Re: [PATCH] Dissociate store_expr's temp from exp so that it is not marked as addressable

[Martin Jambor]

Hi,

On Tue, Apr 03, 2012 at 11:02:11AM +0200, Eric Botcazou wrote:
> > Yeah, that sounds reasonable.
> 
> There is a further subtlety in the second temp allocation when the expression 
> doesn't use the alias set of its type.  In that case, we cannot pass the type 
> to set_mem_attributes.  In fact, since assign_stack_temp_for_type already 
> calls the appropriate set_mem_* routines, the best thing to do might be to 
> remove the call to set_mem_attributes altogether in that case.
> 

So, something like this?  Bootstrapped and tested on x86_64-linux and
ia64-linux, I'm currently having problems bootsrapping sparc64 which
is what I need this mainly for but those are unelated and this should
help.

Thanks,

Martin



2012-04-03  Martin Jambor  <mjam...@suse.cz>

        * expr.c (expand_expr_real_1): Pass type, not the expression, to
        set_mem_attributes for a memory temporary.  Do not call the
        function for temporaries with a different alias set.

Index: src/gcc/expr.c
===================================================================
--- src.orig/gcc/expr.c
+++ src/gcc/expr.c
@@ -9572,6 +9572,7 @@ expand_expr_real_1 (tree exp, rtx target
        tree tem = get_inner_reference (exp, &bitsize, &bitpos, &offset,
                                        &mode1, &unsignedp, &volatilep, true);
        rtx orig_op0, memloc;
+       bool mem_attrs_from_type = false;
 
        /* If we got back the original object, something is wrong.  Perhaps
           we are evaluating an expression too early.  In any event, don't
@@ -9677,6 +9678,7 @@ expand_expr_real_1 (tree exp, rtx target
            memloc = assign_temp (nt, 1, 1, 1);
            emit_move_insn (memloc, op0);
            op0 = memloc;
+           mem_attrs_from_type = true;
          }
 
        if (offset)
@@ -9849,7 +9851,6 @@ expand_expr_real_1 (tree exp, rtx target
                emit_move_insn (new_rtx, op0);
                op0 = copy_rtx (new_rtx);
                PUT_MODE (op0, BLKmode);
-               set_mem_attributes (op0, exp, 1);
              }
 
            return op0;
@@ -9870,7 +9871,14 @@ expand_expr_real_1 (tree exp, rtx target
        if (op0 == orig_op0)
          op0 = copy_rtx (op0);
 
-       set_mem_attributes (op0, exp, 0);
+       /* If op0 is a temporary because of forcing to memory, pass only the
+          type to set_mem_attributes so that the original expression is never
+          marked as ADDRESSABLE through MEM_EXPR of the temporary.  */
+       if (mem_attrs_from_type)
+         set_mem_attributes (op0, TREE_TYPE (exp), 0);
+       else
+         set_mem_attributes (op0, exp, 0);
+
        if (REG_P (XEXP (op0, 0)))
          mark_reg_pointer (XEXP (op0, 0), MEM_ALIGN (op0));