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re PR middle-end/37135 (code size increase for struct assignment)

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PR middle-end/37135
	* dse.c (find_shift_sequence): Optimize extraction from a constant.

From-SVN: r142157
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Jakub Jelinek 2008-11-24 13:57:37 +01:00 committed by Jakub Jelinek
parent 5b19c351a4
commit 72a2609f5d
2 changed files with 28 additions and 0 deletions
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gcc/ChangeLog
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@ -1,3 +1,8 @@
2008-11-24 Jakub Jelinek <jakub@redhat.com>
PR middle-end/37135
* dse.c (find_shift_sequence): Optimize extraction from a constant.
2008-11-23 John David Anglin <dave.anglin@nrc-cnrc.gc.ca>
* pa.c (function_arg): Revert 2008-10-26 change.

23
gcc/dse.c
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@ -1447,6 +1447,29 @@ find_shift_sequence (int access_size,
rtx target, new_reg, shift_seq, insn, new_lhs;
int cost;
/* If a constant was stored into memory, try to simplify it here,
otherwise the cost of the shift might preclude this optimization
e.g. at -Os, even when no actual shift will be needed. */
if (CONSTANT_P (store_info->rhs))
{
unsigned int byte = subreg_lowpart_offset (new_mode, store_mode);
rtx ret = simplify_subreg (new_mode, store_info->rhs, store_mode,
byte);
if (ret && CONSTANT_P (ret))
{
ret = simplify_const_binary_operation (LSHIFTRT, new_mode,
ret, GEN_INT (shift));
if (ret && CONSTANT_P (ret))
{
byte = subreg_lowpart_offset (read_mode, new_mode);
ret = simplify_subreg (read_mode, ret, new_mode, byte);
if (ret && CONSTANT_P (ret)
&& rtx_cost (ret, SET, speed) <= COSTS_N_INSNS (1))
return ret;
}
}
}
/* Try a wider mode if truncating the store mode to NEW_MODE
requires a real instruction. */
if (GET_MODE_BITSIZE (new_mode) < GET_MODE_BITSIZE (store_mode)