[PATCH] Fix PR 52631 (VN does not use simplified expression for lookup)

[Andrew Pinski]

Hi,
  Before tuples was introduced, VN used to lookup the simplified
expression to see if it was available already and use that instead of
the non simplified one.  This patch adds the support back to VN to do
exactly that.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

Thanks,
Andrew Pinski

ChangeLog:

        * tree-ssa-sccvn.c (visit_use): Look up the simplified
        expression before visting the original one.

        * gcc.dg/tree-ssa/ssa-fre-9.c: Update the number of
        eliminatations that happen.

Index: gcc/tree-ssa-sccvn.c
===================================================================
--- gcc/tree-ssa-sccvn.c        (revision 189800)
+++ gcc/tree-ssa-sccvn.c        (working copy)
@@ -3366,6 +3366,19 @@ visit_use (tree use)
                    case GIMPLE_UNARY_RHS:
                    case GIMPLE_BINARY_RHS:
                    case GIMPLE_TERNARY_RHS:
+                     /* First try to lookup the simplified expression. */
+                     if (simplified && valid_gimple_rhs_p (simplified))
+                       {
+                         tree result = vn_nary_op_lookup (simplified, NULL);
+                         if (result)
+                           {
+                             changed = set_ssa_val_to (lhs, result);
+                             goto done;
+                           }
+                         changed = set_ssa_val_to (lhs, lhs);
+                         vn_nary_op_insert (simplified, lhs);
+                       }
+                     /* Otherwise visit the original statement. */
                      changed = visit_nary_op (lhs, stmt);
                      break;
                    case GIMPLE_SINGLE_RHS:
Index: gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-9.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-9.c   (revision 189800)
+++ gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-9.c   (working copy)
@@ -23,6 +23,6 @@ void __frame_state_for1 (volatile char *
     }
 }
 
-/* { dg-final { scan-tree-dump-times "Eliminated: 1" 2 "fre1" } } */
+/* { dg-final { scan-tree-dump-times "Eliminated: 2" 2 "fre1" } } */
 /* { dg-final { scan-tree-dump-times "Insertions: 1" 2 "fre1" } } */
 /* { dg-final { cleanup-tree-dump "fre1" } } */