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tree.c (build_int_cst_type): Take sign of the value into account when deciding whether sign extend the value. 

* tree.c (build_int_cst_type): Take sign of the value into account
	when deciding whether sign extend the value.

From-SVN: r94633
This commit is contained in:
Zdenek Dvorak 2005-02-03 00:13:53 +01:00 committed by Zdenek Dvorak
parent 740ca4b2b1
commit 89d12f5d49
2 changed files with 41 additions and 13 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2005-02-02 Zdenek Dvorak <dvorakz@suse.cz>
* tree.c (build_int_cst_type): Take sign of the value into account
when deciding whether sign extend the value.
2005-02-02 Joseph S. Myers <joseph@codesourcery.com>
PR c/18502

49
gcc/tree.c
View File

@ -497,39 +497,62 @@ build_int_cstu (tree type, unsigned HOST_WIDE_INT low)
return build_int_cst_wide (type, low, 0);
}
/* Create an INT_CST node with a LOW value zero or sign extended depending
on the type. */
/* Create an INT_CST node with a LOW value in TYPE. The value is sign extended
if it is negative. This function is similar to build_int_cst, but
the extra bits outside of the type precision are cleared. Constants
with these extra bits may confuse the fold so that it detects overflows
even in cases when they do not occur, and in general should be avoided.
We cannot however make this a default behavior of build_int_cst without
more intrusive changes, since there are parts of gcc that rely on the extra
precision of the integer constants. */
tree
build_int_cst_type (tree type, HOST_WIDE_INT low)
{
unsigned HOST_WIDE_INT val = (unsigned HOST_WIDE_INT) low;
unsigned HOST_WIDE_INT hi;
unsigned bits;
bool signed_p;
bool negative;
tree ret;
if (!type)
type = integer_type_node;
bits = TYPE_PRECISION (type);
signed_p = !TYPE_UNSIGNED (type);
negative = ((val >> (bits - 1)) & 1) != 0;
if (signed_p && negative)
{
if (bits < HOST_BITS_PER_WIDE_INT)
val = val | ((~(unsigned HOST_WIDE_INT) 0) << bits);
ret = build_int_cst_wide (type, val, ~(unsigned HOST_WIDE_INT) 0);
}
if (bits >= HOST_BITS_PER_WIDE_INT)
negative = (low < 0);
else
{
if (bits < HOST_BITS_PER_WIDE_INT)
/* If the sign bit is inside precision of LOW, use it to determine
the sign of the constant. */
negative = ((val >> (bits - 1)) & 1) != 0;
/* Mask out the bits outside of the precision of the constant. */
if (signed_p && negative)
val = val | ((~(unsigned HOST_WIDE_INT) 0) << bits);
else
val = val & ~((~(unsigned HOST_WIDE_INT) 0) << bits);
ret = build_int_cst_wide (type, val, 0);
}
return ret;
/* Determine the high bits. */
hi = (negative ? ~(unsigned HOST_WIDE_INT) 0 : 0);
/* For unsigned type we need to mask out the bits outside of the type
precision. */
if (!signed_p)
{
if (bits <= HOST_BITS_PER_WIDE_INT)
hi = 0;
else
{
bits -= HOST_BITS_PER_WIDE_INT;
hi = hi & ~((~(unsigned HOST_WIDE_INT) 0) << bits);
}
}
return build_int_cst_wide (type, val, hi);
}
/* These are the hash table functions for the hash table of INTEGER_CST