handle_gimple_call (gimple_stmt_iterator *gsi)
{
call_info info = call_info ();
info.callstmt = gsi_stmt (*gsi);
if (!gimple_call_builtin_p (info.callstmt, BUILT_IN_NORMAL))
- return;
+ return false;
info.func = gimple_call_fndecl (info.callstmt);
info.fncode = DECL_FUNCTION_CODE (info.func);
@@ -2904,7 +2924,7 @@ pass_sprintf_length::handle_gimple_call
break;
default:
- return;
+ return false;
}
/* The first argument is a pointer to the destination. */
@@ -2969,11 +2989,9 @@ pass_sprintf_length::handle_gimple_call
}
if (idx_objsize != HOST_WIDE_INT_M1U)
- {
- if (tree size = gimple_call_arg (info.callstmt, idx_objsize))
- if (tree_fits_uhwi_p (size))
- objsize = tree_to_uhwi (size);
- }
+ if (tree size = gimple_call_arg (info.callstmt, idx_objsize))
+ if (tree_fits_uhwi_p (size))
+ objsize = tree_to_uhwi (size);
if (info.bounded && !dstsize)
{
@@ -2998,7 +3016,7 @@ pass_sprintf_length::handle_gimple_call
location_t loc = gimple_location (info.callstmt);
warning_at (EXPR_LOC_OR_LOC (dstptr, loc),
OPT_Wformat_length_, "null destination pointer");
- return;
+ return false;
}
/* Set the object size to the smaller of the two arguments
@@ -3027,12 +3045,12 @@ pass_sprintf_length::handle_gimple_call
location_t loc = gimple_location (info.callstmt);
warning_at (EXPR_LOC_OR_LOC (info.format, loc),
OPT_Wformat_length_, "null format string");
- return;
+ return false;
}
info.fmtstr = get_format_string (info.format, &info.fmtloc);
if (!info.fmtstr)
- return;
+ return false;
/* The result is the number of bytes output by the formatted function,
including the terminating NUL. */
@@ -3048,7 +3066,8 @@ pass_sprintf_length::handle_gimple_call
&& optimize > 0
&& flag_printf_return_value
&& (!flag_rounding_math || !res.floating))
- try_substitute_return_value (gsi, info, res);
+ return try_substitute_return_value (gsi, info, res);
+ return false;
}
/* Execute the pass for function FUN. */
@@ -3059,14 +3078,14 @@ pass_sprintf_length::execute (function *
basic_block bb;
FOR_EACH_BB_FN (bb, fun)
{
- for (gimple_stmt_iterator si = gsi_start_bb (bb); !gsi_end_p (si);
- gsi_next (&si))
+ for (gimple_stmt_iterator si = gsi_start_bb (bb); !gsi_end_p (si); )
{
/* Iterate over statements, looking for function calls. */
gimple *stmt = gsi_stmt (si);
- if (is_gimple_call (stmt))
- handle_gimple_call (&si);
+ if (is_gimple_call (stmt) && handle_gimple_call (&si))
+ continue;
+ gsi_next (&si);
}
}
--- gcc/testsuite/gcc.dg/tree-ssa/builtin-snprintf-1.c.jj 2017-01-02
13:13:09.401499255 +0100
+++ gcc/testsuite/gcc.dg/tree-ssa/builtin-snprintf-1.c 2017-01-02
13:14:33.000000000 +0100
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fprintf-return-value -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-not "__builtin_snprintf" "optimized"} } */
+
+int
+foo (void)
+{
+ int a = __builtin_snprintf (0, 0, "%s", "abcdefgh");
+ return a;
+}
+
+void
+bar (void)
+{
+ __builtin_snprintf (0, 0, "%s", "abcdefgh");
+}
Jakub
