Hi!
The following patch shows a performance regression caused by the C++ changes
to evaluate side-effects in x += foo (); first and only then do the
addition. Previously if x was say int and foo () returned unsigned long
long, convert_to_integer would narrow the addition to unsigned int, but
as we now pass to convert_to_* a COMPOUND_EXPR with the side-effects on the
op0 and addition on op1 of the COMPOUND_EXPR, convert_to_integer doesn't
perform this shortening and unfortunately we don't have any gimple
optimization yet to do this later on. This patch fixes it by handling
COMPOUND_EXPR in convert_to_* where we care about TREE_CODE of the expr.
Ok for trunk? Ok for 4.8 as well after a while?
2013-06-17 Jakub Jelinek <ja...@redhat.com>
PR c++/56493
* convert.c (convert_to_real, convert_to_expr, convert_to_complex):
Handle COMPOUND_EXPR.
* c-c++-common/pr56493.c: New test.
--- gcc/convert.c.jj 2013-05-13 09:44:53.000000000 +0200
+++ gcc/convert.c 2013-06-16 12:16:13.754108523 +0200
@@ -95,6 +95,15 @@ convert_to_real (tree type, tree expr)
enum built_in_function fcode = builtin_mathfn_code (expr);
tree itype = TREE_TYPE (expr);
+ if (TREE_CODE (expr) == COMPOUND_EXPR)
+ {
+ tree t = convert_to_real (type, TREE_OPERAND (expr, 1));
+ if (t == TREE_OPERAND (expr, 1))
+ return expr;
+ return build2_loc (EXPR_LOCATION (expr), COMPOUND_EXPR, TREE_TYPE (t),
+ TREE_OPERAND (expr, 0), t);
+ }
+
/* Disable until we figure out how to decide whether the functions are
present in runtime. */
/* Convert (float)sqrt((double)x) where x is float into sqrtf(x) */
@@ -366,6 +375,15 @@ convert_to_integer (tree type, tree expr
return error_mark_node;
}
+ if (ex_form == COMPOUND_EXPR)
+ {
+ tree t = convert_to_integer (type, TREE_OPERAND (expr, 1));
+ if (t == TREE_OPERAND (expr, 1))
+ return expr;
+ return build2_loc (EXPR_LOCATION (expr), COMPOUND_EXPR, TREE_TYPE (t),
+ TREE_OPERAND (expr, 0), t);
+ }
+
/* Convert e.g. (long)round(d) -> lround(d). */
/* If we're converting to char, we may encounter differing behavior
between converting from double->char vs double->long->char.
@@ -854,6 +872,14 @@ convert_to_complex (tree type, tree expr
if (TYPE_MAIN_VARIANT (elt_type) == TYPE_MAIN_VARIANT (subtype))
return expr;
+ else if (TREE_CODE (expr) == COMPOUND_EXPR)
+ {
+ tree t = convert_to_complex (type, TREE_OPERAND (expr, 1));
+ if (t == TREE_OPERAND (expr, 1))
+ return expr;
+ return build2_loc (EXPR_LOCATION (expr), COMPOUND_EXPR,
+ TREE_TYPE (t), TREE_OPERAND (expr, 0), t);
+ }
else if (TREE_CODE (expr) == COMPLEX_EXPR)
return fold_build2 (COMPLEX_EXPR, type,
convert (subtype, TREE_OPERAND (expr, 0)),
--- gcc/testsuite/c-c++-common/pr56493.c.jj 2013-06-17 10:24:36.891659600
+0200
+++ gcc/testsuite/c-c++-common/pr56493.c 2013-06-17 10:24:33.164720149
+0200
@@ -0,0 +1,16 @@
+/* PR c++/56493 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-gimple" } */
+
+unsigned long long bar (void);
+int x;
+
+void
+foo (void)
+{
+ x += bar ();
+}
+
+/* Verify we narrow the addition from unsigned long long to unsigned int type.
*/
+/* { dg-final { scan-tree-dump " (\[a-zA-Z._0-9]*) = \\(unsigned int\\)
\[^;\n\r]*;.* (\[a-zA-Z._0-9]*) = \\(unsigned int\\) \[^;\n\r]*;.* = \\1 \\+
\\2;" "gimple" { target { ilp32 || lp64 } } } } */
+/* { dg-final { cleanup-tree-dump "gimple" } } */
Jakub
