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fold-const.c (optimize_bit_field_compare): Only use one mode for both RHS and LHS in non-constant case. 

* fold-const.c (optimize_bit_field_compare): Only use one mode
	for both RHS and LHS in non-constant case.

From-SVN: r30800
This commit is contained in:
Richard Kenner 1999-12-06 17:28:18 +00:00 committed by Richard Kenner
parent d593d1d2b8
commit 5826cacf19
2 changed files with 25 additions and 37 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
Mon Dec 6 12:24:52 1999 Richard Kenner <kenner@vlsi1.ultra.nyu.edu>
* fold-const.c (optimize_bit_field_compare): Only use one mode
for both RHS and LHS in non-constant case.
1999-12-06 Nathan Sidwell <nathan@acm.org>
* frame.c (start_fde_sort): Only allocate erratic array, if

57
gcc/fold-const.c
View File

@ -2809,12 +2809,11 @@ optimize_bit_field_compare (code, compare_type, lhs, rhs)
tree compare_type;
tree lhs, rhs;
{
int lbitpos, lbitsize, rbitpos, rbitsize;
int lnbitpos, lnbitsize, rnbitpos = 0, rnbitsize = 0;
int lbitpos, lbitsize, rbitpos, rbitsize, nbitpos, nbitsize;
tree type = TREE_TYPE (lhs);
tree signed_type, unsigned_type;
int const_p = TREE_CODE (rhs) == INTEGER_CST;
enum machine_mode lmode, rmode, lnmode, rnmode = VOIDmode;
enum machine_mode lmode, rmode, nmode;
int lunsignedp, runsignedp;
int lvolatilep = 0, rvolatilep = 0;
int alignment;
@ -2848,55 +2847,39 @@ optimize_bit_field_compare (code, compare_type, lhs, rhs)
/* See if we can find a mode to refer to this field. We should be able to,
but fail if we can't. */
lnmode = get_best_mode (lbitsize, lbitpos,
TYPE_ALIGN (TREE_TYPE (linner)), word_mode,
lvolatilep);
if (lnmode == VOIDmode)
nmode = get_best_mode (lbitsize, lbitpos,
const_p ? TYPE_ALIGN (TREE_TYPE (linner))
: MIN (TYPE_ALIGN (TREE_TYPE (linner)),
TYPE_ALIGN (TREE_TYPE (rinner))),
word_mode, lvolatilep || rvolatilep);
if (nmode == VOIDmode)
return 0;
/* Set signed and unsigned types of the precision of this mode for the
shifts below. */
signed_type = type_for_mode (lnmode, 0);
unsigned_type = type_for_mode (lnmode, 1);
signed_type = type_for_mode (nmode, 0);
unsigned_type = type_for_mode (nmode, 1);
if (! const_p)
{
rnmode = get_best_mode (rbitsize, rbitpos,
TYPE_ALIGN (TREE_TYPE (rinner)), word_mode,
rvolatilep);
if (rnmode == VOIDmode)
return 0;
}
/* Compute the bit position and size for the new reference and our offset
within it. If the new reference is the same size as the original, we
won't optimize anything, so return zero. */
lnbitsize = GET_MODE_BITSIZE (lnmode);
lnbitpos = lbitpos & ~ (lnbitsize - 1);
lbitpos -= lnbitpos;
if (lnbitsize == lbitsize)
nbitsize = GET_MODE_BITSIZE (nmode);
nbitpos = lbitpos & ~ (nbitsize - 1);
lbitpos -= nbitpos;
if (nbitsize == lbitsize)
return 0;
if (! const_p)
{
rnbitsize = GET_MODE_BITSIZE (rnmode);
rnbitpos = rbitpos & ~ (rnbitsize - 1);
rbitpos -= rnbitpos;
if (rnbitsize == rbitsize)
return 0;
}
if (BYTES_BIG_ENDIAN)
lbitpos = lnbitsize - lbitsize - lbitpos;
lbitpos = nbitsize - lbitsize - lbitpos;
/* Make the mask to be used against the extracted field. */
mask = build_int_2 (~0, ~0);
TREE_TYPE (mask) = unsigned_type;
force_fit_type (mask, 0);
mask = convert (unsigned_type, mask);
mask = const_binop (LSHIFT_EXPR, mask, size_int (lnbitsize - lbitsize), 0);
mask = const_binop (LSHIFT_EXPR, mask, size_int (nbitsize - lbitsize), 0);
mask = const_binop (RSHIFT_EXPR, mask,
size_int (lnbitsize - lbitsize - lbitpos), 0);
size_int (nbitsize - lbitsize - lbitpos), 0);
if (! const_p)
/* If not comparing with constant, just rework the comparison
@ -2904,11 +2887,11 @@ optimize_bit_field_compare (code, compare_type, lhs, rhs)
return build (code, compare_type,
build (BIT_AND_EXPR, unsigned_type,
make_bit_field_ref (linner, unsigned_type,
lnbitsize, lnbitpos, 1),
nbitsize, nbitpos, 1),
mask),
build (BIT_AND_EXPR, unsigned_type,
make_bit_field_ref (rinner, unsigned_type,
rnbitsize, rnbitpos, 1),
nbitsize, nbitpos, 1),
mask));
/* Otherwise, we are handling the constant case. See if the constant is too
@ -2957,7 +2940,7 @@ optimize_bit_field_compare (code, compare_type, lhs, rhs)
/* Make a new bitfield reference, shift the constant over the
appropriate number of bits and mask it with the computed mask
(in case this was a signed field). If we changed it, make a new one. */
lhs = make_bit_field_ref (linner, unsigned_type, lnbitsize, lnbitpos, 1);
lhs = make_bit_field_ref (linner, unsigned_type, nbitsize, nbitpos, 1);
if (lvolatilep)
{
TREE_SIDE_EFFECTS (lhs) = 1;