[PATCH] Fold RHS when open-coding memcpy

[Richard Biener]

I noticed that we fail to fold the source to a constant if possible.

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.

Richard.

2016-06-10  Richard Biener  <rguent...@suse.de>

        * gimple-fold.c (gimple_fold_builtin_memory_op): Make sure
        to fold the RHS to a constant if possible.

Index: gcc/gimple-fold.c
===================================================================
*** gcc/gimple-fold.c   (revision 237286)
--- gcc/gimple-fold.c   (working copy)
*************** gimple_fold_builtin_memory_op (gimple_st
*** 1020,1033 ****
        gimple *new_stmt;
        if (is_gimple_reg_type (TREE_TYPE (srcvar)))
        {
!         new_stmt = gimple_build_assign (NULL_TREE, srcvar);
!         if (gimple_in_ssa_p (cfun))
!           srcvar = make_ssa_name (TREE_TYPE (srcvar), new_stmt);
!         else
!           srcvar = create_tmp_reg (TREE_TYPE (srcvar));
!         gimple_assign_set_lhs (new_stmt, srcvar);
!         gimple_set_vuse (new_stmt, gimple_vuse (stmt));
!         gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
        }
        new_stmt = gimple_build_assign (destvar, srcvar);
        gimple_set_vuse (new_stmt, gimple_vuse (stmt));
--- 1020,1039 ----
        gimple *new_stmt;
        if (is_gimple_reg_type (TREE_TYPE (srcvar)))
        {
!         tree tem = fold_const_aggregate_ref (srcvar);
!         if (tem)
!           srcvar = tem;
!         if (! is_gimple_min_invariant (srcvar))
!           {
!             new_stmt = gimple_build_assign (NULL_TREE, srcvar);
!             if (gimple_in_ssa_p (cfun))
!               srcvar = make_ssa_name (TREE_TYPE (srcvar), new_stmt);
!             else
!               srcvar = create_tmp_reg (TREE_TYPE (srcvar));
!             gimple_assign_set_lhs (new_stmt, srcvar);
!             gimple_set_vuse (new_stmt, gimple_vuse (stmt));
!             gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
!           }
        }
        new_stmt = gimple_build_assign (destvar, srcvar);
        gimple_set_vuse (new_stmt, gimple_vuse (stmt));