and set by `-m...' switches. Must be defined in rtlanal.c. */
int target_flags;
+
+/* Truncation narrows the mode from SOURCE mode to DESTINATION mode.
+ If TARGET_MODE_REP_EXTENDED (DESTINATION, DESTINATION_REP) is
+ SIGN_EXTEND then while narrowing we also have to enforce the
+ representation and sign-extend the value to mode DESTINATION_REP.
+
+ If the value is already sign-extended to DESTINATION_REP mode we
+ can just switch to DESTINATION mode on it. For each pair of
+ integral modes SOURCE and DESTINATION, when truncating from SOURCE
+ to DESTINATION, NUM_SIGN_BIT_COPIES_IN_REP[SOURCE][DESTINATION]
+ contains the number of high-order bits in SOURCE that have to be
+ copies of the sign-bit so that we can do this mode-switch to
+ DESTINATION. */
+
+static unsigned int
+num_sign_bit_copies_in_rep[MAX_MODE_INT + 1][MAX_MODE_INT + 1];
\f
/* Return 1 if the value of X is unstable
(would be different at a different point in the program).
total = COSTS_N_INSNS (7);
break;
case USE:
- /* Used in loop.c and combine.c as a marker. */
+ /* Used in combine.c as a marker. */
total = 0;
break;
default:
allow_cc_mode, valid_at_insn_p);
}
+/* Initialize the table NUM_SIGN_BIT_COPIES_IN_REP based on
+ TARGET_MODE_REP_EXTENDED.
+
+ Note that we assume that the property of
+ TARGET_MODE_REP_EXTENDED(B, C) is sticky to the integral modes
+ narrower than mode B. I.e., if A is a mode narrower than B then in
+ order to be able to operate on it in mode B, mode A needs to
+ satisfy the requirements set by the representation of mode B. */
+
+static void
+init_num_sign_bit_copies_in_rep (void)
+{
+ enum machine_mode mode, in_mode;
+
+ for (in_mode = GET_CLASS_NARROWEST_MODE (MODE_INT); in_mode != VOIDmode;
+ in_mode = GET_MODE_WIDER_MODE (mode))
+ for (mode = GET_CLASS_NARROWEST_MODE (MODE_INT); mode != in_mode;
+ mode = GET_MODE_WIDER_MODE (mode))
+ {
+ enum machine_mode i;
+
+ /* Currently, it is assumed that TARGET_MODE_REP_EXTENDED
+ extends to the next widest mode. */
+ gcc_assert (targetm.mode_rep_extended (mode, in_mode) == UNKNOWN
+ || GET_MODE_WIDER_MODE (mode) == in_mode);
+
+ /* We are in in_mode. Count how many bits outside of mode
+ have to be copies of the sign-bit. */
+ for (i = mode; i != in_mode; i = GET_MODE_WIDER_MODE (i))
+ {
+ enum machine_mode wider = GET_MODE_WIDER_MODE (i);
+
+ if (targetm.mode_rep_extended (i, wider) == SIGN_EXTEND
+ /* We can only check sign-bit copies starting from the
+ top-bit. In order to be able to check the bits we
+ have already seen we pretend that subsequent bits
+ have to be sign-bit copies too. */
+ || num_sign_bit_copies_in_rep [in_mode][mode])
+ num_sign_bit_copies_in_rep [in_mode][mode]
+ += GET_MODE_BITSIZE (wider) - GET_MODE_BITSIZE (i);
+ }
+ }
+}
+
/* Suppose that truncation from the machine mode of X to MODE is not a
no-op. See if there is anything special about X so that we can
assume it already contains a truncated value of MODE. */
bool
truncated_to_mode (enum machine_mode mode, rtx x)
{
- return REG_P (x) && rtl_hooks.reg_truncated_to_mode (mode, x);
-}
+ /* This register has already been used in MODE without explicit
+ truncation. */
+ if (REG_P (x) && rtl_hooks.reg_truncated_to_mode (mode, x))
+ return true;
+
+ /* See if we already satisfy the requirements of MODE. If yes we
+ can just switch to MODE. */
+ if (num_sign_bit_copies_in_rep[GET_MODE (x)][mode]
+ && (num_sign_bit_copies (x, GET_MODE (x))
+ >= num_sign_bit_copies_in_rep[GET_MODE (x)][mode] + 1))
+ return true;
+ return false;
+}
\f
/* Initialize non_rtx_starting_operands, which is used to speed up
for_each_rtx. */
const char *first = strpbrk (format, "eEV");
non_rtx_starting_operands[i] = first ? first - format : -1;
}
+
+ init_num_sign_bit_copies_in_rep ();
}
\f
/* Check whether this is a constant pool constant. */