Hi!
The following testcase ICEs, because move_plus_up attempts to
optimize (subreg:HI (plus:SI (...) (const_int 0xff78)) 0)
into (plus:HI (subreg:HI (...) 0) (const_int 0xff78)) which is
incorrect, HImode CONST_INT with MSB set should be (const_int -136)
instead. The patch also punts if the second operand of PLUS is
some CONSTANT_P that can't be simplified into a CONSTANT_P in the
narrower mode.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2016-01-08 Jakub Jelinek <ja...@redhat.com>
PR target/69071
* lra-eliminations.c (move_plus_up): Only move plus up
if subreg of the constant can be simplified into constant
and use the simplified subreg of the constant instead of
the original constant.
* gcc.dg/pr69071.c: New test.
--- gcc/lra-eliminations.c.jj 2016-01-04 14:55:50.000000000 +0100
+++ gcc/lra-eliminations.c 2016-01-08 10:28:39.954706210 +0100
@@ -296,9 +296,14 @@ move_plus_up (rtx x)
if (GET_CODE (x) == SUBREG && GET_CODE (subreg_reg) == PLUS
&& GET_MODE_SIZE (x_mode) <= GET_MODE_SIZE (subreg_reg_mode)
&& CONSTANT_P (XEXP (subreg_reg, 1)))
- return gen_rtx_PLUS (x_mode, lowpart_subreg (x_mode, subreg_reg,
- subreg_reg_mode),
- XEXP (subreg_reg, 1));
+ {
+ rtx cst = simplify_subreg (x_mode, XEXP (subreg_reg, 1), subreg_reg_mode,
+ subreg_lowpart_offset (x_mode,
+ subreg_reg_mode));
+ if (cst && CONSTANT_P (cst))
+ return gen_rtx_PLUS (x_mode, lowpart_subreg (x_mode, subreg_reg,
+ subreg_reg_mode), cst);
+ }
return x;
}
--- gcc/testsuite/gcc.dg/pr69071.c.jj 2016-01-08 10:24:50.029922989 +0100
+++ gcc/testsuite/gcc.dg/pr69071.c 2016-01-08 10:24:34.000000000 +0100
@@ -0,0 +1,22 @@
+/* PR target/69071 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -g" } */
+
+void *bar (void *);
+
+void
+foo (int c)
+{
+ unsigned char bf[65400];
+ unsigned char *p2 = bar (bf);
+ unsigned char *p3 = bar (bf);
+ for (; *p2; p2++, c++)
+ {
+ if (c)
+ {
+ short of = p2 - bf - 6;
+ unsigned ofu = of;
+ __builtin_memcpy (p3, &ofu, sizeof (ofu));
+ }
+ }
+}
Jakub
