-2002-10-02 Matt Austern <austern@apple.com
+2002-10-02 Richard Henderson <rth@redhat.com>
+
+ PR opt/7124
+ * config/i386/i386.c (ix86_register_move_cost): Increase cost
+ for secondary_memory_needed pairs.
+
+2002-10-02 Matt Austern <austern@apple.com>
+
* class.c (check_field_decls): Changed warning about const member
variables so that it doesn't get issued for a class aggregate.
enum reg_class class1, class2;
{
/* In case we require secondary memory, compute cost of the store followed
- by load. In case of copying from general_purpose_register we may emit
- multiple stores followed by single load causing memory size mismatch
- stall. Count this as arbitarily high cost of 20. */
+ by load. In order to avoid bad register allocation choices, we need
+ for this to be *at least* as high as the symmetric MEMORY_MOVE_COST. */
+
if (ix86_secondary_memory_needed (class1, class2, mode, 0))
{
- int add_cost = 0;
+ int cost = 1;
+
+ cost += MAX (MEMORY_MOVE_COST (mode, class1, 0),
+ MEMORY_MOVE_COST (mode, class1, 1));
+ cost += MAX (MEMORY_MOVE_COST (mode, class2, 0),
+ MEMORY_MOVE_COST (mode, class2, 1));
+
+ /* In case of copying from general_purpose_register we may emit multiple
+ stores followed by single load causing memory size mismatch stall.
+ Count this as arbitarily high cost of 20. */
if (CLASS_MAX_NREGS (class1, mode) > CLASS_MAX_NREGS (class2, mode))
- add_cost = 20;
- return (MEMORY_MOVE_COST (mode, class1, 0)
- + MEMORY_MOVE_COST (mode, class2, 1) + add_cost);
+ cost += 20;
+
+ /* In the case of FP/MMX moves, the registers actually overlap, and we
+ have to switch modes in order to treat them differently. */
+ if ((MMX_CLASS_P (class1) && MAYBE_FLOAT_CLASS_P (class2))
+ || (MMX_CLASS_P (class2) && MAYBE_FLOAT_CLASS_P (class1)))
+ cost += 20;
+
+ return cost;
}
+
/* Moves between SSE/MMX and integer unit are expensive. */
if (MMX_CLASS_P (class1) != MMX_CLASS_P (class2)
|| SSE_CLASS_P (class1) != SSE_CLASS_P (class2))