The following patch fixes
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57963
The page contains a good analysis of the PR from Andreas Krebbel.
The patch was successfully bootstrapped and tested on x86/x86-64 and s390x.
Committed as rev. 201438.
2013-08-02 Vladimir Makarov <vmaka...@redhat.com>
PR rtl-optimization/57963
* lra-constraints.c (reverse_equiv_p, contains_reloaded_insn_p):
New.
(lra_constraints): Use them.
Index: lra-constraints.c
===================================================================
--- lra-constraints.c (revision 201435)
+++ lra-constraints.c (working copy)
@@ -3600,6 +3600,40 @@ init_insn_rhs_dead_pseudo_p (int regno)
return false;
}
+/* Return TRUE if REGNO has a reverse equivalence. The equivalence is
+ reverse only if we have one init insn with given REGNO as a
+ source. */
+static bool
+reverse_equiv_p (int regno)
+{
+ rtx insns, set;
+
+ if ((insns = ira_reg_equiv[regno].init_insns) == NULL_RTX)
+ return false;
+ if (! INSN_P (XEXP (insns, 0))
+ || XEXP (insns, 1) != NULL_RTX)
+ return false;
+ if ((set = single_set (XEXP (insns, 0))) == NULL_RTX)
+ return false;
+ return REG_P (SET_SRC (set)) && (int) REGNO (SET_SRC (set)) == regno;
+}
+
+/* Return TRUE if REGNO was reloaded in an equivalence init insn. We
+ call this function only for non-reverse equivalence. */
+static bool
+contains_reloaded_insn_p (int regno)
+{
+ rtx set;
+ rtx list = ira_reg_equiv[regno].init_insns;
+
+ for (; list != NULL_RTX; list = XEXP (list, 1))
+ if ((set = single_set (XEXP (list, 0))) == NULL_RTX
+ || ! REG_P (SET_DEST (set))
+ || (int) REGNO (SET_DEST (set)) != regno)
+ return true;
+ return false;
+}
+
/* Entry function of LRA constraint pass. Return true if the
constraint pass did change the code. */
bool
@@ -3643,7 +3677,6 @@ lra_constraints (bool first_p)
else if ((x = get_equiv_substitution (reg)) != reg)
{
bool pseudo_p = contains_reg_p (x, false, false);
- rtx set, insns;
/* After RTL transformation, we can not guarantee that
pseudo in the substitution was not reloaded which might
@@ -3675,13 +3708,13 @@ lra_constraints (bool first_p)
removed the insn. When the equiv can be a
constant, the right hand side of the init insn can
be a pseudo. */
- || (! ((insns = ira_reg_equiv[i].init_insns) != NULL_RTX
- && INSN_P (XEXP (insns, 0))
- && XEXP (insns, 1) == NULL_RTX
- && (set = single_set (XEXP (insns, 0))) != NULL_RTX
- && REG_P (SET_SRC (set))
- && (int) REGNO (SET_SRC (set)) == i)
- && init_insn_rhs_dead_pseudo_p (i))
+ || (! reverse_equiv_p (i)
+ && (init_insn_rhs_dead_pseudo_p (i)
+ /* If we reloaded the pseudo in an equivalence
+ init insn, we can not remove the equiv init
+ insns and the init insns might write into
+ const memory in this case. */
+ || contains_reloaded_insn_p (i)))
/* Prevent access beyond equivalent memory for
paradoxical subregs. */
|| (MEM_P (x)
