constant pool references to identify stack mode constants.
* rtlanal.c (constant_pool_constant_p): New predicate to check
whether operand is a floating point constant in the pool.
* rtl.h (constant_pool_constant_p): Prototype here.
* loop.c (scan_loop): Avoid hoisting constants from the constant
pool on STACK_REGS targets.
(load_mems): Likewise.
* loop-invariant.c (get_inv_cost): Make hoisting constant pool
loads into x87 registers expensive in terms of register pressure.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@111283
138bc75d-0d04-0410-961f-
82ee72b054a4
2006-02-19 Roger Sayle <roger@eyesopen.com>
+ Steven Bosscher <stevenb.gcc@gmail.com>
+
+ * gcse.c (want_to_gcse_p): On STACK_REGS targets, look through
+ constant pool references to identify stack mode constants.
+ * rtlanal.c (constant_pool_constant_p): New predicate to check
+ whether operand is a floating point constant in the pool.
+ * rtl.h (constant_pool_constant_p): Prototype here.
+ * loop.c (scan_loop): Avoid hoisting constants from the constant
+ pool on STACK_REGS targets.
+ (load_mems): Likewise.
+ * loop-invariant.c (get_inv_cost): Make hoisting constant pool
+ loads into x87 registers expensive in terms of register pressure.
+
+2006-02-19 Roger Sayle <roger@eyesopen.com>
* gthr-posix.h: On Tru64, map __gthr_foo as a weak reference to
__foo and not foo when _PTHREAD_USE_MANGLED_NAMES_ is defined.
static int
want_to_gcse_p (rtx x)
{
+#ifdef STACK_REGS
+ /* On register stack architectures, don't GCSE constants from the
+ constant pool, as the benefits are often swamped by the overhead
+ of shuffling the register stack between basic blocks. */
+ if (IS_STACK_MODE (GET_MODE (x)))
+ x = avoid_constant_pool_reference (x);
+#endif
+
switch (GET_CODE (x))
{
case REG:
(*regs_needed)++;
(*comp_cost) += inv->cost;
+#ifdef STACK_REGS
+ {
+ /* Hoisting constant pool constants into stack regs may cost more than
+ just single register. On x87, the balance is affected both by the
+ small number of FP registers, and by its register stack organisation,
+ that forces us to add compensation code in and around the loop to
+ shuffle the operands to the top of stack before use, and pop them
+ from the stack after the loop finishes.
+
+ To model this effect, we increase the number of registers needed for
+ stack registers by two: one register push, and one register pop.
+ This usually has the effect that FP constant loads from the constant
+ pool are not moved out of the loop.
+
+ Note that this also means that dependent invariants can not be moved.
+ However, the primary purpose of this pass is to move loop invariant
+ address arithmetic out of loops, and address arithmetic that depends
+ on floating point constants is unlikely to ever occur. */
+ rtx set = single_set (inv->insn);
+ if (set
+ && IS_STACK_MODE (GET_MODE (SET_SRC (set)))
+ && constant_pool_constant_p (SET_SRC (set)))
+ (*regs_needed) += 2;
+ }
+#endif
+
EXECUTE_IF_SET_IN_BITMAP (inv->depends_on, 0, depno, bi)
{
dep = VEC_index (invariant_p, invariants, depno);
if (GET_MODE_CLASS (GET_MODE (SET_DEST (set))) == MODE_CC
&& CONSTANT_P (src))
;
+#ifdef STACK_REGS
+ /* Don't hoist constant pool constants into stack regs. */
+ else if (IS_STACK_MODE (GET_MODE (SET_SRC (set)))
+ && constant_pool_constant_p (SET_SRC (set)))
+ ;
+#endif
/* Don't try to optimize a register that was made
by loop-optimization for an inner loop.
We don't know its life-span, so we can't compute
&& SCALAR_FLOAT_MODE_P (GET_MODE (mem)))
loop_info->mems[i].optimize = 0;
+#ifdef STACK_REGS
+ /* Don't hoist constant pool constants into stack registers. */
+ if (IS_STACK_MODE (GET_MODE (mem))
+ && constant_pool_constant_p (mem))
+ loop_info->mems[i].optimize = 0;
+#endif
+
/* If this MEM is written to, we must be sure that there
are no reads from another MEM that aliases this one. */
if (loop_info->mems[i].optimize && written)
extern unsigned int subreg_regno (rtx);
extern unsigned HOST_WIDE_INT nonzero_bits (rtx, enum machine_mode);
extern unsigned int num_sign_bit_copies (rtx, enum machine_mode);
+extern bool constant_pool_constant_p (rtx);
/* 1 if RTX is a subreg containing a reg that is already known to be
non_rtx_starting_operands[i] = first ? first - format : -1;
}
}
+\f
+/* Check whether this is a constant pool constant. */
+bool
+constant_pool_constant_p (rtx x)
+{
+ x = avoid_constant_pool_reference (x);
+ return GET_CODE (x) == CONST_DOUBLE;
+}
+