Hi!
The following testcase is miscompiled in 4.8+ on x86_64 at -O2+,
because REE widens for ZERO_EXTEND mode on
(set (reg:QI ax) (const_int -1)) instruction to SImode, but doesn't
adjust REG_EQUAL note of (const_int -1) also to (const_int 0xff)
like it changes the pattern.
The following patch attempts to adjust the notes if they are CONST_INT,
or drop otherwise (not sure if it would be desirable to emit
a ZERO_EXTEND of the previous content of the note), and both through
validate_change, so that if we give up later on, it is undone.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
What about 4.9.2 (after release) and 4.8.x?
2014-10-27 Jakub Jelinek <ja...@redhat.com>
PR rtl-optimization/63659
* ree.c (update_reg_equal_equiv_notes): New function.
(combine_set_extension, transform_ifelse): Use it.
* gcc.c-torture/execute/pr63659.c: New test.
--- gcc/ree.c.jj 2014-10-22 15:52:18.000000000 +0200
+++ gcc/ree.c 2014-10-27 19:18:37.287412478 +0100
@@ -266,6 +266,50 @@ typedef struct ext_cand
static int max_insn_uid;
+/* Update or remove REG_EQUAL or REG_EQUIV notes for INSN. */
+
+static bool
+update_reg_equal_equiv_notes (rtx_insn *insn, enum machine_mode new_mode,
+ enum machine_mode old_mode, enum rtx_code code)
+{
+ rtx *loc = ®_NOTES (insn);
+ while (*loc)
+ {
+ enum reg_note kind = REG_NOTE_KIND (*loc);
+ if (kind == REG_EQUAL || kind == REG_EQUIV)
+ {
+ rtx orig_src = XEXP (*loc, 0);
+ /* Update equivalency constants. Recall that RTL constants are
+ sign-extended. */
+ if (GET_CODE (orig_src) == CONST_INT
+ && HOST_BITS_PER_WIDE_INT >= GET_MODE_BITSIZE (new_mode))
+ {
+ if (INTVAL (orig_src) >= 0 || code == SIGN_EXTEND)
+ /* Nothing needed. */;
+ else
+ {
+ /* Zero-extend the negative constant by masking out the
+ bits outside the source mode. */
+ rtx new_const_int
+ = gen_int_mode (INTVAL (orig_src)
+ & GET_MODE_MASK (old_mode),
+ new_mode);
+ if (!validate_change (insn, &XEXP (*loc, 0),
+ new_const_int, true))
+ return false;
+ }
+ loc = &XEXP (*loc, 1);
+ }
+ /* Drop all other notes, they assume a wrong mode. */
+ else if (!validate_change (insn, loc, XEXP (*loc, 1), true))
+ return false;
+ }
+ else
+ loc = &XEXP (*loc, 1);
+ }
+ return true;
+}
+
/* Given a insn (CURR_INSN), an extension candidate for removal (CAND)
and a pointer to the SET rtx (ORIG_SET) that needs to be modified,
this code modifies the SET rtx to a new SET rtx that extends the
@@ -287,6 +331,7 @@ static bool
combine_set_extension (ext_cand *cand, rtx_insn *curr_insn, rtx *orig_set)
{
rtx orig_src = SET_SRC (*orig_set);
+ enum machine_mode orig_mode = GET_MODE (SET_DEST (*orig_set));
rtx new_set;
rtx cand_pat = PATTERN (cand->insn);
@@ -323,9 +368,8 @@ combine_set_extension (ext_cand *cand, r
{
/* Zero-extend the negative constant by masking out the bits outside
the source mode. */
- enum machine_mode src_mode = GET_MODE (SET_DEST (*orig_set));
rtx new_const_int
- = gen_int_mode (INTVAL (orig_src) & GET_MODE_MASK (src_mode),
+ = gen_int_mode (INTVAL (orig_src) & GET_MODE_MASK (orig_mode),
GET_MODE (new_reg));
new_set = gen_rtx_SET (VOIDmode, new_reg, new_const_int);
}
@@ -364,7 +408,9 @@ combine_set_extension (ext_cand *cand, r
/* This change is a part of a group of changes. Hence,
validate_change will not try to commit the change. */
- if (validate_change (curr_insn, orig_set, new_set, true))
+ if (validate_change (curr_insn, orig_set, new_set, true)
+ && update_reg_equal_equiv_notes (curr_insn, cand->mode, orig_mode,
+ cand->code))
{
if (dump_file)
{
@@ -414,7 +460,9 @@ transform_ifelse (ext_cand *cand, rtx_in
ifexpr = gen_rtx_IF_THEN_ELSE (cand->mode, cond, map_srcreg, map_srcreg2);
new_set = gen_rtx_SET (VOIDmode, map_dstreg, ifexpr);
- if (validate_change (def_insn, &PATTERN (def_insn), new_set, true))
+ if (validate_change (def_insn, &PATTERN (def_insn), new_set, true)
+ && update_reg_equal_equiv_notes (def_insn, cand->mode, GET_MODE (dstreg),
+ cand->code))
{
if (dump_file)
{
--- gcc/testsuite/gcc.c-torture/execute/pr63659.c.jj 2014-10-27
19:26:57.720902738 +0100
+++ gcc/testsuite/gcc.c-torture/execute/pr63659.c 2014-10-27
19:26:36.000000000 +0100
@@ -0,0 +1,29 @@
+/* PR rtl-optimization/63659 */
+
+int a, b, c, *d = &b, g, h, i;
+unsigned char e;
+char f;
+
+int
+main ()
+{
+ while (a)
+ {
+ for (a = 0; a; a++)
+ for (; c; c++)
+ ;
+ if (i)
+ break;
+ }
+
+ char j = c, k = -1, l;
+ l = g = j >> h;
+ f = l == 0 ? k : k % l;
+ e = 0 ? 0 : f;
+ *d = e;
+
+ if (b != 255)
+ __builtin_abort ();
+
+ return 0;
+}
Jakub
