[PATCH] Better comparison of BINFOs in IPA-CP

[Martin Jambor]

Hi,

the patch below improves the comparisons of BINFOs in IPA-CP.  The
problem is that we can read different BINFOs for the same type (or a
base type component) from the LTO summaries because BINFOs coming from
different compilation units are not unified.  Because we now have the
BINFO_VTABLE available, we can compare those instead since the VMT
variables are unified.

Bootstrapped and tested on x86_64-linux, also tested by LTO-building
Firefox and 483.xalancbmk on the same platform (I lost the actual
numbers but the new test returned true hundreds of times in both
these cases).  OK for trunk?

Thanks,

Martin


2011-09-02  Martin Jambor  <mjam...@suse.cz>

        * ipa-cp.c (values_equal_for_ipcp_p): When comparing BINFOs, compare
        their BINFO_VTABLE,

Index: src/gcc/ipa-cp.c
===================================================================
--- src.orig/gcc/ipa-cp.c
+++ src/gcc/ipa-cp.c
@@ -800,6 +800,33 @@ values_equal_for_ipcp_p (tree x, tree y)
   if (x == y)
     return true;
 
+  if (TREE_CODE (x) == TREE_BINFO && TREE_CODE (y) == TREE_BINFO)
+    {
+      unsigned HOST_WIDE_INT ox, oy;
+      tree vx = BINFO_VTABLE (x);
+      tree vy = BINFO_VTABLE (y);
+
+      if (!vx || !vy
+         || TREE_CODE (vx) != POINTER_PLUS_EXPR
+         || TREE_CODE (vy) != POINTER_PLUS_EXPR)
+       return false;
+
+      ox = tree_low_cst (TREE_OPERAND (vx, 1), 1);
+      oy = tree_low_cst (TREE_OPERAND (vx, 1), 1);
+
+      if (ox != oy)
+       return false;
+
+      vx = TREE_OPERAND (vx, 0);
+      vy = TREE_OPERAND (vy, 0);
+      if (TREE_CODE (vx) != ADDR_EXPR
+         || TREE_CODE (vy) != ADDR_EXPR)
+       return false;
+
+      if (TREE_OPERAND (vx, 0) == TREE_OPERAND (vy, 0))
+       return true;
+    }
+
   if (TREE_CODE (x) == TREE_BINFO || TREE_CODE (y) == TREE_BINFO)
     return false;