On 11/20/22 20:07, Jiufu Guo wrote:
Jiufu Guo <guoji...@linux.ibm.com> writes:
Hi,
As mentioned in the previous version patch:
https://gcc.gnu.org/pipermail/gcc-patches/2022-October/604646.html
The suboptimal code is generated for "assigning from parameter" or
"assigning to return value".
This patch enhances the assignment from parameters like the below
cases:
/////case1.c
typedef struct SA {double a[3];long l; } A;
A ret_arg (A a) {return a;}
void st_arg (A a, A *p) {*p = a;}
////case2.c
typedef struct SA {double a[3];} A;
A ret_arg (A a) {return a;}
void st_arg (A a, A *p) {*p = a;}
For this patch, bootstrap and regtest pass on ppc64{,le}
and x86_64.
* Besides asking for help reviewing this patch, I would like to
consult comments about enhancing for "assigning to returns".
I updated the patch to fix the issue for returns. This patch
adds a flag DECL_USEDBY_RETURN_P to indicate if a var is used
by a return stmt. This patch fix the issue in expand pass only,
so, we would try to update the patch to avoid this flag.
diff --git a/gcc/cfgexpand.cc b/gcc/cfgexpand.cc
index dd29ffffc03..09b8ec64cea 100644
--- a/gcc/cfgexpand.cc
+++ b/gcc/cfgexpand.cc
@@ -2158,6 +2158,20 @@ expand_used_vars (bitmap forced_stack_vars)
frame_phase = off ? align - off : 0;
}
+ /* Collect VARs on returns. */
+ if (DECL_RESULT (current_function_decl))
+ {
+ edge_iterator ei;
+ edge e;
+ FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR_FOR_FN (cfun)->preds)
+ if (greturn *ret = safe_dyn_cast<greturn *> (last_stmt (e->src)))
+ {
+ tree val = gimple_return_retval (ret);
+ if (val && VAR_P (val))
+ DECL_USEDBY_RETURN_P (val) = 1;
+ }
+ }
+
/* Set TREE_USED on all variables in the local_decls. */
FOR_EACH_LOCAL_DECL (cfun, i, var)
TREE_USED (var) = 1;
diff --git a/gcc/expr.cc b/gcc/expr.cc
index d9407432ea5..20973649963 100644
--- a/gcc/expr.cc
+++ b/gcc/expr.cc
@@ -6045,6 +6045,52 @@ expand_assignment (tree to, tree from, bool nontemporal)
return;
}
+ if ((TREE_CODE (from) == PARM_DECL && DECL_INCOMING_RTL (from)
+ && TYPE_MODE (TREE_TYPE (from)) == BLKmode
+ && (GET_CODE (DECL_INCOMING_RTL (from)) == PARALLEL
+ || REG_P (DECL_INCOMING_RTL (from))))
+ || (VAR_P (to) && DECL_USEDBY_RETURN_P (to)
+ && TYPE_MODE (TREE_TYPE (to)) == BLKmode
+ && GET_CODE (DECL_RTL (DECL_RESULT (current_function_decl)))
+ == PARALLEL))
+ {
+ push_temp_slots ();
+ rtx par_ret;
+ machine_mode mode;
+ par_ret = TREE_CODE (from) == PARM_DECL
+ ? DECL_INCOMING_RTL (from)
+ : DECL_RTL (DECL_RESULT (current_function_decl));
+ mode = GET_CODE (par_ret) == PARALLEL
+ ? GET_MODE (XEXP (XVECEXP (par_ret, 0, 0), 0))
+ : word_mode;
+ int mode_size = GET_MODE_SIZE (mode).to_constant ();
+ int size = INTVAL (expr_size (from));
+
+ /* If/How the parameter using submode, it dependes on the size and
+ position of the parameter. Here using heurisitic number. */
+ int hurstc_num = 8;
Where did this come from and what does it mean?
Note that BLKmode subword values passed in registers can be either right
or left justified. I think you also need to worry about endianness here.
Jeff
