[PATCH] regalloc: Ignore '^' in early costing [PR114766]

[Wilco Dijkstra]

According to documentation, '^' should only have an effect during reload.
However ira-costs.cc treats it in the same way as '?' during early costing.
As a result using '^' can accidentally disable valid alternatives and cause
significant regressions (see PR114741).  Avoid this by ignoring '^' during
costing.

Passes bootstrap and regress, OK for commit?

gcc:
        PR rtl-optimization/114766
        * ira-costs.cc (record_reg_classes): Ignore '^' during costing.

---

diff --git a/gcc/ira-costs.cc b/gcc/ira-costs.cc
index 
c86c5a16563aeefac9d4fa72839bee8d95409f4b..04d2f21b023f3456ba6f8c16c2418d7313965b2f
 100644
--- a/gcc/ira-costs.cc
+++ b/gcc/ira-costs.cc
@@ -771,10 +771,6 @@ record_reg_classes (int n_alts, int n_ops, rtx *ops,
                  c = *++p;
                  break;
 
-               case '^':
-                 alt_cost += 2;
-                 break;
-
                case '?':
                  alt_cost += 2;
                  break;