[PATCH] sel-sched: fix merging of LHS reg availability (PR 50340)

[Alexander Monakov]

Hello,

This patches fixes an ICE on an assert that performs a sanity check on
target_available field of expr_t, which is tri-state: LHS register is
available (1), not available (0) or unknown (-1).

The problem is, when merging expr data of separable exprs with differing
LHSes, we can't claim we know anything about availability of the target
register if the unavailable LHS of the other expr is not the same register.
Thus, we should set the field to -1, not 0.

Fixed as follows, bootstrapped and regtested on x86_64-linux and ia64-linux
(without java, with one recent SRA patch reverted to unbreak bootstrap) with
sel-sched enabled at -O2.  OK for trunk?

(a small testcase is not available at the moment, but I can try to produce one
using delta before committing)


2011-09-13  Andrey Belevantsev  <a...@ispras.ru>

        * sel-sched-ir.c (update_target_availability): LHS register
        availability is not known if the unavailable LHS of the other
        expression is a different register.

diff --git a/gcc/sel-sched-ir.c b/gcc/sel-sched-ir.c
index 4878460..b132392 100644
--- a/gcc/sel-sched-ir.c
+++ b/gcc/sel-sched-ir.c
@@ -1746,7 +1746,13 @@ update_target_availability (expr_t to, expr_t from,
insn_t split_point)
             EXPR_TARGET_AVAILABLE (to) = -1;
         }
       else
-        EXPR_TARGET_AVAILABLE (to) &= EXPR_TARGET_AVAILABLE (from);
+    if (EXPR_TARGET_AVAILABLE (from) == 0
+        && EXPR_LHS (from)
+        && REG_P (EXPR_LHS (from))
+        && REGNO (EXPR_LHS (to)) != REGNO (EXPR_LHS (from)))
+      EXPR_TARGET_AVAILABLE (to) = -1;
+    else
+      EXPR_TARGET_AVAILABLE (to) &= EXPR_TARGET_AVAILABLE (from);
     }
 }