Eric Botcazou <ebotca...@adacore.com> writes:
> This is the PR about the useless spilling to memory of structures that are
> returned in registers. It was essentially addressed last year by Easwaran
> with
> an enhancement of the RTL DSE pass, but Easwaran also noted that we still
> spill
> to memory in the simplest cases, e.g. gcc.dg/pr44194-1.c, because expand_call
> creates a temporary on the stack to store the value returned in registers...
>
> The attached patch solves this problem by copying the value into pseudos
> instead by means of emit_group_move_into_temps. This is sufficient to get
> rid
> of the remaining memory accesses for gcc.dg/pr44194-1.c on x86-64 for example,
> but not on strict-alignment platforms like SPARC64.
Thanks for doing this. It'll obviously help n32 and n64 long doubles too.
I hit one problem building libgfortran for mips64-linux-gnu.
The calls.c change was:
Index: calls.c
===================================================================
--- calls.c (revision 191198)
+++ calls.c (working copy)
@@ -3272,16 +3272,8 @@ expand_call (tree exp, rtx target, int i
else if (GET_CODE (valreg) == PARALLEL)
{
if (target == 0)
- {
- /* This will only be assigned once, so it can be readonly. */
- tree nt = build_qualified_type (rettype,
- (TYPE_QUALS (rettype)
- | TYPE_QUAL_CONST));
-
- target = assign_temp (nt, 1, 1);
- }
-
- if (! rtx_equal_p (target, valreg))
+ target = emit_group_move_into_temps (valreg);
+ else if (!rtx_equal_p (target, valreg))
emit_group_store (target, valreg, rettype,
int_size_in_bytes (rettype));
/* We can not support sibling calls for this case. */
sibcall_failure = 1;
But if we're trying to use a sibcall, we go through this loop twice,
and the second iteration has to cope with a PARALLEL target created
by the first. How about the patch below? Tested on mips64-linux-gnu,
where a full testrun looked good.
In some ways it's a bit silly to emit anything at all in the first iteration,
given that we then go on to set sibcall_failure. It's not the kind of loop
we can just continue out of though. Also, your patch probably means that
we only need to set sibcall_failure for the emit_group_store case,
although I've not tested that.
Richard
gcc/
* calls.c (expand_call): Use emit_group_move for PARALLEL->PARALLEL
moves.
Index: gcc/calls.c
===================================================================
--- gcc/calls.c 2012-09-15 11:15:46.000000000 +0100
+++ gcc/calls.c 2012-09-15 11:15:46.522857695 +0100
@@ -3273,7 +3273,13 @@ expand_call (tree exp, rtx target, int i
{
if (target == 0)
target = emit_group_move_into_temps (valreg);
- else if (!rtx_equal_p (target, valreg))
+ else if (rtx_equal_p (target, valreg))
+ ;
+ else if (GET_CODE (target) == PARALLEL)
+ /* Handle the result of a emit_group_move_into_temps
+ call in the previous pass. */
+ emit_group_move (target, valreg);
+ else
emit_group_store (target, valreg, rettype,
int_size_in_bytes (rettype));
