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combine.c (try_widen_shift_mode): Factor out code to check if an integer constant is a low-order bitmask from here ... 

* combine.c (try_widen_shift_mode): Factor out code to check if an
        integer constant is a low-order bitmask from here ...
	* rtlanal.c (low_bitmask_len): ... to here.
	* rtl.h (low_bitmask_len): Declare.

From-SVN: r150656
This commit is contained in:
Adam Nemet 2009-08-11 17:31:09 +00:00 committed by Adam Nemet
parent c53c2591f6
commit 842e098c5f
4 changed files with 27 additions and 6 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2009-08-11 Adam Nemet <anemet@caviumnetworks.com>
* combine.c (try_widen_shift_mode): Factor out code to check if an
integer constant is a low-order bitmask from here ...
* rtlanal.c (low_bitmask_len): ... to here.
* rtl.h (low_bitmask_len): Declare.
2009-08-11 Uros Bizjak <ubizjak@gmail.com>
PR target/8603

8
gcc/combine.c
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@ -9027,13 +9027,9 @@ try_widen_shift_mode (enum rtx_code code, rtx op, int count,
/* We can also widen if the bits brought in will be masked off. This
operation is performed in ORIG_MODE. */
if (outer_code == AND
&& GET_MODE_BITSIZE (orig_mode) <= HOST_BITS_PER_WIDE_INT)
if (outer_code == AND)
{
int care_bits;
outer_const &= GET_MODE_MASK (orig_mode);
care_bits = exact_log2 (outer_const + 1);
int care_bits = low_bitmask_len (orig_mode, outer_const);
if (care_bits >= 0
&& GET_MODE_BITSIZE (orig_mode) - care_bits >= count)

1
gcc/rtl.h
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@ -1095,6 +1095,7 @@ extern unsigned HOST_WIDE_INT nonzero_bits (const_rtx, enum machine_mode);
extern unsigned int num_sign_bit_copies (const_rtx, enum machine_mode);
extern bool constant_pool_constant_p (rtx);
extern bool truncated_to_mode (enum machine_mode, const_rtx);
extern int low_bitmask_len (enum machine_mode, unsigned HOST_WIDE_INT);
/* 1 if RTX is a subreg containing a reg that is already known to be

17
gcc/rtlanal.c
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@ -5032,3 +5032,20 @@ constant_pool_constant_p (rtx x)
x = avoid_constant_pool_reference (x);
return GET_CODE (x) == CONST_DOUBLE;
}
/* If M is a bitmask that selects a field of low-order bits within an item but
not the entire word, return the length of the field. Return -1 otherwise.
M is used in machine mode MODE. */
int
low_bitmask_len (enum machine_mode mode, unsigned HOST_WIDE_INT m)
{
if (mode != VOIDmode)
{
if (GET_MODE_BITSIZE (mode) > HOST_BITS_PER_WIDE_INT)
return -1;
m &= GET_MODE_MASK (mode);
}
return exact_log2 (m + 1);
}